AudioCircle

Audio/Video Gear and Systems => Cheap and Cheerful HiFi => Topic started by: S Clark on 27 Oct 2015, 01:44 pm

Title: Folsom's great little 7297 Chip Amp
Post by: S Clark on 27 Oct 2015, 01:44 pm
A year of so back, many of us were singing the praises of the $6 Chinese 7297 amp available on ebay.  None sang louder than our own Folsom.  I bought several, modded them, used them, gave them away, and raved about them a bit myself. 
Fast forward to a few months back when Folsom offered a handful of boards of his own design with a recommended parts list.  I picked one up, ordered the list from Mouser, and got to work with the soldering gun.
Understand that in Texas summers, you really don't want to use a large tube amp like my Dodd, so I needed a better option, and this little amp fit the bill perfectly.  Driving a set of 93 dB efficient speakers, 10-15 watts was all I needed.
So I've had this little amp in the system for a couple of months and decided to write my impressions.

First, board and parts clearly qualify as Cheap and Cheerful, coming in well less than $100, but how does it sound. 
Clear, clear, clear.  Details abound, instruments are defined and placed precisely, even soundstage widens beyond the speakers well.  With efficient speakers, there is very solid dynamics.  In short, it held it's own with the much more expensive amp it replaced.  Bass was solid and most of all very clean.  Voices are natural but still clear in their enunciation.  This little guy is serious. 

How does it compare to the Chinese amp?  Better bass, a couple of more watts, better dynamics ( and the $6 had good dynamics).  Now that the weather has cooled, does it replace the Dodd?  No, the Dodd still has a fluidity and weight that I like.... but at 15X the price.  One more interesting comparison to note is with the much ballyhooed Crown amp that I had for a week.  No comparison. The Folsom was far superior on every front except pure power. 
These boards are a great way to build a high quality amp for peanuts.  I got one of the first batch, but they are about to be available on https://www.indiegogo.com/projects/diy7297-pcb-board#/
For what it's worth, my opinion is that they are a steal. 

Almost forgot to mention.  I built the amp from the basic parts list.  Cap upgrades to follow.   :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 27 Oct 2015, 03:48 pm
I was hoping he would put up these for sale again. What power supply do you use it with?

This review is what made me more than curious where the reviewer used the Folsom chip amp to evaluate Vapor's  Perfect Storm speakers.
http://www.hometheatershack.com/forums/speaker-subwoofer-reviews/127042-vapor-audio-perfect-storm-speaker-review.html#/forumsite/20818/topics/127042?page=1

I just need to practice my soldering skills before getting one.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: S Clark on 27 Oct 2015, 06:25 pm
I've used 18.5V from a variable regulated supply (a Hy1803D).  Folsom told me that a couple of more volts more hits the sweet spot and strengthens the bass.  I've got batteries ordered with the intent to put two 12v's in series to get 24V (that the US Post Office lost yesterday in shipping-althought the torn and crushed box was delivered sans batteries :cuss:).  I have to call after 4PM today to get their official runaround about why it's not their fault.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 27 Oct 2015, 06:34 pm
Yup, the "infinite capacitor" only activates with enough voltage (listed on my IndieGoGo). S Clark is going to get a very nice improvement soon switching to 24v input (gets regulated to 17.8-18v on amplifier board).

The PSU used in the review with The Perfect Storm is my Antipole (http://igg.me/at/antipole/x/10632390), also now up as an IndieGoGo. It needs a transformer with it, 16v works best at 80va+. I prefer dual bobbin design for the best noise performance. The Hammond 185 series is what I used.

(http://www.audiocircle.com/image.php?id=130594)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: S Clark on 27 Oct 2015, 10:21 pm
I figured what the hey, I can always use another amp somewhere, so I got the Indiegogo started.  Hope you sell it out soon.  Thirty bucks down, 470 left to go.   :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 29 Oct 2015, 07:09 am
Here's a word from my friend whom I made a full amplifier for

"I’m not convinced that critical listening of one audio product versus another is worth anyone’s time, unless you have a whole lot of it.  I therefore don’t understand those who are reviewers for all or part of their living, appears to take the fun right out of it.  The differences (in my experience) are generally minor and it’s difficult, if not impossible, to absolutely decide which one is better.  It ends up like choosing which flavor of ice cream to eat before bed, there is no wrong way to go.  However, audio equipment is expensive and ice cream is not.  Weigh in that cost factor and it’s no wonder my system has not changed in many years.  I require a rather large benefit per expenditure and a clear winner.

Nevertheless, every now and again I am compelled to purchase, the cost overcome by the improvement.  In late 2008, a friend of mine from the stereo shop contacted me to demo a power conditioner he had on loan.   The conditioner was custom-made by a young fellow named Jeremy Hood, right here in Missoula, and I really needed to “listen” to it in my room.  I’d demoed several power conditioners over the years from the local stereo shop and online vendors and had not thought any on them really improved the sound.  They all went back to where they came from.  This was different and after a few days, I begged to rent the unit until Jeremy could build a conditioner for me.  I suffered for weeks in silence as the rental option was not really an option (nobody in their right mind would be without this conditioner once it’s in their possession) and I had little interest in listening without it.

That was my last improvement until just recently.  Sure, I replaced my Bel Canto cd player in 2014 with a new one from the same manufacturer after the transport started acting up. It didn’t change the sound any, at least after the new unit broke in a bit.  I’ve considered my system complete since 2009 and I spent my money elsewhere.  That doesn’t mean Jeremy and others weren’t trying to tempt me with other “upgrades”.  They would bring the upgrade to the house and we’d listen to the change in sound.  In 6 years I bought nothing but more music.

That changed this summer when Jeremy hooked up his new chip amplifier in my rig.  He had already brought several previous amps to me for demonstration.  He trusts my ears, my system and my listening room. Plus I am likely his toughest critic, at least in person as it’s easy to be unimpressed over social media.  None of the previous amps were nearly as competent as my already broken in and paid for Bryston 3B-SST.  The rather expensive Bryston is powerful yet refined, quiet as a mouse and a great match for my Bel Canto CD transport and DAC as all appreciate a balanced connection.

After a few hours to let the demo amp settle in, I was pretty sure this was going to cost me as the Bryston was suddenly muffled and slow by comparison.  After a day, I had to have the new amp.  My daughter’s wedding would have to wait (kidding).  I once again suffered without much music during the build process.  A few days of burn-in time, a quick yet convincing A/B test of the two amps and the Bryston went into the closet.  Jeremy’s amp provides gloriously articulate, colorless gain.  I have so much music to relisten to.

For those who care and have inquiring minds, my system:
Piega Premium 5.2 speakers         Bel Canto transport 3 and DAC 3        Jeremy Hood Amplifier and Power Conditioner
Analysis Plus speaker cables         Zenwave Audio IC's, Nordost XLR and Heavens Gate AES/EBU
Shunyata and Cardas  AC cables        Oyaide power outlet"
Title: Re: Folsom's great little 7297 Chip Amp
Post by: ebag4 on 1 Nov 2015, 04:56 am
I finally picked up a couple of these (now $8.) eBay amps.  Powered it up from a 12v battery and fed it via an iFi iTube preamp, it sounds pretty great.  So I decided to pick up one of the Folsom amps, should be an excellent cool running backup to my Bottlehead, the extra power doesn't hurt either.  Anxious to give the Folsom amp a try.

Does anyone know what the input impedance is for these little amps?

Best,
Ed
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 1 Nov 2015, 05:07 am
I finally picked up a couple of these (now $8.) eBay amps.  Powered it up from a 12v battery and fed it via an iFi iTube preamp, it sounds pretty great.  So I decided to pick up one of the Folsom amps, should be an excellent cool running backup to my Bottlehead, the extra power doesn't hurt either.  Anxious to give the Folsom amp a try.

Does anyone know what the input impedance is for these little amps?

Best,
Ed

25-30kohm

That's why I recommend 1.5uf input cap for best bass.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Tyson on 1 Nov 2015, 06:03 pm
I got a chance to demo the amp a few weeks ago and I thought it sounded better than the Pass First Watt F5 I'd built a while back - more forward, more dynamic, clean and clear but not sterile.  The F5 in fact sounded somewhat sterile in comparison. 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: OzarkTom on 1 Nov 2015, 07:36 pm
With so many very expensive components out there, it is very nice to see these chip amps, IFI components, and the new Andrew Jones speakers. My buddy Rex is going to order a pair of those from Music Direct and he might order the Auralic mini music streamer for $575. He owns several chip amps now. Rex was sad to see the Auralic go from $395 to $575, I guess that does include a one year subscription to Tidal. According to the Auralic Faceook page, German dealers are now receiving them.

For around $1500, this system with IFI Itube and a chip amp will come very close to the mega buck systems. A person does not need to rob a bank to get high SQ these days.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 5 Nov 2015, 04:04 am
I'm assuming the parts list and instructions are included? Would this be a good first time project for someone like me who has never built up an amp from a board before?

What's the approx price for the parts?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 5 Nov 2015, 05:46 am
Yes a BOM (bill of materials) is available.

Parts price depends, just the amp board it's about $35 worth of parts including a heatsink. The Antipole parts are about $42. The transformer I recommend can be had for $26/35 (depending on what's available).

So far I've found it doesn't really take instructions. The board is well labeled with very few parts. But I have a few notes like making sure the large transistor has long enough legs to get the heatsink on (best to put on heatsink and then solder it in last). Also the output for speakers doesn't have a "ground" because it's balanced, so no forms of ground can make contact with them. Thermal paste is recommended for the chip to heatsink. And most important is not to connect the amplifier while the power supply has any power in it's capacitors.

All of that makes it a pretty good first build option for an amplifier. It's also a nice choice because it's hard to screw it up since the chip has many fail safes and is the last line in the parts before your speakers.

I'll be taking a few more photos when the boards are printed up, to illustrate the few things you need to know.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: GentleBender on 5 Nov 2015, 10:31 am
I've been checking out this interesting thread, but am unable to find many details about this amp. This would be my first project of this type and the indiegogo page does not contain much info for a newbie such as myself. What additional parts would I need to order for the DIY7297 and the Antipole PSU?

Would this work as a headphone amp? What type of connections, input/output? So many questions... :oops:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 5 Nov 2015, 02:39 pm
Yes a BOM (bill of materials) is available.

Parts price depends, just the amp board it's about $35 worth of parts including a heatsink. The Antipole parts are about $42. The transformer I recommend can be had for $26/35 (depending on what's available).

So far I've found it doesn't really take instructions. The board is well labeled with very few parts. But I have a few notes like making sure the large transistor has long enough legs to get the heatsink on (best to put on heatsink and then solder it in last). Also the output for speakers doesn't have a "ground" because it's balanced, so no forms of ground can make contact with them. Thermal paste is recommended for the chip to heatsink. And most important is not to connect the amplifier while the power supply has any power in it's capacitors.

All of that makes it a pretty good first build option for an amplifier. It's also a nice choice because it's hard to screw it up since the chip has many fail safes and is the last line in the parts before your speakers.

I'll be taking a few more photos when the boards are printed up, to illustrate the few things you need to know.

Does the BOM just state part values or actual part numbers from Digi-Key and Mouser? Actual PN's would really make life easier. Also, when do you expect the boards will be available, assuming you reach your goal.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: DaveC113 on 5 Nov 2015, 03:19 pm
I just got the amp yesterday, thanks Jeremy!  :thumb:

I have a few amps and a couple of speakers in the house. Pioneer S-1EX which are an Andrew Jones TAD design, and Omega Super 3 XRS. Amps are my own EL34 SET which is used with the Omegas, Crown XLS 1500 with Pomona posts and a top end Odyssey Stratos stereo amplifier. My preamp is an Aikido running 6SN7s and soon (hopefully) a zero-gain pre using Tortuga LDR + Aikido tube buffer.

The chip amp also came with a volume control and I'll also use my Aikido, which may have too much gain at 20 dB, and my zero-gain pre which should be done within 2 weeks, I hope...



Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 5 Nov 2015, 04:07 pm
Dave, I'm already sold on it, but I'm still curious to hear your impression of it compared to the other amps.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 5 Nov 2015, 05:17 pm
Does the BOM just state part values or actual part numbers from Digi-Key and Mouser? Actual PN's would really make life easier. Also, when do you expect the boards will be available, assuming you reach your goal.

Yes it does! I'll show you. Here's the parts for just the amplifier section (not including the capacitor multiplier, voltage regulator section)

Amp parts: Mouser      # of parts



I've been checking out this interesting thread, but am unable to find many details about this amp. This would be my first project of this type and the indiegogo page does not contain much info for a newbie such as myself. What additional parts would I need to order for the DIY7297 and the Antipole PSU?

Would this work as a headphone amp? What type of connections, input/output? So many questions... :oops:

What kind of details are you looking for? The datasheet (https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0CEEQFjAAahUKEwjR5Pu_5fnIAhUE2GMKHUS6Aow&url=http%3A%2F%2Fwww.st.com%2Fweb%2Fen%2Fresource%2Ftechnical%2Fdocument%2Fdatasheet%2FCD00001048.pdf&usg=AFQjCNF95cXzBYxubRNtXQvIXjavY94vwQ&sig2=na3yGtUIuiWBSV1EvZIUgQ) for the chip will tell you many. It uses singled ended connections. That means RCA phono jacks are used. The speaker outputs are whatever binding posts you'd like to use. I've used Ponoma's and Furutech Torq's, two different amps. The wire is your choice, and enclosure. I like Landfall systems (https://landfallsystems.com/) enclosures; they'll CNC panels for what you want as well. I recommend a heatsink from Heatsink USA (http://www.heatsinkusa.com/3-500/). And as stated above I have a recommended transformer, but you can use anything 80va+ that's 16v output for transformers or two 12v batteries, or a SMPS that can do 21v.

As far as a headphone amp I haven't tried, mainly because you have to either add a lot of resistance to the input or output. Other amps that get used for a headphone amp often control the power going in by modifying the feedback network to lower the signal strength greatly. This is uncharted territory thus far, but I can say if it did work I'd expect it to drive difficult loads effortlessly.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 5 Nov 2015, 05:42 pm
It seems that there's a lot of newbies to amp building that are interested. That's good :thumb:. It's a bit different than over on the DIYaudio website because half those guys are like gimmie a PCB, I'll figure it out! When the boards are released I'll make a thread just for showing some pictures, and answering some questions as well.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Peter J on 5 Nov 2015, 06:08 pm
It seems that there's a lot of newbies to amp building that are interested. That's good :thumb:. It's a bit different than over on the DIYaudio website because half those guys are like gimmie a PCB, I'll figure it out! When the boards are released I'll make a thread just for showing some pictures, and answering some questions as well.

That newbie moniker would certainly apply to me. I know my way around a soldering iron, but way outside my element on something like this. Some handholding would be appreciated and most probably a necessity.

I'll jump on both Indiegogo offerings out of curiosity more than need. Compared to almost anything else in the audio world, it seems like an inexpensive way to learn something new.

Edited to add: Top prove how green I am, I have to ask about the optional inclusion of a transistor in the Indiegogo offer. Do I need that? What would be the option for the neophyte?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 5 Nov 2015, 07:18 pm
Peter, you can buy several thousands of them from another place that carries NOS.

You have to have the transistor. I include it for free! Maybe I should check because I mean for it to not sound optional. It's from my personal stash (I have a lot, maybe 1000 or so). There's lots of replacements, but the one I have has better specifications.

I hope the future holds more DIY, for those that can't lay down real big stacks of cash on gear, but want to have something truly good.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: bentconvert on 5 Nov 2015, 07:36 pm
Maybe it should be obvious but are the amp and PSU boards stereo or mono? Trying to determine if I need to order one or two of each for stereo.

Thanks,
Steve
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 5 Nov 2015, 07:42 pm
The amp is stereo. You only need one of each.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 5 Nov 2015, 09:04 pm
Yes it does! I'll show you. Here's the parts for just the amplifier section (not including the capacitor multiplier, voltage regulator section)

Amp parts: Mouser      # of parts
TDA7297                                    511-TDA7297   1
330uf                                    667-25SEPF330M   12
47kohm                                    CFR16J47K   2
Vishay/Sprague 10uf                    75-515D106M035JA6AE3   1
input cap recommended            80-PHE426KF7150JR6L2    2
input bypass cap recommended   MKP1837322161G     2


What's the deal with the capacitor multiplier, voltage regulator section ? Is that populated on the same board?

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 5 Nov 2015, 09:11 pm
What's the deal with the capacitor multiplier, voltage regulator section ? Is that populated on the same board?

Yes. You can see it at the bottom before the capacitor array.


(http://www.audiocircle.com/image.php?id=131235)

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Mmaxed on 5 Nov 2015, 10:04 pm
Ordered both.  Sounds like a fun project with good or better results, plus I felt a need to support a fellow Montanan even if he is in Missoula.

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 5 Nov 2015, 10:24 pm
Ordered both.  Sounds like a fun project with good or better results, plus I felt a need to support a fellow Montanan even if he is in Missoula.

I must moved :oops: , but I've always wondered if there was anyone in Montana! If you're going to Missoula anytime PM me, I might be able to get you a little audition with a system that's got this amp in it.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Peter J on 5 Nov 2015, 10:58 pm
Peter, you can buy several thousands of them from another place that carries NOS.

You have to have the transistor. I include it for free! Maybe I should check because I mean for it to not sound optional. It's from my personal stash (I have a lot, maybe 1000 or so). There's lots of replacements, but the one I have has better specifications.

I hope the future holds more DIY, for those that can't lay down real big stacks of cash on gear, but want to have something truly good.

Duh, I guess I should have looked a little closer at the offering, it is indeed spelled out.  Anyway, I'm in for both boards, looks like the Antipole is somewhat behind amp board in funding.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mikeeastman on 5 Nov 2015, 11:20 pm
How do I order an antipole board?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Mmaxed on 5 Nov 2015, 11:43 pm
I must moved :oops: , but I've always wondered if there was anyone in Montana! If you're going to Missoula anytime PM me, I might be able to get you a little audition with a system that's got this amp in it.

Sorry, had to rib a little.  Thanks for the offer but don't get that way often except heading to ID to see the inlaws.  Usually a quick trip each way.  I will hear the amp when I get mine built.

By the way, what is the power of the amp?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 5 Nov 2015, 11:56 pm
15w , Danny Richie told me he thinks it sounds like 30w, maybe more. I'll confirm it sounds more like 15 tube watts.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Peter J on 6 Nov 2015, 12:01 am
How do I order an antipole board?

https://www.indiegogo.com/projects/antipole-pcb-filtered-psu#/

If you're ordering both, it looks like you should choose less expensive option and they'll ship together. That I read after pulling the trigger on the option including shipping.

Man, I just keep bumbling along here, hope that's not a harbinger of things to come...
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mikeeastman on 6 Nov 2015, 12:32 am
Thanks.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 7 Nov 2015, 08:59 pm
Yes. You can see it at the bottom before the capacitor array.


(http://www.audiocircle.com/image.php?id=131235)

(http://i.imgur.com/KD758fIl.jpg)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: shadowlight on 7 Nov 2015, 10:14 pm
Is there a pcb available for power supply?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 7 Nov 2015, 10:32 pm
(http://i.imgur.com/KD758fIl.jpg)

The transistor that feeds the DC to the supply capacitors and chip, controlled by the other transistor and TL431 for voltage regulation. The numbers and letters there punched into Mouser would have led you to one. It also requires a small heatsink on it.

Is there a pcb available for power supply?

shadowlight, yes, the Antipole (http://www.vice.com/read/is-america-ready-for-safe-injection-rooms-1106) that's posted in this thread.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 7 Nov 2015, 10:54 pm
Here's one in Ireland. I'll link to comments if he posts them publicly. (He says it's much more impressive than his Amp Camp Amp)

(http://www.audiocircle.com/image.php?id=131356)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: jtwrace on 8 Nov 2015, 02:50 am
What's the excitation of the board requirement?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 8 Nov 2015, 03:16 am
What's the excitation of the board requirement?

?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: jtwrace on 8 Nov 2015, 03:58 am
?
Power requirement. 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 8 Nov 2015, 06:57 am
Battery power use 24v, SMPS can be as low as 21v, and transformer should be 16v to get rectified around 23-24v.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: jtwrace on 8 Nov 2015, 01:13 pm
OK, so if battery power is 24Vdc what is the current requirement?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 8 Nov 2015, 01:46 pm
The transistor that feeds the DC to the supply capacitors and chip, controlled by the other transistor and TL431 for voltage regulation. The numbers and letters there punched into Mouser would have led you to one. It also requires a small heatsink on it.


Actually I did try finding the number at Mouser, but no luck? Is that the transistor you are supplying?



[/quote]
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 8 Nov 2015, 01:54 pm
Here's one in Ireland. I'll link to comments if he posts them publicly. (He says it's much more impressive than his Amp Camp Amp)

(http://www.audiocircle.com/image.php?id=131356)

It looks like he left the 12 Oscon's proud of the board. Is that suggested to prevent possible shorting of the caps aluminum case?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 9 Nov 2015, 08:40 pm
Actually I did try finding the number at Mouser, but no luck? Is that the transistor you are supplying?

Try 863-D45H11G
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 9 Nov 2015, 08:44 pm
It looks like he left the 12 Oscon's proud of the board. Is that suggested to prevent possible shorting of the caps aluminum case?

No idea what's up with that. I noticed as well. Perhaps his technique isn't down-pat.  I apply solder, then hold the unit with my hand, pressing on the cap gently, and touch the joint again. The capacitor goes into place, and when I release the iron it stays. That way when I do the other lead on it, it's in place. After the second is done, I typically add enough to finish the first joint/ clean it up.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 11 Nov 2015, 03:15 am
OK, so if battery power is 24Vdc what is the current requirement?

It's possible to run as low as 4.3a, but I would have more available, personally. The chip is regulated (internally) at 2A x 2, and the capacitor multiplier uses just a tiny bit.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 18 Nov 2015, 03:51 am
I've got batteries ordered with the intent to put two 12v's in series to get 24V (that the US Post Office lost yesterday in shipping-althought the torn and crushed box was delivered sans batteries :cuss:).  I have to call after 4PM today to get their official runaround about why it's not their fault.

Any updates how you like the 24V?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: S Clark on 18 Nov 2015, 04:00 am
Any updates how you like the 24V?
Afraid not.  While mounting it in a case, I managed to blow out the chip, so it's down for now.  Hopefully by the end of the week I'll have something to report.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Vapor Audio on 18 Nov 2015, 04:14 am
I can't believe that I haven't yet posted my thoughts after Folsom was so kind to let me live with his prototype for a few weeks.  My sincere apologies, I should have posted weeks ago. 

My thoughts on the amp were first that it seems much more powerful than the spec would suggest.  It controlled and drove our Perfect Storm White, Arcus, Cirrus Black, and Uber Aurora all with ease.  The first impression was clear and open, great soundstage and layering of images in the stage.  Independent stage elements were easily discernable and separated in space.  There was a nice sense of ease in that the details were delivered without any edge.  The amp was an especially nice match for the Arcus, there was plenty of current to drive them to quite high levels, and the Folsom amp really added an extra layer of presence through the mids and upper mids. 

From 100hz up I'd say this amp was very good in all phases, and excellent in some.  The amp was completely non-finicky, giving predicable results on many different speakers.  It ran cool, is a great manageable size, and his case was actually quite nice as well.  My only negative was bass was noticeably truncated on the Perfect Storm.  Folsom said he was going to chance some cap values to help alleviate that, but I haven't heard it since those changes were made. 

I do plan on having my own pair of Arcus setup permanently in a room here, and when I do plan to have one of the Folsom amps in that room as well. 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Peter J on 18 Nov 2015, 05:58 pm
I'm selfishly bumping this in an effort to draw attention and $$ to the power supply which needs some more neophytes like me to support it. Or anyone, I guess...newbie or not! I'd just like to see it come to fruition.

https://www.indiegogo.com/projects/antipole-pcb-filtered-psu#/
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 18 Nov 2015, 07:02 pm
I can't believe that I haven't yet posted my thoughts after Folsom was so kind to let me live with his prototype for a few weeks.  My sincere apologies, I should have posted weeks ago. 

My thoughts on the amp were first that it seems much more powerful than the spec would suggest.  It controlled and drove our Perfect Storm White, Arcus, Cirrus Black, and Uber Aurora all with ease.  The first impression was clear and open, great soundstage and layering of images in the stage.  Independent stage elements were easily discernable and separated in space.  There was a nice sense of ease in that the details were delivered without any edge.  The amp was an especially nice match for the Arcus, there was plenty of current to drive them to quite high levels, and the Folsom amp really added an extra layer of presence through the mids and upper mids. 

From 100hz up I'd say this amp was very good in all phases, and excellent in some.  The amp was completely non-finicky, giving predicable results on many different speakers.  It ran cool, is a great manageable size, and his case was actually quite nice as well.  My only negative was bass was noticeably truncated on the Perfect Storm.  Folsom said he was going to chance some cap values to help alleviate that, but I haven't heard it since those changes were made. 

I do plan on having my own pair of Arcus setup permanently in a room here, and when I do plan to have one of the Folsom amps in that room as well.

Ryan's correct. When he listened it had 1uf input capacitors. While the corner frequency was low enough, that's an electrical engineers wish, and not the reality. Since I've updated to 1.5uf sized input capacitors and the bass should have a -3db at 20hz like the chip is capable. But also I've begun bypassing this capacitor with a smaller one. There's far better detail, particularly in the information around what most people call detail.

Boy, I hope I get to hear some Arcus speakers with it! I can see how it would play quiet well with them. I love it's control it exerts for only being 15w. Another member might chime in some time, he said he doesn't think it has the highest dampening factor so one pair of speakers he tried it on, didn't give him the articulation in the bass that other speakers did. The good news is generally inefficient, moderately designed speaker drivers seem to behave that way. For example in a small/medium-small room with some 87db GR-Research speakers, you wouldn't be disappointed; but Danny's drivers have some careful attention paid that make them not as demanding on dampening, if I understand correctly.

I'm selfishly bumping this in an effort to draw attention and $$ to the power supply which needs some more neophytes like me to support it. Or anyone, I guess...newbie or not! I'd just like to see it come to fruition.

https://www.indiegogo.com/projects/antipole-pcb-filtered-psu#/

They'll be printed. If the IndieGoGo didn't go through, I could still collect from those that paid, separately. A few more orders would fully pay for printing, since $500 isn't how much I have to have, but how much IndieGoGo requires.

The Antipole is good for a lot of projects, btw. It's got a wide range of capability.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: ebag4 on 19 Nov 2015, 06:49 pm
I'm selfishly bumping this in an effort to draw attention and $$ to the power supply which needs some more neophytes like me to support it. Or anyone, I guess...newbie or not! I'd just like to see it come to fruition.

https://www.indiegogo.com/projects/antipole-pcb-filtered-psu#/
Done, thanks for the nudge  :thumb:.  I have a couple 100ah Powersonic AGM batts ready to use but I am curious about Folsom's power supply.  I may build my amp to use either.

Best,
Ed
Title: Re: Folsom's great little 7297 Chip Amp
Post by: shadowlight on 21 Nov 2015, 03:01 am
Jeremy,

Can this be run as mono blocks in a single chassis?  2 x 7297 board and 2 psu boards but a single power cable?  If yes, what changes need to occur on the chip board?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lokie on 21 Nov 2015, 12:06 pm
OK I'm in.

A DIY project I think i can pull off.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: jtwrace on 21 Nov 2015, 12:22 pm
It's possible to run as low as 2.3a, but I would have more available, personally. The chip is regulated (internally) at 2a, and the capacitor multiplier uses just a tiny bit.
So like 2.5A @ 24Vdc? 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 21 Nov 2015, 06:38 pm
Well,

Yes you can. You can parallel the channels on each board but you may lose some detail. But it's best to match chips because the input impedance varies from chip to chip within 5k.

You can also just run one channel on a board.

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 21 Nov 2015, 06:41 pm
So like 2.5A @ 24Vdc?

Sure.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 23 Nov 2015, 03:07 pm
Jeremy,
 Do you think we will see the boards before the new year?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 24 Nov 2015, 02:05 am
Unfortunately no. The IndieGoGo ends early December, payment takes 15 days, and printing takes two weeks.

If I had a way to get them out now, I would.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: jseipp on 24 Nov 2015, 03:31 am
I'm in!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: DaveC113 on 24 Nov 2015, 04:23 pm
I've had this amp for a while and have enjoyed it.  :thumb:

I have Omega Super3 XRS (94.5 dB single drivers) and Pioneer S-1EX (3-way 89.5 dB floorstanders), surprisingly enough the amp worked great with both of them. It's overall character is refined and laid-back but it doesn't smooth out all the detail. It's a very refined, relaxed and easy to listen to amp.

On the Pioneers the Folsom amp is a bit less damped than my other amps (an Odyssey Stratos with upgrades and a Crown XLS 1500), which worked pretty well as the Pioneer's bass is a bit overdamped. The XLS accentuates the overdamped bass but has great control over the woofer, with the Folsom amp the bass was a bit more free sounding, not boomy/uncontrolled as that's probably not possible with these speakers. Overall it felt a bit more natural and musical with the Folsom amp vs the XLS. The Odyssey amp is more damped but not as much as the XLS, it's a very good match with the Pioneers and the mids/highs are very precise. In comparison the Folsom amp is more relaxed sounding, a bit more romantic, a bit softer and more forgiving. It's not an amp you'd normally pair with these speakers yet it did really well, I was surprised how good it sounded. Of course it can't go past moderate volumes but it did fine up until clipping.

Where the Folsom amp really shined was with my Omegas... I have a DIY EL34 SET that's close to as good as it gets for low-powered tube gear, the driver is a 6SN7 Aikido with it's own power supply, Jupiter copper caps, Clarity TC power supply caps, pure copper connectors, James OPTs, etc... It has over $2k in parts invested. The Folsom amp came darn close, way too close for the kind of money it costs, a small fraction of the cost of my SET amp. Interestingly enough if you listened to the 2 amps blind you'd probably guess the Folsom amp is the tube amp and the EL34 amp solid-state. The Folsom amp was smoother and more laid-back vs my amp, but with the Omegas it controlled the bass really well and it also has plenty of power for them too. This is an amazingly good combination... My SET otoh was clearer, more detailed, slightly more controlled. Overall it's a better amp but it's so many multiples of the Folsom amp's price it's hard for me to believe the Folsom amp comes so close.

In conclusion, the value for the money you get with the Folsom amp is the best I've ever seen. It has a smooth, refined, tube-like presentation that is musical and non-fatiguing... a perfect set of characteristics for the speakers and sources it's likely to be paired with. This amp would be my top recommendation before spending a lot of cash on a high end tube amp. Yes, it is possible to do better but it's going to cost you a lot of cash. This kind of amp would also be great for a DIY active speaker powering mids and tweeters.

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 24 Nov 2015, 05:09 pm
Dave - what a great review. Did you use the Folsom power supply as well, and was this with the
1uf input capacitors or the 1.5?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: DaveC113 on 24 Nov 2015, 05:21 pm
Dave - what a great review. Did you use the Folsom power supply as well, and was this with the
1uf input capacitors or the 1.5?

The PS is built into the amp so I'd guess yes. Not sure which caps are in there... I didn't notice any bass roll off but my speakers don't get down to 20 Hz without rolling off themselves. The difference in damping factor was apparent but I really didn't notice any lack of bass from the Folsom amp.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 24 Nov 2015, 05:45 pm
It has the 1.5uf.

The input RCA's are not copper on the demo. They work fine, but I've used copper ones on another build and it does very good things.

Dave's capacitors, probably just the input capacitors, cost more than the parts for the 7297. One could always upgrade the input capacitors on the 7297 if they wanted. His amp with chassis and labor would probably run $10k as a commercial product, maybe more. Lamm amplifiers don't use more expensive parts, but they have more parts overall and probably better transformers.

Also a buffered signal would get the amp much closer to more expensive amplifiers, as volume controls steal a bit of refinement on their own. And we have yet to find out what Nichicon capacitors for the DC side of the amplifier will do.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 24 Nov 2015, 05:57 pm
Thanks for the input.
Can you please expand a bit what you mean by "buffered signal."
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 24 Nov 2015, 06:02 pm
Buffered means it doesn't have trouble driving the amplifier due to impedance mismatch.

A 1:10 ratio is often desired. But that would mean you'd need a 2-3kohm volume device and there is no such thing.

So a buffer in front of it helps such as a Pass B1/DCB1 or Kuartlotron, or some sources are buffered on their output such as a Bel Canto DAC3.7, that uses a digital volume control.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mboxler on 27 Nov 2015, 07:55 pm
So a buffer in front of it helps such as a Pass B1...

The Pass B1 has capacitors on its outputs.  Might this eliminate the need for the input caps to pins 4 and 12?

Mike

 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 27 Nov 2015, 08:27 pm
They're big enough on the B1, so I suppose you could give it a try. The amplifier does tend to bias electrolytic input caps, so it may have undesirable affects without it's own capacitors.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Markvdv on 28 Nov 2015, 02:41 pm
Buffered means it doesn't have trouble driving the amplifier due to impedance mismatch.

A 1:10 ratio is often desired. But that would mean you'd need a 2-3kohm volume device and there is no such thing.

So a buffer in front of it helps such as a Pass B1/DCB1 or Kuartlotron, or some sources are buffered on their output such as a Bel Canto DAC3.7, that uses a digital volume control.
Standard 10k pot is exactly that at maximum 2500 ohm ????
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 28 Nov 2015, 04:34 pm
I don't understand what you're saying/asking.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Markvdv on 28 Nov 2015, 07:42 pm
I assume you want 1/10th of tda7297 inputimpedance at most, the 1 to 10 ratio. Max outputside impedance 10k pot is 2500 ohm I believe, not 10k, so very common and ordinary pots exist that gives you 1 to 10 ratio.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 28 Nov 2015, 07:49 pm
I use a 10k stepped attenuator, and it works quite good. But it's not as good as with a buffer, even if it fits the ratio. However that's true with most amplifiers to begin with.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Markvdv on 28 Nov 2015, 08:33 pm
So question could be: why not include buffer on pcb ? You paid a lot of attention to power and that probably makes bigger difference, your anticipated answer:)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 28 Nov 2015, 08:53 pm
Some day, when I've got one thoroughly tested out. But I'd actually prefer a separate board, maybe with the same footprint.

I don't use a buffer in my own stereo yet, btw, and I don't feel like I'm pinged on needing one.

Title: Re: Folsom's great little 7297 Chip Amp
Post by: ronu9400 on 29 Nov 2015, 07:19 pm
Hi, Folsom & all the rest

I've been a lurker for a good while, but just had to join today - so that I could continue the discussion from posts #49 & #50 (etc.) about the Antipole PSU (for Folsom's 7297).

I sent my $ for the Antipole & 7297 boards early on in those offers, and I have continuously checked on how close the Antipole is getting to the IndieGoGo target...hopefully it gets there. However, if the Indiegogo route doesn't work out, i would still be interested in getting the Antipole pcb (c/r post #50).

I could have probably covered this via e-mail, but it was also a good opportunity to bump the thread.

Thanks again, Folsom
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 4 Dec 2015, 06:34 am
Don't worry, I'll contact everyone and collect enough to print the Antipole if IndieGoGo isn't going to work out.

Title: Re: Folsom's great little 7297 Chip Amp
Post by: shadowlight on 4 Dec 2015, 03:21 pm
How do you go about ordering multiple Antipole?  I did not see an option to do that.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 4 Dec 2015, 04:47 pm
Click here. (https://www.indiegogo.com/projects/antipole-pcb-filtered-psu#/)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 9 Dec 2015, 07:06 am
Been practicing my soldering skills on one of the cheap generic boards. Against all odds, I manage to get it to make sound... actually very good sound thanks to the great instructions and help from Folsom. I'm now excited to get the Folsom board.

BTW: these 7297 amps may be a great way to split the signal and send it to both main speakers as well as balanced inputs on a crown xls amp for active or subwoofer duties. I'm ordering the XLR connectors now and will hopefully try it out this weekend.

I'm still going back and forth on the psu - more on the fact that I'm not yet comfortable with the A/C.

If you haven't purchased yet, you better hurry up since it's just about to expire.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 9 Dec 2015, 07:09 am
Boards will be available after, many boards.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: gychang on 12 Dec 2015, 12:35 am
is there a link on ebay for this amp?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 12 Dec 2015, 12:55 am
No, this isn't the eBay amplifier. It's a Folsom proprietary design.

Funding is complete for both now. It takes about 15 days for the $, and then I'll have the boards printed 1-2 weeks. Then all of you will know what Scott, Dave, and Tyson have said about it.

For those of you that are new to this, I suggest you freshen up your knowledge and skills (https://www.youtube.com/results?search_query=how+to+solder+electronics) and it should be real easy.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: gychang on 12 Dec 2015, 02:36 am
No, this isn't the eBay amplifier. It's a Folsom proprietary design.

Funding is complete for both now. It takes about 15 days for the $, and then I'll have the boards printed 1-2 weeks. Then all of you will know what Scott, Dave, and Tyson have said about it.

For those of you that are new to this, I suggest you freshen up your knowledge and skills (https://www.youtube.com/results?search_query=how+to+solder+electronics) and it should be real easy.

sounds good, I have a basic soldering skills...
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 12 Dec 2015, 02:43 am
sounds good, I have a basic soldering skills...

 :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 13 Dec 2015, 08:42 pm
Just now noticed this, too late for the campaign.  Did you say you will have extra boards for those who missed the boat?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 13 Dec 2015, 09:49 pm
Sure will!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 13 Dec 2015, 11:36 pm
Great!! Thanks

Now if I can just learn how to work with and solder ity-bity parts with big, fat, clumsy fingers  :o

Mike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: robert1325 on 18 Dec 2015, 06:50 am
Hello Folsom,

I've been running my modded 6$ tda7297 for a while now, swapping it in and out with my dual chip tpa3116, and would like to get one of your boards too once it becomes available. Hope there will be one left.   :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 18 Dec 2015, 07:03 am
Guy's, don't worry, there will be plenty. No one is going to get turned down anytime soon. It won't be until at least after the first people to build and post results that I could even conceive of selling them all out. It's important to understand that went printing PCB's I can get 10x for $100, but I can also get 150 for around $250. So you see, there was plenty of funding to order enough boards to last for awhile.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: gil41 on 23 Dec 2015, 12:28 am
Hi,
Been lurking and following your board updates but too late for the funding phase. Just starting to mess up/play/explore/have fun/etc. the world of chip/cheap/affordable amps and joined today to formalize my intent in acquiring boards. Once available, could you please let me know how to buy them.
thanks and more power to you.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 25 Dec 2015, 04:18 am
Hi,
Been lurking and following your board updates but too late for the funding phase. Just starting to mess up/play/explore/have fun/etc. the world of chip/cheap/affordable amps and joined today to formalize my intent in acquiring boards. Once available, could you please let me know how to buy them.
thanks and more power to you.

Hi, you can PM me for now. Otherwise I'll be posting in Industry ads when I find the best place to sell from (somewhere that people can click "buy").
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 7 Jan 2016, 01:19 am
Hey everyone who's been following the thread, I had to switch PCB suppliers. Sadly the one I liked more than doubled their price. But I was able to find a US based outfit with comparable prices, and they're ordered. China has a few good suppliers but I prefer to do US based business if possible. (The price difference believe it or not isn't really a thing if you find a US printer that doesn't charge an arm and leg until you get into the thousands of boards amount; and consider shipping from China is like $110, so it can cost more without a discount)



Title: Re: Folsom's great little 7297 Chip Amp
Post by: Letitroll98 on 7 Jan 2016, 03:04 am
Hi, you can PM me for now. Otherwise I'll be posting in Industry ads when I find the best place to sell from (somewhere that people can click "buy").

Thanks Folsom, I'd agree with that 100%, and I appreciate how you've followed the guidelines and not promoted your product, only answering direct questions about the amp and ps.  I think it's the hardest to walk that fine line for guys like you for whom it's much more a hobby than a business.  And about the time you have a place people can click "buy" is about the time you'd need to move the business side over there.  Thanks for steering that side of it to Industry Ads without being asked, and please don't be shy about posting info on this thread, it's really cool to have the designer tell you about a product directly.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 7 Jan 2016, 05:45 am
Thanks. I'm trying to work towards paying for my own circle and what not, but I'm not there yet so I want to be respectful to the rules and to the people interested (many which have paid money to make this project happen).

It's fun trying to bring something truly good to people at a price anyone can do. 

BTW

(http://www.audiocircle.com/image.php?id=134800)

:thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: jseipp on 7 Jan 2016, 06:18 am
It's much appreciated!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 13 Jan 2016, 06:52 pm
I just checked on the boards. They ship to me tomorrow.  :thumb: :thumb: :thumb:

Oh and I have some Great News.

While I've been writing up some instructions and checking the BOM over for like the 10th time to make sure it's perfect, I decided to do a test with another part. The result is you guys will save $10, and the best part... It's a huge upgrade, the amp sounds way better than when anyone heard it before. 8)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: jseipp on 13 Jan 2016, 07:54 pm
Ready to make some solder fumes here....
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 16 Jan 2016, 01:54 am
Folsom ;
been really busy at work and missed the group buy
I need another amp like ( fill in the blank ) , but am interested for a fun project this spring and summer to match the volume control I built
PM sent
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 19 Jan 2016, 08:50 pm

(http://www.audiocircle.com/image.php?id=135460)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: flavo on 20 Jan 2016, 11:06 pm
Hi there, these look fantastic.
What is the cost of the boards shipped to CT? And what is the cost of the components to populate them? Is there a volume pot or should I use a pre-amp with this?
I hope when some of these get built that they get some images posted up here.
I'd like to put both boards in the same box. Can you tell me roughly how tall and wide the populated boards are and how much clearance should be left around them?
Thanks so much.
Mike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: pinkfloyd4ever on 21 Jan 2016, 02:19 am
You need to give it a cool name. Allow me to suggest "The Piledriver"  :weights:  :banana piano:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: pinkfloyd4ever on 21 Jan 2016, 02:25 am
Anyone have an approximate Mouser BOM cost yet?

Also, Folsom, you're just selling boards right, not complete kits?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 21 Jan 2016, 03:00 am
Anyone have an approximate Mouser BOM cost yet?

Also, Folsom, you're just selling boards right, not complete kits?

A commercial version will have a name (and won't be cheap). This one I just call the DIY7297, and Antipole PSU.

No complete kits. The only way I'll match pricing for a complete kit is if I can get about 50 orders. Otherwise it's 2x what it costs you. And that would be a parts kit, actually.

Hi there, these look fantastic.
What is the cost of the boards shipped to CT? And what is the cost of the components to populate them? Is there a volume pot or should I use a pre-amp with this?
I hope when some of these get built that they get some images posted up here.
I'd like to put both boards in the same box. Can you tell me roughly how tall and wide the populated boards are and how much clearance should be left around them?
Thanks so much.
Mike

Shipping is $6. There's no place for volume on the boards. You can add one to your enclosure if you like (there's plenty of wiring guides online). In my BOM and guide I recommend the chinese DACT 10k D-shaft from eBay, in order to achieve full results.

I just redid the total cost, now all available on Mouser, at $126.08. That's with larger capacitors and transformer than originally used, and a few updated parts. It also saves you $10 shipping from another company. This is with full updates. Obviously you'll have to pick up your own fasteners, heatsink (I provided details of what I used), enclosure, connectors, etc. I've also included notes for different PSU caps and transformers. Unfortunately the transistor heatsink is out of stock.

The Antipole has parts on it that reach up to 2in high, so a bit more than that with leads and wires sticking out the bottom. The board size is 7 1/4" x 3" in.  The amplifier board is 4 1/2" x 2" in. However you must remember the chip needs a heatsink so the 2" measurement needs to include the heatsink (and the chip extends beyond the board just a hair).

The BOM and build notes go out tomorrow after I receive an overnight-ed package, so I can check once last thing :thumb:

The paid for items are being packaged up. I assembled all the boxes and am working on packaging so they can go out tomorrow!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 21 Jan 2016, 03:10 am
Digikey has the transistor heatsink (http://www.digikey.com/product-detail/en/6237BG/HS411-ND/1625500) in stock, so no waiting! (just a little more $ to ship)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: jseipp on 21 Jan 2016, 04:01 am
You've been really generous throughout with sharing your experience and the results of your experiments -- congratulations and thanks for producing a design with all the best of your work included and that is truly your own!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 21 Jan 2016, 07:51 am

(http://www.audiocircle.com/image.php?id=135582)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 21 Jan 2016, 03:14 pm
Do you have the BOM for both Mouser and Digikey? I find Digikey shipping to less than Mouser. I live in the East.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: uroford on 21 Jan 2016, 05:08 pm
I've been lurking on this thread for awhile and the TPA3116 for years, actually just joined so I could get one of these. Newbie so no PM yet, do you have any idea when you will be up in the Industry ads section so I can purchase one? I hope this question doesn't violate protocol.
Thanks,
-Steve
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 21 Jan 2016, 05:19 pm
I do not. Mouser isn't perfect but the tools it offers are so much more useful to me.

It is however fairly easy to plug part numbers into digikey after you've uploaded the BOM to Mouser.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 22 Jan 2016, 12:49 am

(http://www.audiocircle.com/image.php?id=135606)


(http://www.audiocircle.com/image.php?id=135607)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 22 Jan 2016, 12:59 am
 :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 22 Jan 2016, 11:24 pm
Quote
You've been really generous throughout with sharing your experience and the results of your experiments -- congratulations and thanks for producing a design with all the best of your work included and that is truly your own





+1
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 24 Jan 2016, 10:18 pm
For those of you that haven't put in an order, and got the email, here's the board populated; that several of you received yesterday, or tomorrow.

(http://www.audiocircle.com/image.php?id=135867)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 26 Jan 2016, 04:41 am
Got it today! Impressed by the packaging and the look and feel of the PCB. Now I only need to get all the parts and free up some time for putting it all together...
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 26 Jan 2016, 06:29 am
I can't wait for the builds to come in!

Hell, I've even got my first "hey my amp isn't as refined as compared to my XXXX commercial expensive thing" solution, depending on what their source is like.  :thumb:

Title: Re: Folsom's great little 7297 Chip Amp
Post by: uroford on 28 Jan 2016, 05:28 pm
Is there a link to the BOM and build notes? I received the boards but no other info.
Thanks,
-Steve
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 28 Jan 2016, 08:45 pm
Did you check email? I'll resend it.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: uroford on 29 Jan 2016, 01:40 pm
Got it now, thanks.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 30 Jan 2016, 10:05 pm
I received my PCB's , thanks to Folsom . I printed out the BOM and other files and will get an order in . Due to work constraints I won't be assembling this until spring but plan on building and posting pics here . I hope it works well with the Folsom posted Volume Control Device I built this summer .
A question , do you keep the Panasonic capacitors a little off the board or mount flush ?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 30 Jan 2016, 10:28 pm
I received my PCB's , thanks to Folsom . I printed out the BOM and other files and will get an order in . Due to work constraints I won't be assembling this until spring but plan on building and posting pics here . I hope it works well with the Folsom posted Volume Control Device I built this summer .
A question , do you keep the Panasonic capacitors a little off the board or mount flush ?

Flush
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mrmky on 1 Feb 2016, 05:21 am
I'm a brand new member here and would like your amp to be my next project, how do I get a board and bom ordered?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 1 Feb 2016, 04:10 pm
I need to get some solder. Whats the current suggested type? I have always used Kester 44, 60/40, .031 diameter. Should I switch to Kester 63/37 Eutectic, and what diameter is best? How about Cardas, worth the $?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: S Clark on 1 Feb 2016, 04:17 pm
I need to get some solder. Whats the current suggested type? I have always used Kester 44, 60/40, .031 diameter. Should I switch to Kester 63/37 Eutectic, and what diameter is best? How about Cardas, worth the $?
Don't know about the Cardas being worth the money, but it is easier to work with than Kester 60/40.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Mmaxed on 2 Feb 2016, 08:53 pm
Heads up for any one using Jeremy's Mouser BOM.  I put my order in last week using the BOM and did not check the cart over.  Today when the package arrived I had ordered one of each component not the quantity indicated in the BOM.  Not a big deal to me as I had forgotten some other stuff needed any way.  No idea if that's just the way it works or if I made an error importing it to Mouser. 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 2 Feb 2016, 09:19 pm
Heads up for any one using Jeremy's Mouser BOM.  I put my order in last week using the BOM and did not check the cart over.  Today when the package arrived I had ordered one of each component not the quantity indicated in the BOM.  Not a big deal to me as I had forgotten some other stuff needed any way.  No idea if that's just the way it works or if I made an error importing it to Mouser.

Seriously?  :duh:  The BOM's have the quantity... I'll pass this on with email.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 2 Feb 2016, 11:53 pm
I've been in contact with Mouser.

As long as I make sure to specify the quantity column when I upload it, it works fine. Their system is a bit complicated for such a simple task.

You can also use the "EZ Buy" tool.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Mmaxed on 3 Feb 2016, 12:09 am
Awe crap, my mistake.  I am pretty sure I did not specify the quantity column.  I just ASSumed that the columns would all follow in as in Jeremy's BOM.  It does seem like a kinda strange process getting it in.

Sorry for the alarm, but maybe it will prevent someone else having the same issue.

Mark
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 3 Feb 2016, 12:11 am
Well I tried to sell kits instead but that didn't go so hot :lol: .
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Mmaxed on 3 Feb 2016, 04:04 am
No worries Jeremy, it seems there is a learning curve for a lot of us.  That's part of the fun and challenge. :beer:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 3 Feb 2016, 02:40 pm
I've been in contact with Mouser.

As long as I make sure to specify the quantity column when I upload it, it works fine. Their system is a bit complicated for such a simple task.

You can also use the "EZ Buy" tool.

 

I did specify the quantity column with my order. However, Mouser's system must be buggy, as it INCREASED some of the parts quantities. Example: It changed the Oscon caps quantity from 12 to 27 ?? Some other parts were increased as well. I had to go line by line and change everything to the correct quantity. 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 3 Feb 2016, 03:06 pm
Don't know about the Cardas being worth the money, but it is easier to work with than Kester 60/40.

OK... Cardas is easier to work with. I will get a small amount of Cardas to try with the amp board, but how about Kester 63/37 Eutectic? I need solder for everyday use. I am going to buy a 1# roll so should I stay with 60/40 or go with 63/37??  Opinions/experiences appreciated!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Mmaxed on 3 Feb 2016, 04:17 pm
When I first started DIY a few years ago, I bought a pound of Kester 63/37 .031 diam.  It was what I started with and all I used for several years.  Don't really do a lot of solder work.  A while back when ordering a new soldering station to replace the cheapie that died, I added a lb of 60/40 to try, don't remember the brand.  Took it for a test run and didn't like using it.  With the 63/37 eutectic when you lift the iron it almost instantly solidifies.  The 60/40 takes several seconds to do so.  For a fellow like me that shakes the quick to set makes life easier.  Maybe if I'd learned on 60/40 my opinion would be different.   
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 3 Feb 2016, 05:10 pm
I've been using Kester 44, for a long time. It's like the roll doesn't end. I have some WBT too, for doing silver connections. It's ok, nothing overly special. Technique is what seems to be the most important.

On another note... someone get one running :lol:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Brad on 4 Feb 2016, 08:04 pm
I just checked on the boards. They ship to me tomorrow.  :thumb: :thumb: :thumb:

Oh and I have some Great News.

While I've been writing up some instructions and checking the BOM over for like the 10th time to make sure it's perfect, I decided to do a test with another part. The result is you guys will save $10, and the best part... It's a huge upgrade, the amp sounds way better than when anyone heard it before. 8)

Hopefully silly question:   Is this change included in the boards/BOM that shipped?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 4 Feb 2016, 08:09 pm
Yes.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 9 Feb 2016, 02:00 am
Surely someone here has got the amp running?  :lol:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Peter J on 9 Feb 2016, 02:59 am
Surely someone here has got the amp running?  :lol:

Gonna be a while for me, I'm eyeball deep in speaker project and heading into busy season. Any chance you could resend BOM? I just changed over to new computer and had Outlook go sideways which took yours and some others to never-to-be-seen-again ethers. Thanks!

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 9 Feb 2016, 03:46 am
Certainly.

I bet some of you will regret not building it sooner. A week ago I did the upgrade to the amp I sold to my buddy to replace his Bryston. A few highlights...

Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 9 Feb 2016, 11:59 pm
Certainly.

I bet some of you will regret not building it sooner. A week ago I did the upgrade to the amp I sold to my buddy to replace his Bryston. A few highlights...

  • It's more like a $3000 upgrade.
  • The power it has now, it's as if it is more powerful than my Bryston [3BSST2]
  • I can hear everything now, even stuff I didn't think you were suppose to be able to understand without it cranked.
  • There's no need to really increase the volume, you get everything you want at all volume levels.
  • It's the easiest listening I've ever had. In fact I found myself a few times going into a meditative trance, which has never happened before.

Upgrade??
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 10 Feb 2016, 12:03 am
It's included in the BOM everyone received. It's an upgrade over the versions other people heard that have posted in the thread. There's nothing for you to "change".
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 10 Feb 2016, 12:15 am
Hey Jeremy,
Can I use 20ga wire for power, and speakers if the lengths are just a few inches?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Ultralight on 10 Feb 2016, 12:22 am
Apologies.  I've randomly scanned a few pages, including the first.  I'm still a bit confused - is there a web page that explains exactly what is involved her ?

For example, what parts to order?  How much for all the parts? And what type of work involved in soldering it?

And is this hands down better than the best of the breed in  TPA3116 chip amps?

Sorry for the basic queries.

Thanks
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 10 Feb 2016, 01:05 am
Funny you mention it. I'm using a TPA3116 while my demo is out and about. It's a nice little budget amp. My TPA3116 has SEPF caps, my own PSU (that won out with many others on DIYaudio), and BlackGate N caps for input. It's not bad, but... I don't think it holds a candle to the TDA7297. ClassD is too soft if you ask me. It ultimately limits it a lot.

I'll PM you for $ and such.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: JeffB on 10 Feb 2016, 01:56 am
I had assumed the 7297 was class D.  What is the design?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 10 Feb 2016, 01:58 am
AB , I'm not sure at what level it goes from A to AB.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 10 Feb 2016, 06:30 am
Parts finally ordered. Now I only need to get some decent wire and I will be ready to go.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Philistine on 14 Feb 2016, 05:11 pm
This is my first project, Amp and Antipole, and reasonably confident with the build.
I'm procrastinating at the moment because of finding the right case and heat sink combination - if anyone has any suggestions/recommendations it would be appreciated, or maybe a group buy?

I've got a few pairs of GR Research speakers, Neo 2's and Criterions, that I'm looking to fire up with the Chip Amp.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 14 Feb 2016, 08:29 pm
I recommended some in the notes that I emailed. There's a number of enclosures on eBay as well.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: chocoking_118 on 15 Feb 2016, 03:25 pm
Hi,
I am looking for a 6 channel amp for LXmini speakers where the recommended power is 50W per channel. Is this little amp powerful enough for the task? Appreciate your advice please.

Thanks.
 8)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 15 Feb 2016, 09:11 pm
The sensitivity on those speakers is awfully low as raw drivers. Unless they get a healthy boost from the construction of their enclosures to 87+ then I would say no, I wouldn't do it. I prefer 91db+ but I still get a good time out of less.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: hdspeakerman on 15 Feb 2016, 09:43 pm
Rane MA-6

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 19 Feb 2016, 03:01 am
This should be arriving in Indonesia some time soon along with a PSU, heatsink, and transformer. It's replacing a F5 that just makes too much heat.


(http://www.audiocircle.com/image.php?id=137523)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 19 Feb 2016, 03:18 am
Got my desk full of small component bag packages. Just waiting for the final package. Hope to start putting it together this weekend
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 21 Feb 2016, 03:42 pm



This should be arriving in Indonesia some time soon along with a PSU, heatsink, and transformer. It's replacing a F5 that just makes too much heat.


(http://www.audiocircle.com/image.php?id=137523)


It looks like you opted for a different heat sink from the clip-on one in the BOM. I was thinking of using one I pulled from an old PC to save me ordering the correct one separately. Also, does  this heat sink need any mica/thermal paste, and hole bushing, or is it just bolted/clipped on with no insulation?

Another question, this one about the chip heat sink: Are you instructing that the mica sheet, and thermal paste be applied before installing the chip, tack solder the chip, and THEN removing the heat sink for final soldering of the chip? What happens to the thermal paste, does it need to be re-applied? Wouldn't it be better to assemble everything dry before applying the thermal paste? Confused :? Please clarify....
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 21 Feb 2016, 05:29 pm
No need for insulation on the transistor heatsink. But don't let it touch other parts like the two resistors below it. I used that heatsink because I had it, and wanted to not wait on another package.

Why would you use thermal paste during the fitting process on the chip? I don't follow. The only place I'd consider using before final mounting of chip is wiping it on and off the heatsink because the mica might stay in place on it without you needing to hold it if you wiggle it into place. So you really are dry fitting the chip.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 21 Feb 2016, 05:30 pm
This is going to be my first attempt at building out a PC board. I have some experience with point to point wiring crossover networks but not with boards.

What tools, other than a soldering iron, do I need and/or would be very helpful for building the amp and Antipole?

Mike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 21 Feb 2016, 06:48 pm
I like a little worklight (http://www.amazon.com/Ikea-201-696-58-Jansjo-Light-Black/dp/B0055IVM1I/ref=sr_1_1?s=hi&ie=UTF8&qid=1456001710&sr=8-1&keywords=desk+light+ikea). Also useful is one of these (http://www.amazon.com/Mokingtop-Fashion-Welding-Soldering-Cleaning/dp/B00J84N48E/ref=sr_1_8?ie=UTF8&qid=1456005563&sr=8-8&keywords=solder+tip+cleaner) for cleaning the tip of the soldering iron. For solder I recommend something sized for electronics and not speakers. I've been using Kester 44 (http://www.amazon.com/Kester-Solder-Rosin-Core-Spool/dp/B00068IJPO/ref=sr_1_1?s=hi&ie=UTF8&qid=1456001840&sr=8-1&keywords=kester+44), the same roll, for years (the label on mine is ancient and unreadable) But you could spring for some Cardas solder (http://www.amazon.com/Cardas-Soldering-Eutectic-Silver-Solder/dp/B015X68HXW) too, if you want. Lastly a fine tip is needed. The big fatties won't work!

The most important thing is patients. Make sure the spot is heated so the solder forms on the vias hole on the PCB board as well as the component. If the component got pretty warm during the process start on another one and come back to it. Sometimes on the Antipole it may be easier to do the little EPCOS caps from the top.

Soldering heat for the amp board is pretty standard, approximately 750-775F/400-412C. For the Antipole board with the snap caps and CMC you can run hotter, like 850F/454C, but make very sure you're contacting the PCB board and not just the component. This is all pretty standard stuff.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 21 Feb 2016, 07:41 pm


Why would you use thermal paste during the fitting process on the chip? I don't follow.



Sorry - I guess I misinterpreted your instructions below:

On the chip it needs to be thicker, you can wiggle the chip until it pushes it as close as it’ll get, you can check to make sure you got coverage once you remove it, a few steps down in this guide.

Then I finished soldering it after removing it from the heatsink and chassis, with PCB board.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 21 Feb 2016, 08:19 pm
Yes perhaps I'll go back over that area. I updated it.

Honestly it's hard to go wrong so long as you have decent coverage, the thermal paste isn't super thick, and the chip is flat onto the mica. I thought the real trick was making sure the chip tab and bolt don't touch so you have good isolation. In fact if anyone has way too much trouble with that I have a work around where you drill a little oversized hole into the heatsink a 1-2mm and use a different shoulder washer that extends just past the chip tab.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 21 Feb 2016, 08:20 pm
I like a little worklight (http://www.amazon.com/Ikea-201-696-58-Jansjo-Light-Black/dp/B0055IVM1I/ref=sr_1_1?s=hi&ie=UTF8&qid=1456001710&sr=8-1&keywords=desk+light+ikea). Also useful is one of these (http://www.amazon.com/Mokingtop-Fashion-Welding-Soldering-Cleaning/dp/B00J84N48E/ref=sr_1_8?ie=UTF8&qid=1456005563&sr=8-8&keywords=solder+tip+cleaner) for cleaning the tip of the soldering iron. For solder I recommend something sized for electronics and not speakers. I've been using Kester 44 (http://www.amazon.com/Kester-Solder-Rosin-Core-Spool/dp/B00068IJPO/ref=sr_1_1?s=hi&ie=UTF8&qid=1456001840&sr=8-1&keywords=kester+44), the same roll, for years (the label on mine is ancient and unreadable) But you could spring for some Cardas solder (http://www.amazon.com/Cardas-Soldering-Eutectic-Silver-Solder/dp/B015X68HXW) too, if you want. Lastly a fine tip is needed. The big fatties won't work!

The most important thing is patients. Make sure the spot is heated so the solder forms on the vias hole on the PCB board as well as the component. If the component got pretty warm during the process start on another one and come back to it. Sometimes on the Antipole it may be easier to do the little EPCOS caps from the top.

Soldering heat for the amp board is pretty standard, approximately 750-775F/400-412C. For the Antipole board with the snap caps and CMC you can run hotter, like 850F/454C, but make very sure you're contacting the PCB board and not just the component. This is all pretty standard stuff.

Thanks

I have an Ottlite desk lamp but was thinking of getting an LED light with a magnifying lens. Any suggestions as to a good one or what power magnification works best?

My soldering iron is a 25W Radio Shack Pro-Line with a point tip and a maximum heat output of 1003F (539C). That's a lot hotter than you are suggesting. Looks like a different iron may be in order.

For solder I use Cardas Quad Eutectic

I have one of the small black helping hands with the alligator clips but I am not fond of it. Any other suggestions for something to hold the board while working on it?

Mike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 21 Feb 2016, 09:22 pm
Today I created a cart with BOM for the amp and Antipole at Mouser. Before ordering
Does Mouser carry the heat sink or is the recommended link to HeatsinkUSa the preferred choice ?
Will the amp fit in one of the Hammond cases ?
I didn't see prices on the link for Folsoms suggested case seller at their site
Is it preferable to mount the Antipole and Antipole in separate cases ?
I have some Radio shack thermal compound , is that "good enough" or should I get something else ?
thanks
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 21 Feb 2016, 09:32 pm
Yes, I think you might struggle with that iron, Mike. You want the joint to heat up fast enough that you don't have to fry the parts.

Here's something to note, as the joint sinks the heat the iron must make up for it wattage to try and retain that same heat level. You have a 25w iron, I have a 60w station. The moment yours touches the heat will run down so fast that it won't be as effective.

I have this exact station (http://www.ebay.com/itm/like/281925930033?ul_noapp=true&chn=ps&lpid=82). New replacement pieces for it are rather expensive. I've also been told this has a Hakko (http://www.yescomusa.com/products/digital-hot-air-rework-solder-smt-soldering-station-unit) heater core so it's worth the gamble for the price. I hate digital button stations... But these days I'd just buy a Metcal if I were to upgrade. Their smartheat is really nice. They however are very expensive and the tips are not cheap.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 21 Feb 2016, 09:41 pm
Today I created a cart with BOM for the amp and Antipole at Mouser. Before ordering
Does Mouser carry the heat sink or is the recommended link to HeatsinkUSa the preferred choice ?
Will the amp fit in one of the Hammond cases ?
I didn't see prices on the link for Folsoms suggested case seller at their site
Is it preferable to mount the Antipole and Antipole in separate cases ?
I have some Radio shack thermal compound , is that "good enough" or should I get something else ?
thanks

I don't know what Mouser carries for Heatsinks off the top of my head. Heatsink USA does custom sizing so I never had to think much about what Mouser carried.

I'm sure it'll fit in a Hammond case. You can base the case size off of the size of transformer for height. For planning the width you may want to consider all of the connectors on the back.

What prices are you asking about, for what?

Mounting the Antipole and transformer (I assume you meant that) in a separate case is just one way to isolate some of the radiation transformers produce, as well as the AC line. Also if the transformer has any hum at all it'll isolate that from the amp board as well. If you do have a tiny bit of hum consider using some dampening material around the transformer area of the enclosure it is in, "dynamat' type stuff. There's also Herbie Audio's products for washers and such that reduce vibrations etc.

The radioshack compound is probably just fine.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 21 Feb 2016, 10:55 pm
Thanks

I have an Ottlite desk lamp but was thinking of getting an LED light with a magnifying lens. Any suggestions as to a good one or what power magnification works best?

My soldering iron is a 25W Radio Shack Pro-Line with a point tip and a maximum heat output of 1003F (539C). That's a lot hotter than you are suggesting. Looks like a different iron may be in order.

For solder I use Cardas Quad Eutectic

I have one of the small black helping hands with the alligator clips but I am not fond of it. Any other suggestions for something to hold the board while working on it?

Mike

Mike,
 Knowing the wood worker you are, you can make your own board holder, although this board can probably be done just as easily on a bench top.

Here's one I made:

(http://i.imgur.com/vPfZHDe.jpg?1)

(http://i.imgur.com/9mUCMoR.jpg?1)

And here's my "cheap-n-cheerful" (freebee) magnifer:

(http://i.imgur.com/63T2Anu.jpg?1)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 21 Feb 2016, 11:08 pm
How many PCB boards for two of those Larco?  :green:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 21 Feb 2016, 11:24 pm
Larry,

That's sharp. Even has a adjustable and replaceable tension mechanism  :thumb:

Mike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 22 Feb 2016, 02:09 am
Thanks for your reply Folsom , I'll put the Antipole and amp in 2 cases I think, and decide which Hammond cases to get for them .
I already built your Volume Control Device into a Hammond, so maybe they'll be stackable if I stay with Hammond.
Will check Mouser to see if the heat sink is available there .
My question was regarding the price for the custom cases you linked to since I couldn't find a price there , just a diagram
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 22 Feb 2016, 02:10 am
Lacro - I want one of those board holders too. That looks great :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 22 Feb 2016, 02:32 am
Thanks for your reply Folsom , I'll put the Antipole and amp in 2 cases I think, and decide which Hammond cases to get for them .
I already built your Volume Control Device into a Hammond, so maybe they'll be stackable if I stay with Hammond.
Will check Mouser to see if the heat sink is available there .
My question was regarding the price for the custom cases you linked to since I couldn't find a price there , just a diagram

You have to select desired sized with Landfall systems.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 22 Feb 2016, 02:52 pm
How many PCB boards for two of those Larco?  :green:

Lacro - I want one of those board holders too. That looks great :thumb:

Guys: I knew I should have made several when I was making this one :duh: Doing a one-off like this took me an entire morning, plus 3 days of staining/oiling the pieces. If you want to make your own, I can list a BOM, or the internet has several designs including one similar to this one.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 22 Feb 2016, 02:55 pm

I already built your Volume Control Device into a Hammond,


Is there a thread (link) for building this Volume Control?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 22 Feb 2016, 06:05 pm
Is there a thread (link) for building this Volume Control?

It's a device that stops ground loops and noise. It helps with some devices; particularly with SMPS powered amps. Ultimately I prefer not using it unless you have a ground loops so far.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Tyson on 26 Feb 2016, 06:15 am
Just wanted to put in an update - I had this amp through here for the second time and I can attest that it's a substantial improvement over the first time (and it already sounded great the first time).  More clarity, better flow, and smoother sound.  This amp is a winner.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 26 Feb 2016, 07:38 pm
Question about Mouser part #80-C320C471J1G (470pF cap). I looks the board spacing for this ceramic cap is twice the lead spacing of the cap I received (5mm vs 2.5mm). This thing is really tiny, and doesn't come close to the dimensions in the Kemet spec. sheet, and it looks smaller than the one on your board. One side is labeled 471, and the other side is labeled K1J. Do I have the right part?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 26 Feb 2016, 07:50 pm
It is small. You're welcome to substitute it for any other 470pf cap you like. It just needs to be 470pf. But recall some ceramic caps change based on voltage. MLCC's not so much, X7R/X5R do. It doesn't have to be ceramic but they're small so they fit well.

(http://www.audiocircle.com/image.php?id=138051)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 27 Feb 2016, 09:34 pm
Made some progress today. I don't have any wire so I can't try it yet. While inspecting my solder joints, I discovered I bridged one of the chip legs to the tiny via close to it. Should I remove this bridge or ok to leave it? See second photo.

(http://i.imgur.com/EyZXr8K.jpg?1)

(http://i.imgur.com/EnAvGgv.jpg?1)


Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 27 Feb 2016, 10:14 pm
It's fine. That via is really only for people that would know they need it, and what it does. It's not useful for typical operation, just like the little diode spots.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 27 Feb 2016, 10:19 pm
a question Jeremy  , the link on page 1 to HeatsinkUSA goes right to a 3.5" heatsink . Is this the one for the project ?
thanks
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 27 Feb 2016, 10:49 pm
That's what I used.

You can see larco chose something else. You almost can't go wrong here. Even the side of a 1/8in enclosure is probably sufficient for playback. But the cooler you keep it, the better you can maintain full output power.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 27 Feb 2016, 11:01 pm
another q , I am going to order the 3.5" wide from Heatsink USA and the length is options in inches . Which is the preferred length in inches of the sink ?
thanks again
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 27 Feb 2016, 11:38 pm
Length will be the height when you order. I suggest sizing it to the enclosure or so. As far as heat goes 3" is very good.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 28 Feb 2016, 03:39 pm
Thanks J.
I'm ordering the 3 inch length from Heat Sink USA.
Would the Glassware Aikido Buffer PCB work with the 7297 amp ?
I've been eyeing their kit for a while .Here's the description from their website.

Octal Aikido Cathode Follower
"The Aikido cathode follower PCB/kit is a modest affair, consisting of one tube per channel (two triodes per tube envelope) and a handful of capacitors and resistors. This unity-gain buffer, using a modified cathode follower, offers a high input impedance, a low output impedance, low distortion, and a great PSRR figure. In addition, the ACF does not invert the phase. The ACF use is not limited to line-stages, as the ACF can be used in creating an active crossover or even a headphone driver, if the headphone's impedance is high enough and the tube robust enough.
$24.00"
I just noticed they have a resistor stepped attenuator on sale there for $10.
Is this better than the 10K DACT ?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: shadowlight on 28 Feb 2016, 04:21 pm
PCB holder similar to what Lacro posted but not as good looking - Amazon (http://www.amazon.com/gp/product/B00Q2TTQEE?psc=1&redirect=true&ref_=oh_aui_detailpage_o02_s00)

Anyone have good link for good cheap magnifying glass?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 28 Feb 2016, 07:49 pm
Thanks J.
I'm ordering the 3 inch length from Heat Sink USA.
Would the Glassware Aikido Buffer PCB work with the 7297 amp ?
I've been eyeing their kit for a while .Here's the description from their website.

Octal Aikido Cathode Follower
"The Aikido cathode follower PCB/kit is a modest affair, consisting of one tube per channel (two triodes per tube envelope) and a handful of capacitors and resistors. This unity-gain buffer, using a modified cathode follower, offers a high input impedance, a low output impedance, low distortion, and a great PSRR figure. In addition, the ACF does not invert the phase. The ACF use is not limited to line-stages, as the ACF can be used in creating an active crossover or even a headphone driver, if the headphone's impedance is high enough and the tube robust enough.
$24.00"
I just noticed they have a resistor stepped attenuator on sale there for $10.
Is this better than the 10K DACT ?

The Aikido adds gain so it's not my favorite choice. But tube selection can keep the gain down and it'll work. DaveC used one with the amp. I prefer no gain line stages with an amp that has 32db gain.

Their stepped attenuator is mono only. That too me is a big pain, so I would never rock it. I doubt it sounds as good either.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: shadowlight on 28 Feb 2016, 07:55 pm
Can you change the gain on the amp from 32 to say 26db or 20db, if you plan to use it with preamp that has gain?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 28 Feb 2016, 08:54 pm
No, the amp gain doesn't change.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 28 Feb 2016, 09:55 pm
Is the heat sink supposed to just hang off the chip?

Lacro - that looks nice!

Btw - Where do you buy those nylon (?) standoffs?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Mmaxed on 28 Feb 2016, 11:03 pm
Please refer to the transformer diagram for wiring of it, if you’re using one. You need 16v out of the transformer before rectification (and 80+va). SMPS 21v min, and batteries 24v.

I assume the above quote from the construction notes PDF means that I can use 2 SLA batteries wired for 24 volts to power the amp. 

I may get the amp board together and would like to get it powered up this way.

Will need some instruction later on wiring the trans in the PS.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 28 Feb 2016, 11:09 pm
Please refer to the transformer diagram for wiring of it, if you’re using one. You need 16v out of the transformer before rectification (and 80+va). SMPS 21v min, and batteries 24v.

I assume the above quote from the construction notes PDF means that I can use 2 SLA batteries wired for 24 volts to power the amp. 

I may get the amp board together and would like to get it powered up this way.

Will need some instruction later on wiring the trans in the PS.

That's correct, you can use two 12v batteries wired in series.

I'll post some photos on the transformer soon.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 29 Feb 2016, 12:44 am
Is the heat sink supposed to just hang off the chip?

Lacro - that looks nice!

Btw - Where do you buy those nylon (?) standoffs?

I mounted (drilled/tapped) mine so the heat sink will support it's own weigh, not hanging off the chip. The one on the transistor is one I salvaged from an old PC, and cut down to size. It's really light, and it is hanging off the Transistor.

I got the stand-offs from the "bay" Lot's of choices from China.

Here's a kit with black ones that I just ordered:

http://www.ebay.com/itm/180-Pcs-Black-M3-Nylon-Hex-Spacers-Screw-Nut-Stand-off-Plastic-Assortment-Kit-/381537029579?hash=item58d5610dcb:g:x1MAAOSwvUlWsbdG (http://www.ebay.com/itm/180-Pcs-Black-M3-Nylon-Hex-Spacers-Screw-Nut-Stand-off-Plastic-Assortment-Kit-/381537029579?hash=item58d5610dcb:g:x1MAAOSwvUlWsbdG)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 29 Feb 2016, 01:09 am
If you're worried about the transistor and the rather light heatsink you can add a little solder to the legs of the transistor to coat them top to bottom. But the one I recommend doesn't seem to budge at all during shipping.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 29 Feb 2016, 02:33 pm
Jeremy,
Are the 47K resistors, and the 10uF cap part of a mute/standby circuit to prevent on/off pop? Also, are signal grd. and power grd. isolated from each other or shared?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 29 Feb 2016, 06:45 pm
Jeremy,
Are the 47K resistors, and the 10uF cap part of a mute/standby circuit to prevent on/off pop? Also, are signal grd. and power grd. isolated from each other or shared?

Correct on the mute/standby circuit. SG and PG are connected at the point that proved to be the best sounding. They cannot be isolated because if they are they amp will never turn on. Believe me, the first PCB board was very frustrating trying to figure that one out!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 1 Mar 2016, 06:47 pm
The datasheet for the transformer shows all you need. I don't think I'm going to draw anything better. The connections for 115/230v are your hot and neutral from your power inlet, hot being the one you'd put a switch on. To achieve 16v output you use the series configuration.

(http://www.audiocircle.com/image.php?id=138282)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 2 Mar 2016, 06:17 am
Finally there is some progress to report and got the first few things soldered to the board. Since I'm pretty much a newbie to soldering it was a little bit tricky to get the chip on. Fortunately I remembered I had a finer tip for the iron which made it so much easier. Think one hole didn't really fully fill up with the solder so will retouch tomorrow.

Also realized I forgot to buy a bolt to actually attach the hit sink with. Hoping they have something I can use at Home Depot. Fun project and I'm learning a lot.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 2 Mar 2016, 06:22 am
#4 fits the isolation to-220 washer. (4-40 or 4-48)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Markvdv on 2 Mar 2016, 09:27 am
The Aikido adds gain so it's not my favorite choice. But tube selection can keep the gain down and it'll work. DaveC used one with the amp. I prefer no gain line stages with an amp that has 32db gain.


ACF is (close to) unity gain, it slighly attenuates input, post you react to has the information.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 3 Mar 2016, 06:39 am
Almost there! Just need to put on the heat sink and connect the wires.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: shadowlight on 3 Mar 2016, 04:28 pm
What is everyone using for case?  Are there in pre-drilled cases available?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 3 Mar 2016, 06:51 pm
What is everyone using for case?  Are there in pre-drilled cases available?

Landfall systems will CNC whatever you want.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 5 Mar 2016, 06:57 am
For some reason my paint program isn't doing yellow... or something. I'm going to reinstall it. I've got a few requests for this,


(http://www.audiocircle.com/image.php?id=138607)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Mmaxed on 5 Mar 2016, 05:12 pm
Thanks Jeremy, confirms everything.  I have the amp running o batteries, need to get some kind of enclosure for the PS.

Is the Antipole capable of powering more than one amp?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 5 Mar 2016, 05:31 pm
It can, yes.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 5 Mar 2016, 07:23 pm
Jeremy,

I received about 95% of the parts. Still waiting on wire and a power switch. I still need to decide on an enclosure, but I'm leaning towards your recommendation, Landfall Systems. I just need to do some measurements to see what size works.

I did have one question concerning the Bourns Common Mode Filters. I installed it with the part number facing toward the inside, caps and regulators. I thought that this way would provide the best results, because the wires leaving the coil have the shortest distance back to the board. If it is better to install it the other way please let me know and I will change it.

Thanks,
Brad 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 5 Mar 2016, 07:28 pm
I doubt it matters on direction.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 5 Mar 2016, 08:28 pm
Question about thermal paste:
 Which type is best for this application, Metal based, ceramic based or carbon based? Is it critical that the paste is non electrically conductive given that the mica sheet is between the heatsink and the chip? In others words does it not matter which type compound is used because the mica sheet is the insulator?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 5 Mar 2016, 10:02 pm
I would use non-conductive because it likes to get all over. Pretty much anything will do. I've got a small collection from PC building/fixing so I just use those.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 6 Mar 2016, 06:31 am
We are finally live! And yes, this amp is really really good. I will listen for a couple of days before doing a proper writeup. Once I had all the parts, it didn't take too long to put it all together.

Not sure about all of you, but every time I turn on something new for the first time, I'm holding my breath hoping for the best. Had a moment of panic when I only had sound in the left speaker, but it turned out it was just a loose IC between source and DAC.

I was listening to a TPA3116 amp (unmodded audiobah board, green) with an Astron while putting it all together. It was a very obvious change when I replaced it with the Folsom amp: Bass is lower and more detailed which is a big plus in my book.

Other first impressions was the clarity and the strong stereo image.

I don't have a case for it yet so it is still on the test setup. Btw: wired up all the signal connections with zenwave wire. Highly recommended.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 6 Mar 2016, 03:32 pm
We are finally live! And yes, this amp is really really good. I will listen for a couple of days before doing a proper writeup. Once I had all the parts, it didn't take too long to put it all together.

Not sure about all of you, but every time I turn on something new for the first time, I'm holding my breath hoping for the best. Had a moment of panic when I only had sound in the left speaker, but it turned out it was just a loose IC between source and DAC.

I was listening to a TPA3116 amp (unmodded audiobah board, green) with an Astron while putting it all together. It was a very obvious change when I replaced it with the Folsom amp: Bass is lower and more detailed which is a big plus in my book.

Other first impressions was the clarity and the strong stereo image.

I don't have a case for it yet so it is still on the test setup. Btw: wired up all the signal connections with zenwave wire. Highly recommended.

Good for you man :thumb: Glad to hear there is no smoke :nono: What are using for a PS? BTW/ "a picture is worth a thousand words"  :lol:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 6 Mar 2016, 04:12 pm
Picture...well...if I make it out of focus and blur it even more in photoshop one can maybe with a little bit of a stretch say my soldering efforts looks about the same as in the picture you or Folsom posted  :lol: I will put something up once I get around to it.

I'm using the same Astron PSU I have been using for the TPA3116. I wanted to make sure I could actually finish the amp before taking on too much (according to my wife, my basement is already full of unfinished projects of all kinds  :roll: ). I think I'm now ready to take on the next project, which maybe will be the PSU Folsom is offering. However, what I really need now is to upgrade my DAC. Any suggestions of DIY or fully assembled DAC boards out there (Has to be somewhat easy to put together and preferably multi-channel so I can use it for DSP)?
Title: RFI/EMI Schaffner FN9244B 1A
Post by: maty on 6 Mar 2016, 04:33 pm
Maybe is a good idea add an IEC inlet like: RFI/EMI Schaffner FN9244B 1A.

-> http://www2.mouser.com/ProductDetail/Schaffner/FN9244B-1-06/

(http://uk.farnell.com/productimages/standard/en_GB/1877480-40.jpg)

Datasheet: http://www.farnell.com/datasheets/1563480.pdf

BIG image -> http://maty.galeon.com/WP-imagenes/hard/IEC-inlet-filter-Schaffner-FN_9244-specs.png

BIG image -> http://maty.galeon.com/WP-imagenes/hard/IEC-inlet-filter-Schaffner-FN_9244-typical-filter-attenuation.png


Or you can add it after, building a cable with and IEC C13 connector (I "love" Schurter). Careful not to reverse the phase!

(http://maty.galeon.com/WP-imagenes/hard/cable-filtro-linea-schaffner-piezas.jpg)

IEC C13 at Mouser -> http://www2.mouser.com/All-Manufacturers/_/N-0?Keyword=iec+c13
Title: Re: Folsom's great little 7297 Chip Amp
Post by: HAL on 6 Mar 2016, 04:36 pm
You might look for a Wolfson Micro (now Cirrus Logic) WM8741 based DAC.

The DAC Gary use to build with that IC, sounded really good at Danny's with the amps.

Title: Re: RFI/EMI Schaffner FN9244B 1A
Post by: annamarykahn on 6 Mar 2016, 05:24 pm
Maybe is a good idea add a IEC inlect like: RFI/EMI Schaffner FN9244B 1A.

-> http://www2.mouser.com/ProductDetail/Schaffner/FN9244B-1-06/

(http://uk.farnell.com/productimages/standard/en_GB/1877480-40.jpg)

Datasheet: http://www.farnell.com/datasheets/1563480.pdf

BIG image -> http://maty.galeon.com/WP-imagenes/hard/IEC-inlet-filter-Schaffner-FN_9244-specs.png

BIG image -> http://maty.galeon.com/WP-imagenes/hard/IEC-inlet-filter-Schaffner-FN_9244-typical-filter-attenuation.png


Or you can add it after, building a cable with and IEC C13 connector (I "love" Schurter). Careful not to reverse the phase!

(http://maty.galeon.com/WP-imagenes/hard/cable-filtro-linea-schaffner-piezas.jpg)

IEC C13 at Mouser -> http://www2.mouser.com/All-Manufacturers/_/N-0?Keyword=iec+c13

i got a TE Connectivity / Corcom AC Power Entry Modules 15A FILTERED FLANGE MOUNT that i was going to try out

http://www.mouser.com/Search/ProductDetail.aspx?R=15CUFE1virtualkey59210000virtualkey592-15CUFE1 (http://www.mouser.com/Search/ProductDetail.aspx?R=15CUFE1virtualkey59210000virtualkey592-15CUFE1)

(http://www.mouser.com/images/LPTycoCUSeries.jpg)

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 6 Mar 2016, 07:07 pm
I highly recommend not using those filter IEC inputs; they ruin sound. If you want an input filter contact me.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: jtwrace on 6 Mar 2016, 07:14 pm
I highly recommend not using those filter IEC inputs; they ruin sound. If you want an input filter contact me.
Does a fuse ruin the sound and that's why you've omitted that?   :o   
Title: Re: Folsom's great little 7297 Chip Amp
Post by: maty on 6 Mar 2016, 07:36 pm
It is only one stage filter.

(http://maty.galeon.com/WP-imagenes/hard/IEC-inlet-filter-Schaffner-FN_9244-cicuit.png) (http://maty.galeon.com/WP-imagenes/hard/IEC-inlet-filter-Schaffner-FN_9244-cicuit.png)

Devialet D200

(http://www.computeraudiophile.com/content/attachments/15289d1415125575-devialet-open-adh.png/)

NuPrime IDA-8

(http://totallywired.co.nz/images/IDA-8_internal.jpg)

Double stage? NuPrime IDA-16

(http://audiorevelation.com/wp-content/uploads/2015/04/nuprime-ida-16-integrated-amplifier-inside1.jpg)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 6 Mar 2016, 07:45 pm
Does a fuse ruin the sound and that's why you've omitted that?   :o

Audiophile grade ones work better, but if you want a fuse add one.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 6 Mar 2016, 07:49 pm
It is only one stage filter.


My recommendation is what it is, and just because other types of equipment use them doesn't mean I endorse them nor believe those wouldn't sound better without them.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: jtwrace on 6 Mar 2016, 07:50 pm
Audiophile grade ones work better, but if you want a fuse add one.
So are you saying that in your opinion it's not a requirement to have a fuse? 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: maty on 6 Mar 2016, 07:51 pm
Hypex (SMPS) has a good RFI/EMI filter inside. Maybe a Schaffner filter ruin the sound.

What RFI/EMI filter incorporates your design?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: annamarykahn on 6 Mar 2016, 07:58 pm
My recommendation is what it is, and just because other types of equipment use them doesn't mean I endorse them nor believe those wouldn't sound better without them.

this was just something that i wanted to experiment with ... as a test ... if it ruins the sound, i'll remove it... hey, its only money, lol
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 6 Mar 2016, 08:07 pm
So are you saying that in your opinion it's not a requirement to have a fuse?

Not for any form of protection for other equipment connected to it, no. So long as you're not wiring the hot to the enclosure this is one of the safest amplifiers out there. If it were a transistor driven unit then it would be advisable. 

Technically so long as you isolate the chip tab from the heatsink, there's no requirement to even ground the enclosure because of the complete isolation. But you can do so anyway (I did).


Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 6 Mar 2016, 08:08 pm
Would you elaborate on this warning a bit more? I am using a 24V SMPS (laptop brick). Are you saying I need to discharge the bricks caps if I disconnect, and reconnect power?? Is it safe to unplug the SMPS from mains, but leave it connected to amp, and then re-plug back into power mains?


 UNDER NO CIRCURMSTANCES connect the PSU board or any other power supply to the amplifier board with a charge in capacitors, or without a switch for say batteries. The spark that can occur can toast the transistors. If you test the PSU then you must discharge the capacitors before connecting the amplifier to it. There’s a place on the PSU board for a discharge resistor (I haven’t defined a size, because it varies for the wide use of the Antipole, 10kohm would be fine for this project)

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 6 Mar 2016, 08:09 pm
Hypex (SMPS) has a good RFI/EMI filter inside. Maybe a Schaffner filter ruin the sound.

What RFI/EMI filter incorporates your design?

Hypex uses much larger filters with the type of parts I use for discrete filters on inputs/on AC. And people have repeatedly reported bad sound from them being plugged into many types of power conditioners, so it wouldn't be a big surprise if people thought those little IEC devices were bad with say some NC500 amps.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 6 Mar 2016, 08:13 pm
Would you elaborate on this warning a bit more? I am using a 24V SMPS (laptop brick). Are you saying I need to discharge the bricks caps if I disconnect, and reconnect power?? Is it safe to unplug the SMPS from mains, but leave it connected to amp, and then re-plug back into power mains?


 UNDER NO CIRCURMSTANCES connect the PSU board or any other power supply to the amplifier board with a charge in capacitors, or without a switch for say batteries. The spark that can occur can toast the transistors. If you test the PSU then you must discharge the capacitors before connecting the amplifier to it. There’s a place on the PSU board for a discharge resistor (I haven’t defined a size, because it varies for the wide use of the Antipole, 10kohm would be fine for this project)

I would discharge the SMPS's caps prior to connecting it to amplifier, yes. The spike that can happen when an arc occurs can be too much for the transistors. For battery users the solution is using a switch; that may work for you as well. Switches reduce the spike, but I still prefer them on the AC because it's totally safe.

Unplugging and plugging back in SMPS from mains while SMPS is still connected to amplifier is perfectly safe, you could do it all day.
Title: Schurter switch
Post by: maty on 6 Mar 2016, 08:18 pm
You can add a fuse with:

-> http://www2.mouser.com/_/?Keyword=schurter+switch
Title: Re: Folsom's great little 7297 Chip Amp
Post by: maty on 6 Mar 2016, 08:26 pm
Class D amplifiers are very fast and they have problems with conditioners.

But RFI/EMI one stage filter (without conditioner) is a good idea with ALL amplifiers.

Class A, class AB... are not than fast and more of they can use two stage filters (and Würth 150 kHz ferrites). A fast class AB amplifiers, one stage filter only.

My class AB AV Marantz SR4500 and AV Yamaha RX-V2700: two Schaffner cables and one 8mm Würth 150 kHz ferrite.

My class A ifi iCAN (headphones amp) is very fast, with bandwith up 500 kHz. One Schaffner cable and one Würth 150 kHz 12.5 mm (two rounds) ferrite.

-> http://aficionados.foroactivo.com/t197p210-usb-isolator-ifi-iusb-vs-teradak-u9va-teralink-adum4160-filtros-schaffner-lampizator-ac-filter-diy-esa-silk-estabilizador-regulador-de-tension-voltaje-isolation-balanced-transformer-dc-blocker-blocking-pc-silencioso-en-aussar-variac#16121

To English -> https://translate.google.com/translate?sl=es&tl=en&js=y&prev=_t&hl=es&ie=UTF-8&u=http%3A%2F%2Faficionados.foroactivo.com%2Ft197p210-usb-isolator-ifi-iusb-vs-teradak-u9va-teralink-adum4160-filtros-schaffner-lampizator-ac-filter-diy-esa-silk-estabilizador-regulador-de-tension-voltaje-isolation-balanced-transformer-dc-blocker-blocking-pc-silencioso-en-aussar-variac%2316121&edit-text=

My second system.

RFI/EMI Schaffner filters + Würth 150 kHz ferrites (power and RCA cables) and DC & Ripple Blocker to ALL SYSTEM.

I have:

1 Shaffner + 1 Würth ferrite => Power Strip => DC & Ripple Blocker (4 outputs, in star) =>

=> 1 Schaffner -> AV Marantz SR 4500

=> ifi iCAN

=> 1 Schaffner -> PC (with Bequiet! L8 400 PSU: 5mV/10mV ripple in 5V – USB)

1 Schaffner + 1 Würth 150 kHz -> old 17″ Hitachi CRT monitor (1998), with very good image!

PC => 1 Würth 150 kHz (two rounds) in cheap USB cable -> ODAC =>

ODAC -> RCA cable with 2 Würth 150 kHz ferrites -> ifi iCAN

ODAC -> RCA cable with 2 Würth 150 kHz ferrites -> AV Marantz SR4500

And now, in my KEF Q100 speakers, a Würth 150 kHz ferrite ONLY in woofer cable.

********** **********

By the way, the ifi iCAN does not have a fuse!!! And the others ifi amps and DACs not   :(

Title: Re: Folsom's great little 7297 Chip Amp
Post by: annamarykahn on 6 Mar 2016, 08:58 pm
Technically so long as you isolate the chip tab from the heatsink, there's no requirement to even ground the enclosure because of the complete isolation. But you can do so anyway (I did).

i was going to ask about the reason for isolating the chip tab from the heatsink ... the drok tda7297 that i got from amazon isn't ... can someone elaborate on the reasons for isolation? it also doesn't have heat sink compound, which i didn't like, so i added my own, which was when i discovered that it wasn't isolated

thanks!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 6 Mar 2016, 09:16 pm
maty, there's good ideas and what works, too. Honestly I feel like you've made a topic within a topic, it's a bit obtrusive.

I've got a PCB board that's never been printed that's for offering an input filter that isn't so cheap as the IEC version. If there was sufficient interest for a buy in to get them printed I'd do that.

As far as filtering the Antipole features AC filtration that's very effective. You'd think because the transformer provides such low impedance that the CMC and capacitors would do a lot, but that's not the case. The caps work better because of the CMC in place, first, and second if you swap between CMC/no-CMC by soldering directly to the CMC legs you can quickly and easily hear a very audible difference.

The boards are also based on copper pours (plains). The amp itself has better PSRR from the KMR section that provides low impedance, and the OSCON's in parallel drop their impedance to almost nothing.

The transformer I've been recommending also is good at rejecting noise since it's a dual bobbin.

There's quite a bit of work for noise done on this amplifier. That's a huge focus with anything I do.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: maty on 6 Mar 2016, 09:22 pm
The main is increasingly dirty by the cheap switched transformer connecting.

Anyway, everyone decides for himself that enough information has been provided.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 6 Mar 2016, 09:23 pm
i was going to ask about the reason for isolating the chip tab from the heatsink ... the drok tda7297 that i got from amazon isn't ... can someone elaborate on the reasons for isolation? it also doesn't have heat sink compound, which i didn't like, so i added my own, which was when i discovered that it wasn't isolated

thanks!

With my amplifier's PCB board it provides a very low impedance path for RF that can go through the chip. The chinese ones don't have this so the RF doesn't go through the chip nearly as much. Also I use bigger heatsinks (and recommend) on top of a metal enclosure so it all becomes a potential antenna. The enclosure and heatsink can either act like a shield or an antenna depending on the paths you allow.

The chinese versions basically lower their performance greatly by designing the way they did, which avoids some RF, but doesn't take anywhere near full advantage of the chip. They sound nice, and would be great for a TV, but as far as being truly high end their high impedance, high noise, often bad grounding paths, etc, aren't going to get them there. For $6 they're a bargain so long as you can resolder all the connections and hope the pot didn't break in shipping. They're especially good if modified. But they aren't high end. The chips aren't even up to standards.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 6 Mar 2016, 09:25 pm
The main is increasingly dirty by the cheap switched transformer connecting.

Can we get a better translation on that Maty?

I'd say you should get some boards, but you'll need some more efficient speakers :)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: maty on 6 Mar 2016, 09:34 pm
The guilty:

(http://image.ec21.com/image/mosoalice/oimg_GC03978067_CA03978268/9W_Switching_Power_Supply_-AC_DC_SMPS_Adapter_-Wall-Mount.jpg)

I apologise for my poor English.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 6 Mar 2016, 11:47 pm
I came up with a layout I like more than the demo, thought I'd share with you all considering enclosures. You'll notice I didn't include a switch because location for that is your choice. I kind of like them in back,

(http://www.audiocircle.com/image.php?id=138611)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: annamarykahn on 7 Mar 2016, 12:24 am
i'm in the process of building/planning an enclosure ... i was thinking of using wood ... is that a bad idea?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: G Georgopoulos on 7 Mar 2016, 12:43 am
The main is increasingly dirty by the cheap switched transformer connecting.

Anyway, everyone decides for himself that enough information has been provided.

Hi maty,nice avatar Mate! :thumb:

it's not mains noise but rather smps operating frequency,you can get rid of it by an C L C type pi filter folowing the smps plugpack, it's that simple...

all the best Maty... :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 7 Mar 2016, 12:57 am
i'm in the process of building/planning an enclosure ... i was thinking of using wood ... is that a bad idea?

It provides no shielding of any kind. Performance won't be as good. It may look nice if you'd good with wood however.

The back panel where you mount everything is very challenging on wood, it's much easier with a metal plate of sorts, at least.

Also it's best to have some distance from transformer and amplifier board.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 8 Mar 2016, 08:09 pm
I came up with a layout I like more than the demo, thought I'd share with you all considering enclosures. You'll notice I didn't include a switch because location for that is your choice. I kind of like them in back,

(http://www.audiocircle.com/image.php?id=138611)


I like this layout. It is very clean, providing separation between the power supply and amp. I just need to make sure that there is room between the amp and the speaker terminals.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 8 Mar 2016, 08:26 pm
Standoff height should help you do that.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: devinkato on 9 Mar 2016, 06:09 am
Any reason why there is so much extra space in that layout, especially on the amp side?  Or is that a standard chassis size?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 9 Mar 2016, 06:19 am
It's just how it ends up due to the size of the Antipole board. I suppose you could reduce it by making the enclosure tall and standing the Antipole up, it would probably be around 8" tall, or more with feet, while having a short depth. I think it'd look weird, sort of a pillar. You could then turn the amp side ways and have the speaker terminals close together. Maybe I'll draw a picture.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 10 Mar 2016, 11:41 pm
Just wondering what folks are using as a 90 bracket to attach and support the Antipole PCB upright in the case  ?
I just got the 3 X 2.75" heat sink from Heatsink USA , well machined  8 oz. piece of aluminum  and have to determine the best way to anchor that to the case so it doesn't put a load on the chip . Best practice for this ?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 11 Mar 2016, 01:02 am
I'm not sure I follow with 90* brackets? My builds use standoffs for PCB, and the heatsink is either drilled and tapped on the bottom or on the face so it can be bolted to the enclosure wall (aluminum).
Title: Re: Folsom's great little 7297 Chip Amp
Post by: G Georgopoulos on 11 Mar 2016, 02:32 am
Jeremy

you're doing great,your pcbs are great,enclosure layout great,as a finished amp looks great...

all the best Mate... :thumb:

ps:if you want to make it even better give some time to yourself to do it,"great things take time"
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 11 Mar 2016, 11:01 pm
Thanks for your reply Jeremy , I do have standoffs for the PCB to lay flat but just haven't stood a PCB on end yet . I just wondered how you attached the vertical PCB to the case when you build .
I'll drill out and tap the heat sink to mount it per your suggestion .
Should the transformer have a rubber washer between it and the case when attaching it with nut and bolt ? or is it not nessa'
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 12 Mar 2016, 01:13 am
The transformer does do well with some rubber washers. EI cores have less noise but like to hum a little bit.

The Antipole PSU PCB mounting can be done with using couplers that receive an end of a bolt from each side, and several nuts to secure everything: against PCB board, against coupler, and against chassis wall. In fact two and washers may be advisable for the ones against the chassis wall and PCB board. You can lock them together.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: sorinv on 14 Mar 2016, 11:15 am
Hey Folsom, do you still sell these boards? If you do, how can I get one?

Thanks
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 14 Mar 2016, 04:23 pm
PM (as you did)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: matt_garman on 16 Mar 2016, 10:31 pm
Also it's best to have some distance from transformer and amplifier board.

I recently performed an experiment, albeit unintentionally, that demonstrated the effects of transformer EMI leakage...

I'm building a DAC based on the Soekris dam1021 board.  I'm powering it with a 15W R-core transformer and +/- 12V DC supply.  But the shipping on that R-core was painfully slow, and the dam1021 will also run directly off a fairly wide range of AC power.  So I borrowed the Hammond 185E16 from my Folsom tda7297 build, using it's parallel 8V AC outputs to power the DAC board.

It worked, but I had random dropouts in the music.  In particular, the DAC board's status LED would occasionally flash to indicate loss of signal lock.

I posed this question to the big diyaudio thread (http://www.diyaudio.com/forums/vendors-bazaar/259488-reference-dac-module-discrete-r-2r-sign-magnitude-24-bit-384-khz.html) about this board, and the designer suggested i2s signal integrity issues.  My on-desk implementation of this board had wires coupling my Amanero (usb to i2s device) to the dam1021 board.  This coupling is via the i2s protocol, and it's really designed for super-short wire runs (generally on board traces, or wires no longer than 10cm in length).  My wires were indeed exactly 10cm in length, and I saw plenty of other people with effectively the same setup (but not reporting these drops).

Well, I finally got the R-core transformer, and replaced the Hammond with that plus the DC supply.  I ran the thing non-stop all weekend without a single drop or signal loss!  (I have the DAC logging to a serial console so I can check for issues even if I'm not listening to it.)

The distance between the Hammond transformer and i2s wires, versus the distance between the R-core and i2s wires is basically the same.  The wires I had running from the Hammond to the dam1021 weren't long enough to see how far away the transformer needed to be to stop affecting signal integrity.

Bringing this back on topic: I don't know how sensitive the tda7297 is to EMI, but based on my recent experience, some distance between the psu+amp PCB and transformer can't hurt.  Or maybe a mu-metal cover (if you can find one)?  Or perhaps an R-core transformer?  (If you can even find a big enough one and are willing to pay!)  Dunno if a toroid is appropriate for this amp or not?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 16 Mar 2016, 11:03 pm
R cores are good. They cost more and aren't available from Mouser. I tried to make everything from mouser, for ease of use.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 16 Mar 2016, 11:27 pm
Jeez , I feel like Captain Obvious after asking above about rubber insulation when mounting the transformer ( it's addressed early in this thread ) and size of the heat sink ( it's listed in the construction page from Folsom that came )
Too many hours at work this month dimming my bulb
Anyway when mentioning the term 90 in my last post .....I meant the right angle mounting brackets to attach the Antipole board vertically . I can see them in the photo of the board when I zoom in on the amp insides .
The 90 is a holdover term from my previous job.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 17 Mar 2016, 12:35 am
You don't have to use 90° . As I was saying, you can mount it off a vertical panel as well.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 17 Mar 2016, 01:58 am
Matt - curious the learn more about your Soekris DAC build. How does the 7297 sound with it?

To not get off topic here, do you have another thread on AC somewhere explaining your build? I started to read the DIY thread a while ago but coming late to long threads is a bit overwhelming sometimes...
Title: Re: Folsom's great little 7297 Chip Amp
Post by: matt_garman on 17 Mar 2016, 04:29 pm
Matt - curious the learn more about your Soekris DAC build. How does the 7297 sound with it?

I actually haven't heard Folsom's 7297 with any DAC, as I think I made some mistake when building it.  Haven't put in enough time to fix it yet (though Jeremy has been quite generous with his time giving tips and suggestions).

To not get off topic here, do you have another thread on AC somewhere explaining your build? I started to read the DIY thread a while ago but coming late to long threads is a bit overwhelming sometimes...

I don't have any build thread (here or anywhere else), as my "build" is still just boards and wires in a mess on my desk.  :)  And my plans are pretty pedestrian (i.e. nothing fancy).  That said, I'll try to do a little writeup here when the project is farther along, as I think the finished product will be "Cheap and Cheerful".  (Similar to what I did with the tda1387 x8 dac (http://www.audiocircle.com/index.php?topic=134972.0).)

But the short version is: so far I really like what I hear, though I haven't had an opportunity for a long critical listening session (and the "build" is too messy to easily switch between other DACs for comparisons).  But the most basic config is almost trivial to assemble (if you can do the Folsom 7297 board, you can do a dam1021 build).  Perhaps the biggest selling point is that it presents so many options (i.e. make it as simple or fancy as you want).

Oh, the diyAudio thread is a bit long.  See glt's blog (https://hifiduino.wordpress.com/2015/03/16/soekris-dam-1021-r-2r-dac-users-guide/) for a more accessible overview of the dam1021.  Near the bottom of the linked page, he gives links to other posts he's done on it.

Apologies for the off-topic digression!   :oops:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 17 Mar 2016, 04:49 pm
Thanks for the info - you need to hurry getting it fixed because it's really good.

I'm actually thinking of ordering a second one.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 17 Mar 2016, 05:10 pm
I've seen some pics of Matt's. Best guess is an arc fried a transistor, from connecting a charged PSU capacitor.

He did a nice job soldering, so I sent him a new small transistor to check with before anything drastic could be looked at (shipping/chip replacement for example)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 18 Mar 2016, 05:00 pm
What is the ideal voltage for SMPS's I haven't yet committed to building the Antipole PS, so I have a couple of 24V SMPS (bricks) one is delivering 24v, the other is 24.4V. So... is a 24v SMPS too high voltage to use?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 18 Mar 2016, 05:21 pm
Those will be fine.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 20 Mar 2016, 03:27 pm
A couple of Chassis questions:

One: Do the standoff holes in the board have to be insulated from an earth grounded metal chassis? My chassis has PCB slide-in grooves (115mm) so I won't be using stand-off's, but the holes in the board could make contact with the chassis groove unless I isolate them.

Two: If I mount the Transistor that has the heat sink to a bulkhead divider to act as a heat sink, does it have to be insulated with a ceramic washer and mica sheet if this metal divider is grounded?

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 20 Mar 2016, 05:58 pm
1. No, not less you tried to drill them out or something odd.

2. No, it has connection between tab and any of its legs.

3. Please post a pic when you're done, I'm curious.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: sorinv on 23 Mar 2016, 08:41 pm
I am having a hard time finding a transformer for the Antipole power supply. Hammond costs $25 to be shipped to Europe, which is ridiculous.

Anybody using toroidal transformers, like this one (http://www.tme.eu/en/details/tst100w_2x8v/toroidal-transformers/indel/tst100002/)?

I am planing to build the power supply in a different chassis than the amp, so transformer would not be close to the audio path.

Any other suggestion of a good transformer for this?

Thanks
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 23 Mar 2016, 09:02 pm
Sorin, that should be fine since it's 16v output with plenty of amperes. I might try a James OA (http://jamestransformer.com/en/transformer/O_core_transformer.html) type in near future. They're $60 shipped to USA, so maybe less to you. That's for 100VA, 16v out. They seem higher quality than most transformers.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: matt_garman on 25 Mar 2016, 08:28 pm
FWIW, I just ordered an AnTek AS-1218 (18V/100VA) (http://www.antekinc.com/as-1218-100va-18v-transformer/) to go with my Folsom tda7297... which I finally got working this morning!  I swapped all three transistors on the board, and now it's singing nicely.  I think at some point I failed to heed Jeremy's warning, and connected "live" power that killed one or more of those transistors.

Sounds good, although it's too soon to do any kind of detailed writeup or comparison with other amps.  But at first listen it's certainly good enough to warrant a proper case.  :)

A question for Folsom: I think I'm going to use this Modushop Galaxy 2U chassis (http://diyaudiostore.com/collections/chassis/products/2u-w-aluminum-covers) (since I already have one).  The sides are a "quasi" heatsink, which I'm thinking are probably enough to keep the tda7297 cool.  Question is: do you think using a thermal pad between the tda7297 and heatsink is acceptable?  Example: t-Global Technology H48-6-45-25-6 (http://www.digikey.com/product-detail/en/t-global-technology/H48-6-45-25-6/1168-1702-ND/3300360).  My thought is that it would simplify the heatsinking a bit, as the pad is thermally conductive, but not electrically conductive.

Thanks again for your help getting my 7297 running!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 25 Mar 2016, 08:48 pm
The heatsink side is probably ok. It doesn't have good convection but the 7297 doesn't exactly run hot.

I'd use the mica I specified (http://www.mouser.com/ProductDetail/Keystone-Electronics/4661/?qs=sGAEpiMZZMsQtlBhqKq43fXDiIgDSWVF). It's just for a TO-3 transistor but it's square. The pad you have there is so thick that it may hurt overall power ability.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: matt_garman on 26 Mar 2016, 08:25 pm
Here's the chassis layout I'm thinking about.  The goals are compactness and reasonable cost.  This is designed around the Modushop Galaxy 2U 230x230 chassis (http://diyaudiostore.com/collections/chassis/products/2u-w-aluminum-covers?variant=12174803716).  Internal dimensions are 80x210x230 (HxWxD).  I found on ebay a heatsink with dimensions 150x60x25 (DxHxW) for $7.  In the schematic below, I'm calling for the AnTek AS-1218 transformer.  The Hammond Folsom recommends would also fit, however, I'm a little concerned about magnetic leakage in something this compact.  A toroid "should" be better in that regard.

(http://www.audiocircle.com/image.php?id=139917)

I don't think it really does anything, but that heatsink "feels" like it separates the amplifier from the transformer.  :)  Another approach would be to remove the heatsink entirely, and move the transformer to the left side, and the amp+psu board to the far right.  Then the side of the chassis itself could be used as the heatsink.

Folsom, how much heat does that big D45H11G transistor generate?  How about using a thermal pad to bridge that to the chassis?

Thoughts?

Note: that drawing is mostly to scale.  I used Front Panel Designer to get the dimensions/scale right, took a screenshoot, then used Microsoft Paint to make the colors and annotations.  ;)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 26 Mar 2016, 08:57 pm
The D45 doesn't make enough heat to be concerned with. If the heatsink is inside it needs some airflow from top to bottom (holes). But it also doesn't need a pad or anything for electrical conductive isolation.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 5 Apr 2016, 02:59 pm
Hi all...thanks, Jeremy, for your work on designing the boards for this, and your helpful build suggestions. Here is mine...need to add the heatsink yet, but ran out of time last night. This shouldn't be too big of a deal, as I dry fitted earlier--just didn't want to mess with the grease  8)
(http://www.audiocircle.com/image.php?id=140523)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 5 Apr 2016, 07:10 pm
So close!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 5 Apr 2016, 07:48 pm
Looking nice. :thumb:
 I didn't get hold of any good mounting hardware and fitting the heatsink without getting a reading on my multimeter took a few tries.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 5 Apr 2016, 08:26 pm
Looking nice. :thumb:
 I didn't get hold of any good mounting hardware and fitting the heatsink without getting a reading on my multimeter took a few tries.

If it's too hard you can use a deeper isolation washer if you drill out a slightly bigger hole for 1-2mm before the smaller hole you need for mounting. Also you could maybe take the chip tab and remove a little material on the side that goes against the heatsink to help it not touch the bolt - very carefully.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 5 Apr 2016, 10:46 pm
Hi Guys...starting the troubleshooting process...ahem... :oops: :duh: I powered up the amp and no smoke but...no sound. I am getting 19.2 VAC out of the transformer and 25.2 VDC through the antipole and to the amp board. Does this sound ok?

That's about as far as I have gotten. Nothing appears wrong. Oh, except for the no sound part. I didn't power anything thing up until then...that's what you get for being overly confident...ugh...
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 5 Apr 2016, 10:52 pm
Let's see a close up of the board. If you measure from any connection that's a ground (speaker output won't work) to the positive leg of one of the OSCONs what do you get?

90% of the time the mute/stdby is preventing turn on, but we'll see.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 5 Apr 2016, 11:10 pm
Ok...so I will take a pic of the amp board...the bottom of it, right? Positive leg of one of the 10 caps to the voltage input ground to the board ok?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 5 Apr 2016, 11:13 pm
I think there's 12, but yes.

Top pic too.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 5 Apr 2016, 11:59 pm
Well crap. Measured 1.7 volts positive leg to ground. Until the amp chip tab touched metal. It made its first sound. Breifly  (pop)...right...12 caps...I said 10, but I ended up soldering in 14, as I put 2 in the alternate location. And fixed :-(  This one is fighting me a bit...
(http://www.audiocircle.com/image.php?id=140553)

(http://www.audiocircle.com/image.php?id=140555)



Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 6 Apr 2016, 12:18 am
Are you certain you didn't mix the TL431 and BC337?

You didn't drill the holes for the incoming DC did you? or any others?

BTW the two accidental mounts, it would be preferred to put a capacitor that's 35v, and 47uf+ in one of them. I sent an email and I think I got everyone but perhaps not.

I'm not seeing any major problems, yet. Pics are so-so however.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 6 Apr 2016, 12:35 am
Hi. Thanks...really don't want to tie up your time. Sorry about the bad pics...phone...snow...April... :-(  no...on both drilling out the holes and switching the transistors. I did notice an iffy solder joint on the middle leg of the the431. Will try to reflow that. And replace the amp chip, right (based on the pop)?  Assume that one is done. First good news of the day... Mr. Fat finger has another 7297. Things are looking up...
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 6 Apr 2016, 12:38 am
Hi. Not sure what the reference to the accidental mount cap and location is though
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 6 Apr 2016, 01:19 am
I don't know for sure about replacing the chip. I didn't hear the pop. I'm wondering why it would pop touching something? The Antipole's bottom isn't touching the case anywhere is it?

The popping makes me wonder if the ground connection to the amp isn't working, and then it found ground through the chassis, which doesn't make a lot of sense...
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 6 Apr 2016, 01:35 am
Here's a photo of the caps I sent an email about, as they add stability because the inductance of the wires to the antipole is a little too high for the KMR section (resulting in some turn on noise, at least).

(http://www.audiocircle.com/image.php?id=140573)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: 1108 on 6 Apr 2016, 01:03 pm
I'm having the same problem. How can I check the mute/standby?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 6 Apr 2016, 06:05 pm
mute/stdby won't affect the voltage at the capacitor, it just turns the chip off.

Have you checked where your voltage stops?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 6 Apr 2016, 06:29 pm
I didn't get the email about adding the two additional caps. What are the values for each location?

Trying to figure out a path forward to try to get my amp working...do the readings I mentioned earlier seem ok? I measured 19.2 VAC out of the transformer, 25.2 VDC through the antipole to the input of the amp board, and 1.7 volts (assume this is DC also) from Oscon positive leg to ground. I would like to eliminate things that are likely ok, so I can hopefully narrow in on the problem.

My plan tonight is to re-solder the middle leg of the TL431, which looks a bit suspect, and solder in a new 7297, as I think I fried the one on the board last night.

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 6 Apr 2016, 06:39 pm
1.7 from an OSCON means the power is not getting through. It is not related to mute/stdby.

Set your DMM to ohm reading and check between the ground wire coming in and several OSCON ground legs (the side with marking). And then check to chip tab.

Your soldering looks like you needed to wait just a moment longer to get enough heat on the board, in several locations, because the solder tended to pool up first on the leads. Hopefully there's no cold joints. A light wiggle can often identify them.

The TL431 does look like it needs the center leg touched up.

I don't know if the chip is bad, could be. Do you have solder wick? You'll need that. I'd suggest cutting the chip off and then pulling the legs out when heat is applied, and solder wicking to clean. If you have a heated desolder tool you might get a good clean spot on the legs once chip is removed. It's certainly not the easiest task with 15 pins, but it's doable (I did it with the first PCB I had, before anyone knew that SG and PG had to be connected outside of the chip for it to turn on; all boards are correct this way now).
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 6 Apr 2016, 06:59 pm
Hi Folsom...thanks for the reply. Yeah--my impatience in using the crappy solder iron tip that I should have replaced before I started the board really cost me...I will pick up some supplies today.

So, I am assuming the check from Oscon neg. to ground should give the same reading (or similar) as touching the two leads of the DMM together, right? What reading should I get between the chip tab and ground?

Do you know of any way to check if I fried my 7297 before I remove it?

Thanks! Very much appreciated.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 6 Apr 2016, 07:21 pm
Correct the reading should be close to touching the meter tips together. That goes for the chip tab too.

I do not have a clear way to test the chip besides turning it on and checking for voltage on the outputs; but it might turn itself off without a load. The good protection qualities in the chip are a double-edged sword you might say.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: sorinv on 7 Apr 2016, 04:58 am
Quote
I didn't get the email about adding the two additional caps. What are the values for each location?

I didn't get that either. I have in the BOM 220uf, speced for primary use with battery supply. Should I install those with the altipole in a different enclosure with one foot DC cable to the amp?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 7 Apr 2016, 05:25 am
Yes, I would. The inductance is too much otherwise.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: matt_garman on 10 Apr 2016, 11:17 pm
Here's the chassis layout I'm thinking about...
(http://www.audiocircle.com/image.php?id=139917)

It's becoming a reality:

(http://www.audiocircle.com/image.php?id=140960)

I need to have the back panel cut for RCA, speaker terminals, and IEC.  I'll probably have that done by Front Panel Express.

I'll shorten those AC leads in and out of the transformer before it's all done.

For the front panel, I'll go with a power LED and maybe on/off switch (or the on/off switch will be integrated into the IEC, haven't decided on that yet).

Coming along nicely I think!


Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 10 Apr 2016, 11:52 pm
Looking good, Matt :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 11 Apr 2016, 08:38 am
Ok guys, it's been random for turn on noise. I sent out two emails. One about the input caps for DC, which Matt has (gold caps). That stabilizes performance and stops turn on noise two people have had. And one or two have a small bump sound during turn on, which I sent the second email about. The 10uf blue cap can be bypassed by a 100uf (or replaced, but I wouldn't try it unless you're very good with a soldering iron, and even then it's risky due to hole size). Here's a capacitor (http://www.mouser.com/ProductDetail/Cornell-Dubilier-CDE/107CKS016M/?qs=sGAEpiMZZMsnnVx9hWj0EdwDxVnCKiAeAzw8rwnSpdc%3d) that'll work and fit everyone's budget (I hope).

I tested it this evening in order to make everyone happy. The turn on bump was harmless at 15w max (if you even had it), but hey we can do silent worry free so why not!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: 1108 on 19 Apr 2016, 11:54 am
I have the Bourns 8120 for the Antipole. Does it need to be oriented in any particular way?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Gopher on 19 Apr 2016, 03:13 pm
I had the opportunity to meet Folsom at AXPONA and give his amp a listen after hours and can say it is coming along quite well.  The bass in particular was impressive.   :thumb:

Cool meeting you, man and good luck with this endeavor!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 19 Apr 2016, 03:48 pm
Well - I finally finished building my DIY TDA7297 Folsom amp. I have been playing around with the Class D amplifier boards (TPA3110/3116/3118) for several years now. Trying different boards,and mods with resulting great sound for cheap.
However, Folsom's implementation of the Class A/B TDA7297 chip amp is definitely a leap forward by a big margin. I finally have a DIY amp that truly meets my expectations without needing further mods to make it sound right. I am listen now at pretty high levels; the bass is just amazing on my GR Research X-LS Encores. These speakers always sounded good to me, but this amp really brings out their best! Good job Folsom :thumb:

(http://i.imgur.com/leoJhGT.jpg?1)

(http://i.imgur.com/hgq96gy.jpg?1)

(http://i.imgur.com/M0tz8Hn.jpg?1)

(http://i.imgur.com/QGc2HKp.jpg?1)

(http://i.imgur.com/su0GsUi.jpg?1)

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 19 Apr 2016, 03:54 pm
Wow! The award for most compact design goes to Lacro!

How funny is it that the Folsom name is on someone else's project before anything of my own?  :lol:

It looks great Lacro. I'm glad you're enjoying the amp!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 19 Apr 2016, 03:58 pm
I had the opportunity to meet Folsom at AXPONA and give his amp a listen after hours and can say it is coming along quite well.  The bass in particular was impressive.   :thumb:

Cool meeting you, man and good luck with this endeavor!

Thank you Gopher.  :D
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 19 Apr 2016, 04:19 pm
Lacro - Double wow! That's super nice. Well done. I can't tell from the pics but are the heatsinks mounted on the case/middle plate or do they go straight through to allow direct contact with the chip and transistor? Is it keeping pretty cool in the case?

Please tell us more about your build spec.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 19 Apr 2016, 04:41 pm
Nice, NICE, work, lacro!! My fingers are growing ever big and clumsy when I look at your packaging :-) Dang--that's tight! Very attractive build...Congrats!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: shadowlight on 19 Apr 2016, 04:46 pm
@lacro, where did you get the case from?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: matt_garman on 19 Apr 2016, 05:03 pm
Well - I finally finished building my DIY TDA7297 Folsom amp. I have been playing around with the Class D amplifier boards (TPA3110/3116/3118) for several years now. Trying different boards,and mods with resulting great sound for cheap.
However, Folsom's implementation of the Class A/B TDA7297 chip amp is definitely a leap forward by a big margin. I finally have a DIY amp that truly meets my expectations without needing further mods to make it sound right. I am listen now at pretty high levels; the bass is just amazing on my GR Research X-LS Encores. These speakers always sounded good to me, but this amp really brings out their best! Good job Folsom :thumb:

 :o Lacro, that is super nice!  I love how compact it is, yet (to my eyes anyway), I don't see any compromises.

What SMPS are you using?  (I know people debate SMPS vs linear, but if space/compactness is a concern, SMPS is the clear winner.)

And is that heatsink in the back (the one for the tda7297 chip) integrated with the case, or did you add it on?

Once again, great work.  Nothing short of impressive!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 19 Apr 2016, 06:19 pm
Hi Everybody;

I finally got back to troubleshooting my build. I re-did some of my really bad solder joints, and now get 17.7 VDC from positive Oscon leg to amp board ground. Does this sound right?

I might have a blown 7297 chip (touched it against the amp case and it went 'pop' in an earlier troubleshooting attempt), but I would rather not replace it until I know what voltages the caps should see.

Not being familiar with the circuit, I don't know what to check next...

Thanks for any help you may be able to provide.

limits
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 19 Apr 2016, 06:22 pm
...Also checked continuity of Chip tab to negative on amp board and that was OK...
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 19 Apr 2016, 06:24 pm
The voltage is correct. Can you take pics? That helps us tremendously.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 19 Apr 2016, 06:45 pm
Certainly...not pretty, I know...
(http://www.audiocircle.com/image.php?id=141553)

(http://www.audiocircle.com/image.php?id=141554)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 19 Apr 2016, 09:54 pm
Thanks for the kind words guys.....


@lacro, where did you get the case from?

Shadowlight:
http://www.aliexpress.com/snapshot/7493007269.html?

:o Lacro, that is super nice!  I love how compact it is, yet (to my eyes anyway), I don't see any compromises.

What SMPS are you using?  (I know people debate SMPS vs linear, but if space/compactness is a concern, SMPS is the clear winner.)

And is that heatsink in the back (the one for the tda7297 chip) integrated with the case, or did you add it on?

Once again, great work.  Nothing short of impressive!

Matt: The SMPS is one that was talked about on DIY Audio. I did the suggested mods replacing all electrolytics, and adding a couple of ceramic SMD caps on the secondary outputs. It doesn't produce any audible noise (hiss/hum), and stays pretty cool. The main reason I used it was it is the same length as the amp board (115mm) so it fits the PCB groves in the case. It just slides into the case without mounting hardware being needed. The Antipole would have required me to install it in a separate case as it's 7" long. I do feel Linear PS are superior, and the Antipole is probably the best choice for this amp, but so far I am pretty happy with this one.

The heatsink is a separate piece; got it from PE. It is mounted with screws from the back (5 total). The back panel was sand blasted to remove the powder coating where the HS mounts; then bedded in thermal grease. The chip is bolted through the back to the HS (sandblasting/thermal grease again on the inside) 

Lacro - Double wow! That's super nice. Well done. I can't tell from the pics but are the heatsinks mounted on the case/middle plate or do they go straight through to allow direct contact with the chip and transistor? Is it keeping pretty cool in the case?

Please tell us more about your build spec.

Odal3: The heatsinks, both the chip and transistor are sandwiched with the back plate, and bulkhead. The heatsinks are bolted to the chip and transistor through the back plate and bulkhead creating a secondary heatsink. At high listening levels the case stays only slightly warm when driving 89db speakers; when driving 84db speakers, it gets a lot warmer. There are a lot of ventilation holes I drilled in the top, bottom and back to aid in cooling.

What else do you want to know about my build specs?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 19 Apr 2016, 10:16 pm
Certainly...not pretty, I know...


I don't see anything obvious about it that's wrong. You've got correct voltage. You might have fried the mute/stby section somehow (that's in the chip), if you get zero sound.

Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 19 Apr 2016, 11:31 pm
Ok. I will try hooking it up again, hopefully tonight. Unless I read the meter wrong on my first try (1.7 VDC is what I noted before-- Oscon positive leg to board ground), I should at least have more power running through the board. Really hoping I don't have to replace that chip...Fingers crossed...
Title: Re: Folsom's great little 7297 Chip Amp
Post by: matt_garman on 20 Apr 2016, 02:20 am
Thanks for the kind words guys.....

They are well-deserved.  Just when I think my builds are starting to look half-decent, you come along and post that!   :green:

Matt: The SMPS is one that was talked about on DIY Audio. I did the suggested mods replacing all electrolytics, and adding a couple of ceramic SMD caps on the secondary outputs. It doesn't produce any audible noise (hiss/hum), and stays pretty cool. The main reason I used it was it is the same length as the amp board (115mm) so it fits the PCB groves in the case. It just slides into the case without mounting hardware being needed. The Antipole would have required me to install it in a separate case as it's 7" long. I do feel Linear PS are superior, and the Antipole is probably the best choice for this amp, but so far I am pretty happy with this one.

Do you happen to have a link to the DIYAudio thread discussing that SMPS?

I keep going back and looking at the pics of your build, Lacro.  It's really nice.  Since you made such efficient use of space, did you find it hard to get everything in place?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 20 Apr 2016, 02:23 am
Thanks for the info!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 20 Apr 2016, 01:38 pm
I keep going back and looking at the pics of your build, Lacro.  It's really nice.  Since you made such efficient use of space, did you find it hard to get everything in place?

Matt: The case is bigger than the photos make it look. It's 4-1/2" Wide; 3" high, and 6" long. I made everything to be modular. The PS module, and amp module can be removed from the case in less than 5 minutes. Everything either unplugs or is held with screws. The modules slide into the grooves provided in the case.

Typical 5 minute dis-assembly:

This is pretty much how I put it together; treating it as a case, and two separate modules. There wasn't any tight, difficult assembly, or wiring. The hardest part for me was laying out the back panel so everything fit since the heat sink took so much space. Compared to my stuffing a TPA 3110 into an Altoids mint tin, this build has lots of room:D  http://www.audiocircle.com/index.php?action=profile;u=74671;area=showposts;start=140 (http://www.audiocircle.com/index.php?action=profile;u=74671;area=showposts;start=140)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: 1108 on 20 Apr 2016, 04:18 pm
I have the Bourns 8120 for the Antipole. Does it need to be oriented in any particular way?


Anyone?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 20 Apr 2016, 04:32 pm
Hi...I believe it was discussed earlier, but the Bournes can go either way on the antipole board.

I tried hooking my amp up again last night, and it still doesn't work. I guess I will try cutting off the 7297 and fitting in a new chip. If that doesn't work, it might be closet-city for this project :-(

Title: Re: Folsom's great little 7297 Chip Amp
Post by: 1108 on 20 Apr 2016, 04:38 pm
Thanks. I thought I read that someplace but couldn't find it again.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 20 Apr 2016, 04:40 pm
Hi...I believe it was discussed earlier, but the Bournes can go either way on the antipole board.

I tried hooking my amp up again last night, and it still doesn't work. I guess I will try cutting off the 7297 and fitting in a new chip.

That might be the best option for right now, since you clearly have enough voltage. Do you have any solder wick? I suggest using it after cutting the chip, then pulling the legs out one by one. It's a little bit of a tricky operation but I've done it, so I know it's possible.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 20 Apr 2016, 04:48 pm
I picked up some solder wick the other day, so yes--I will give it a shot. Fifteen teeny-tiny holes...ugh :-)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 20 Apr 2016, 05:08 pm
A word of caution on removing the chip: If you soldered the legs so the solder flowed from the bottom to the top in excess; solidly anchoring the legs at the top of the via as well as bottom, you will need to be careful to remove as much solder with the wick from both sides of the board before trying to pull the leads out. If you try to just heat one side, and pull on the lead with tweezers, the solder on the opposite side may not have melted, and you risk tearing the via.


This tool works pretty good for removing solder:
http://www.amazon.com/Tenma-21-8240-Vacuum-Desoldering-Iron/dp/B008DJRYIG/ref=sr_1_4?s=hi&ie=UTF8&qid=1461171099&sr=1-4&keywords=electric+solder+sucker (http://www.amazon.com/Tenma-21-8240-Vacuum-Desoldering-Iron/dp/B008DJRYIG/ref=sr_1_4?s=hi&ie=UTF8&qid=1461171099&sr=1-4&keywords=electric+solder+sucker)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 20 Apr 2016, 05:23 pm
lacro -- Brilliant! Just ordered this. Thank you!

I'll spend 16 bucks for less frustration any day. I used some of the solder wick I had to clean up some of my bad/globby joints earlier this week with only so-so success, so I definitely wasn't looking forward to the chip replacement.

Appreciate the suggestion...
Title: Re: Folsom's great little 7297 Chip Amp
Post by: matt_garman on 20 Apr 2016, 07:48 pm
Ok guys, it's been random for turn on noise. I sent out two emails. One about the input caps for DC, which Matt has (gold caps). That stabilizes performance and stops turn on noise two people have had. And one or two have a small bump sound during turn on, which I sent the second email about. The 10uf blue cap can be bypassed by a 100uf (or replaced, but I wouldn't try it unless you're very good with a soldering iron, and even then it's risky due to hole size). Here's a capacitor (http://www.mouser.com/ProductDetail/Cornell-Dubilier-CDE/107CKS016M/?qs=sGAEpiMZZMsnnVx9hWj0EdwDxVnCKiAeAzw8rwnSpdc%3d) that'll work and fit everyone's budget (I hope).

Hi Jeremy, sorry I didn't follow-up on this sooner.  I got your recommendation for the 100uF cap to replace the 10uF as a solution to the power-on thump.  I didn't want to place a Mouser order for just one cap, so I rummaged through my parts collection.  I found a small 22uF cap that I put in place of the 10uF.  There's still a thump, but it's substantially quieter.  In fact, it's practically silent.  I can still see the speaker drivers moving a bit, but I really don't think it's nearly as bad as it was before.  So even 22uF is noticeably better, at least in my case.  (I'll order the 100uF cap when I have a critical mass of parts I need.)

Also: when I installed the 22uF cap, I also changed to the heatsink shown in the picture back a page or two.  My previous heatsink was not electrically isolated from the tda7297 chip.  But I took the time to do it with the new heatsink (exactly per your recommendation, with the rubber screw isolator and mica film).  I highly doubt that had anything to do with the power-on thump, but it's an additional change.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 20 Apr 2016, 07:52 pm
Yes, you should have less RF with the mica and shoulder washer.

Again the turn on sound was only 15w max, so it was never a harmful thing. It just isn't as pleasant as nothing at all.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 20 Apr 2016, 10:27 pm
Hi Jeremy, sorry I didn't follow-up on this sooner.  I got your recommendation for the 100uF cap to replace the 10uF as a solution to the power-on thump.  I didn't want to place a Mouser order for just one cap, so I rummaged through my parts collection.  I found a small 22uF cap that I put in place of the 10uF.  There's still a thump, but it's substantially quieter.  In fact, it's practically silent.  I can still see the speaker drivers moving a bit, but I really don't think it's nearly as bad as it was before.  So even 22uF is noticeably better, at least in my case.  (I'll order the 100uF cap when I have a critical mass of parts I need.)

Matt, Did you bypass the existing cap on the bottom as Jeremy suggested or removed/replaced it?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: matt_garman on 21 Apr 2016, 04:58 pm
Matt, Did you bypass the existing cap on the bottom as Jeremy suggested or removed/replaced it?

I did an outright replacement.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 21 Apr 2016, 06:03 pm
Matt has skills.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: matt_garman on 21 Apr 2016, 09:27 pm
Matt has skills.

You're being far too generous.  :)

I just used some solder wick then rocked the old cap as I heated the leads.  Any residual solder got cleaned up with solder wick.  Failing that I just use my pin vise and precision drill bits to clean out any remaining solder.

I developed these skills doing through-hole replacements on the cheap tpa311x boards.  The pin vise was the game-changer for me, as I was able to stop worrying about over-heating the boards/traces.  I just quickly absorb as much solder as I can with the wick, then clean out the rest (if necessary) with the drill.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 21 Apr 2016, 10:21 pm


I just used some solder wick then rocked the old cap as I heated the leads.  Any residual solder got cleaned up with solder wick.  Failing that I just use my pin vise and precision drill bits to clean out any remaining solder.

I developed these skills doing through-hole replacements on the cheap tpa311x boards.  The pin vise was the game-changer for me, as I was able to stop worrying about over-heating the boards/traces.  I just quickly absorb as much solder as I can with the wick, then clean out the rest (if necessary) with the drill.

I have used the pin vise too, but I have to be very careful I am starting the drill in the center of the hole or I run the risk of drilling off center, possibly doing damage. Don't ask how I know this :oops:

I am having pretty good luck with this tool:


(http://ecx.images-amazon.com/images/I/31py-xFEfFL.jpg)

http://www.amazon.com/Tenma-21-8240-Vacuum-Desoldering-Iron/dp/B008DJRYIG/ref=sr_1_4?s=hi&ie=UTF8&qid=1461171099&sr=1-4&keywords=electric+solder+sucker (http://www.amazon.com/Tenma-21-8240-Vacuum-Desoldering-Iron/dp/B008DJRYIG/ref=sr_1_4?s=hi&ie=UTF8&qid=1461171099&sr=1-4&keywords=electric+solder+sucker)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 22 Apr 2016, 06:17 pm
Lacro, thanks  for posting your pictures and thoughts on the amp design
My seasonal job finished yesterday so I can begin my spring project build of Folsoms amp
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lasgoofus on 22 Apr 2016, 07:10 pm
what  would be the safe procedure   to discharge the Antipole power supply caps... if just  testing after assembly?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 22 Apr 2016, 07:13 pm
Screw driver's have insulated handles typically.  :green:

It's not good to do that a lot. You can add a 10k resistor on the discharge location on the Antipole, after discharging, if you think you'll need to often.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lasgoofus on 26 Apr 2016, 06:30 pm
yikes discharging the caps right after unplugging it creates quite a spark...I tested it the power supply is putting out 24 volts so I'm at the point of finding an affordable enclosure..I might go to thethrift store and purchase some old electronics's and reuse metal case. fun project so far.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 10 May 2016, 11:08 pm
There are still some boards available.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: restrav on 10 May 2016, 11:47 pm
There are still some boards available.

how much do they cost? is it just the boards or complete kit? the first post is a little confusing, it is someone else that has made the topic and it has a link to indiegogo so im not sure.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 11 May 2016, 12:00 am
The best way is to send Folsom a message.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Onlysleeping on 11 May 2016, 05:28 am
PM sent

Found some mods on another forum that worked well for bass.  Interested in checking this version out. 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: drew_t on 15 May 2016, 10:34 pm
Folsom, I'm going to PM you as soon as they let me use the PM system . . .
Title: Re: Folsom's great little 7297 Chip Amp
Post by: richidoo on 15 May 2016, 11:16 pm
I think your PMs will work after you make 3 posts.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 16 May 2016, 12:59 am
PM's sent, we'll see if it works with me sending, otherwise makes some posts please.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 16 May 2016, 02:51 pm
Hi All:

I would like to extend a huge thank you to lacro for suggesting the Tenma desoldering iron. It made replacing the 7297 chip a breeze. Unfortunately, my amp still does not work  :scratch:

At that point, I put it away. I may pick it up again this week and check voltages, but I feel so snake-bit that I'm tempted to give up, or possibly try a new board...
Title: Re: Folsom's great little 7297 Chip Amp
Post by: keith_correa on 24 May 2016, 06:16 am
Found some mods on another forum that worked well for bass......
Can you post the link please?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Garytr on 26 May 2016, 03:03 pm
Hi,
I have tried the Chinese TDA7297 and I like it. I was wondering if any boards/kits are still available?
Garytr
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 3 Jun 2016, 02:20 am
I finally built my amp. The boards came together easily. I did not run into any issues and everything fired up the first time. The chassis is from Landfall Systems. Dave was great work with and it's great being able to design a chassis the way you want it. In addition,the chassis has a great fit and finish. Well worth the cost.

The amp is fresh out of the box and needs to break in, but based on initial listening i think we have a winner. I'm going to let it break in over the next couple of weeks before I say anything else. I will say one thing, my Blumenstein Orca speakers like the extra power, over my Decware ZKIT1 amp.

(http://www.audiocircle.com/image.php?id=144101)

(http://www.audiocircle.com/image.php?id=144102)

(http://www.audiocircle.com/image.php?id=144100)

(http://www.audiocircle.com/image.php?id=144099)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 3 Jun 2016, 02:36 am
That looks really good!!!   :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 3 Jun 2016, 06:14 am
BRN, I think you're the first person to use the Nichicon FP caps instead of the Panasonic's. I'm excited to hear about what you think.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 3 Jun 2016, 01:45 pm
Nice clean work, looks great  :thumb: No ventilation holes? 

Title: Re: Folsom's great little 7297 Chip Amp
Post by: lokie on 3 Jun 2016, 02:18 pm
Sorry for being such a putz but does anyone have one of these for sale? or starting a build and want's to build an extra one simultaneously?

Thanks
Title: Re: Folsom's great little 7297 Chip Amp
Post by: happyrabbit on 3 Jun 2016, 04:40 pm
BRN - looks excellent   :thumb: ! 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 3 Jun 2016, 11:58 pm
Nice clean work, looks great  :thumb: No ventilation holes?

The 7297 chip was installed to the back of the chassis as described in the instructions. I attached the heatsink to the back of the chassis and applied thermal paste to help with the heat transfer. Should work fine to dissipate the heat.

Thanks for the nice comments. It was fun putting together.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 4 Jun 2016, 12:08 am
The chip doesn't put out a lot of heat, but keeping it cools retains the power output. If it did run hot the heatsink would need to be rotated 90* to allow convection to work better.

My vent holes were because the heatsink is on the inside.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 4 Jun 2016, 02:40 pm
The chip doesn't put out a lot of heat, but keeping it cools retains the power output. If it did run hot the heatsink would need to be rotated 90* to allow convection to work better.

My vent holes were because the heatsink is on the inside.

My case definitely needs vents as it can get warm, not from the chip which has an external heatsink (oriented correctly), but from the transistor heatsink which is internal. BRN's case is pretty large so maybe vents are not needed, but probably worth checking.

Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 9 Jun 2016, 10:36 pm
Hi guys. Well. Amp board attempt number two. New board, all new parts. And...it works!! This time I heeded Folsom's advice, and took my time. Thank you VERY much for designing this, and making it available for others.

Seems to have a fair bit more gain than my tube amp...15 watts is plenty for my B1 buffer/Exodus Audio Kepler speakers. Really, really liking what I am hearing :thumb:

Reported to have great mids on up, which it does. The thing that surprised me most was the bass, which is also excellent.

Will upload some pics of it in a bit--thought I could just do it directly from my phone, but can't get it to work...

Thanks again, Folsom!

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 9 Jun 2016, 11:14 pm
 :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 10 Jun 2016, 03:08 pm
Some shots of my Folsom 7297 amp. Didn't appreciate how dang big those caps were until I tried to fit them on the board... :lol: :duh:


(http://www.audiocircle.com/image.php?id=144628)

(http://www.audiocircle.com/image.php?id=144630)

(http://www.audiocircle.com/image.php?id=144629)

(http://www.audiocircle.com/image.php?id=144631)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 10 Jun 2016, 08:42 pm
Some shots of my Folsom 7297 amp. Didn't appreciate how dang big those caps were until I tried to fit them on the board... :lol: :duh:


(http://www.audiocircle.com/image.php?id=144628)

(http://www.audiocircle.com/image.php?id=144630)

(http://www.audiocircle.com/image.php?id=144629)

(http://www.audiocircle.com/image.php?id=144631)

Wow! Great work, that's a really nice looking build  :thumb: It makes mine look so ghetto  :cry:
What's up with the high end Jentzen caps, think they make a difference? Give it time to burn-in, it gets better with time. I never gave much credence to the theory of component burn-in except with speakers, but I think the Folsom amp really comes alive with some time on it. BTW, what's the rest of your nice looking system consist of?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 11 Jun 2016, 02:55 pm
Hi lacro; Thanks--And I love the way your build turned out. In fact it was your posted pics that got me over the hump to try again with a second amp board.

 Thanks also for the Tenma suggestion.  Although the attempt to replace the chip on the first board proved unsuccessful,  it made the process a lot easier.

I have no idea if the Jentzen caps make a difference, as I haven't heard another build. I have used them in the past for speakers, and liked them, so I figured what the heck...I am really liking the amp, tho... :thumb:

My mess...uhh, I mean my test setup, to see if I finally have a working amp, consists of a Nelson Pass B1 buffer (in the repurposed wooden wine box), a Schiit Audio multibit Bifrost, which is awesome, an Oppo (bdp-83, I think), and Exodus Audio Kepler speakers, which I can't say enough good things about. They sound amazing for a 1/2 cu. ft. Vented box.

I will continue to let the amp settle in, and let you know how that progresses...can't imagine improvement from here, as what I am currently hearing is very nice, but if it happens,  I'll take it... :green:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 11 Jun 2016, 04:24 pm
Reported to have great mids on up, which it does. The thing that surprised me most was the bass, which is also excellent.

Limits,

I thought the same thing with the bass. Compared to my ZKIT1 the bass extension was much better and having the extra power is a nice plus.

When I put the amp together I was also thinking about putting in different input caps, but decided to go with the BOM on the build. Maybe I will change them out later with some boutique type.

I'm still in the process of letting the Folsom break-in. I only have about 30 hours on it. The changes so far have been subtle but noticeable. The mid-range is opening up nicely, and seems to be the biggest change. 

This is the first amp I have had in about 11 years that does not use tubes and so far I'm happy with how it sounds, and the price is hard to beat.   
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 11 Jun 2016, 08:42 pm
Hi BRN;

My congratulations on your build--Wow; very nice--appearance worthy of the sound  :thumb: :thumb:

The Folsom 7297 amp to me sounds as 'tubey' as my tube amp (in the good way) without the hum. Oh, and was/is quite a bit cheaper, especially considering the re-tubing roller coaster :lol:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 12 Jun 2016, 06:39 pm
Hi All:

I have been running my amp, letting it settle in this weekend. Ran it for most of the day yesterday, and again this afternoon.

I noticed the D45H11G with the suggested slip-on heatsink from Mouser gets HOT, like 'burn your finger when you touch it hot'. The 7297 chip/heatsink is just warm.

Is this similar to what you all are seeing, or is this unusual?

Thanks; All else seems normal, and it sounds great (this is using the Folsom antipole, btw)...

limits
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 12 Jun 2016, 06:59 pm
Ugh...I think I answered my own question. I installed the D45H11G BACKWARDS!! :oops: :duh:

I will shut things down, and take a look at the datasheet, but what a dumb a$$...Geez...

Assuming I will need to fix this...

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 12 Jun 2016, 07:11 pm
Ops. If you're finding it too hard to get it back into the holes, you can mounted it on the bottom sort of like an SMD device.

Don't feel bad, all of us didn't notice in your pics.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 12 Jun 2016, 07:46 pm
Hi Jeremy; Can I do this now, or should I wait for the caps to discharge? Man, this build has been a humbling experience  :lol:

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 12 Jun 2016, 08:02 pm
Discharged is best, or it could blow up the transistor. You can check their voltage to see if they have.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 12 Jun 2016, 09:03 pm
 :oops: :oops: :oops: :oops:

Alrighty...fixed.

Surprised it worked before? :scratch:

It sounds the same, and don't think the finger burner is any cooler, but at least it is oriented correctly. Used my other board's transistor after I cut the leads to the reversed one too short... Feel like the court jester. Oh well, ultimately this sounds great. Humbling? Yep. Hopefully entertaining to you all (...at least I didnt do THAT...) ;-)

 :duh:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: snake69fast on 13 Jun 2016, 11:07 pm
What part number is the transformer from your build? Thank you!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 14 Jun 2016, 12:19 am
Hammond 185F16 but E and G can work as well.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: shadowlight on 14 Jun 2016, 05:38 pm
Is it better to get a G instead of E in case F is not available?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 14 Jun 2016, 06:15 pm
I would go with the highest letter available, yes. I prefer a robust PSU, but all of them will sound good.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: shadowlight on 18 Jun 2016, 01:09 am
Anyone interested in soldering the parts on the board for me?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 18 Jun 2016, 02:53 am
Anyone interested in soldering the parts on the board for me?

I'll do it for ya! Send me a PM.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: S Clark on 18 Jun 2016, 03:44 am
Thank goodness for Lacro.  I was thinking about volunteering, but I've already fried one 7297 chip and did my best to ruin a board.  Not sure I'm the guy to trust with someone else's project. 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: shadowlight on 18 Jun 2016, 08:14 pm
Lacro, S Clark,

I realized that I want to use the amp as my primary amp with either a Dodd Audio unity gain preamp or a 4P1L based preamp driving a Zu Audio Druid V so do not want to use my amateur soldering skills and screw it up.


I have couple of the original 5 dollar Chinese amps around which I will use to practice my soldering skills on  :lol:


Lacro, thanks for helping with the build.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: S Clark on 18 Jun 2016, 09:05 pm
It should work very well with your Dodd.  If you go back to the first post in this thread, the review I wrote was with it connected to one of the original Dodd battery preamps, and it was a nice match. 
It's really not difficult to build this amp, and the problems that I ran into were in trying to put it in too small of a case- shorting the chip and having to resolder several wires.  That said, you might note that I'm not the only one that's fried the chip on this amp. 
Mine hasn't been hooked up for a while, but with hot weather arriving in Texas, it's nearly time to put the tubes up until Oct.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 19 Jun 2016, 04:23 am
I had a mechanical noise coming from the amp that was caused by the power transformer. I did not think that I was going to have an issue when building the amp into such a solid chassis, but the noise was there. It was not a big deal since the amp is located in a cabinet, but I knew that I was going to have to take care of it. I took the advice Jeremy posted, about using rubber washer with the transfer, and I'm happy to report that the transformer is silent.

I'm really enjoying the amp. It has broken-in nicely, and has good controlled bass, smooth mids, and extended highs. I was not getting the extension from my tube amp that I get from the Folsom, and having the extra power helps as well. 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 21 Jun 2016, 09:22 pm
Finally got some time and began construction using Folsom's helpful illustrated and well written guidelines. I purchased a 4-40 tap for the heat sink mounting bolt from Lowes made by Irwin which quickly broke confirming similar reviews of it on the Lowes site . I used the insulating washers on both sides of the bolt mounting to isolate the chip from the heat sink metal.
Using my multimeter set to Ohms I get a reading of 1 with the probes on the chip tab and heat sink at all of the different ohm settings.
Is this correct ?
(http://www.audiocircle.com/image.php?id=145339)

(http://www.audiocircle.com/image.php?id=145340)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 21 Jun 2016, 09:27 pm
Hi KR500...if that is the reading you get when you touch the two probe tips together, then it is not correct (this would indicate you have continuity between the chip tab and the heatsink).

limits
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 21 Jun 2016, 10:14 pm
Hi , thanks for your post . I get a reading of zero when touching the 2 probe tips together
When touching 1 probe tip to the chip tab and 1 probe to the heat sink per the instruction I get a reading of 1
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 21 Jun 2016, 10:37 pm
That would indicate that the screw is touching the chip tab. It should be 1000ohm to infinite.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 21 Jun 2016, 11:26 pm
Or - the thermal grease used was electrically conductive?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 22 Jun 2016, 12:57 am
I guess that's possible.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 22 Jun 2016, 02:39 am
KR500,

Does your volt meter have a continuity tester? If so you can double check with that setting to see if there is a electrical connection.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 22 Jun 2016, 01:31 pm
Thank you for your help ,
I used the continuity check on the Multi Meter and get a reading of "1" ,which the MM manual states indicates an open circuit . This is what is desired ?
If I change one probe from the chip tab to the bolt itself I then get an audible sound from the meter and the reading changes to "0.00"
Using the 200K through 2000K Ohm setting with one probe on the chip tab and one probe on the heat sink I get a reading of "1" ( just to be clear, a number 1 on the left side of the display , not 1.0 , 1.1 , 0.1 or 0.01 )
I'm using Radio Shack thermal grease which I used successfully last year to replace a burnt out power chip on a Samson Amp (which is still working fine )
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 22 Jun 2016, 06:24 pm
If it indicates an open circuit you're fine.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 22 Jun 2016, 07:47 pm
okey-doke , thanks for confirming .
A dumb question I guess is if the heat sink dissipates heat and the chip is isolated by the mica and insulating washers from it is the heat transfer taking place by radiant transfer?
When I changed the power chip last year in a Samson amp it was bolted directly to the heat sink with only thermal grease between the 2 . It was a much larger chip
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 22 Jun 2016, 09:00 pm
The mica is electrically insulating, not thermally. It has about the same thermal properties as the chip. There are some higher performing versions other than mica, but they're very hard to source and wouldn't change much here.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 23 Jun 2016, 09:23 pm
for the amp board are there polarity issues on the provided BC337 chip or the TL431 regulator, or can they be installed in either direction ?
Also , the unmarked capacitor spot in front of the 470pF slot is for the 1uF cap, right ?
I see others pictured their boards showing a green cap there like the 1uF but just wanted to make sure since it isn't labeled

thanks
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 23 Jun 2016, 09:48 pm
You're correct on the little green cap. It's labeled just it got moved over a little  :duh:

And no you can't orient the TL431 and BC337 anyway you want - good god no. There's a very specific orientation correctly shown on the PCB board. Look at their datasheets, "polarity" doesn't even really apply.

Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 23 Jun 2016, 11:10 pm
Thanks Jeremy ,
Yes the orientation was hiding in plain sight with the little white outline for the 2 , I was so intent on reading numbers to match up I blew by the little outline. Better slow down and look more closely next time
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 29 Jun 2016, 10:24 pm
Hi all...Amp is sounding quite awesome...thanks, again Folsom!

So, I had this evil thought, and was hoping somebody would  stop me. Or not...how 'bout a felix-hammond transformer  combo in the shielded chamber of the amp case I previously built (a new one, of course http://www.surplussales.com/Cab-RacksHardware/encl_2.html). There is plenty of room in the case. It ain't pretty, but is roomy.

 Then the antipole, which would power (easily) both the Folsom 7297 board, and a Nelson Pass B1 buffer. The 19+/- VDC output from the antipole is about right for the B1. I love my buffer, but wonder how it would sound sans my crappy PC SMPS that it is currently using. And maybe put some fancy caps in it, too :-)

I think this would be a KILLER combo. And I have a spare B1 board and matched JFETs...

Jeremy, do you have any more antipole and amp boards?

...best Jim Carey voice 'Somebody stop me'  :P 8) 8) :green:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 29 Jun 2016, 11:10 pm
Yes I have some boards.

1. I can't tell you what will happen if you use the 7297 and B1 off the same power supply. It should work but because they're not isolated via the transformer there's a potential you'll have to fiddle with it. You could run a separate Antipole just for the B1 and choose smaller version of the transformer for size, weight, and $, that'll give a lower output that's safer for the B1 transistors.

2. If you use a "felix" you can use the same Bourne's CMC with it, but I probably wouldn't use caps on the side towards the transformer.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: snake69fast on 2 Jul 2016, 03:43 am
How about TDA7379? Any chance to be better than TDA7297?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 2 Jul 2016, 04:53 am
It's very different. It doesn't have balanced outputs is a real big difference. Could it sound good? Probably, but as good? Who knows... I wouldn't expect it to.

If someone starts talking real big about another chipamp maybe I'll start a path with it. I may have a 7293 in the works, as a much more powerful DIY option.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: snake69fast on 2 Jul 2016, 09:05 am
Speaking about balanced it is possible  an TDA7297 amplifier  with balanced inputs?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 2 Jul 2016, 04:39 pm
If you use transformer inputs, yes. They would convert the balanced into single ended once inside the amp. This way you get the benefits of the noise rejection. But there's no true balanced possible.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: moremoremore on 8 Jul 2016, 08:26 pm
I've got a theoretical question (or more) for you guys.  I bought two sets of amp/power boards from Folsom in anticipation of building an active bi-amped version of his 7297 using a miniDSP, which has worked well when I used a couple of cheap class D stereo amps.

But I'm wondering if I ought to cobble together an Econowave XO for my Large Advent Econowaves that use the original Advent woofers and Dayton polyimide compression drivers.  The reason for this about-face is lower parts cost and for simplification's sake.  Basically I'm wondering if 15 watts will be enough for the woofers for my not-so-demanding listening requirements.  Obviously 15 watts is more than plenty for the horns, but I think the Advent woofers are only about 89 dB/w/m sensitivity.  Anybody running a roughly equivalent setup?

Also, I have a Meanwell 24-volt 350-watt SMPS.  I've used it to power my miniDSP.  Will it work okay as the power source for the 7297 board?   :nono:  Pre-emptive no-no.  :lol:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 8 Jul 2016, 08:52 pm
The SMPS will work to power an amp.

How big is your room? In a small room the 7297 is plenty for 87db speakers, so 89db would be fine in a room that isn't too big.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: moremoremore on 8 Jul 2016, 11:44 pm
About 2500 cubic feet.  My little SMSL amps use TPA3118D2 chips, which put out about 20 watts per channel.

Hmm, I think you just made me focus on the essentials, and now I have the answer.   :duh:

 :thumb:

I'll probably experiment with using the Mean Well and see if in the end I Meant Well.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 9 Jul 2016, 01:48 am
That's probably small enough.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: S Clark on 11 Jul 2016, 02:03 am
It finally got too hot to run my Dodd tube amp, so my 7297 amp came out of storage for the summer.  I'd forgotten what great detail it has.  It's running 24V of battery power and sounding good.   :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 11 Jul 2016, 02:41 am
It finally got too hot to run my Dodd tube amp, so my 7297 amp came out of storage for the summer.  I'd forgotten what great detail it has.  It's running 24V of battery power and sounding good.   :thumb:

Are you running it with a single 24 volt battery or two 12's?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: S Clark on 11 Jul 2016, 02:46 am
Actually, it's a cobbled together set of two 5 AH's in parallel, connected to a 18 AH in series to get to 24. 
Right now I don't even have a charger on it- used the battery tender off my Goldwing.  I'll look at getting another 18AH asap. 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: nik.d on 27 Jul 2016, 02:33 pm
Here's another (almost) finished amp, need to install mica insulator (not wanted silicon one) and some feets that will have
double role here: They are also used for fastening sub-chassis carrying Alu bracket(s) / PCB boards / heatsink etc.
Enclosure is 220 x 100 x 300 mm WHD.

George

(http://www.audiocircle.com/image.php?id=147596)  (http://www.audiocircle.com/image.php?id=147597) 
(http://www.audiocircle.com/image.php?id=147598)  (http://www.audiocircle.com/image.php?id=147599) 
(http://www.audiocircle.com/image.php?id=147600)  (http://www.audiocircle.com/image.php?id=147601) 
(http://www.audiocircle.com/image.php?id=147602)  (http://www.audiocircle.com/image.php?id=147603)





 

Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 27 Jul 2016, 06:08 pm
Wow! that's superb work!!! :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: wushuliu on 27 Jul 2016, 06:48 pm
Here's another (almost) finished amp, need to install mica insulator (not wanted silicon one) and some feets that will have
double role here: They are also used for fastening sub-chassis carrying Alu bracket(s) / PCB boards / heatsink etc.
Enclosure is 220 x 100 x 300 mm WHD.

George


Impressive.

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 27 Jul 2016, 07:17 pm
Very nice indeed!

Is the AC shield grounded? It should be.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 27 Jul 2016, 07:28 pm
 :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 27 Jul 2016, 08:00 pm
Great job, George!! Enjoy!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Peter J on 28 Jul 2016, 03:06 pm
Here's another (almost) finished amp, need to install mica insulator (not wanted silicon one) and some feets that will have
double role here: They are also used for fastening sub-chassis carrying Alu bracket(s) / PCB boards / heatsink etc.
Enclosure is 220 x 100 x 300 mm WHD.

George

Wow, nicely done George. It appears to be really clean and well thought out...something to aspire to. You've set the bar way up there and it really appeals to the detail freak in me.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: nik.d on 28 Jul 2016, 04:56 pm
Thank you all. Special thanks for PeterJ who's marvelous and well documented speaker building is really, really inspiring.

@Folsom
Yes Jeremy, whole enclosure including 2 brackets is/are grounded - pic #4, green wire -> GND @ Neutrik powercon -> lower screw to enclosure's back plate. The only non grounded objects are heatsink
and this nickel plated brass tube for AC 230V wires. Removing heat shrink 'collars' (short, red one's) will make contact with both aluminum brackets. Re-thinking, adding a GND wire to tube beginning,
removing 'collars' and this way I have 1 point grounding, not via bottom plate / profiles. Hmm, not bad and very simple to apply... :)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 29 Jul 2016, 12:19 am
I think I remember reading somewhere that the gain for this amp is 32dB. Is that correct?

What is the input sensitivity?

Thanks,

Mike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 29 Jul 2016, 12:24 am
http://www.radiotechnika.hu/images/TDA7297.pdf
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 29 Jul 2016, 02:54 am
http://www.radiotechnika.hu/images/TDA7297.pdf

Thanks

I saw where the gain was listed but couldn't find, or didn't understand what I was looking at if I did, where the input sensitivity was listed.

Mike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 29 Jul 2016, 06:55 am
Gain is 32db. Input sensitivity I think is 1.1v
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mboxler on 29 Jul 2016, 03:19 pm
Gain is 32db. Input sensitivity I think is 1.1v

For my own education...

32db voltage gain equates to almost 40 times input voltage.
With 18 volt PS, the max output voltage would be 12.7 volts RMS.

12.7 / 40 = .3175 volts.  Seems like any input over .3175 volts RMS would clip the outputs.

Am I missing something?

Mike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 29 Jul 2016, 03:51 pm
For my own education...

32db voltage gain equates to almost 40 times input voltage.
With 18 volt PS, the max output voltage would be 12.7 volts RMS.

12.7 / 40 = .3175 volts.  Seems like any input over .3175 volts RMS would clip the outputs.

Am I missing something?

Mike

I thought input sensitivity was the minimum amount of voltage required at the RCA input jacks (from the source) needed to drive the amp to to full power and that this was something different than voltage from the power supply.

However, with my less than basic understanding of the physics behind electronics I could be way off base.

Mike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mboxler on 29 Jul 2016, 06:22 pm
I thought input sensitivity was the minimum amount of voltage required at the RCA input jacks (from the source) needed to drive the amp to to full power and that this was something different than voltage from the power supply.

However, with my less than basic understanding of the physics behind electronics I could be way off base.

Mike

The power supply voltage (and current) dictates the maximum output power.  These are internally bridged amps...1 amp for each + speaker out and 1 amp for each - speaker out.  Each speaker out can swing from 0 volts to the power supply voltage.  The signal to the - amp is inverted, so it will swing the exact opposite of the + amp.  With no signal, there is 1/2 PS voltage on each speaker out.  With an 18 volt PS, you should measure 9 volts between ground and either speaker out.

In reality, the amp will distort if the output signal is amplified too close to 18 volts peak to peak, but hopefully you get the picture.  If the signal is amplified more and 18 volts , the signal is clipped...a bad thing.

As you can see, a PS of less voltage (say a 12 volt battery) will lower the maximum output voltage, and therefore lower the maximum output power.

Mike

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 29 Jul 2016, 07:48 pm
The fact that it is bridged (balanced output) means that your calculations (if correct) need to be doubled for input sensitivity.

Also it's been tested to not clip a fair bit higher than 15w (24w into a 6ohm resistor).
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 30 Jul 2016, 06:08 pm
OK so two different issues. Instead of clipping, I'm looking at component matching.

Specifically whether a passive preamp (tube buffer) with 0 gain will work for switching and volume control with a source that has an output of 2V or whether an active preamp with additional gain and a higher output voltage will be needed.

I take it from Jeremy's response that with 32dB of gain and input sensitivity of 1.1V the passive tube buffer I currently use will also work with this amp.

Mike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 30 Jul 2016, 07:07 pm
It's not passive if power goes to it.

I'd recommend zero gain buffers for best match.

If it's truly passive (no tube or transistors) then 10kohm is the highest rated volume attenuator I would use.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 30 Jul 2016, 07:40 pm
It's not passive if power goes to it.

I'd recommend zero gain buffers for best match.

If it's truly passive (no tube or transistors) then 10kohm is the highest rated volume attenuator I would use.

Ok not passive then. It's a Dodd Audio Battery Powered Tube Buffer with 0 gain

Mike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 30 Jul 2016, 09:18 pm
Should work good. The attenuator impedance won't matter with the buffer following it.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 30 Jul 2016, 09:29 pm
Should work good. The attenuator impedance won't matter with the buffer following it.

Thanks

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 1 Aug 2016, 03:03 am
Someone emailed me, but they're address doesn't work when I try to reply. I assume it's someone on here that typed their address incorrectly. In case whomever it was, is wondering.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: slefley on 1 Aug 2016, 08:18 pm
Gain is 32db. Input sensitivity I think is 1.1v

Another question on input sensitivity - I am using a LampizatOr with volume control to drive my power amp directly.  Recently I tried a Fleawatt amp but because if it's high sensitivity I couldn't get the Lampi volume control above -50bB before the it got too loud.  Unfortunately the Lampi volume control works much better at the high end of it's range, so I couldn't use the Fleawatt in my system.  Do you expect that I'll have the same issue with the Folsom 7297? 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 1 Aug 2016, 08:44 pm
What are some good sources for wire? What different gauges would you recommend?

Thanks,

Mike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 1 Aug 2016, 08:51 pm
Another question on input sensitivity - I am using a LampizatOr with volume control to drive my power amp directly.  Recently I tried a Fleawatt amp but because if it's high sensitivity I couldn't get the Lampi volume control above -50bB before the it got too loud.  Unfortunately the Lampi volume control works much better at the high end of it's range, so I couldn't use the Fleawatt in my system.  Do you expect that I'll have the same issue with the Folsom 7297?

I don't know for sure, because for example a Golden Gate Lampizator didn't take issue with this. However the high output impedance was a problem, so the sound wasn't as good as it could be. You may want to try adding a resistor off of the RCA jacks to get some voltage drop, making the Lampizator have to increase volume.

I'd like to link to a buffer I'm using, that I think is an excellent buffer. But DIYaudio is down right now or something, so maybe later.

if I had the Lampizator spec's for your model, I'd know more.

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 1 Aug 2016, 09:15 pm
What are some good sources for wire? What different gauges would you recommend?

For signal wire, I got the 24 Neutech solid core from Dave at Zenwave. http://www.zenwaveaudio.com/diy-parts/
He got a few different options and is very helpful giving guidance. For power I got some mil spec Ptfe silver plated wire  from ApexJr: http://www.apexjr.com/wire.html

The ApexJr wire is super cheap so I got a whole bunch so I can play around with some different configurations.

Edit: To clarify, I used two runs of the 24 gauge twisted together. I'm sure there are many other excellent alternatives out there but this worked well for me. Since I'm also new at doing this, I have to admit it took a little practice to work with the 24 solid core wires since thin wire in general is a little bit fragile.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 1 Aug 2016, 11:10 pm
Yes, you can only move solid core around so much before it decided to break. My least favorite thing is how few companies offer two colors for different wires of the correct size. In fact I sort of hate their guts when it comes to that subject. More than once I've just had to use my multimeter because I ended up using the same color of wire, with no other option.

I believe in the build guide I included notes about wire sizes that work for the DIY7297. 20-30ga for signal, 20ga or 18ga solid works for output to binding posts, 18ga works nice for linking the boards together (16ga solid may fit the amp board input), Antipole can take up to 14ga solid at both ends.


Here's what I used (http://www.partsconnexion.com/wire_hookup_kimber_dtc23.html) in my buffer. And then for the power (http://www.partsconnexion.com/product7556.html) between rectifiers and buffer boards. You can see I repurposed an old enclosure. I might wire up the switch in the future, I don't know yet. In order to make it easier I might switch to a two pole switch though, in order to have twisted wires going to it.

(http://www.audiocircle.com/image.php?id=147845)



BTW if you want to get this buffer, here's the DIYaudio thread about it (http://www.diyaudio.com/forums/analog-line-level/251413-kuartlotron-keantokens-simple-error-correction-superbuffer-59.html#post4767276). Let's just say it's for advanced people, however.


Title: Re: Folsom's great little 7297 Chip Amp
Post by: walkern on 2 Aug 2016, 09:21 pm
Any thoughts or suggestions on layout for the transformer, antipole and amp board in a nice roomy enclosure like this?  I've put the various pieces where I think they will be easy to hook up... but not sure how sensitive the amp board or the antipole are to being near the transformer (which does have a nice steel plate between it and the boards)

(http://www.audiocircle.com/image.php?id=147892)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 2 Aug 2016, 09:46 pm
That's a pretty big chassis. If you didn't have the IEC connector already in the narrow compartment, the amp would fit there with room for speaker, and input connectors. The divider/bulkhead could be the heat sink for the chip or the HS could be added to the other side of the bulkhead like I did on the back of mine. The amp would be completely isolated from AC mains, transformer, and PS. Power switch on the back, and LED on the front. Or you could add one more divider/bulkhead in the large compartment.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 2 Aug 2016, 10:45 pm
That will work.

You could move the transformer to the front, face it's connections towards the back. Then put the antipole up against the dividing wall so its ground faces the transformer. The rest of the space... I guess you have enough room to add another transformer and dual rail power supplies, then use buffers too. Big project, but you've got room to fit everything I put in my preamp thing, inside of that chassis! The only minor issue is the buffer has to be turned on before the amp. I suppose that would be a more advanced thing to do.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 3 Aug 2016, 12:16 am
Jeremy,

Really enjoying the sound of the amp. I have no issues using an 10k eBay DACT to control the volume. I just purchased a phono preamp with a high output impedance that recommends at lest 15k input impedance, so I'm thinking that a buffer would be a good idea. I was looking at the Pass B1 or the Aikido cathode follower. I did not hear of the buffer you are using and wanted to know what you thought of it?

Thanks,
Brad
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 3 Aug 2016, 01:02 am
I think it works great. It doesn't use caps like the B1, so you can put on good parts for less than $40. Joachim Gerhard said it's the best he's used so far.

It could be combined with something like Salas regulators to bump performance a bit. With the 7297 and a very low impedance source, with a 10k DACT it was an upgrade.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 3 Aug 2016, 12:12 pm


(http://www.audiocircle.com/image.php?id=147845)



BTW if you want to get this buffer, here's the DIYaudio thread about it (http://www.diyaudio.com/forums/analog-line-level/251413-kuartlotron-keantokens-simple-error-correction-superbuffer-59.html#post4767276). Let's just say it's for advanced people, however.

Jeremy,
Is that 2 buffer boards stacked together (blue ones)? You say this is for advanced people, but with a good build guide would it be possible to be dumbed down so the the not so advanced could combine this buffer with our Folsom amps?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 3 Aug 2016, 03:13 pm
Hi walkern:

I am using the same enclosure as you. Pictures of my build are further up in this thread.

I have rubber washers on the bottom, between transformer (the Hammond 185F16) and enclosure bottom, and between the top nut and transformer legs, and I am getting a slight bit of hum (not through the speakers) from my amp.

I'm wondering if doing what Folsom suggests might be a better option?





You could move the transformer to the front, face it's connections towards the back. Then put the antipole up against the dividing wall so its ground faces the transformer. The rest of the space... I guess you have enough room to add another transformer and dual rail power supplies, then use buffers too. Big project, but you've got room to fit everything I put in my preamp thing, inside of that chassis! The only minor issue is the buffer has to be turned on before the amp. I suppose that would be a more advanced thing to do.

Folsom--If going this route, would you have the ground plane of the antipole board directly opposite the dividing wall from the transformer, or would putting the transformer on one end and the antipole with ground plane facing the dividing wall on the other end of the enclosure be best?

Best of luck on your build  :thumb:
limits

Title: Re: Folsom's great little 7297 Chip Amp
Post by: walkern on 3 Aug 2016, 03:37 pm
Thanks for the feedback and suggestions Lacro and Folsom and Limits.   I thought of putting the amp board in the narrow area (where the transformer is in the photo) but hooking it up to RCA inputs and binding posts (for outputs) would be a real space challenge there.  And thanks too to Limits for your suggestion about where to get the enclosure for not much $.  I was gonna use a big cigar box, or maybe two with 1 box for the transformer and Antipole, and a separate little guy for the amp board.  This one seems nice 'cause it's roomy and steel, which should offer some noise rejection/blocking.  I'm awaiting my Furutech IEC connector (what you see in the photo is the on/off switch), and a little run of wire (thanks SonicCraft) and I'll be getting everything hooked up shortly. 

Neil
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 3 Aug 2016, 05:08 pm
Jeremy,
Is that 2 buffer boards stacked together (blue ones)? You say this is for advanced people, but with a good build guide would it be possible to be dumbed down so the the not so advanced could combine this buffer with our Folsom amps?

Keantoken is selling them, they're his design. I can probably come up with a small guide that'll help avoid problems, but you unless someone wants to pay to have rectification boards printed, then you may be on your own for the power supply area. My boards are not meant just for this project, and have a lot of holes that will be confusing, so new ones would have to be made and paid for up front. I could use DirtyPCB so they'd be fairly cheap, but maybe not pretty. *Yes I have two stacked, and I'm using an eBay DACT 10k in front of them.


Folsom--If going this route, would you have the ground plane of the antipole board directly opposite the dividing wall from the transformer, or would putting the transformer on one end and the antipole with ground plane facing the dividing wall on the other end of the enclosure be best?

Best of luck on your build  :thumb:
limits

I'm not certain, but my guess is blocking the transformer is probably the most useful. Lacro's suggestion is a good one too.

As far as hum, that's the downside to these transformers that block a lot of RF. I've even put dynamat around them in the enclosure to help. If I could find someone other than Hammond who had some in stock I'd probably go with them instead, as they'd probably make less noise. Might need rubber where the bolt makes contact to the chassis, too, with a washer. That way you've got three of them.

Thanks for the feedback and suggestions Lacro and Folsom and Limits.   I thought of putting the amp board in the narrow area (where the transformer is in the photo) but hooking it up to RCA inputs and binding posts (for outputs) would be a real space challenge there.

Neil

Work within your comfort. Obviously Larco is a magician so don't feel absolutely obligated to live up to his build. But it's not Larco's first build either I don't think!



Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 4 Aug 2016, 08:37 pm
As far as hum, that's the downside to these transformers that block a lot of RF. I've even put dynamat around them in the enclosure to help. If I could find someone other than Hammond who had some in stock I'd probably go with them instead, as they'd probably make less noise. Might need rubber where the bolt makes contact to the chassis, too, with a washer. That way you've got three of them.

I used 2 rubber washers for each screw and it was very affective at removing the transformer hum I had without the washers.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Captainhemo on 10 Aug 2016, 03:26 pm

I believe in the build guide I included notes about wire sizes that work for the DIY7297. 20-30ga for signal, 20ga or 18ga solid works for output to binding posts, 18ga works nice for linking the boards together (16ga solid may fit the amp board input), Antipole can take up to 14ga solid at both ends.


Was it ever determined if  solid core 16 ga would fit through the amp board (both speakaer outputs and  power inputs)? I don't have a board sitting in front o me ......

jay
Title: Re: Folsom's great little 7297 Chip Amp
Post by: walkern on 10 Aug 2016, 06:01 pm
I used 16 ga solid (on one leg)  from the Antipole to the amp board without any issue, but I'm not sure about the speaker connections on the amp board.  I used 18 gauge stranded, and it fit, so I'm thinking 16 solid might.  Hopefully Folsom will know for sure.

Also a quick note to constructors: just finished my amp (sound is very promising, and it's just started to break in; had no issues with assembly or instructions), however you MUST use rubber washers between the transformer and the chassis.  I tried my amp (testing to make sure everything was correct with voltages etc) before hooking it up in my system, and it had no hum what so ever just plugged into a wall socket and nothing else hooked up to it.  As soon as I got it installed in my system, got the dreaded mechanical transformer hum and had to disassemble and install rubber washers as described by several posters.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 10 Aug 2016, 06:07 pm
Yes 16ga solid will work in place of 18ga stranded.

The hum really is annoying, I know. If Mouser had another transformer that could given the same level of performance without it, I'd change the BOM. But right now the only other choice I think I'd make is from somewhere totally different, overseas.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Captainhemo on 10 Aug 2016, 06:23 pm
Thanks fellas   :beer:

jay
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 10 Aug 2016, 08:40 pm
Yes 16ga solid will work in place of 18ga stranded.

The hum really is annoying, I know. If Mouser had another transformer that could given the same level of performance without it, I'd change the BOM. But right now the only other choice I think I'd make is from somewhere totally different, overseas.

Jeremy,

What transformer options would you recommend, both as direct replacement and as upgrade?

I'm starting to pull the parts together to build my first one. I don't mind waiting for an overseas shipment and/or paying more if it results in better performance.

Thanks,


Mike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 10 Aug 2016, 08:43 pm
I used 16 ga solid (on one leg)  from the Antipole to the amp board without any issue, but I'm not sure about the speaker connections on the amp board.  I used 18 gauge stranded, and it fit, so I'm thinking 16 solid might.  Hopefully Folsom will know for sure.

Also a quick note to constructors: just finished my amp (sound is very promising, and it's just started to break in; had no issues with assembly or instructions), however you MUST use rubber washers between the transformer and the chassis.  I tried my amp (testing to make sure everything was correct with voltages etc) before hooking it up in my system, and it had no hum what so ever just plugged into a wall socket and nothing else hooked up to it.  As soon as I got it installed in my system, got the dreaded mechanical transformer hum and had to disassemble and install rubber washers as described by several posters.

Is there any particular type of rubber washer to use i.e. particular durometer, type of compound, thickness, etc.?

Thanks,

Mike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 10 Aug 2016, 08:47 pm
I've been meaning to try James Transformer OA core. They have the most sound principles.; including a shield I've chatted briefly with them, and they can offer exactly what I want. 150/200va is enough juice, 120v primary, 16v secondary.

But I haven't done a direct ear comparison yet. The shield should give benefits like the dual bobbin does, but I want to confirm that.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 10 Aug 2016, 08:56 pm
I've been meaning to try James Transformer OA core. They have the most sound principles.; including a shield I've chatted briefly with them, and they can offer exactly what I want. 150/200va is enough juice, 120v primary, 16v secondary.

But I haven't done a direct ear comparison yet. The shield should give benefits like the dual bobbin does, but I want to confirm that.

What's the max secondary voltage of the transformer that should be used? I would like to be able to use the Antipole PS with the TDA 7297, and some class D amps (TPA3116/3118) amps. 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 10 Aug 2016, 09:40 pm
The Antipole rectified voltage should not exceed 45v, which is about 30v AC from transformer.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: shadowlight on 10 Aug 2016, 10:20 pm
I like to thank Larry (Lacro) for building my amp for me.  I have not had a chance to listen to it yet (life getting in the way :duh: ).  Here are some pictures of the build.


(http://i1051.photobucket.com/albums/s428/dvaidya/Folsom%20Amp/IMGP0591%202_zpsw04ltdsb.jpg) (http://s1051.photobucket.com/user/dvaidya/media/Folsom%20Amp/IMGP0591%202_zpsw04ltdsb.jpg.html)


(http://i1051.photobucket.com/albums/s428/dvaidya/Folsom%20Amp/IMGP0591%202_zpsw04ltdsb.jpg) (http://s1051.photobucket.com/user/dvaidya/media/Folsom%20Amp/IMGP0591%202_zpsw04ltdsb.jpg.html)


(http://i1051.photobucket.com/albums/s428/dvaidya/Folsom%20Amp/IMGP0594_zpsncfjqnl3.jpg) (http://s1051.photobucket.com/user/dvaidya/media/Folsom%20Amp/IMGP0594_zpsncfjqnl3.jpg.html)


(http://i1051.photobucket.com/albums/s428/dvaidya/Folsom%20Amp/IMGP0578_zpsn7qte83l.jpg) (http://s1051.photobucket.com/user/dvaidya/media/Folsom%20Amp/IMGP0578_zpsn7qte83l.jpg.html)


(http://i1051.photobucket.com/albums/s428/dvaidya/Folsom%20Amp/IMGP0586%202_zps4r79val3.jpg) (http://s1051.photobucket.com/user/dvaidya/media/Folsom%20Amp/IMGP0586%202_zps4r79val3.jpg.html)


I currently have a Astron and a Dell laptop power brick.  Need to order power connector for Astron and transformer/case for the Antipole.  Until then can I use a power strip with the laptop brick (19.5v @ 6A) with out impacting the amp?



Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 10 Aug 2016, 10:30 pm
 :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 11 Aug 2016, 12:24 am
As long as the laptop power brick can maintain 19.5v it'll work. So power it up and play some music loud and watch the voltage with a volt meter, if it stays above 19v easily, it's ok. With linear power supplies you can watch the voltage drop, so they need a much larger buffer over 19v. The recommend transformer lands it around 24v and does a great job of not going too low during big loads.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 11 Aug 2016, 12:45 am
I'm using an Astron with my amp, and it works really well in my set-up. I rarely play very loud so the lower voltage still works fine in my system, plus it sounded better than a laptop power brick.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 11 Aug 2016, 12:57 pm
As long as the laptop power brick can maintain 19.5v it'll work. So power it up and play some music loud and watch the voltage with a volt meter, if it stays above 19v easily, it's ok. With linear power supplies you can watch the voltage drop, so they need a much larger buffer over 19v. The recommend transformer lands it around 24v and does a great job of not going too low during big loads.


Jeremy, thanks for that description...
So to clarify in my mind: The Transformers secondary delivers 16V AC; it's rectified to 24V DC by the Antipole PS, and is regulated to 17.8-18V on the amp board. Is that correct? So what is happening when the DC voltage delivered to the amp is lower than 19.5V continuous such as when someone is using the 13.8V Astron linear PS? Does that take the regulator and 12 Oscon capacitor bank out of the circuit, and power the chip with the 13.8V?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 11 Aug 2016, 03:10 pm
When it's lower the amp sees very significantly reduced power. The KMR only turns on as an "infinite capacitor" once it hits sufficient voltage. When I tried it, the bass wasn't that great at all volumes.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: shadowlight on 11 Aug 2016, 08:47 pm
I rarely play loud and the speakers that I have are the Zu Druid V @ 101db efficient so I think I will be good for the couple of weeks that it will take me to get the antipole up and running.  I already have the transformer, just need to find the case for it and build it out.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 12 Aug 2016, 05:00 pm
This may be a dumb question but I'll ask it anyway. If the Antipole, or other PS, supplies 24VDC to the amp board, can you connect a 24V battery directly to the amp board without using the Antipole?

If so, what are the pros and cons of connecting the battery direct to the amp vs going through the Antipole?

OK so that was two questions...

Mike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: S Clark on 12 Aug 2016, 05:04 pm
Yes you can.  That's the way I've been running mine all summer, and so far, I'm happy with the results. 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 12 Aug 2016, 05:06 pm
S Clark - what battery are you using?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: S Clark on 12 Aug 2016, 05:10 pm
Twin 12V 18AH connected in series.  They are about $35 each from Amazon w free shipping. 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 12 Aug 2016, 05:24 pm
Thanks for the info. How long does the charge last for?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Captainhemo on 12 Aug 2016, 05:32 pm
Twin 12V 18AH connected in series.  They are about $35 each from Amazon w free shipping.

Scott, did you get a charger  for your batteries yet, seem to recall yo uwere using your bike  "charger"
I've already got the 75ah  single 12v batter  and my C-TEK but it won't charge  2 of them  wired in  series, I don't want to have to re wire in parallel every time I want to cahrge

Been thinking of a setup that I could run my Dodd pre  at 12v, the folsom at 24v, and have a simple charging solutioin , a fw ideas but not sure any would actually work  :dunno:

jay
Title: Re: Folsom's great little 7297 Chip Amp
Post by: S Clark on 12 Aug 2016, 06:40 pm
No, I'm still using a motorcycle tender with everything put together with alligator patch cords.  It only takes me a couple of seconds to redo the wiring to charge, or to put it back again to play.  It's a little bit of a pain, but not bad.  When the Texas heat breaks, the Folsom amp will go back in the closet and the Dodd tubes come out. 
When I do finally get around to it, I've got a 24v charger for a DAC that Gary D built for me years ago... and it hasn't worked in a while.  I need to adapt it to the Folsom amp batteries.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: S Clark on 12 Aug 2016, 06:44 pm
Thanks for the info. How long does the charge last for?
I don't know... it's never run down to the point of any noticeable degradation. I'd say you are probably good for at least a long day of listening- 12 hours???
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 12 Aug 2016, 08:02 pm
Radioshack sells alligator test leads. I use them for a lot of things but I got mine somewhere I forget a bit cheaper.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 13 Aug 2016, 12:52 pm
my amp project is at a standstill due to  not finding an affordable case .
I did look at the C+C one from Surplus Sales but it didn't seem tall enough to accommodate the height of the transformer .
Since other builders appear to be using that case I was curious how they are dealing with that issue ?
I've scoured the area and online for a case my budget can handle but nothing so far.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: walkern on 13 Aug 2016, 02:41 pm
You are correct that the height of the Surplus Sales case is not quite tall enough for the transformer to be mounted upright to the bottom of the chassis.  You can just force the top on, at which time it buzzes like a fancy sex toy (hums like it completely forgot all the words?).  I've taken to just fitting the top mounted up about 3/4 of an inch by resting on the set screws instead of inserting the set screws through the designated holes in the sides of the top.  It's pretty sturdy that way, doesn't buzz or hum, but there's a 3/4" gap at the front and back which looks completely stupid (but does provide ventilation).  Needless to say, not an ideal scenario.  I suspect it MAY be possible to mount the transformer to the steel divider (sideways) and it MAY fit that way?  I was so done with fiddling with mine after I got everything hooked up (and I'm so thrilled with the sound) that I haven't gone back to investigate this option... but I may when I'm feeling more ambitious.
Needless to say, if anyone knows of another C & C chassis that will accommodate the amp, I too would be interested.  I have used cigar boxes in the past for amps with no apparent downside (no shielding issues), but the trick with those is finding one big enough to fit all the components into it.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: nik.d on 13 Aug 2016, 03:42 pm
@KR500 and all (future) builders as well:

There's no particular reason this amp (or any other) has to be built with 'Hammond' or any other 'classical', 'EI' type of transformer. Toroidal transformers even offer
several benefits over 'EI' trafo, like lower magnetic & heat dissipation, mass, dimensions etc. If you are just starting your build, do not limit yourself by strictly following
every component. Toroidal transformer would be just fine and much easier to pack into planned enclosure. What really counts as 'advantage' of classical 'EI' trafo is
somewhat 'softer' start, meaning less stress to components after it (diodes, capacitors etc.) at startup.

George
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 13 Aug 2016, 03:59 pm
Scott, did you get a charger  for your batteries yet, seem to recall yo uwere using your bike  "charger"
I've already got the 75ah  single 12v batter  and my C-TEK but it won't charge  2 of them  wired in  series, I don't want to have to re wire in parallel every time I want to cahrge

Been thinking of a setup that I could run my Dodd pre  at 12v, the folsom at 24v, and have a simple charging solutioin , a fw ideas but not sure any would actually work  :dunno:

jay

Jay,

Let me know if you come up with something for this since it's the same setup I have.

Mike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Captainhemo on 13 Aug 2016, 04:19 pm
Jay,

Let me know if you come up with something for this since it's the same setup I have.

Mike

Yup, will do Mike

jay
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 13 Aug 2016, 04:51 pm
This 15v + 15v unit (http://shop.plitron.com/shopdisplayproducts.asp?id=26&cat=Power+Level+%2D+120VA) will work, first on the list. It may take several weeks to get it though. Plus it cost more. It's the closest thing to domestic as I know of at the moment. Antek is sold out and doesn't make to order I don't think.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 13 Aug 2016, 06:00 pm
I'm looking over the TDA7297 board to make sure I understand what goes where and have a few questions.


(http://www.audiocircle.com/image.php?id=148395)


Mike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 13 Aug 2016, 06:25 pm
You don't need to use the places you indicated.

LED? Well you'd have to bring the voltage down since they're typically only around 1-2v capable. I'd run an LED off of the Antipole's AUX outputs, to keep the noise away from the Amp board.

Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 13 Aug 2016, 06:48 pm
You don't need to use the places you indicated.

LED? Well you'd have to bring the voltage down since they're typically only around 1-2v capable. I'd run an LED off of the Antipole's AUX outputs, to keep the noise away from the Amp board.

Jeremy,

Thanks

Which ones are the Aux outputs on the Antipole?

Mike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 13 Aug 2016, 06:49 pm
They're tiny, right behind the main outputs.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 13 Aug 2016, 06:57 pm
OK, Thanks
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 13 Aug 2016, 07:16 pm
The Amp Camp Amps use Keratherm Transistor Insulators in place of mica and thermal paste. Will these work in this application?

http://diyaudiostore.com/products/keratherm-transistor-insulators

Mike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 13 Aug 2016, 07:37 pm
Yes. Careful not to crush them.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 13 Aug 2016, 07:57 pm
Yes. Careful not to crush them.

Thanks
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 13 Aug 2016, 09:19 pm
(http://www.audiocircle.com/image.php?id=148395)

Mike, Looks like you will be making sound (or smoke :icon_twisted:) pretty soon.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 13 Aug 2016, 10:16 pm
Mike, Looks like you will be making sound (or smoke :icon_twisted:) pretty soon.

Larry,

Getting there. A few more things to order in first. I'm going to hold off on the chassis until I can lay the parts out and see what size I want.

I'm seriously thinking of building the first one in separate chassis with female Neutrik PowerCon connectors in the chassis and an interconnect with male PowerCon connectors to connect them.

Mike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Peter J on 14 Aug 2016, 12:45 am
Would these cases work OK? I just happen to have two...

Utility knife there for size reference
(http://www.audiocircle.com/image.php?id=148450)


(http://www.audiocircle.com/image.php?id=148451)



Title: Re: Folsom's great little 7297 Chip Amp
Post by: shadowlight on 14 Aug 2016, 09:56 pm
Peter J,
Which cases are those?  How high are those?  If they are around 2.5 or 3" and are looking to sell let me know.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 15 Aug 2016, 12:07 am
When it comes to on/off switches what parameters do I need to look for? Voltage seems pretty straight forward at 110-125V but what about amperage?

If I go with a lighted switch what voltage for the light? Would I still connect it to the aux position on the Antipole board?

If I put the amp and Antipole in separate boxes does the caution about not connecting the Antipole to the amp board with charged caps still hold? If so how do I work around it since I won't be able to discharge the caps inside the Antipole chassis?

Thanks,

Mike

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 15 Aug 2016, 12:26 am
The switch can be just about anything, the amp operates under 1A at 120v. Few switches are rated under 5A even. I often use ones that are larger because I don't like the feel of tiny switches.

Yes you could connect the light to the AUX on the antipole if it fits the correct voltages the light needs. I don't know what light and what voltage it says, so I can't really answer that question.

You connect the two boxes before you ever turn it on, or discharge the capacitors on the Antipole before you connect it to the amp box. There's a place on the Antipole for a discharge resistor, but it might take a moment before they do. A 10k resistor would work.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 15 Aug 2016, 12:39 am
The switch can be just about anything, the amp operates under 1A at 120v. Few switches are rated under 5A even. I often use ones that are larger because I don't like the feel of tiny switches.

Yes you could connect the light to the AUX on the antipole if it fits the correct voltages the light needs. I don't know what light and what voltage it says, so I can't really answer that question.

You connect the two boxes before you ever turn it on, or discharge the capacitors on the Antipole before you connect it to the amp box. There's a place on the Antipole for a discharge resistor, but it might take a moment before they do. A 10k resistor would work.

I was thinking about an on/off switch on the Antipole chassis, not necessarily on the amp chassis. Should I put a switch on both?

What is the voltage off the aux position on the Antipole? Maybe I can find a lighted switch to match.

With separate chassis the units will be disconnected and reconnected anytime the amp is switched out or the system reconfigured so having some way to discharge the caps in the Antipole would be a real help unless putting a second switch on the amp chassis would accomplish the desired results.

Where would the bleeder resistor go on the Antipole board?

Thanks

Mike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 15 Aug 2016, 12:55 am
Mike,

You could use a switch like this one from eBay:

http://m.ebay.com/itm/16mm-12V-Latching-Push-Button-Power-Switch-Aluminum-Metal-Blue-LED-Waterproof-/141700412231?nav=WATCHING_ACTIVE

You would wire the the section rated at 250v 3 amps to the AC before the power transformer and the LED to the aux of the Antipole. You will need to pad the LED with a resistor since the Antipole aux puts out around 24v DC and the LED is only rated for 12v DC.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 15 Aug 2016, 02:07 am
Mike,

You could use a switch like this one from eBay:

http://m.ebay.com/itm/16mm-12V-Latching-Push-Button-Power-Switch-Aluminum-Metal-Blue-LED-Waterproof-/141700412231?nav=WATCHING_ACTIVE

You would wire the the section rated at 250v 3 amps to the AC before the power transformer and the LED to the aux of the Antipole. You will need to pad the LED with a resistor since the Antipole aux puts out around 24v DC and the LED is only rated for 12v DC.

Isn't 3A a little light duty?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 15 Aug 2016, 02:52 am
Not for this application. Let's say the amp uses 4.1a full load, times 25v (actually 17.8v). You've got about 100w. 100w/120v = .84A.

Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 15 Aug 2016, 02:37 pm
Hi KR500--The case I linked earlier from Surplus Sales is tall enough to fit the Hammond 185F16 transformer. It is pretty close, but it fits. I have a thin mat and rubber shoulder washers and washers between the bottom of the enclosure and transformer, and a thin foam pad sandwiched between the top of the transformer and the top cover of the enclosure.

I ended up using the captive power cord and the steel heatsink (for the 7297 chip) that came with the enclosure. I removed everything else.

Good luck with your build!  :thumb:

limits
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 18 Aug 2016, 08:37 pm
thanks for your feedback on the case limits, I ordered one today.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 18 Aug 2016, 08:47 pm
Jeremy,

You've said a 10k Ohm resistor is OK for discharging the caps in the power supply.

Is more than 10K better?

Does it matter if it is a 1W, 10W or 12W resistor?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 18 Aug 2016, 09:02 pm
1w is fine. Higher just means it's slower. It wont hurt anything.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 18 Aug 2016, 09:19 pm
Hi KR500--Good deal...nothing fancy, but it worked well for me. Best of luck on your build. Despite my (self imposed) issues, I had a lot of fun building it, and am loving how well it has settled in--sounds awesome!

 :thumb:
limits
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 18 Aug 2016, 09:30 pm
Regarding the transformer, I used the Hammond 185F16 part. I noticed the 185G16 is another quarter inch taller, which would be a deal breaker in my enclosure. I wonder if this was the issue walkern ran into?...

limits
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 18 Aug 2016, 09:33 pm
1w is fine. Higher just means it's slower. It wont hurt anything.

Thanks
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 19 Aug 2016, 01:20 pm
Regarding the transformer, I used the Hammond 185F16 part
Yes , just checked and that is the same one I have . It is 3 and 3/8 inches tall and 4.25 pounds
Title: Re: Folsom's great little 7297 Chip Amp
Post by: walkern on 19 Aug 2016, 02:29 pm
I have the 185F16 transformer, and it WILL fit in the chassis.  I used fairly thick rubber washers under the mounting tabs, and then added a layer of rubber damping under the transformer itself, and that bumped it up to a height where the top of the transformer was touching the top of the chassis.  I went back in and removed the layer of rubber damping under the transformer, and got thinner rubber washers for the mounting tabs and re-mounted the whole thing with a thin layer of rubber damping on the top (last night), and now it is (a) not humming like it forgot the words, and (2) is not making the top of the chassis buzz.  Whew!   

So, go ahead and order up the cheap chassis if you like...(it comes stuffed with stuff that you need to gut, so it will require some effort on your part, and it will have some extra holes in the back and bottom) and know for sure that the transformer can be mounted in a fashion where it isn't making any audible noise.  While I was in there I checked to see if the transformer could be mounted to the steel chassis divider (thereafter sitting sideways), and it will fit that way too (although without much room to spare... maybe 1/4 inch).

Sorry to have been reporting an issue that was my fault and not an actual problem with the chassis or transformer.

Neil
Title: Re: Folsom's great little 7297 Chip Amp
Post by: skrstc on 22 Aug 2016, 08:29 pm
Folsom thanks for your great little 7297 Chip Amp.
(http://www.audiocircle.com/image.php?id=148931)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 22 Aug 2016, 08:48 pm
Yes you could connect the light to the AUX on the antipole if it fits the correct voltages the light needs. I don't know what light and what voltage it says, so I can't really answer that question.

The light is 12VDC

You connect the two boxes before you ever turn it on, or discharge the capacitors on the Antipole before you connect it to the amp box. There's a place on the Antipole for a discharge resistor, but it might take a moment before they do. A 10k resistor would work.

Where does the discharge resistor go?

Would adding a 24VDC On/Off switch to the amp section be a viable alternative to the discharge resistor or would doing both, discharge resistor in the PS housing and 24VDC On/Off switce in the amp housing, be better?

Mike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: S Clark on 24 Aug 2016, 03:45 pm
I've been very please with the sound of batteries, until last night.  I don't know why, but when I connected power, my amp blew up... yep, both my 220 uF caps swelled and blew in seconds and all the magic smoke is now gone. :cry: :cry:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 24 Aug 2016, 04:56 pm
Mike, it goes near the PSU caps where there's a symbol for a resistor. I wouldn't add a switch.

Scott that's terrible, did you reverse the polarity on accident? Generally that or severe over voltage can make caps explode. I doubt it was severe over voltage...
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 24 Aug 2016, 05:54 pm
The light is 12VDC

Mike, I assume you mean it's an LED?  Do you have any other specs or a link to the light (LED), and does it come apart?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: S Clark on 24 Aug 2016, 07:41 pm
Mike, it goes near the PSU caps where there's a symbol for a resistor. I wouldn't add a switch.

Scott that's terrible, did you reverse the polarity on accident? Generally that or severe over voltage can make caps explode. I doubt it was severe over voltage...
Almost certainly.  It was late, I was tired, ... But now I get to start over and upgrade parts!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 25 Aug 2016, 03:22 am
Mike, it goes near the PSU caps where there's a symbol for a resistor. I wouldn't add a switch.

Jeremy,

Thanks

Mike, I assume you mean it's an LED?  Do you have any other specs or a link to the light (LED), and does it come apart?

Larry,

The light is built into the rocker switch, I guess it is an LED.

Almost certainly.  It was late, I was tired, ... But now I get to start over and upgrade parts!

That's one way to look at it? Like the saying goes... "The difference between an ordeal and an adventure is your attitude"  :thumb:

Mike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 25 Aug 2016, 04:35 am
Mike some switches run on 12v, some have resistors in them for 120v. Here's one (https://www.radioshack.com/collections/maker-parts-kits/products/spst-125v-illuminated-switch?variant=5717498117) that doesn't require you to mess around dropping the voltage to 12v. It's my go to for projects that don't have to be overly pretty.

Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 25 Aug 2016, 04:59 am
Mike some switches run on 12v, some have resistors in them for 120v. Here's one (https://www.radioshack.com/collections/maker-parts-kits/products/spst-125v-illuminated-switch?variant=5717498117) that doesn't require you to mess around dropping the voltage to 12v. It's my go to for projects that don't have to be overly pretty.

Jeremy,

Thanks. I thought Radio Shack was out of business

Mike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 25 Aug 2016, 05:15 am
Lots of local stores closed, but no, they are not online or locally to me (yet).
Title: Re: Folsom's great little 7297 Chip Amp
Post by: poseidonsvoice on 25 Aug 2016, 11:58 am
Quote
Founded in 1921, at its peak in 1999, it operated stores in the United States, Mexico, United Kingdom, Australia, and Canada. On February 5, 2015, the company filed for Chapter 11 protection under United States bankruptcy law after 11 consecutive quarterly losses.[4][5] By then it was operating only in the United States and Mexico. On March 31, 2015, the United States Bankruptcy Court for the Northern District of Texas approved a $160 million offer by General Wireless, which gained ownership of 1,743 RadioShack locations, and immediately leased them to Sprint

More info @ Wikipedia.

Best,
Anand.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 25 Aug 2016, 02:09 pm
Larry,

The light is built into the rocker switch, I guess it is an LED.
Mike

Mike, You should probably get a switch like Jeremy suggests, or use a separate switch, and LED as I did. That way you switch the AC mains, and pull LED power from the 24V output of the PS. You could have the switch on the back, and the LED on the front panel.

You can use this calculator to find the correct resistor:
http://led.linear1.org/1led.wiz

 I used this LED:
http://www.digikey.com/product-search/en/optoelectronics/led-indication-discrete/524729?k=p563-nd

 and this resistor:
 http://www.digikey.com/product-detail/en/vishay-bc-components/PR01000101501JR500/PPC1.5KW-1CT-ND/597203

(http://i.imgur.com/wmq52Vc.jpg?3)

(http://i.imgur.com/wkRxXRw.jpg?1)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 25 Aug 2016, 03:03 pm
I received my case from Surplus Sales and took out the insides ,saving all bolts washers etc and tossed the circuit boards . I popped the plastic legend for the LED functions off the front panel which will be the access for the front panel switch and DACT . Probably will spray paint the plastic cover to cover the industrial brown look of it .Steel wooled off some type of corrosion from something on the divider panel seam .
Home Depot has bags of 3/16" and 1/4" rubber washers so I grabbed one of each . I thought about trying to mount the transformer sideways to the divider panel to save a tad of space, but it's pretty heavy iron balancing on those brackets, so I'm staying upright with installation of it. The Antipole board will be mounted on the divider panel in the larger compartment.
There is a nice paddle SPST toggle switch ( Digi-Key 679-1246 ) in my parts drawer marked 15 amp 125 V, so I filed out one of the 4 LED cutouts on the front panel a little and the switch fits in perfectly. I'll run an LED to the adjacent hole. Thank you Lacro for posting the illustration for us in the previous post on the wiring of this . I will use the 3rd original LED hole for the 10K DACT pot and then have the remaining hole available if I add a buffer or something in the future.
I'm going to mount the reccommended heat sink from Heatsink USA inside and will drill vent holes for it top and bottom in the case. Now I just have to decide if I should use the existing power cord or go with a Furutech IEC . Convenience or upgrade ? I would have to use an insulated adaptor to get the power wire to the on/off switch to reach the front panel .
Title: Re: Folsom's great little 7297 Chip Amp
Post by: walkern on 25 Aug 2016, 04:49 pm
I mounted the amp board with the heatsink right next to the back center of the chassis, and drilled lots of spaced out holes in the back of the chassis and the under side immediately below the heatsink (so no holes in the top).  This has been more than sufficient cooling / ventilation for the amp/heatsink.  Just saying you may not need to drill holes in the top.
And I used a Furutech IEC AC inlet rather than the stock AC cord that came with the chassis, and I'm very pleased with the result.  Don't know how good that AC cord is that comes with the chassis.

N
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 26 Aug 2016, 03:00 am
More info @ Wikipedia.

Best,
Anand.
Lots of local stores closed, but no, they are not online or locally to me (yet).

Thanks. The store close to me closed last year.

Mike, You should probably get a switch like Jeremy suggests, or use a separate switch, and LED as I did. That way you switch the AC mains, and pull LED power from the 24V output of the PS. You could have the switch on the back, and the LED on the front panel.

You can use this calculator to find the correct resistor:
http://led.linear1.org/1led.wiz

 I used this LED:
http://www.digikey.com/product-search/en/optoelectronics/led-indication-discrete/524729?k=p563-nd

 and this resistor:
 http://www.digikey.com/product-detail/en/vishay-bc-components/PR01000101501JR500/PPC1.5KW-1CT-ND/597203

(http://i.imgur.com/wmq52Vc.jpg?3)

(http://i.imgur.com/wkRxXRw.jpg?1)

Larry,

Thanks. I have two different red LEDs on hand. One says it is 1.7Vdc-2.2Vdc @ 15mA-25mA and the other is 1.7Vdc-2.2Vdc @ 20-30mA. 

When I run the four permutations of this through the calculator I get four different resistors: 820 Ohm, 2W; 1.0 kOhm, 2W; 1.2 kOhm,1W; and 1.5 kOhm, 1W.

How do I know which one to use?

Also, I have ordered in some of the switches Jeremy recommended so I have options.

Mike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: nik.d on 26 Aug 2016, 07:15 am
Hi Mike,

You can use resistor in range of 10K to 15K (KiloOhm) 1/4W, whichever you have on hand. With such resistor
value your LED will not shine like car's head light but softly indicate the amp is switched / powered on :)

Brgds
George
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 26 Aug 2016, 01:41 pm
Thanks. The store close to me closed last year.

Larry,

Thanks. I have two different red LEDs on hand. One says it is 1.7Vdc-2.2Vdc @ 15mA-25mA and the other is 1.7Vdc-2.2Vdc @ 20-30mA. 

When I run the four permutations of this through the calculator I get four different resistors: 820 Ohm, 2W; 1.0 kOhm, 2W; 1.2 kOhm,1W; and 1.5 kOhm, 1W.

How do I know which one to use?

Also, I have ordered in some of the switches Jeremy recommended so I have options.

Mike

The specs for the LED's you have are probably a usable range for using a battery to power the LED. If your LED lists 2.2 forward voltage then it is the same as I used, so a 1.5K ohm 1 watt resistor should work fine. On mine the illumination is about perfect, not too dim, and not too bright. a 1 watt resistor is probably overkill, I think 1/2 Watt is closer to the formula calculation, but the calculator makes this statement: Resistor power ratings are chosen based on operating within 60% of the rated value. for best heat dissipation 1 Watt is probably a better choice as the calculator suggests.

 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 26 Aug 2016, 08:48 pm
The built in power cord of the Surplus NABU case is pretty good although plug end  is molded plastic.... but I decided to go with the Furutech IEC socket.
Seems a better interface plus I won't have to use an inline disconnect to get the power wire to reach the switch like I would have with the built in OEM cord
The Furutech Jeremy suggests are on sale at Sonic Craft but shipping priority is $12
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 26 Aug 2016, 09:12 pm
Yup, and there's the new NCF version that's not too expensive either!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 26 Aug 2016, 09:47 pm
The specs for the LED's you have are probably a usable range for using a battery to power the LED. If your LED lists 2.2 forward voltage then it is the same as I used, so a 1.5K ohm 1 watt resistor should work fine. On mine the illumination is about perfect, not too dim, and not too bright. a 1 watt resistor is probably overkill, I think 1/2 Watt is closer to the formula calculation, but the calculator makes this statement: Resistor power ratings are chosen based on operating within 60% of the rated value. for best heat dissipation 1 Watt is probably a better choice as the calculator suggests.

Larry.

Thanks. How did you secure the LED into the wood face plate?. I have some plastic grommet type devices that are designed to secure an LED to the thin metal of a chassis but I'm unsure how it would work with wood. I have my eye on a nice piece of spalted Tamarind for the front.

Mike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 27 Aug 2016, 01:06 pm
Larry.

Thanks. How did you secure the LED into the wood face plate?. I have some plastic grommet type devices that are designed to secure an LED to the thin metal of a chassis but I'm unsure how it would work with wood. I have my eye on a nice piece of spalted Tamarind for the front.

Mike

Mike,

I opted not to use an LED panel mount holder, instead I just drilled a 3mm through hole, and a larger counter bore to control the amount of protrusion of the LED. The LED has a slight taper so it's just a nice friction fit in the hole. A dab of hot glue would work if the fit was loose.

(http://i.imgur.com/SOP3YZ6.jpg)

(http://i.imgur.com/s6S4qOY.jpg)

(http://i.imgur.com/cvarrAB.jpg?1)



Title: Re: Folsom's great little 7297 Chip Amp
Post by: walkern on 27 Aug 2016, 03:36 pm
I've been listening to this amp for a few weeks now (long enough to be certain that it's fully run in) and I wanted to post my impressions.  Here they are in a long winded nutshell:

Treble: best I've ever heard from any amp I've ever owned (includes an assortment of Class A and Class A/B solid state amps, 2 other types of chip amps, two different class D amps, and a few different tube amps).  Instruments with lots of harmonics and overtones have a clarity that is outstanding, while completely lacking any extra distortion products.  Assuming a good recording, there is no 'honk' or 'clank' in the upper range of the piano, no spit or sizzle (but plenty of shimmer) with cymbals, no grit in the upper ranges of the violin, and no glare in higher notes from trumpets or soprano singers.   There is plenty of 'air' around instruments, and the amp does ambiance recovery beautifully (you can hear the bounce and echoes off walls and ceilings in the recording venue).  High frequency transients are fast without having any extra emphasis, and treble extension seems excellent (note that I'm an older guy, so my hearing doesn't extend as well into the extreme highs as it used to).

Midrange: wonderfully balanced and even.  It is very revealing of subtle details without shoving anything untoward in your face.  Vocals are very convincing (female and male) and instruments with plenty of midrange energy sound like the 'real thing' (please note that I attend classical music concerts on a regular basis, and played a modest assortment of instruments in my youth).  Again, no trace of any sort of emphasis anywhere in the mids, but the amp sounds energetic / lively and has good pace and rhythm.

Bass: seemed a little tight and reticent at first, but as the amp settled in this tendency vanished.  Currently I am using bookshelf speakers and a self-powered subwoofer, so I can't judge the deep bass capability of the amp.  I can however say that the bass down to about 50 hz or so sounds powerful, controlled and articulate.  No 'one note' humps anywhere, and bass transients and harmonics seem beautifully balanced.  The transition from my standpoint speakers to the sub is as seamless as I've ever heard.

Imaging: With a decent recording, this amp has palpable presence on par with the best tube amps I've heard (owned a SET 300B amp, as well as tried and pentode based amps with more oomph - up to 100 wpc).  The amp is almost spooky in how well it captures placements of people and instruments within space.  I would describe it as corporeal.  Images are not enlarged or diminished (as best I can tell), and the overall imaging leans toward precision rather than vagueness.

Dynamics and power: Subtle shifts (micro dynamic changes) are very well captured and articulated.  For me this effect tends to draw me into a performance and lends to the appreciation of the emotional character of the music.  I can't speak to macro dynamics well because I don't listen to music very loud (occasional 95 db peaks maybe), but I can say that when I have cranked up the volume a bit (Pink Floyd's 'Comfortably Numb" sounds best to me when LOUD) the amp has not audibly clipped or run out of gas.  My speakers are not rated as high sensitivity, so I'm pleased that the little bugger doesn't shy away from an occasional crank on the volume control.

Overall impressions: This is an amp that compels me to listen to the music.  I find myself drawn into recordings no matter how familiar they are.  I also find myself listening to the whole disc and enjoying songs or segments that I'd previously ignored or found boring or lackluster.  This amp will clearly convey those occasions when different cuts on an album where recorded in different studios/venues, or by different mixing engineers.  I've been able to make out lyrics that I've never before been able to hear or understand, yet this is not due to some emphasis or highlighting of the singer's range.  The amp just seems to dig out a bit more detail, while still sounding very refined and composed.

As far as I'm concerned, this amp is an absolute triumph.  My hat is off to Jeremy for all of his efforts to bring out the best in the 7297 amp chip.  Consider me not only impressed, but completely enamored.  FAR and away the best 'bang for the buck' amp I've ever owned (I currently have 4 amps sitting around), and one of the best amps I've ever heard at any price.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 27 Aug 2016, 04:44 pm
Thats a great review! Thank you.

Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 27 Aug 2016, 09:41 pm
walkern...Are you sure you aren't a professional writer?  :lol:

Nice review--you pretty much nailed every aspect of this amp.

I have three systems. The other two are 2.0 and 5.1 channel setups. Both of these systems cost much more than the one with my Folsom amp, yet I have been using my Folsom setup for probably 80 percent of the time...

The imaging on this thing can be startling at times  :thumb:

Title: Re: Folsom's great little 7297 Chip Amp
Post by: zek on 27 Aug 2016, 11:31 pm
@walkern
Did you use a preamp with Folsom amp, and which one?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 28 Aug 2016, 03:33 am
walkern,

That was a great review and I have had the same experience with the Folsom amp. I'm using it with bookshelf speakers and a powered sub as well with great results. I'm not using a preamp, just a passive with a 4 pole 3 position switch and 10k ebay DACT stepped attenuator.

I ordered a Bottlehead Eros phono preamp which has a high output impedance and does not like 10k input impedance of my passive, so I'm going to build the Kuartlotron  buffer and use a 100k DACT.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: poseidonsvoice on 28 Aug 2016, 11:33 am
Walkern,

Thank you for the review.

Please list your system in some detail.

Which amplifier(s) specifically did you compare them to? Did you have them on hand or did you compare them from memory?

Can you list some of the recordings you listen to and format?

Thank you,

Anand.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 28 Aug 2016, 03:35 pm
Thanks for the excellent review walker .
Title: Re: Folsom's great little 7297 Chip Amp
Post by: walkern on 28 Aug 2016, 03:48 pm
My system includes a Sain Smart tube preamp (still amazes me for how cheap it is, although I have a Aikido buffer build in progress), Zen Wave ICs and SCs, an Oppo 103 used as a transport except when playing SACDs (as well as an Asus laptop for hi rez files), and an SMSL M8 DAC.  The speakers are Dennis Murphy MB27s on 28" Paradigm stands, and a GR-Research servo 12" subwoofer. My listening room is modestly sized (our spare bedroom), however it has a sloping ceiling (up to 14 feet). It has no special acoustic properties and is filled with full bookcases, has wall-to-wall carpet and a nice queen sized bed in there in addition to my recliner.

Amps I have used for comparison (that I still have around) include a Chip Amp dot com LM3875 and LM3886 (built from kits), a modded (Fulsom suggestions) Chinese 7297 amp, a Class D Audio Amp (that's the brand name) SDS 120 (slightly modded and using an SMPS power supply), and a TPA 3116 (again Chinese) amp.  Amps I've owned in the past and remember fairly well include a Nakamichi PA 7 (Threshold era Pass design), Golden Tube Audio 300B monos, RAM Labs RM 100s (I think that was the model number), and an Oddyssey Stratos... and I'm sure there are others that are not coming to mind right now. I used to work as a salesman in a brick and mortar Hi Fi shop, so I got access to lots of nicer products at dealer cost, or cool stuff that was traded in.

I listen to and enjoy a wide range of music... much of it classical.  I also enjoy some pop, some jazz, and occasionally a little folk and country.  I'm really impressed by how 'listenable' the Folsom 7297 makes some of my older (1980's era) CDs (Al Jarreau, James Taylor, Rikkie Lee Jones, Julia Fordham, the Rippingtons, Pink Floyd, lots of older Telarc discs, etc.).  The amp doesn't hide the flaws, it just doesn't emphasize them, and it allows the music to shine through in spite of them. Modern hi rez downloads can sound absolutely fantastic, but most of my music has been collected over many many years, and I have very eclectic taste.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Dmason on 28 Aug 2016, 05:35 pm
Anyone gearing up to build some?  The anecdotes, and inpouring of talent is too much... I now need one.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: S Clark on 28 Aug 2016, 06:45 pm
Anyone gearing up to build some?  The anecdotes, and inpouring of talent is too much... I now need one.
I'm in the process of repairing mine.  When done, I'm looking to sell it and upgrade. 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: poseidonsvoice on 28 Aug 2016, 06:48 pm
Thanks Walkern for the details, very useful to put your review in context.

Best,
Anand.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 28 Aug 2016, 09:36 pm
Would 2.0uF input caps work and/or what would be the expected result?

I'm going to build the first one with the 1.5uF caps speced in the BOM but am looking at doing some upgrades for the second build.   The caps I'm considering are:

1.5uF, 400VDC Clarity Cap MR,
1.5uF, 600VDC Jupiter Copper Foil & Wax, or
2.0uF, 300VDC Sonicraft Platinum

Mike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 28 Aug 2016, 09:46 pm
1.5 or larger are fine.

I've been itching to try Lefson caps. You could ask Dave at PI what he likes, he was saying it was a huge upgrade whatever he is using.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 28 Aug 2016, 09:53 pm
1.5 or larger are fine.

I've been itching to try Lefson caps. You could ask Dave at PI what he likes, he was saying it was a huge upgrade whatever he is using.

I'll check, thanks.

The reason I asked about the 2.0 is because apparently the Sonicap Platinums are not available in 1.5uF

Mike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 28 Aug 2016, 09:56 pm
The cap size determines the corner frequency, and when bass begins to roll off. Under 1.5uf sounds like attenuated bass, anything over will not. You could use 10uf and it should work fine, but it'll cost a lot more for no gain in performance.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: wushuliu on 28 Aug 2016, 09:56 pm
What about transformers like Jensen or cinemag instead of input caps?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 28 Aug 2016, 10:11 pm
That should be tested, the grounding on the 7297 is sensitive to anything interrupting it, but may not be an issue.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Captainhemo on 29 Aug 2016, 02:36 am
I'll check, thanks.

The reason I asked about the 2.0 is because apparently the Sonicap Platinums are not available in 1.5uF

Mike

Mike, I'm assuming you'll be driving your Wedgies with the    amp, if you only want it to play flat down to the  180-200 hz  the Wedgies are capable of,  ther ei s no reason to even go with 1.5uF caps, if you do the math  you'll find you'll get away with a  smaller value and save some  $, and a  bit of workload on the amp..    If you are  wantting to run the amp with the MTM's,  or even at full range with other speakers, you'll want  it to play lower  and use the   at least the 1.5 uf caps recommeneded or do the math to  determine what you need to reach the roll off point you   desire.
IIRC,  a 1.0 uF cap on the standard 7297  resulted in a  -3db at around 20 Hz
The above being said, I also believe you could  go the other way, your Dodd buffer runs  output caps so i don't think you  even require input caps  on the amp....  this would limit  what you could play the amp behind but  remove a cap(s) from the cirucit. 

jay
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 29 Aug 2016, 02:38 am
1uf -3db was around 10hz or so, it still caused low bass.

Ya, it's weird, but that's how it works. Many designers shoot for 7hz, some say 4hz...
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Captainhemo on 29 Aug 2016, 02:56 am
Jeremy,
Have you by chance calculated the  roll of points of different  valued caps for the amp ?
Can't recall the input impedence off hand.... 

jay
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 29 Aug 2016, 03:04 am
I have in the past. My point is that roll off has negative consequences in ranges you're not trying to meddle with.

Turns out 1uf was closers to 6hz. Input impedance is 25-30kohm.

http://www.muzique.com/schem/filter.htm
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 31 Aug 2016, 02:30 pm
Hey Jeremy,
I know you said the 15V Antek 200VA Toroidal transformer would work with the Antipole, but would the 15V 100VA 3.3A Transformer also work? http://www.antekinc.com/as-1215/ (http://www.antekinc.com/as-1215/). Antek states:  "this transformer can be output 20% more power from its rating at 60Hz power source without any problem" I know you have mentioned earlier that the transformer should have at least an 80VA power rating.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 31 Aug 2016, 03:13 pm
Yes that'll be fine ; it needs higher voltage. Just wire the outputs in parallel for enough current.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 31 Aug 2016, 05:12 pm
Would the damping layer from a piece of NoRez work for isolating the transformer from the case?

I could get rubber washers but I have quite a few various size pieces of NoRez left over from speaker builds. I was thinking of using a piece a little larger than the base of the transformer, removing the foam, then sticking the NoRez damping layer to the case under the transformer.

Mike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 31 Aug 2016, 05:18 pm
You tell me :)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: walkern on 31 Aug 2016, 05:22 pm
I tried a variety of damping choices before settling on rubber washers (including rubber bands, and a piece of rubberized foam) and I'm pretty sure that damping layer (without the foam) should work well.  I ended up using something like that between the top of my transformer and the top of the case, and it works there.  My only concern would be that it's thickness may extend the transformer up high enough to make the top of it come into contact with the top of the chassis, at which time the top of the chassis will hum and buzz no matter how well damped the under side of the transformer is.  Then you'll need to figure out something to put between the top of the transformer and the top of the chassis (maybe another piece of the same stuff?).

Give it a shot!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 31 Aug 2016, 07:05 pm
I have used, and really like these anti vibration pads: http://www.supplyhouse.com/DiversiTech-MP-3E-EVA-Anti-Vibration-Pad-3-x-3-x-7-8 (http://www.supplyhouse.com/DiversiTech-MP-3E-EVA-Anti-Vibration-Pad-3-x-3-x-7-8) These are probably too thick for the Hammond Transformer, as it would raise it too much, but probably could be sliced thinner with a fine cut hand saw of sharp knife.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 1 Sep 2016, 01:16 pm
I have some bicycle tire tubes I bought a while back for clamping a large 2.8 cu. ft. speaker cabinet after glueing the sides and front and back together. I might try cutting a piece to fit on top of the transformer or gluing it to the case top above and see how it fits/works . I was thinking about trying that for the transformer base but decided to go with neoprene rubber washers instead
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 2 Sep 2016, 07:13 pm
Helping a friend build his Folsom; he opted for a few different components. Below are photos of it mounted on temporary test board being powered by a 24V switching PS. The extra long wires, cheap connectors, and PS just for initial testing. Final resting place will be in a nice aluminum case with a not yet built Antipole PS. It sounds great!

(http://i.imgur.com/UJ5aUYm.jpg?2)

(http://i.imgur.com/5wHBiyV.jpg?1)

(http://i.imgur.com/IaLcx6X.jpg?1)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 2 Sep 2016, 07:17 pm
How does it compare to yours with different caps?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 2 Sep 2016, 07:20 pm
Wow, Larry--nice job!!

Are the Jupiter caps the 0.022 uf bypass caps instead of the smaller ones in the standard BOM?

Sure is purdy  :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 2 Sep 2016, 07:22 pm
Nice :thumb:

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Captainhemo on 2 Sep 2016, 07:29 pm
Helping a friend build his Folsom; he opted for a few different components. Below are photos of it mounted on temporary test board being powered by a 24V switching PS. The extra long wires, cheap connectors, and PS just for initial testing. Final resting place will be in a nice aluminum case with a not yet built Antipole PS. It sounds great!

(http://i.imgur.com/UJ5aUYm.jpg?2)

(http://i.imgur.com/5wHBiyV.jpg?1)

(http://i.imgur.com/IaLcx6X.jpg?1)

It looks great Larry  :thumb:
Really looking forward to hearing it and comparing with the Dodd prototype 7297 I've got now

limits, yeah the Jupiter's are the .02s and replace the standard bypass caps,  had a few pairs that I picked up on  sale a while back

jay
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 2 Sep 2016, 07:51 pm
How does it compare to yours with different caps?

Somehow I knew you would ask that. I just finished this morning, so I only have a few hours of listening so far. Certainly not enough time for it to settle in. I can't directly compare it to mine because it now resides a half a world away. However, I am in the process of building another. From memory only, I would say its a little brighter, not in a bad way, just notice the highs a bit more. Bass and mids seem the same from memory. So far I like the sound. Not better/worse, just a little different.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 2 Sep 2016, 10:16 pm
The Nichicon Aluminum Electrolytic Capacitors - Leaded 35volts 220uF 85c 10x20 5LS are out of stock until December at Mouser
Any suggestions for a substitute ?
I applied parameter filters to something similar at Mouser and just came up with 2 different Nichicon models that are both out of stock
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 3 Sep 2016, 12:38 am
647-UPA1V181MPD

That should work fine.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 3 Sep 2016, 02:07 am
Larry,

Looks good. You by-passed the Sonicaps with the Jupiter's above the board just like you would in a crossover network, correct?

What size is the heat sink?

Jay,

What do you think of the Jupiters as by-pass caps compared to Sonicap Platinums?

You got enough speakers for all your amps?  :thumb:

Mike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Captainhemo on 3 Sep 2016, 05:05 am
Larry,

Looks good. You by-passed the Sonicaps with the Jupiter's above the board just like you would in a crossover network, correct?

What size is the heat sink?

Jay,

What do you think of the Jupiters as by-pass caps compared to Sonicap Platinums?

You got enough speakers for all your amps?  :thumb:

Mike

Hey Mike
I can't really do a direct comparison  betweenthe  Juiter and Platinum bypass yet...I haven't used them in identical positions.  But , from wht i have heard, I am a fan of the Jupiter's... I'm using  oe on the high pass bundle on the Otticas right now and the  high pass filter on a pair of Encores... both are bypassing  Gen1 Sonicaps.
If there had been more room and  no real  concern about expense, I'd have sent Larry a pair of either the  Jupiter 1.5 uF or  SC Platinum 1.5 uf's (not even sure ther eis any stock of the SCP 1.5's left, I beleive there are some 1.0's)and gone with no bypass cap, but  both opotions are big  and not exactly inexpensive.
Just had someone leave a pair of LGK's here for an extended  stay but i haven't had a chance to thry them  yet, kind of looking forward to that actually 

jay
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 3 Sep 2016, 05:36 am
Hey Mike
I can't really do a direct comparison  betweenthe  Juiter and Platinum bypass yet...I haven't used them in identical positions.  But , from wht i have heard, I am a fan of the Jupiter's... I'm using  oe on the high pass bundle on the Otticas right now and the  high pass filter on a pair of Encores... both are bypassing  Gen1 Sonicaps.
If there had been more room and  no real  concern about expense, I'd have sent Larry a pair of either the  Jupiter 1.5 uF or  SC Platinum 1.5 uf's (not even sure ther eis any stock of the SCP 1.5's left, I beleive there are some 1.0's)and gone with no bypass cap, but  both opotions are big  and not exactly inexpensive.
Just had someone leave a pair of LGK's here for an extended  stay but i haven't had a chance to thry them  yet, kind of looking forward to that actually 

jay

Jay,

I couldn't find any SC Platinum 1.5uF caps either which is why I asked about using 2.0uF the other day.

Pricewise I think the 1.5uF Jupiter copper foil wax caps are about $145 each while the SC Platinum 2.0uF are $224 ea.

These amps start out pretty reasonable but it's easy to run the price up pretty quick.

I look forward to hearing your impressions of the LGK (1.0's I take it?). 

Mike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 3 Sep 2016, 11:54 am
Larry,

Looks good. You by-passed the Sonicaps with the Jupiter's above the board just like you would in a crossover network, correct?

What size is the heat sink?
Mike

Mike,
 Yes the caps are piggy backed per Jay's request instead of soldering them on the bottom pads.

The heat sink is the one recommended in the BOM. It's from heat sink USA 3.5" long x 3" tall.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Captainhemo on 3 Sep 2016, 04:15 pm
Jay,

I couldn't find any SC Platinum 1.5uF caps either which is why I asked about using 2.0uF the other day.

Pricewise I think the 1.5uF Jupiter copper foil wax caps are about $145 each while the SC Platinum 2.0uF are $224 ea.

These amps start out pretty reasonable but it's easy to run the price up pretty quick.

I look forward to hearing your impressions of the LGK (1.0's I take it?). 

Mike

Mike,  are you wanting this amp to be able to  play full range ? I know the  10 uF's would be fine with your  Wedgies or the Ottica MTM's I sent down.  At 25kohms input impeence, the calcualtor says  you'd have a -3db point of 6.37 hz (seems low to me  but ? )... I know Jeremy says  results may vary a bit but  for those speakers and your subs ability to play way  up, you'd be fine.
Other option is go  capless, as mentioned , your  Dodd  buffer  uses output caps so don't think there is any need to be redundent on the DC blocking unless you ara concerned about compatability or want the filtering from the caps.

Yes, those  speakers i mentioned  are the  LGK 1.0's, I may try and have a listen to them this weekend

All  these DIY builds  start off as inexpensive but CAN quickly ramp up.. amps speakers  etc, all can grow quickily but i guess without  trying the parts, one never knows .
I've actually been offered a  great deal on  a couple of 300VA 15V  transformers, they'd be over kill for this but I'm considering using one in place of he  Hammond if I go with the Antipole anyway, haven't decided yet  :scratch:

jay
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 3 Sep 2016, 11:41 pm
Mike,  are you wanting this amp to be able to  play full range ? I know the  10 uF's would be fine with your  Wedgies or the Ottica MTM's I sent down.  At 25kohms input impeence, the calcualtor says  you'd have a -3db point of 6.37 hz (seems low to me  but ? )... I know Jeremy says  results may vary a bit but  for those speakers and your subs ability to play way  up, you'd be fine.
Other option is go  capless, as mentioned , your  Dodd  buffer  uses output caps so don't think there is any need to be redundent on the DC blocking unless you ara concerned about compatability or want the filtering from the caps.

Yes, those  speakers i mentioned  are the  LGK 1.0's, I may try and have a listen to them this weekend

All  these DIY builds  start off as inexpensive but CAN quickly ramp up.. amps speakers  etc, all can grow quickily but i guess without  trying the parts, one never knows .
I've actually been offered a  great deal on  a couple of 300VA 15V  transformers, they'd be over kill for this but I'm considering using one in place of he  Hammond if I go with the Antipole anyway, haven't decided yet  :scratch:

jay

Jay,

I want at least the first amp to be able to play full range. That way I can use it with any of my speakers. I may build out an amp without input caps to see what it sounds like with the Dodd tube buffer. It looks like the output caps in my Dodd are Sonicap Gen1s by-passed with SC Platinums.

I'm going to build the amp and power supply in separate chassis. That way I can compare different amp builds without having to build multiple power supplies up front.  The first Antipole I build will use the Hammond but I may try a toroidal transformer in another Antipole later on.

Mike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: ebag4 on 4 Sep 2016, 07:16 pm
I finally got around to building my amp and ps.  Question, having never used an insulator between a chip and a heat sink, should I pull what appears to be a plastic protection layer off the insulator?

Thanks,
Ed
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 4 Sep 2016, 07:18 pm
Are you sure there's not just two? I never had anything like that on any of the mica I ordered...
Title: Re: Folsom's great little 7297 Chip Amp
Post by: ebag4 on 4 Sep 2016, 07:41 pm
I did recieve two because I ordered two chips (just in case  :wink:), but what I am referring to is what appears to be separation of layers around the holes at at some of the edges.  I had a couple of pieces peel off but when they didn't pull off as a complete sheet but in shards I thought I should ask. 

Thanks,
Ed
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 4 Sep 2016, 07:57 pm
I really don't know, I didn't experience anything like that.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 4 Sep 2016, 09:27 pm
I did recieve two because I ordered two chips (just in case  :wink:), but what I am referring to is what appears to be separation of layers around the holes at at some of the edges.  I had a couple of pieces peel off but when they didn't pull off as a complete sheet but in shards I thought I should ask. 

Thanks,
Ed

That's just a characteristic of mica, if you peel it, it will come off in flakes. What appears to be layer separations around the holes and the edges is normal. The thermal grease fills the tiny scratches you can't see or feel on the aluminum chip, and heat sink so you get the best thermal conductivity. The mica sheet electrically insulates the chip from the heat sink. Both sides of the mica should be glass smooth.

 If you peel off mica layers it will no longer be smooth, and you will lose some thermal contact with chip or heat sink. It may not be a problem, but be sure there is no electrical continuity between the chip and heat sink.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 4 Sep 2016, 10:16 pm
Just try to keep the thermal grease thin. You only want it as thick as you absolutely need it. As the insulation and grease increase, the power of the amp can decrease.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: ebag4 on 5 Sep 2016, 12:46 am
Thanks Lacro, the part that peeled was on the unused end so no worries.

Powered my amp up in its temporary dual case setup (built into a couple of previously used project boxes).  I used a small pair of speakers and a portable player before putting it in the big rig, no magic smoke so I put it in the main system, sounds good, zero time on it.  I'll let it burn in for a while and see how it comes along, but right off the bat, not bad.  It has a lot more gain than the Bottlehead Kaiju, so I had to adjust the subs a bit to match the output.  The gain is high enough that it is really loud at 50 on the Vega, I typically run between 75 and 85.

One nit to pick is that the transformer is loud, I currently have it on rubber feet and it is still loud, not so loud that you hear it with music playing but loud enough you hear it when you power up. 

In the current setup it will be very easy to compare to a pair of 12V 100ah PowerSonic AGM batteries I have, I will report on what I find.  If I end up liking the Antipole best, I will probably move to a toroidal transformer.

Best,
Ed

(http://www.audiocircle.com/image.php?id=149781)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: G Georgopoulos on 5 Sep 2016, 01:57 am
Just try to keep the thermal grease thin. You only want it as thick as you absolutely need it. As the insulation and grease increase, the power of the amp can decrease.

ah Jeremy ,what you say is really funny to me. :lol:

even if this chip has thermal protection it would be the heatsink that's causing problem
thermal grease and insulation are highly thermal conductors..
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 5 Sep 2016, 02:09 am
George, you can actually calculate the thermal resistance and how it affects things for power loss. The thing is, the insulation of the chip itself is considerably higher than say mica and grease at reasonable levels.

But when using big transistors at high voltage these factors become more serious. Mica will reduce power output a fair bit compared to keratherm.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 7 Sep 2016, 02:44 am
Hi everyone, I found these, which might be ideal for mounting the transformer.

http://www.mcmaster.com/#rubber-standoffs/=141zebg

Style 1 & 2 make the most sense to me, as a stud sticking up into the transformer holes would be ideal it seems so long as you can get a tightening tool to it.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: ebag4 on 8 Sep 2016, 01:07 am
I have let this amp play for close to 25 hrs now stepping in the room to listen on occasion.  I sat down with it after work tonight to listen to a few tracks.  This is a really good sounding amp, good tone, imaging, pace, etc., it has my toes tapping. 

I will set it up on batteries this weekend to compare.

Great job Jeremy, certainly worth the cost and effort.  As soon as I decide which of the power supplies I will use, I will be picking up better binding post, RCAs, and a suitable case.

Best,
Ed
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 8 Sep 2016, 01:27 am
Good to hear Ed. It's pretty unbeatable for the money! It's a good way into true high end audio.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Captainhemo on 8 Sep 2016, 01:29 am
Hi everyone, I found these, which might be ideal for mounting the transformer.

http://www.mcmaster.com/#rubber-standoffs/=141zebg

Style 1 & 2 make the most sense to me, as a stud sticking up into the transformer holes would be ideal it seems so long as you can get a tightening tool to it.

Cool you like what you are hearing from the amp Ed :beer; I am interested to hear what you think  when you  power it with the batteries. 

jay
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 11 Sep 2016, 12:58 pm
Hey Jeremy,
Do you have issues with using these on the Antipole PS for input/output?

http://www.mouser.com/ProductDetail/TE-Connectivity-AMP/282844-2/?qs=sGAEpiMZZMvZTcaMAxB2AJ%2f79sE4hFAYCpaUmMF7fng%3d (http://www.mouser.com/ProductDetail/TE-Connectivity-AMP/282844-2/?qs=sGAEpiMZZMvZTcaMAxB2AJ%2f79sE4hFAYCpaUmMF7fng%3d)


(http://www.audiocircle.com/image.php?id=150166)

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 11 Sep 2016, 06:26 pm
No, if they fit they work.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: ebag4 on 11 Sep 2016, 10:07 pm
Cool you like what you are hearing from the amp Ed :beer; I am interested to hear what you think  when you  power it with the batteries. 

jay
I have been switching back and forth between the Antipole and a pair of 12VDC batts wired in series.  Because I have the amp wired up to a jack for the input voltage it is quite easy to swap between the Antipole and the batts.  I will say that the amp sounds great with either.  One thing that surprised me a bit was that I had a very slight hum with my ear next to the 94db Wedgies drivers with both supplies, please keep in mind that this is practically inaudible and could be due to the temporary nature in which I have the amp set up (i.e. Amp not enclosed in a metal case, cables laying over each other, etc).

I played several tracks and portions of tracks with which I am quite familiar, however try as I might, I could not detect a difference, not one that I would detect repeatedly.  For a few moments during the beginning of Deacon Blues I thought I heard better leading edge attack with the Antipole, but after going back and forth I could not detect the difference with any certainty.

Of course this is with my system, my room, my ears, etc., others may have more resolving systems or ears.

For the record, this is the system: NAS/Sonic Transpoter/Roon-microRendu(powered by IFi ps)-Auralic Vega DAC-  Folsom amp & Servo Sub Amp (x2)- GR Research Wedgies, Servo Sub Amps drive 2x12" servo drivers housed in an "H" Frame alignment housing per channel   AC Devices: Powered through Pi Audio Uber & Majik Busses   Cables: microRendu hard USB connector, High Fidelity CT-1 RCA (DAC to Amp), Monster RCA (DAC to Servo amps), Morrow Audio Sp-5 speaker cables.

Best,
Ed

Title: Re: Folsom's great little 7297 Chip Amp
Post by: S Clark on 11 Sep 2016, 10:43 pm
Thanks for the review.  It's one I've been waiting for, since I've been on batteries all this time.  I've got an Antipole board, but I haven't gotten around to filling it yet... so I'll probably continue to procrastinate.   
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 11 Sep 2016, 11:15 pm
Try putting an RC of 10r 1uf across the transformer side of the CMC. (a resistor and capacitor in series, one leg of resistor attached to one leg of CMC towards AC input and one leg of capacitor to the other CMC leg toward AC input)

See if you can tell the difference after that.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: ebag4 on 11 Sep 2016, 11:53 pm
Try putting an RC of 10r 1uf across the transformer side of the CMC. (a resistor and capacitor in series, one leg of resistor attached to one leg of CMC towards AC input and one leg of capacitor to the other CMC leg toward AC input)

See if you can tell the difference after that.
I may have those parts in my collection.  Where exactly should it be mounted? 

Thanks,
Ed
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 12 Sep 2016, 12:12 am
I'm not sure how to explain it any more...
Title: Re: Folsom's great little 7297 Chip Amp
Post by: ebag4 on 12 Sep 2016, 12:36 am
I'm not sure how to explain it any more...
How about pointing out the CMC.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Captainhemo on 12 Sep 2016, 12:41 am
Won't you be good pretty much anywhere on the input side of the trans ?  Keeping it close will probably be  easier....

jay
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 12 Sep 2016, 01:36 am
Won't you be good pretty much anywhere on the input side of the trans ?  Keeping it close will probably be  easier....

jay

The best location will be closest to the CMC.

CMC is the common mode choke. It's big, has wires around a core.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: ebag4 on 12 Sep 2016, 01:42 am
The best location will be closest to the CMC.

CMC is the common mode choke. It's big, has wires around a core.
The choke, now I know what you are referencing.

Thanks,
Ed
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 12 Sep 2016, 03:22 am
I can understand why any differences between the battery supply and the Antipole would be almost indistinguishable, because of the power regulation on the amp. The Antipole has the CMC and caps before the regulators to help clean the A/C coming in and a lot of capacitance after for the D/C. This should provide a nice clean source for the amp.

To this point I have been very happy with the amp and have not felt any urge to look for something else.

Brad
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 12 Sep 2016, 03:37 am
Nice to hear Brad, are you working on some buffers from Keantoken? I think he's going to have some regulated ones shortly too. I sure like mine.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 12 Sep 2016, 04:35 am
Jeremy,

I have the first run boards that do not include the regulation. I purchased the RJM X-reg to supply the regulated power. I have all the parts but still need a chassis. Also, I have not had the time to put it together. In addition everything sounds so good with the 10k passive I put together I have not felt the need for the buffer. The reason I wanted the buffer was to match the new phono kit I just got, so I want to put that together first and see how it sounds with the passive first.

I jumped on the buffer based on your recommendation, so can't wait to try it.

Brad
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 13 Sep 2016, 05:07 pm
I mounted the heat sink on the inside of the chassis with the fins butting up against the rear wall interior .
My question is;  by drilling 3/32nd" holes on the back and bottom of the chassis located between each fin of the heat sink ..... is that  adequate ventilation or should I enlarge them or make more of them. don't want to perforate more than I need to
thanks
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 13 Sep 2016, 05:19 pm
Really you want holes on the top and bottom for convection to occur. On the bottom and side won't do too much.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 13 Sep 2016, 07:03 pm
Thanks Folsom !
I will drill in the top also
Title: Re: Folsom's great little 7297 Chip Amp
Post by: shadowlight on 13 Sep 2016, 08:06 pm
Anyone have a recommendation for IEC connector with fuse builtin.  Need something to use with antipole.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 14 Sep 2016, 01:17 pm
Thanks Folsom !
I will drill in the top also

If you want to drill nice evenly spaced ventilation holes in your case, here is a method I developed that works very well.

http://www.audiocircle.com/index.php?topic=142008.msg1514790#msg1514790 (http://www.audiocircle.com/index.php?topic=142008.msg1514790#msg1514790)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: S Clark on 14 Sep 2016, 02:15 pm
Anyone have a recommendation for IEC connector with fuse builtin.  Need something to use with antipole.
Apex Jr. has one cheap that should work.  Scroll to mid page...
http://www.apexjr.com/FuseHolders.htm
Title: Re: Folsom's great little 7297 Chip Amp
Post by: indosmokejon on 14 Sep 2016, 04:27 pm
Hello, my name is Jon, brand new to this forum.  I found my way here from searching for Folsom's 7297 chip amp after seeing it referred to somewhere else on the web.  Are these boards still available for purchase?  I would love to give this a try.  I don't own a single chip amp but I am definitely intrigued after reading quite a bit of this thread as well as others regarding Folsom's work. 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 15 Sep 2016, 11:00 pm
Thanks for the link on how to drill evenly spaced holes. I'll probably add those to the top .
To start I drilled 5/32nd holes between each heat sink fin on the bottom and top of the chassis and also a row on the top of the chassis back.
Putting rubber washers on the transformer mounting screws and a thin layer of rubber on the bottom of the unit allowed me to test fit the chassis top on with no issues.
I was wondering if having the large caps on the Antipole where they are so close to touching the chassis bottom is a potential issue/problem ? The Antipole just fits on the partition height wise or I would have raised it . When I got the NABU surplus case I grabbed a sheet of amplifier isolation rubber for a buck so I could add that if needed.
I soldered the chip to the PCB after lining it up on a flat surface with the heat sink but now I wonder if my wood workbench top wasn't perfectly flat as the chip in the case only matches up to the sink on the top third. The chip isn't perfectly perpendicular to the sink surface or I drilled and tapped the mounting hole at a slight angle.
Might have to desolder and raise the sink with a sheet of something so the mounting screw for the chip lines up properly.

(http://www.audiocircle.com/image.php?id=150372)

(http://www.audiocircle.com/image.php?id=150373)


Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 15 Sep 2016, 11:19 pm
The Antipole's caps are fine.

The heatsink to chip really is the hardest part of building this amp... which isn't very hard compared to lining up a dozen transistors!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: indosmokejon on 16 Sep 2016, 05:36 am
Hey Folsom, is this project still available for purchase?  I would love to give it a try.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 16 Sep 2016, 05:37 am
Yes, I've emailed and personal messaged you.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: indosmokejon on 16 Sep 2016, 09:15 am
Ok. Sorry about that. I am obviously new here and I am not quite up to speed on the site. I will search for that. Thanks!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 16 Sep 2016, 01:56 pm
Thanks for the link on how to drill evenly spaced holes. I'll probably add those to the top .
To start I drilled 5/32nd holes between each heat sink fin on the bottom and top of the chassis and also a row on the top of the chassis back.
Putting rubber washers on the transformer mounting screws and a thin layer of rubber on the bottom of the unit allowed me to test fit the chassis top on with no issues.
I was wondering if having the large caps on the Antipole where they are so close to touching the chassis bottom is a potential issue/problem ? The Antipole just fits on the partition height wise or I would have raised it . When I got the NABU surplus case I grabbed a sheet of amplifier isolation rubber for a buck so I could add that if needed.
I soldered the chip to the PCB after lining it up on a flat surface with the heat sink but now I wonder if my wood workbench top wasn't perfectly flat as the chip in the case only matches up to the sink on the top third. The chip isn't perfectly perpendicular to the sink surface or I drilled and tapped the mounting hole at a slight angle.
Might have to desolder and raise the sink with a sheet of something so the mounting screw for the chip lines up properly.

It looks like there is a gap between the HS and the PCB which would indicate the chip is tipped outward at the top.
You can try bending the chip slightly back in vertical alignment. However, the hole you drilled and tapped in the Heat Sink (HS) may also be out of alignment or drilled at an angle as you mentioned. This could pull the chip outward at the top.

I would take the board and HS out of the chassis, and set it on a known flat surface such as glass or a piece of MDF. Use a combination square to check if the chip is perpendicular to the board. If it's not, try bending it into alignment then check that the the tapped hole is perfectly centered. If the hole is off, flip the HS over, and drill/tap a new hole.

A good way to make a perfect tapped hole is use a drill dress to drill the hole, and use the drill press to tap the hole by inserting the tap in the drill press chuck, and turning the chuck by hand, not under power. This keeps the tapped hole perpendicular.

If bending the chip perpendicular with the board creates a gap between the chip and the heat sink when the HS is pressed tightly to the board, it would indicate that the chip was installed with the straight legs set deeper than the bent legs during soldering. This would make the top of the chip contact the HS, but not the bottom of the chip. The solution would be de-soldering the straight legs only of the chip, and lifting it into perpendicular alignment.

Something else to consider is anchoring the HS to the chassis. The reason being, the heat sink is a little top heavy, and could tip, and bend the chip possibly damaging it if the chassis was carried on its side. With my latest build I am going to drill/tap the thick section of the HS, and screw it directly to the bottom of the chassis.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 16 Sep 2016, 06:03 pm
Thanks for your post and suggestions Lacro , the one about using the tap by hand mounted in the drill press is a good one , the Heat sink is mounted to the chassis base with three #4 bolts and butts right up to the rear plate . I hate to desolder the chip but may have to , shimming the heat sink to make it perpindicular to the chip seems like not the answer
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 16 Sep 2016, 06:09 pm
This is why I only solder the chip in two places at the far ends on the top. It's easy to just hit their solder point and get the chip to adjust. Then do the rest when you're sure.

If there was an easier chip mounting process I'd be all about it. There was another version of the chip but it was lower wattage and discontinued.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 16 Sep 2016, 08:53 pm
Yep Folsom , I definitely should have waited after soldering the first 2 legs on the chip per your instruction sheet . I never thought of tapping with my drill press turning by hand , that would have made the non perpindicular issue go away. Going off the path just a small amount on the heat sink mounting hole made it a problem.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 16 Sep 2016, 10:23 pm
I never thought of tapping with my drill press turning by hand , that would have made the non perpindicular issue go away. Going off the path just a small amount on the heat sink mounting hole made it a problem.

Using the method with the tiny m3 or 4-40 screws requires a bit of finesse. Keeping constant downward pressure on the DP quill with the hand crank requires a gentle, but firm touch. It might be better to have an assistant so your not fighting the quill return spring at the same time your turning the chuck. When tapping these tiny fine threads, I like to tap the first 3-5 threads, and release the tap from the chuck. Then finish tapping with a tap handle.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 20 Sep 2016, 06:43 pm
I'm down to 6 amp boards, and around 20 Antipoles. One gentleman has a claim to 5 amp boards if he claims them soon, but otherwise, I guess... form a line :lol:

If I reprint I don't know when at this point, because they won't pay for themselves anytime too soon.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 20 Sep 2016, 09:08 pm
I'm down to 6 amp boards, and around 20 Antipoles. One gentleman has a claim to 5 amp boards if he claims them soon, but otherwise, I guess... form a line :lol:

If I reprint I don't know when at this point, because they won't pay for themselves anytime too soon.

“I silently smiled at my incessant good fortune.”
― Henry David Thoreau
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 21 Sep 2016, 05:43 pm
Amplifier boards are gone. I have around 15 Antipoles left.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 21 Sep 2016, 07:02 pm
Man I can't believe I missed the post. I would have purchase another board or two.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 21 Sep 2016, 08:21 pm
If I had a sufficient order load I would have more printed.

Maybe if there's enough interest then it will happen. I believe it would require around 20-25 orders. The new boards would be updated slightly, nothing performance wise just slightly cleaner appearance skipping a few things no one uses.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 22 Sep 2016, 06:09 pm
I really didn't want to bend the chip or de/re solder to match the chip up against  the heat sink
So, using a little "strategery" I used the next smaller standoff post on the rear of the amp board and took some pictures to see if you guys think this is acceptable ? The mica is not on it yet .
toothed lock washers on the PCB and heat sink bolts so they don't wander around.
Also some pictures of the bottom top and rear vent holes . If tyhey aren't enough I'll add more
thanks
(http://www.audiocircle.com/image.php?id=150776)

(http://www.audiocircle.com/image.php?id=150777)

(http://www.audiocircle.com/image.php?id=150778)

(http://www.audiocircle.com/image.php?id=150779)


(http://www.audiocircle.com/image.php?id=150782)
(http://www.audiocircle.com/image.php?id=150781)

Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 22 Sep 2016, 07:04 pm
I really didn't want to bend the chip or de/re solder to match the chip up against  the heat sink.

It will probably be fine, You may be overthinking this. I would have tried bending the chip back in alignment. Your not really bending the chip just the leads. One piece of advise I can give after soldering a few of these amp boards is leave the big transistor for last. Trying to keep it from bending while your soldering on the all the wires is difficult. Also, I found that installing the small heat sink on it before soldering to the board was easier. Just my thoughts, your mileage may vary....
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 22 Sep 2016, 07:17 pm
Hey - I just noticed something else with your board. there has been a BOM change from the 10 uF blue cap to this:
http://www.mouser.com/ProductDetail/Cornell-Dubilier/107CKS016M/?qs=%2fha2pyFaduj0NJWQ67zoZIQXKYIad%252bbmZSt3Q9Xez%2fAo6kG9mWogPA%3d%3d (http://www.mouser.com/ProductDetail/Cornell-Dubilier/107CKS016M/?qs=%2fha2pyFaduj0NJWQ67zoZIQXKYIad%252bbmZSt3Q9Xez%2fAo6kG9mWogPA%3d%3d)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 22 Sep 2016, 08:13 pm
The mica will push it out a little bit. You should be fine. You can put it in, and check thermal grease for contact when you take it out.

The bigger cap just prevents the turn on pop, which is harmless to all but the most insanely fragile speakers. I'm not sure such a speaker exist, to be honest, at least that anyone uses an amp with... Headphones maybe?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 23 Sep 2016, 05:08 pm
If I had a sufficient order load I would have more printed.

Maybe if there's enough interest then it will happen. I believe it would require around 20-25 orders. The new boards would be updated slightly, nothing performance wise just slightly cleaner appearance skipping a few things no one uses.

You can put me down for 3 boards.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 23 Sep 2016, 05:11 pm
Thanks for your post and suggestion about leaving the transistor til last.
I think I did order one of those parts for the turn off pop reduction.
I appreciate your help as I'm still a newb moving forward.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 23 Sep 2016, 07:04 pm
Hi guys, I got 2 available amp boards from the claimed 4. They go to whomever also wants Antipoles, first. 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: shadowlight on 23 Sep 2016, 07:28 pm
Folks, who are using the NABU case how did you get the IEC outlet cut into it?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 23 Sep 2016, 07:41 pm
Congratulations on selling out! Hope you'll sell many more!  :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 23 Sep 2016, 07:43 pm
Sorry, shadowlight--I'm no help. I ended up using the captive power cord that came with the case. I am sure they make chassis punches for this, but if you're only doing one (or even a few) it might not be worth the cost.

Maybe a drill press drilling small holes for the profile, and finishing it off with sidecutters?...

Good luck with yours!

limits
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 23 Sep 2016, 08:06 pm
I used a sabre saw with metal blade where I removed the original NABU heat sink from the chassis rear plate for the Furutech power inlet cut out, use a safety face face shield to stop getting metal shrapnel and file the edges of the cut out smooth. The dimensions in MM are on the Furutech site for the cutout size of the inlet. I started from one of the original heat sink mounting holes and drilled each corner I marked out with some drill bits starting small till I got to a size that would allow a saw blade in. Use a slow speed on the drill and lubricating oil.
Jeremy , I will take an amp board unless an Antipole buyer needs it

thanks
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 23 Sep 2016, 08:11 pm
Sales pending.  :lol: :lol:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 23 Sep 2016, 11:39 pm
Ok.

1x DIY7297 board left to go with an Antipole to whomever wants the set.


Sold sold.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: indosmokejon on 26 Sep 2016, 07:37 pm
Can anyone weigh in on which power transformer will work best with the antipole and the amp in general, the Hammond in the BOM or the Anitech that Matt Garman used, http://www.antekinc.com/as-1218-100va-18v-transformer/     I am going to build two units and I can get two of the anitek's to the door for roughly $55, so a little cheaper than going with the Hammond units.  I know that Folsom also mentioned the James Transformer as well which would be a bit more expensive than either of the previously mentioned transformers.  The anitech's would allow me more options with enclosures since they don't sit as high.  Thoughts???
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 26 Sep 2016, 08:05 pm
Speaking of the James O core transformers - anyone tried one?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 26 Sep 2016, 08:18 pm
I've tried to order from James and been met with 0 success. Crying shame, I think they'd be excellent. Also I might order from him for commercial units. But you can't do business with someone that... well, doesn't do business.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 27 Sep 2016, 09:07 pm
I put the jumper on between tabs for #8 and #11 on the Hammond Transformer and wondered how folks are wiring the N leg of the AC connector to 2 separate tabs ( #1 and #5 ) on the transformer ?
I looked at Jeremys photograph but couldn't really see how both connections were made with one wire .
thanks
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 27 Sep 2016, 11:14 pm
KR500,

I wired it with 2 wires connected to a quick connect going to tab 1. One wire went to the N leg and the other went to tab 5 with a quick connect. I did the same thing for tabs 2 and 6.

The power switch I used for my build was a DPST, so both wires from the IEC went to the power switch.

I hope that helps.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 28 Sep 2016, 12:45 pm
Thanks BRN ;
Today I'll head over to Home Depot to see if they have disconnects for 10-12 size, the 14-16 disconnects  I currently have on hand accept the 14 gauge solid I'm using for AC but not 2 .
I've used two wires in one disconnect before but only in speaker crossovers with 18 or 20 gauge wire
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 28 Sep 2016, 02:05 pm
Thanks BRN ;
Today I'll head over to Home Depot to see if they have disconnects for 10-12 size, the 14-16 disconnects  I currently have on hand accept the 14 gauge solid I'm using for AC but not 2 .
I've used two wires in one disconnect before but only in speaker crossovers with 18 or 20 gauge wire

These work good for what I think your trying to do.


(http://www.audiocircle.com/image.php?id=150989)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: pocomo on 29 Sep 2016, 01:23 pm
Hi Guys -

With my solder slinging skills being slim-to-none my chances of completing this project successfully were essentially zero. However, with all the rave reviews I am very interested in trying out one of these amps. Does anyone have a completed amp that they would consider selling?

Thanks.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 5 Oct 2016, 12:43 pm
On the diagram for 7297/Antipole connections the center ground post for the IEC input connector marked "E" is not connected to anything. Do you connect this to a chassis ground nut/bolt ?
correction- I printed out the connections sheet on B+W laser printer for the work bench area and it didn't reproduce the clearly marked gray E connection for ground

Also , my SPST switch has a 1 and 2 terminal that looks like the diagram picture  , ......except upside down . Does the IEC connecter marked "L" get connected with the #2 terminal of the switch ?
I know these are super basic questions but I haven't wired a switch before and want to do it correctly
thanks
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 5 Oct 2016, 02:18 pm
(http://i.imgur.com/kH5IzdP.jpg)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 5 Oct 2016, 04:59 pm
Thanks Lacro for the post/pic . Earth center pin to chassis nut/bolt. Check
Looking at the earlier posted diagram for connections it looks like the SPST switch marked 2 for output is wired to the "live" right pin on the connector marked L and the transformer output from #2 and #6 connected to switch input pin 1 ? Sound correct ?
I guess my confusion surrounds the unmarked terminals of the switch in both your picture and the one Jeremy posted
thanks
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 5 Oct 2016, 06:34 pm
The switch is not as critical since it is either open or closed to break or complete the connection to the power transformer.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 10 Oct 2016, 05:34 pm
Thanks Lacro and BRN for your help
- I had printed out the connections sheet on B+W laser printer for the work bench area and it didn't reproduce the clearly marked gray color  E connection for ground. Doh !
I got the LED and resistor Lacro recommended for the light switch and see he wired it to the AUX terminals on the Antipole .
Would that be the small terminal solder holes between the big caps marked 22 gauge ?
Is it an option to wire the LED and resistor positive connection to the power SPST switch instead of the Antipole  ?
Does the LED negative leg then get wired to the IEC "N" terminal if you use the switch for positive   ?
thanks again for your help
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 10 Oct 2016, 07:30 pm
Thanks Lacro and BRN for your help
correction - I printed out the connections sheet on B+W laser printer for the work bench area and it didn't reproduce the clearly marked gray color  E connection for ground. Doh !
I got the LED and resistor Lacro recommended for the light switch and see he wired it to the AUX terminals on the Antipole .
Would that be the small terminal solder holes between the big caps marked 22 gauge ?
Is it an option to wire the LED and resistor to the power SPST switch instead of the Antipole  ?
Does the LED negative leg then get wired to chassis ground.... or something different ?
thanks again for your help

The LED/resistor I used was connected to a SMPS delivering 24VDC. The Antipole which I didn't use on my first build delivers around 21VDC so the LED resistor value for the Antipole will be a little different, but the one you have will probably work fine.

Powering the LED from the 22ga holes is a good idea (+-). You use both plus and minus holes to power the LED. Don't connect the negative LED lead to chassis ground. Your switch should only be turning on/off the high voltage AC (120V) input.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 10 Oct 2016, 10:40 pm
Thanks for your help Lacro , Antipole power for LED it is .
posting your info on mounting the LED was helpful . I was able to drill out the OEM acrylic display on the NABU surplus case for the power switch and DACT and a small inside flared hole that allows for press fit of the LED.
coming down the home stretch
I'll post some pics next week after finishing up
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 12 Oct 2016, 06:26 pm
Just wrapping up and wondered where the DACT ground #1 terminal gets soldered to ? pcb ground ?
On the connections layout picture the RCA inputs are wired to the 7297 amp pcb input.
I'm assuming that if you are using the DACT pot you would connect the RCA positive output to DACT terminal 3 and DACT terminal 2 to amp input positive ?
thanks

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 12 Oct 2016, 07:45 pm
DACT's are numbered? I don't follow. Anyways if you're making an integrated unit:

Center is output on a DACT. One center pin is right, the other left (your choice, based which you chose on the input for R/L). That goes to the amplifier input. (R and L on each side of SG on the PCB board)

The input to the DACT is either on the right or left of center, depending on which direction you want it to turn for volume. Generally if you're looking at it from the back you'd place it on the left.

Then all the grounds from the input and output would go on the right two pins (for R and L). (SG on the board, and the ground tabs of your RCA jacks)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 12 Oct 2016, 08:46 pm
Thanks Jeremy for the clarification . Just wanted to make sure I had it right before putting it all together and closing up.
I searched around online to see if I could find out the answer but only posts on the input//output wiring showed up ,  not the ground connection
Most posts referred to the DACT potentiometer  terminals as right to left from back . I think the ebay page for the DACT I got shows that too.
3 = IN
2=OUT
1 = ground
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 12 Oct 2016, 09:56 pm
I believe what you're saying is correct.

The ground should be on the side that you want to be turned to in order to have volume all the way down.

Title: Re: Folsom's great little 7297 Chip Amp
Post by: walkern on 13 Oct 2016, 02:51 pm
If this is the version you have, here are the connections for hooking it up.  The #1 position from both channels is the ground.


(http://www.audiocircle.com/image.php?id=151925)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 16 Oct 2016, 02:00 pm
Thanks for clarifying the ground connections Jeremy and Walker.
The IEC is grounded to the chassis
Since I attached wires on the bottom of the PCB and Antipole I went with a taller standoff . A new hole was drilled in the heat sink for the chip mount using Lacro's suggested method of turning the tap bit by hand in my drill press, then chasing the last few threads by hand . It worked out great and I slightly bent the chip legs to get it's orientation straight up.Just have to check the chip bolt with my DMM.
I installed the last part and smaller heat sink after wiring up the PCB ( 'nother suggestion from lacro ) and kept it off the board, but it still was fussy to get the heat sink to clear the resistors . I wound up bending the smaller V tab of the heat sink up to clear the 431 and sliding the sink over and crimping the clasp tight so the sink wouldn't touch the resistor . It's tight and I should have soldered the transistor even higher in retrospect.
I had left over 14 gauge solid copper wire from my garage wiring project that I used on the IEC/transformer/switch wiring . Really stiff stuff ( water and greaseproof ) and I probably just should have bought something easier to work with. HD and Lowe's don't sell it by the foot here anymore though.
No interconnects locally for 12-14 size where I had to double up AC wires on the transformer , just 10-12 and 14-16 size interconnects ,   crimped and then soldered the 10-12 size as they were still a tad loose.
Just have to get a knob to fit in the NABU front panel for the DACT pot.
Doh !  going over the build and realized I forgot to put an insulating washer on both sides of the chip, just have the one side of the chip . Off she comes again


(http://www.audiocircle.com/image.php?id=152043)

(http://www.audiocircle.com/image.php?id=152044)

(http://www.audiocircle.com/image.php?id=152045)

(http://www.audiocircle.com/image.php?id=152046)

 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 16 Oct 2016, 04:06 pm
Why would you want one on both ides of the chip? The 7297 chip? How would you put one on the other side?

Do you mean the mica? I can see it in there, so?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 16 Oct 2016, 04:37 pm
Folsom , I have an insulating washer on the bolt going through the chip, but thought I had to have another insulating washer on the backside of the chip ? . i.e. one on each side of the chip .
Is there just the one washer ? Just want to make sure before plugging in the unit.I made sure not to over tighten the bolt into the heat sink.
I put the DMM probe on the chip and one on the heat sink and get all zeroes at the resistance settings until I set the resistance dial down to the lowest 200 ohm setting, then I get 00.2 on the readout , same 00.2 with probes on the bolt head and heat sink
Continuity check with the probes on chip and heat sink gets a zero readout
thanks


Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 16 Oct 2016, 06:37 pm
Do you have the shoulder washer correctly oriented? You only need the one washer, that prevents contact from the bolt to the tab on the chip. The Mica should insulate the rest of the chip from the heatsink.

It sounds like something is touching, so you may need take a closer look, or nudge the chip.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: slefley on 16 Oct 2016, 07:53 pm
I have one each new/unused circuit board for the AMP and PSU that I will not be using, along with all of the documentation that Folsom provided.  I'll sell them for the same price I paid: $24 Amp PCB, $21 PSU PCB and $8 Shipping priority USA ($55 total thru PayPal).   
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 16 Oct 2016, 08:10 pm
Folsom , I have an insulating washer on the bolt going through the chip, but thought I had to have another insulating washer on the backside of the chip ? . i.e. one on each side of the chip .
Is there just the one washer ? Just want to make sure before plugging in the unit.I made sure not to over tighten the bolt into the heat sink.
I put the DMM probe on the chip and one on the heat sink and get all zeroes at the resistance settings until I set the resistance dial down to the lowest 200 ohm setting, then I get 00.2 on the readout , same 00.2 with probes on the bolt head and heat sink
Continuity check with the probes on chip and heat sink gets a zero readout
thanks

That just doesn't make any sense; it looks like you have the washer (only one is needed) inserted in the chip's hole. If the washers shoulder (wider part) is oriented toward the amp which it looks like it is, there is no way you can have continuity between the screw and the chip unless the mica is not positioned correctly, thus allowing the chip to contact the heat sink. Are you using electrically non-conductive thermal grease?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 16 Oct 2016, 08:45 pm
Sometimes if the bolt is at a little bit of an angle or oritented too far in one direction it can make contact with the tab.

You can also use a drill bit by hand to reduce the tab's edge that it toward the heatsink. You don't want to go all the way through since it would cause issues with the shoulder washer, but a little bit can be enough to help you not make contact with the bolt.

Another option is to drill a bigger hole into the heatsink about 2mm, not enough to ruin the threading for the bolt, and use a shoulder washer that sticks out the other-side a little bit so it's very impossible to make accidental contact.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 16 Oct 2016, 09:25 pm
I slid the washer on to the bolt wider surface first before inserting bolt into the chip tab hole . Just now I loosened the bolt and moved the chip around but am still getting zero readings on the meter continuity test.
When I initially soldered the chip to the pcb and attached the pcb with chip to the heat sink I got good DMM readings. I had slid washers on both sides of the chip at that tryout for fitting to the sink . Maybe the chip is too tight to the sink now ?
I'll take the PCB off and reattach and see what meter readings are.
Thanks for your advice
(http://www.audiocircle.com/image.php?id=152098)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: zek on 16 Oct 2016, 09:54 pm
Is your washer looks like this

(http://www.audiocircle.com/image.php?id=152100)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 16 Oct 2016, 10:14 pm
yes , the insulating shoulder washer at mouser p/n 532-7721-7PPS
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 16 Oct 2016, 11:27 pm
Everything looks good, maybe I just don't understand what your readings are? You should get no reading at all, ideally.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 17 Oct 2016, 02:44 pm
I slid the washer on to the bolt wider surface first before inserting bolt into the chip tab hole . Just now I loosened the bolt and moved the chip around but am still getting zero readings on the meter continuity test.
When I initially soldered the chip to the pcb and attached the pcb with chip to the heat sink I got good DMM readings. I had slid washers on both sides of the chip at that tryout for fitting to the sink . Maybe the chip is too tight to the sink now ?
I'll take the PCB off and reattach and see what meter readings are.
Thanks for your advice

From the shoulder washer spec sheet, the recommended tightening torque for the screw is 4 inch-pounds which is not much. If you over tightened the screw, maybe the washer is broken? Do you have more shoulder washers? I just drilled/tapped mine yesterday, and doing a dry fit without thermal grease I am not getting continuity between chip and heat sink. The washer and mica are doing their job. I am using an M3 screw, what size are you using?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 17 Oct 2016, 05:38 pm
Yesterday I removed the pcb/mica from the chip and inspected the washer , all parts look good with washer intact and chip aligned to sink.
I cleaned the sink / the mica then re-installed. I've been careful not to over torque the bolt/washer when installing .
Using a 4-40 1/2 inch bolt and Radio Shack Silicone Heat Sink grease.
Setting the DMM to continuity test with probes touching nothing results in a reading of "1"    open circuit .
As soon as I touch one probe to sink and one to the metal part of the chip I get a reading of 000 . No decimal point.
Same 000 reading when touching the sink and chip bolt head with the probes
If I set the resistance to the lowest 200 Ohm setting on the meter I get a reading of 00.3 on the display when touching the probes to sink and chip tab.
Higher resistance settings display 000
I touched the probe to heat sink and then each chip leg resulting in a reading of 000 on outer legs and positive numbers on inner legs of the chip.
New battery in the DMM ( Sears Roebuck model , not the cheapest one )
Maybe Folsom is correct about the readings being a problem here ?
thanks for your continued help. I want to plug this amp in but don't want to fry the chip.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 17 Oct 2016, 07:23 pm
Does you DMM have a continuity tester? If so I would use it to check and see if the chip is isolated from the heat sink.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 17 Oct 2016, 07:24 pm
I removed the bolt and moved the pcb/chip a quarter inch from the heat sink so it is not touching, and still get a 000 reading with probes on the chip tab and heat sink in the DMM continuity test setting
Visual inspection of my pcb solder joints don't show any issues that I can see
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 17 Oct 2016, 07:30 pm
It's the 200ohm setting that bothers me. If you have .3ohm you've got continuity. Does it read .3ohms on that setting when they're physically separated?

If you turned it on you'd just have RF, nothing would be hurt, so long as it was mounted to the heatsink.

The most likely thing is the bolt simply is touching the edge of the chip as it leaves the hole. That's why I suggested remove a little material from the heatsink side of the tab, right at the hole. I wouldn't use a drill though unless you spin it backwards. You can even use a razor blade to scrape some material away.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 17 Oct 2016, 07:53 pm
when the chip and sink are separated the 200 ohm setting readout goes up to 00.7
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 17 Oct 2016, 08:48 pm
I suggest you put it back together. Turn the amp on. If you hear a radio station the meter was accurate, if not, you're all good.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 17 Oct 2016, 09:04 pm
You could try and cover the screw close to the head with just enough electrical tape to keep the screw from touching the chip.   
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 17 Oct 2016, 09:09 pm
My experience with trying stuff like that is akin to stubbing one's toe.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 17 Oct 2016, 09:52 pm
I agree with that.

Could it be the thermal paste is conductive? 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 17 Oct 2016, 09:59 pm
I think the meter is stupid, so to speak. Sometimes they just don't understand what they're doing.

You wouldn't hurt the chip at all without the mica or washer, you'd just be listening to the local radio station quietly between tracks.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 17 Oct 2016, 10:33 pm
Thanks guys
Tomorrow a.m. I'll hook it back up .....I'm also thinking the Craftsman meter is muy stupido  .
Looked over my solder connections again with a lighted magnifying visor from HF and though they are not things of beauty, they are also not a mud fence . In other words , looked okay, didn't see any runs drips or errors.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 18 Oct 2016, 01:57 pm
getting ready to power up but took a few pictures first .
I looked at the pcb power supply closely and although the negative and positive terminals are close together there is a distance between the two connections from what I could see. The terminals on the Antipole are a tad further apart and look okay .
Used stranded 16 gauge lamp wire from Antipole to pcb  since my solid copper wire was so stiff.
With the meter probe on heat sink and pcb grnd I get the 000 readout and when moving to the power positive it starts as a number in the several hundreds and just keeps going up on the display

(http://www.audiocircle.com/image.php?id=152215)

(http://www.audiocircle.com/image.php?id=152216)
(http://www.audiocircle.com/image.php?id=152214)

(http://www.audiocircle.com/image.php?id=152213)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 19 Oct 2016, 06:04 pm
Well ,  the LED and switch are working properly, but the meter is right in the continuity test as there is no amp output.
I've looked over the connections and am stumped as to where the circuit is closed.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 19 Oct 2016, 06:38 pm
Well ,  the LED and switch are working properly, but the meter is right in the continuity test as there is no amp output.
I've looked over the connections and am stumped as to where the circuit is closed.

Did you scrape through the mask on the top of your amp and expose the copper where you soldered your + connection on the amp board or is that just the wire sticking up through the hole?

(http://i.imgur.com/SG7RlaR.jpg)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 19 Oct 2016, 06:48 pm
Looks like wire but could be cold joint.

Do you have voltage off of one of the OSCON caps?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: drew_t on 19 Oct 2016, 08:49 pm
Why are carbon comps specified for the pair of 1K8s on the Antipole?  Can I use 1 watt carbon films that I already have on hand instead?

Also, the indicated position for a resistor next to the row of diodes is for a discharge resistor, correct?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 19 Oct 2016, 08:58 pm
I didn't know you had to scrape anything off the eyelets on the boards. I just pushed the 16 gauge stranded copper wire up from underneath and soldered to the terminal . The loose piece is a bit of the stranded copper . I used 16 gauge stranded and it was a tight fit so got messy on the positive side.
Yesterday I touched a probe to the heat sink and one to the positive leg of the pcb power and got a reading in triple positive numbers .
Not sure of how to check the Oscon with a DMM.
Do I have to have the unit plugged in to do this ? I'm assuming the Antipole caps got charged when I powered up today, not sure about the pcb caps ?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 19 Oct 2016, 08:59 pm
No, use 1.8k not 1k. They're a specific value in relation to the CMC. They don't have to be carbon comp. Wattage can be higher.

And yes that's a discharge resistor location.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 19 Oct 2016, 09:03 pm
I didn't know you had to scrape anything off the eyelets on the boards. I just pushed the 16 gauge stranded copper wire up from underneath and soldered to the terminal . The loose piece is a bit of the stranded copper . I used 16 gauge stranded and it was a tight fit so got messy on the positive side.
Yesterday I touched a probe to the heat sink and one to the positive leg of the pcb power and got a reading in triple positive numbers .
Not sure of how to check the Oscon with a DMM.
Do I have to have the unit plugged in to do this ? I'm assuming the Antipole caps got charged when I powered up today, not sure about the pcb caps ?

I assume they got charged too. But since they're connected already you're safe.

Reading of what?

Pick any OSCON capacitor and put a DMM lead on each of the legs. If you have 17.8v~ (or -17.8v~ depending on if you got meters backwards) then you've got power and should be good to go. If no, you can check the output of the antipole by putting DMM leads on the AUX outputs next to the big ones to check for voltage, to make sure you're good up to that point. And then you can check the incoming wires to the amp board too.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 19 Oct 2016, 09:17 pm
okay Jeremy , thanks . I'll follow that and reply .
Reading of what?
Continuity Test on the Antipole output positive with no power to the unit

A dumb question , when checking the Oscon legs and Antipole  terminals with the DMM probes.... that is with the amp plugged in to AC and switched on ?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 19 Oct 2016, 09:22 pm
Yes
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 20 Oct 2016, 05:24 pm
I checked with the meter at the highest 600 setting in the VAC section, and then the lower 200 VAC setting and got readings of zero at the Oscon cap legs and also zero at the pcb power input eyelets.
Reading of zero at the Antipole power output , I couldn't reach the smaller eyelets with the probes so just used the soldered output neg and pos.
Checked again the wiring on the transformer for the jumper and outer terminals to make sure they are correct.
The power switch and LED work .
Title: Re: Folsom's great little 7297 Chip Amp
Post by: S Clark on 20 Oct 2016, 05:32 pm
You need to measure those Oscon caps with the DC setting.  They should read 17.8V DC. Right, Jeremy?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 20 Oct 2016, 06:29 pm
Yes, something would be awfully wrong if you got a VAC reading!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 20 Oct 2016, 06:33 pm
Thanks for that ,
I switched to VDC setting and got readings of 17.7 on the Oscon legs and 24.7 on the pcb power input connections
I watched a video on DMM use this morning and thought the presenter said you use the voltage AC setting for checking consumer electronic circuits ?
Appears the problem is downstream somewhere, can I use a meter to check each leg of the chip ?
When I initially installed the 431 backwards I removed it and cleaned the eyelets with desoldering braid before installing a new one. Hopefully there wasn't something overheated from that procedure.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 20 Oct 2016, 08:31 pm
Have you tried to play music with it?

If you have power at OSCONs then you either don't have an input signal, or the mute/stby isn't working.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 20 Oct 2016, 09:02 pm
Yes. still no music
checked all pcb input/output  and jack/post connections again . They look good
still get the resistance reading when touching probe to chip tab and probe to heat sink
Let me try putting a shoulder washer on each side of the chip
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 20 Oct 2016, 09:09 pm
No, stop. That has NOTHING in the whole damn world to do with getting sound or not. You could have the chip mounted with no mica, no thermal paste, and no washer and it would play music just fine. (You would hear the radio playing through speakers when music was not, however, and lose power due to excess heat)

Either the chip is bad, the mute/stby network isn't working, or you have no incoming signal. There is no other option. You have power to the chip. The signal is either not there, or is turned off, or can't turn on (bad chip).

Show a picture of the mute/stdby area that's to the left of the chip (one cap two resistors). Double check your capacitor placement for the input to make sure you didn't shift them too far to the right and skip the first hole or something.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 20 Oct 2016, 09:39 pm

(http://www.audiocircle.com/image.php?id=152336)

(http://www.audiocircle.com/image.php?id=152337)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 20 Oct 2016, 10:47 pm
And the input caps under?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 21 Oct 2016, 01:08 pm

(http://www.audiocircle.com/image.php?id=152364)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 21 Oct 2016, 01:40 pm
I think Jeremy wants to see the area under the input caps (the big blue ones) Also, you should clean up the residue on the bottom (and top) of the board with alcohol and  Q-tips. Trim the component leads down to the top of each solder peak. Then using powerful magnification such as a jewelers eye loupe, inspect each solder joint for a possible cold solder connection.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 21 Oct 2016, 04:02 pm
Correct.

So far it should turn right on, and does up until the chip, so we need to know why you don't have music.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 21 Oct 2016, 04:04 pm
I assume the negative terminals for the output to speakers are indeed isolated from chassis, correct?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 21 Oct 2016, 04:32 pm
Pomona binding posts with plastic on each side of the chassis
(http://www.audiocircle.com/image.php?id=152386)
Yes
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 21 Oct 2016, 04:44 pm
I think Jeremy wants to see the area under the input caps (the big blue ones)
some q-tip fluff to be cleaned off and thanks for letting me know about that Larry , wasn't aware of that . I hadn't trimmed off the leads yet since there was an issue somewhere

(http://www.audiocircle.com/image.php?id=152385)
[/u]
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 22 Oct 2016, 07:13 pm
Did the chip receive abnormal amounts of heat?

I see no reason why you shouldn't be listening to music.

You didn't drill any holes did you?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 22 Oct 2016, 07:26 pm
No and no
The chip soldered on pretty easily and the joints on each leg look okay on both sides of the board
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 22 Oct 2016, 08:41 pm
What about the potentiometer? How is that wired? If it is not wired properly it could be the problem.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 22 Oct 2016, 08:49 pm
BRN , my suspicions today also , I may have wired it in the opposite way from the picture diagram although I have wired DACTS/pots before
I'll flip them and see
Title: Re: Folsom's great little 7297 Chip Amp
Post by: zek on 22 Oct 2016, 10:05 pm
(http://www.audiocircle.com/image.php?id=152427)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 22 Oct 2016, 11:02 pm
DACT wired backwards. I copied down a diagram from a web site on wiring connections .
Switched to proper terminals, and still nothing
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 23 Oct 2016, 12:11 am
Dead silence when on?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 23 Oct 2016, 01:08 am
Yes, I gotta take a break and look at it again tomorrow
Going to take our granddaughter to the Haunted Pumpkin field Of Fear tonight and re-check .
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 26 Oct 2016, 04:58 pm
finally got a moment to re-check and
I assume the negative terminals for the output to speakers are indeed isolated from chassis, correct?
The Pomona binding posts have ridged plastic collars on each side of the chassis panel, but don't isolate the post completely from the chassis
I removed the four binding posts from the chassis and one channel works ,but not the other channel for some reason .
Back to troubleshoot that and figure how to isolate the binding posts from the chassis
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 26 Oct 2016, 06:10 pm
Ah! Sounds like problem solved, good job, just a little playing around now.

I thought the plastic had a shoulder or something to go into the hole sort of like the one at the chip?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 26 Oct 2016, 08:09 pm
finally got a moment to re-check and
I assume the negative terminals for the output to speakers are indeed isolated from chassis, correct?
The Pomona binding posts have ridged plastic collars on each side of the chassis panel, but don't isolate the post completely from the chassis
I removed the four binding posts from the chassis and one channel works ,but not the other channel for some reason .
Back to troubleshoot that and figure how to isolate the binding posts from the chassis

Only one channel working? Not sure which Pamona binding post you have, but look at the drawing at this link: http://www.mouser.com/ds/2/159/d3750_60_70_1_01-34263.pdf (http://www.mouser.com/ds/2/159/d3750_60_70_1_01-34263.pdf). The 2 plastic washers have a step in them. If you drill a 3/8" hole the step from each plastic washer will fit the opening preventing the washer from moving side to side. Did you drill a 3/8" hole or just one large enough for the threaded shaft?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 26 Oct 2016, 08:36 pm
I thought the plastic had a shoulder or something to go into the hole sort of like the one at the chip?
Yes that's right  , and I thought.... gee that's slick and drilled a small hole that the post went in, but not the shoulder .
Good thing I'm not working on the space program !
Thanks for the link Larry, I need to read the spec sheets for sure
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 28 Oct 2016, 08:13 pm
I drilled out 3/8th holes for the binding posts, mounted them and hooked everything up and am listening to the recent UK remaster Cd of the first Procol Harum CD.
Both left and right channels are working and SOUNDING GRREAT !

Thanks to Jeremy for a cool contribution to the DIY community for us all to enjoy

I just have to drill out the some C+C vent holes on the case cover ( courtesy Lacro ) over the pcb area and find a way for the binding posts to lock in place securely before closing up .
The posts have a circular plastic shoulder with a flat portion so they won't spin but I can only drill a round mounting hole.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 28 Oct 2016, 08:50 pm
Glad to hear you got it sorted!  :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 28 Oct 2016, 08:53 pm
KR500,

That is great news. I'm glade that you were able to finely work it out. I know that it can be very frustrating when you run into a problem on a build. I just built the keantoken simple error-correction superbuffer and was getting hum and picking up radio stations. I looked over everything again and again. I did additional measurements and still could not figure it out. keantoken pointed out, from the picture I posted, that I have wired the output backwards. Once I rewired the buffer it work great.

Brad
Title: Re: Folsom's great little 7297 Chip Amp
Post by: skrstc on 29 Oct 2016, 07:19 am
(http://www.audiocircle.com/image.php?id=152427)
Is this correct way to wire it? My DACT type pot pops with each turn. 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: zek on 29 Oct 2016, 01:37 pm
KR500 said:
"DACT wired backwards. I copied down a diagram from a web site on wiring connections ."
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 29 Oct 2016, 04:23 pm
Yes Zek , but it wasn't that picture , 'nother site for wiring pots which I couldn't find again ( history cleared )

BTW, I'm too cheap to go to the Dollar Store so borrowed from Mama's Kitchen when she wasn't looking and drilled pilot holes in the chassis case top with a 1/16" bit to follow up with a step bit to get them to 1/8" or 3/16"

(http://www.audiocircle.com/image.php?id=152692)

(http://www.audiocircle.com/image.php?id=152693)

Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 29 Oct 2016, 05:00 pm
Yes Zek , but it wasn't that picture , 'nother site for wiring pots which I couldn't find again ( history cleared )

BTW, I'm too cheap to go to the Dollar Store so borrowed from Mama's Kitchen when she wasn't looking and drilled pilot holes in the chassis case top with a 1/16" bit to follow up with a step bit to get them to 1/8" or 3/16"

(http://www.audiocircle.com/image.php?id=152692)

(http://www.audiocircle.com/image.php?id=152693)

Looking good man! Glad you finally got the issues solved, and it's up, and running....
If you finish by de-burring each hole with a countersink, it looks better. On my latest build that I am now burning in while I finish up the case, I am finding both the chip, and the big transistor are staying cold. This is my first build using the Antipole PS. My previous build used a SMPS, and the heatsinks got pretty warm (actually hot). I have vent holes drilled on the bottom of the new chassis, but I may not bother with drilling the top lid as everything is staying cold.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 29 Oct 2016, 05:31 pm
Now I just have to cipher a way to be able to tighten , tried a rubber washer , no good . I thought about putting heat shrink over a toothed lock washer.... but that isn't the answer either.
I have some inexpensive insulated binding posts from ebay I tried that tighten, but they aren't half as well made as the Pomonas. I didn't plan ahead enough on the binding post mounting .
If you have the ability to punch a circular hole with a flat top section it would be no problem
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 29 Oct 2016, 06:08 pm
Now I just have to cipher a way to be able to tighten , tried a rubber washer , no good . I thought about putting heat shrink over a toothed lock washer.... but that isn't the answer either.
I have some inexpensive insulated binding posts from ebay I tried that tighten, but they aren't half as well made as the Pomonas. I didn't plan ahead enough on the binding post mounting .
If you have the ability to punch a circular hole with a flat top section it would be no problem

Are you using bare speaker wire so tightening the nut is making the whole binding post turn? How about just using banana plugs? Or put a dab of super glue on the shoulder washers. 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 29 Oct 2016, 06:18 pm
Hey , thanks for reminding me about the counter sink after using a step bit on the holes ! Nice and smooth now
I forgot I had a cheap little counter sink set from Hazard Fraught

The Pomona Binding posts shoulder washers are for a 3/8" hole with a flat portion on one end of the circle . The flat portion of the circumference is what prevents the post  from continuing to spin as you tighten .
 i.e.  the chassis cut out can't just be round. You can mount bare wire or banana jacks , you just can't get the posts tight to the amp case.
The super glue is my last option unless I can figure something out .
I just wanted to post something about this issue in case someone is using going to use these posts in a build.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 29 Oct 2016, 07:07 pm
I'm so glad you got your unit working KR500. It's always a good day when some changes set a project straight; especially since some can go up in flames! (Not this one, it's nearly impossible to get the chip to do anything but simply turn off or not turn on, the protection in it works good).
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 29 Oct 2016, 07:16 pm
I used Cardas binding post that have a block that holds them in place. Something like this:
http://www.soniccraft.com/product_info.php/cardas-acbp-eu-binding-post-p-5146
Title: Re: Folsom's great little 7297 Chip Amp
Post by: S Clark on 29 Oct 2016, 07:23 pm
... especially since some can go up in flames! (Not this one, it's nearly impossible to get the chip to do anything but simply turn off or not turn on, the protection in it works good).
Yep, run 24V and a bunch of amps into these amps backwards, and I can attest that they are not completely idiot proof!   :oops:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 29 Oct 2016, 08:55 pm
Hey , thanks for reminding me about the counter bore after using a step bit on the holes ! Nice and smooth now
I forgot I had a cheap little counter-bore set from Hazard Fraught

The Pomona Binding posts shoulder washers are for a 3/8" hole with a flat portion on one end of the circle . The flat portion of the circumference is what prevents the post  from continuing to spin as you tighten .
 i.e.  the chassis cut out can't just be round. You can mount bare wire or banana jacks , you just can't get the posts tight to the amp case.
The super glue is my last option unless I can figure something out .
I just wanted to post something about this issue in case someone is using going to use these posts in a build.

I understand about the D-punch opening in a chassis to prevent the post from turning, but you should still be able to tighten the post unless the 3/8" alignment steps (AKA shoulder) on the washers are greater than your chassis thickness. If so, try turning one around so the step is facing away from the chassis, and only one is centering the post in the 3/8" hole. The total amount of the step (shank length in drawing) must be less than the chassis thickness.

(https://secure.microplastics.com/images/scrinsdw.jpg)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 29 Oct 2016, 10:14 pm
Hey , worked GREAT turning one washer the other way round. Thanks Larry , I owe you
When I was dinking around with it this morning I pondered doing that..... but didn't.
One washer shoulder almost makes it through the chassis, but not quite . Getting the other washer's shoulderless face side up against the chassis gave it something better to grip
Now I can button it up and get listening

BRN , thanks for the link to the Cardas posts at Soniccraft
They were on my BOM originally but budget considerations made me opt for the Pomonas, which are less money but still well made
I did wind up getting the Furutech IEC receptacle from Soniccraft though . As Jeremy says , it's a nice piece . I'm glad I skipped the OEM cord that came on the NABU chassis . I'll probably wind up getting a Panagea power cord for this from Audio Advisor
Title: Re: Folsom's great little 7297 Chip Amp
Post by: S Clark on 30 Oct 2016, 01:43 am

With the wife out of town, the bar in the kitchen became the soldering center, and my second Folsom amp has come to life.  Between soldering, smoking some BBQ pork,and a bottle of Muscadet sur lies, it was a great day in the kitchen.   :wine:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 11 Nov 2016, 05:34 pm
I wanted to know what speakers Folsom amp owners are using? I'm using Blumenstein Orca speakers with an old Yamaha 8" down firing sub.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 11 Nov 2016, 06:26 pm
At the moment Klipch MTM speakers while breaking the amp in  ( if needed ? )
Next I'm going to try it in my listening room with my Seas FA 22 Full Range speakers
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 11 Nov 2016, 06:27 pm
 Just completed my latest Folsom amp. I couldn't find a case I liked, so I built my own. I am totally blown away by the sound quality of this one. It's my fourth build, but this one has the Antipole PS with a Lundahl transformer powering it. The amp has the stock BOM except the input caps are Clarity ESA. I have about 100 hours on it, and it is by far the best sounding yet. I have previously only used an SMPS to power these amps. I just can't get over how good this new one sounds. I can listen for hours without fatigue. Jeremy: This is one great design, and I hope you decide to offer another batch of cards so many others can build, and enjoy this superb sounding amplifier!


(http://www.audiocircle.com/image.php?id=153276)

(http://www.audiocircle.com/image.php?id=153277)

(http://www.audiocircle.com/image.php?id=153278)

(http://www.audiocircle.com/image.php?id=153279)

(http://www.audiocircle.com/image.php?id=153289)

(http://www.audiocircle.com/image.php?id=153280)

(http://www.audiocircle.com/image.php?id=153281)

(http://www.audiocircle.com/image.php?id=153282)

(http://www.audiocircle.com/image.php?id=153284)

(http://www.audiocircle.com/image.php?id=153283)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 11 Nov 2016, 06:37 pm
Damn! Nice job Larco, I doubt the pictures even due to full justice (funny lighting). What are the black and white things above the PowerCon inlet?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 11 Nov 2016, 06:51 pm
Damn! Nice job Larco, I doubt the pictures even due to full justice (funny lighting). What are the black and white things above the PowerCon inlet?

Thanks! The Blk/Wh connectors are 10VAC output that powers a DAC that requires 10VAC. The 5.5# 300VA transformer has 4) 16V secondaries that I paralleled, and it has 2) 10V secondaries so I used them to power the DAC instead of a cheap 10VAC wall wart.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: nik.d on 11 Nov 2016, 07:07 pm
Congratulations Lacro, another phenomenal build. And a 300VA Lundahl transformer... What to say! :)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 11 Nov 2016, 08:10 pm
Wow , that is a nice looking piece of gear !
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 11 Nov 2016, 08:46 pm
Wow - Master piece!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 11 Nov 2016, 10:08 pm
 :thumb: :thumb:

Very nice, Larry! Hey--What's up with those fancy input caps? :D It looks as good as I bet it sounds!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: shadowlight on 11 Nov 2016, 11:55 pm
@lacro, wow that is one awesome build.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Captainhemo on 12 Nov 2016, 01:44 am
Awsome Larry   :thumb:
Told ya  that  there  trans had  "  magic pixie dust" in it 

I've gotta get going on mine....
jay
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 12 Nov 2016, 01:51 am
That is one beautiful looking amp. Great job.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 12 Nov 2016, 02:09 pm
Guys: Thanks for the kind words! I am really happy with results of the build, and most of all the amazing sound it produces  :green:
Also, a special thanks to shadowlight, and Captainhemo for their generous donation of parts :thumb:

Hey--What's up with those fancy input caps?

limits: The fancy input caps are just an experiment. Clarity caps are on sale (50% off) at Parts Connection, so they were not much $ I don't know how much the caps are contributing to the great sound with this build, but they don't seem to be hurting the sound. They are keepers!

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Captainhemo on 12 Nov 2016, 04:58 pm
Like I said Larry, the final result is great, I'll  be using  your pics for ideas when I  finally  lay mine out  in a  chassis.

For those interested in maybe tryng some different input caps, Parts Coonexion is having a  25% off sale Sat  Nov 26 but IIRC, it's only on for  1/2 day.

jay
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 12 Nov 2016, 06:55 pm
I soldered 2.5in wire between DAC output and folsom board amp and for me it helped clean up the sound a notch. I used very low cost IC before so it wasn't too surprising it would be better. The source is a RPI streamer with a direct connected I2S DAC so there are now no removable IC in the signal chain.

I'm currently using software volume control for convinience (maybe not ideal) so I don't have the recommended DACT hardware volume control installed.

Many say using a preamp often sounds better than what a DAC itself can produce so are there any recommended tweaks to compensate for this? Buffer? Anything else specific to the Folsom amp?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 12 Nov 2016, 07:01 pm
If you're feeding direct from the DAC you're probably fine. The DACT volume control is excellent but a buffer between it and the amp is best. However you have little need feeding directly from a DAC, so long as the DAC has good outputs.

If you want a buffer I already recommended a very good one (http://www.audiocircle.com/index.php?topic=145992.0). It is however a little more advanced, requiring some work with a multimeter and such to get it correct.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 13 Nov 2016, 03:24 am
Thanks!

The advanced part kind of scared me away last time.  :lol:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 13 Nov 2016, 01:11 pm
I too am interested in the Kuartlotron, but the "advanced" statement has me wondering as well. Is there more than adjusting the correct resistance on the trimmers that makes it advanced? If it makes your already superb sounding amp sound even better, I've got to have one! Jeremy, would you consider putting together a brief "tutorial for dummies"
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 13 Nov 2016, 04:53 pm
It's more advanced because I haven't made a tutorial of any kind, and you need to measure and adjust while it's turned on, and not hooked up to anything. I'd consider making one if someone sent me all the parts and a pair of the (new) PCB boards. The other issue is that you have to provide all of the PSU parts on your own. I could provide a few suggestions but that's about all.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: drew_t on 15 Nov 2016, 08:50 pm
Just completed my latest Folsom amp. I couldn't find a case I liked, so I built my own.

Nice build, but how does the heat get out?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 16 Nov 2016, 01:14 pm
Nice build, but how does the heat get out?

Good observation. The carbon fiber top is intentionally not attached to the case (floating). I purposefully drilled holes between the fins of the heat sink on the bottom. My intention was to drill vent holes in the top; just prop it up similar to a piano top, or remove it altogether during use. However, for some unknown reason, this build does not produce heat (top on), even after a 10 hour high level listening session. I can't explain why as all previous Folsom amps I have built have produced significant heat. I like the clean look of no holes in the top, but, I still have the above mentioned options if ever needed.

Floating top:


(http://www.audiocircle.com/image.php?id=153587)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: S Clark on 16 Nov 2016, 02:11 pm
My latest version also doesn't create any heat to speak of- I can put my finger directly to the heat sink after hours of plaing.  It's enclosed in a hinged Cuervo 1800 box, but I don't feel the need to open while playing. 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Tortorgia on 27 Nov 2016, 04:39 am
Can anyone share a link on where to get the board and an updated parts list? please
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 28 Nov 2016, 06:57 am
I'm out of boards for now.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: zek on 28 Nov 2016, 11:10 pm
Is it possible to get PCBs in pdf and a list of materials for amp and PSU?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 28 Nov 2016, 11:24 pm
Nope.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: zek on 29 Nov 2016, 04:55 pm
Unfortunately. :cry:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Audioillness on 6 Dec 2016, 07:01 pm
Hi Folsom,
I've read this thread avidly, and I too would love have the opportunity to build one of your amps. Do you think you might offer pcb's again at some point?
Dave
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 8 Dec 2016, 11:40 pm
As a matter of fact for Christmas I've got a few from a test run. There's 6 of them and they go to whomever wants to also get Antipole boards with them. They don't have provisions on the bottom for MKP1837 caps. On the top in order to use the PHE426 and MKP1837 you'd have to use some wire. They however are made to fit a cap such as Jantzen's 1.5uf; which is a great option.

(http://www.audiocircle.com/image.php?id=154594)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 10 Dec 2016, 12:49 am
I know some of you want boards, you just haven't looked yet.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Vlad on 10 Dec 2016, 02:33 am
I am interested in the amp/PSU boards (one set).

Thanks,
Vladimir
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Tortorgia on 10 Dec 2016, 12:22 pm
I would like a set please
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Audioillness on 10 Dec 2016, 01:13 pm
I would like to purchase 1x amp, 1x psu boards please.
Dave
Title: Re: Folsom's great little 7297 Chip Amp
Post by: drmike on 12 Dec 2016, 08:47 pm
i have one of each for sale.
thanks,
drmike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 12 Dec 2016, 08:51 pm
You want, or are selling?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: drmike on 12 Dec 2016, 09:02 pm
selling
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 12 Dec 2016, 09:07 pm
Ah ok, that's good. I know there's more people that want boards, they just need to see it. When I ran out lots of people still asked to buy them.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: tubesguy2 on 13 Dec 2016, 03:03 pm
I also have a set of boards, along with most (all?) of the parts necessary, including the recommended Hammond power transformer and, of course, the 7297s. All parts are from Mouser or Digikey. PM me if you're interested in the package. (I assume I can also provide you with a copy of the original documentation, which is Folsom's intellectual property.)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 13 Dec 2016, 06:40 pm
Yes it's ok to forward that information.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Vlad on 14 Dec 2016, 02:06 am
Question to Lacro: where did you buy the LL2728 transformer? It is not listed on the Lundalh site?

Thanks,
Vlad
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 14 Dec 2016, 05:34 pm
Question to Lacro: where did you buy the LL2728 transformer? It is not listed on the Lundalh site?

Thanks,
Vlad

It's not listed because it was originally made for an OEM. It's really overkill for my amp, but it was a gift so I used it. Lundahl transformers in the US can be bought from: http://www.kandkaudio.com/products/ (http://www.kandkaudio.com/products/)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Letitroll98 on 15 Dec 2016, 05:42 am
A couple of posts late, but we do want to pm Folsom about buying any boards instead of posting here.  Don't want to get him in trouble with site policies, he's been so good up till now.   :wink:  And for individuals selling their boards, it's best to post an ad in the trading post and link to it here.  No biggie with what's been posted so far, just going forward we want to stay inside the lines. 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 15 Dec 2016, 06:50 am
It took me a while but I finally got in my mouser order for my first antipole build + my 2nd 7297. Hoping to get get it quickly despite the backorders for a few parts so I will have fun project over the Holidays. Looking forward to it!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 15 Dec 2016, 02:18 pm
It took me a while but I finally got in my mouser order for my first antipole build + my 2nd 7297. Hoping to get get it quickly despite the backorders for a few parts so I will have fun project over the Holidays. Looking forward to it!

Are you going to try different (boutique) input caps on the amp?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 15 Dec 2016, 04:56 pm
I thought about it, but then I couldn't decide so I kept it per the original build spec.

I also noticed there were 1 or 2 minor changes in the BOM since my original build so I'm curious about that too.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Tomy2Tone on 23 Dec 2016, 01:51 pm
Anybody here have one of these amps they built laying around they would like to sell? I pm'd Folsom but thought I'd ask here as well to see if anybody has a decent one they're not using. This would be for desktop use so nothing fancy.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: skrstc on 11 Jan 2017, 09:14 pm
Did anyone tried other types and values of input capacitors?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 11 Jan 2017, 09:32 pm
It's fine to increase the value, but lowering will only reduce bass.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: zek on 12 Jan 2017, 11:39 am
What is the optimum value for the input capacitor - 2uF, 3,3uF?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 12 Jan 2017, 12:05 pm
1.5uf or larger
Title: Re: Folsom's great little 7297 Chip Amp
Post by: herby on 27 Jan 2017, 02:03 pm
Hi Folsom, I wonder where you got the idea for your TDA chip amp :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 28 Jan 2017, 02:29 am
I first tried the amp based on a DIYaudio thread, and thought it had potential.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: herby on 28 Jan 2017, 09:01 am
Remember my post back in 2014 which you responded to? it was entitled byob clone and was based on using the TDA7374 chip. You weren't to favourable to it back then, what made you change your mind? 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 28 Jan 2017, 10:18 am
Don't recall any of that off hand.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: herby on 29 Jan 2017, 03:04 pm
If you google altmann byob clone, its still top of the page.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 29 Jan 2017, 07:06 pm
Ok...


I've got three board sets left over from someone who had claimed them but hasn't come through.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 31 Jan 2017, 03:32 am
Two sets left.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 31 Jan 2017, 08:02 pm
One.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Yatsushiro on 1 Feb 2017, 08:29 am
One.

 :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 2 Feb 2017, 07:09 pm
Here's a tip for anyone using the Hammond 185 series transformer, that I was reminded of from another thread. If you didn't already check, it seems to sound best with hot wired to #6 (and consequently #2 for 115v), over #1. The only safe place to change this is at the transformer.

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Tomy2Tone on 8 Feb 2017, 12:35 am
Just wanted share some pics and thoughts of the Folsom amp I picked up last Friday. I had inquired back in December if anybody had a finished amp they wanted to sell and got a response from forum member Vlad. He only had the boards for sale but with my diy skills not quite ready for something like this he was willing to build it for me. We both picked out parts we thought would be good for the build. I started out thinking just to keep it cheap and simple but it was only a matter of time before I wanted to upgrade this and that.

The case and heat sink are from diyAudio store. Transformer is an Antek AS-1215 - 100VA 15V. All wire is Neotech and the caps are Audyn True Copper. Furutech signal inputs and power inlet with Cardas gold/rhodium binding posts.

I think it came out way better than I could have imagined. Vlad really knows his stuff and did an exceptional job! I only have about 30 hours on it as of now but it really is a sweet sounding amp. I've always associated the term "musical" as being a little on the warm side with not quite enough detail. Well the word I keep thinking when trying to describe this amp is musical but in this case it has more than enough detail but also plenty of spaciousness to the soundstage. I've been finding myself just enjoying the music and not trying to nit pic what's not quite right or what could be improved upon as I really can't find much fault with it. It's definitely a foot tappin kinda amp and I really like that! Great job Folsom and great job Vlad!




(http://www.audiocircle.com/image.php?id=157515)

(http://www.audiocircle.com/image.php?id=157516)

(http://www.audiocircle.com/image.php?id=157517)

(http://www.audiocircle.com/image.php?id=157518)


Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 8 Feb 2017, 01:59 am
Damn those are some barrels for input caps!

You you had it in your big system yet?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Tomy2Tone on 8 Feb 2017, 02:39 am

You you had it in your big system yet?


Yes. Lately I've been using the sainsmart preamp with GE 5670 tubes as a buffer between my dac and integrated amp so for the Folsom amp it's used as preamp/volume control. I think Walkern was first to mention it here but the sainsmart and Folsom amp are a great combo. I have a Tisbury passive that I tried as well and it was good but the sainsmart just has that rich organic sound from those 5670 tubes that makes hard to not keep in there. I'm sure a better preamp would yield even better performance but for now the sainsmart is gettin it done.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 8 Feb 2017, 03:47 am
Very nice work!  :thumb: All it needs now is an LED on that front panel
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 8 Feb 2017, 04:53 am
That looks great! Enjoy!

On a related note, my shipment of parts for my second build finally came from the order I placed before xmas (was backorded)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 8 Feb 2017, 05:43 pm
Yes. Lately I've been using the sainsmart preamp with GE 5670 tubes as a buffer between my dac and integrated amp so for the Folsom amp it's used as preamp/volume control. I think Walkern was first to mention it here but the sainsmart and Folsom amp are a great combo. I have a Tisbury passive that I tried as well and it was good but the sainsmart just has that rich organic sound from those 5670 tubes that makes hard to not keep in there. I'm sure a better preamp would yield even better performance but for now the sainsmart is gettin it done.

Your build looks great. It is interesting reading your comments about using Sainsmart and passive. I first used a passive with my Folsomamp and was very pleased with the results. I built a Kuartlotron buffer which worked better the Folsom and my phono preamp and DAC. Over the Christmas holiday I built a Bottlehead Quickie preamp that I was planning to use in my office. A month and a half later it is still in my main system with the Folsom amp. There is not a great difference between the Kuartlotron buffer and BH Quickie, but for my tastes I Like would the Quickie does. The additional drive and tubes add to the realism of the music ever so slightly. If I was using a tube amp I think it would be different. Both options are great and the reason I have not made a final decision on which will stay.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 9 Feb 2017, 05:29 pm
I'm out of boards again.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: WC on 9 Feb 2017, 05:31 pm
I'm out of boards again.

Are you going to make any more?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: walkern on 11 Feb 2017, 04:52 pm
I just finished up construction of an Aikido line stage to use with my Folsom amp.  I love the way the Sainsmart sounds with the little 7297, but I was curious about how much better a tube line stage might be with better parts and circuit design and boards etc.   The Aikido cost me about 3 times what the Sainsmart did (using stock board and parts from John Broskie, NOS Sylvania 12AU7s, a resistor based stepped attenuator, and decent but not exotic in and output RCA connectors as well as ONO copper and silver hook up wire) but is still C&C, and it does seem to allow me to get a bit more out of the Folsom amp. The dynamics are improved slightly, as is soundstaging and clarity. Overall I am happy with the Aikido, but it is not 3 times better than the Sainsmart and was a great deal more work to get up and running.

In any case, as best I can tell, the Folsom amp will reveal improvements in associated gear and remains (IMHO) a fantastic bargain.  No surprise that you are out of boards again.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Beardy on 17 Feb 2017, 01:20 am
Hi All,

Looking to crowd source here...

Given Folsom is out of boards, what board/sell/origin would you recommend?

I like the idea of a battery supply and this is a convenient deign for a 12V supply it seems like a good time to mess about with this approach.  I have read that you want to add `low impedance’ capacitors as well  - I am assuming that the impedance of the battery is significant and this helps in some way to provide a rapidly responding infinite current source…  is this a near-accurate approximation of what’s going on and what would you suggest?

The crosstalk is noted on the spec sheet at 46db (and typically 60db) – is there anything to be gained in buying two and building up two independent amps or is it more of a case that it can’t be worse, it may be better and it’s so low cost as to not be a concern…? 
I also note Danny's comments about double the current capability, damping etc.  so maybe there are some other potential benefits outside of crosstalk I am missing.  I would guess that the high current capability of a battery supply minimizes the potential benefit of getting away from sharing a single current source.

I have just learned that my BDP-103 uses a digital volume control that loses bits at lower volume levels.  So I need some sort of preamp/volume control.  Output impedance for the OPPO is 100ohms (allegedly) and perhaps I could get away with a passive volume control but otherwise I need to use some volume control on the amp.  I know that the one on the pcb’s from china are not great – what would you recommend (to save me reading back through 40 pages)?

I would guess that the heat sinks on the low cost boards are likely to be places where money can be saved so does any one notice their amps running hot - and just to confirm it the heat sink `live' or grounded (does it need to be isolated from the chip or everything else?

I am sure I will come up with more questions, but your help is gratefully appreciated.
thanks
Beardy
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 17 Feb 2017, 03:10 am
1. I don't know anyone selling another board.

2. eBay boards are compatible with 12v, mine technically isn't for full benefit. 3. Yes capacitors lower noise from battery.

4. Crosstalk figures are probably meaningless. As far as I can tell there's no audio frequency crosstalk to speak of really, as the figure is probably based on tid bits of RF (this is common, to rate chips at crosstalk in unused frequencies). 5. You can gain some current from monoblocking, but that only helps with impedance dips. Proper implementation needs a ballast resistor and I can't inform you of the value on that without a lot of work to test.

6. You loose "bits" on most analog volume controls too, it's not as big of a deal as you might think. My recommendations are you begin to close in on an external DAC to use that has volume, since the Oppo is just OK. 7. Several people have really been digging that little tube-pre mentioned.

8. The low cost boards are probably steel traces, they're single sided, often mislabeled, use all super cheap parts, and use second rate chips that didn't pass quality control to be able to handle full specified voltages.




I'd be happy to print some boards, if there was a min order. It takes about 25-30 orders, of both boards. But so far since I've run out it's been a slow trickle, so it's hard to assume that I can get that min order.






Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 17 Feb 2017, 03:04 pm
Quote from: Folsom link=topic=138229.msg1589811#msg1589811 date=14873010
[b
I'd be happy to print some boards, if there was a min order.[/b] It takes about 25-30 orders, of both boards. But so far since I've run out it's been a slow trickle, so it's hard to assume that I can get that min order.

I for one hate to see this superb sounding amp die on the vine for lack of boards. Why not just start a Group Buy list here where buyers add there name. When the list gets to the predetermined quantity needed, a call for payment is sent to each person on the list.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 17 Feb 2017, 11:38 pm
Where should I post a GB thread?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Letitroll98 on 18 Feb 2017, 04:58 am
Unfortunately you can't post a group buy.  For Industry Participants like you that are not making any real money on these boards we may make an exception and allow that model you've been using of "hey I have some boards, pm me".  And the exception is a tradition, not a rule, so is always subject to the powers that be.  A group buy thread would have to be started by a non-IP member in the appropriate circle, this one in this instance, and would have to organize and run the group buy.

I think if you let a short stretch pass interest will build back up again.  The thread has been going this long, so members are still interested and posting.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 18 Feb 2017, 05:00 am
Thank you, I knew I should ask.

If someone else wants to head up a group buy, that works for me!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: WC on 20 Feb 2017, 04:13 am
Just completed my latest Folsom amp. I couldn't find a case I liked, so I built my own. I am totally blown away by the sound quality of this one. It's my fourth build, but this one has the Antipole PS with a Lundahl transformer powering it. The amp has the stock BOM except the input caps are Clarity ESA. I have about 100 hours on it, and it is by far the best sounding yet. I have previously only used an SMPS to power these amps. I just can't get over how good this new one sounds. I can listen for hours without fatigue. Jeremy: This is one great design, and I hope you decide to offer another batch of cards so many others can build, and enjoy this superb sounding amplifier!



How did you wire up the LED for the front power button?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 20 Feb 2017, 03:53 pm
How did you wire up the LED for the front power button?

There is a wiring diagram at the E-bay sellers listing, link below. The switch LED is 12V, so I used a resistor with the higher voltage supply of the Antipole PS. I don't like super bright LED's so I used a variable resistor (trimmer) to get the illumination I wanted, and then installed a fixed resistor of that R on the switch.


 http://www.ebay.com/itm/16mm-12V-Latching-Push-Button-Power-Switch-Black-Metal-Blue-LED-Waterproof-/141819074705?hash=item2105135891:g:x4QAAOSwdGFYqjOD

Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 17 Mar 2017, 01:31 pm
I've been enjoying listening to my Folsom 7297 amp and since completing the Pass B1 buffer and placing it before the amplifier it even sounds better .
The transformer makes a little noise but unless you're sitting next to it it is not an issue .
The amp is pretty revealing and has good treble and low end reproduction .
Title: Re: Folsom's great little 7297 Chip Amp
Post by: WC on 17 Mar 2017, 02:13 pm
I've been enjoying listening to my Folsom 7297 amp and since completing the Pass B1 buffer and placing it before the amplifier it even sounds better .
The transformer makes a little noise but unless you're sitting next to it it is not an issue .
The amp is pretty revealing and has good treble and low end reproduction .

Which transformer did you use?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 17 Mar 2017, 05:17 pm
The Hammond model in the designers BOM .
It just has a slight audible hum when powered . I have ithe mounting brackets resting on some thin pieces of rubber and there are also rubber washers on the mounting bolts . I will add a layer of rubber on the top of the case to see if it minimizes the hum as the top of the transformer is very close to the case top
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 17 Mar 2017, 06:22 pm
I have had good results reducing hum by using moon gel under the feet of other power supplies that I have used.
Not sure if it will help in your situation but it's only $7

http://www.guitarcenter.com/RTOM/Moongel-Percussion-Dampening-Gels-1274115039839.gc
Title: Re: Folsom's great little 7297 Chip Amp
Post by: absolutk on 20 Mar 2017, 01:59 am
SO many great builds in here! Alas, I'm not in a position to start mine anytime soon so my boards are sitting in their anti-static bags since purchase. Anyone interested, please send me a PM or leave a note here.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: indosmokejon on 23 Apr 2017, 07:40 pm
Hi there. Not sure how many people still have boards out there that are looking for a proper enclosure for their builds. I ran across these on eBay and bought 2 for the builds of the Folsom that I have been planning. They seem to be a great size, they have a built in divider, power cord, heat sink and many other odds and ends. When I get mine I will open it up and take some pics and share with everyone the specifics. I will include a link to the item. I made a "best offer" as well and only paid $30/per to the door!

https://www.ebay.com/itm/192164116930
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 23 Apr 2017, 09:54 pm
Thanks for the heads up on the NABU cases jon
 I used the same one for my chip amp build and I think I paid a little more with shipping from SS,  so its a good deal .
I'll probably pick another one up for future projects
Title: Re: Folsom's great little 7297 Chip Amp
Post by: S Clark on 24 Apr 2017, 01:02 am
They turned down $32, so it may take $35+ to buy one.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: indosmokejon on 24 Apr 2017, 01:23 am
I realize now after reading almost all the way through this build thread again that the NABU chassis is in fact mentioned many times over and even pictured by other builders. Oh well, just trying to look out for people here!  I am excited to get mine and start building.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 26 Apr 2017, 06:48 pm
Just tried putting my Little Dot MkII+ tube headphone/preamp in front of the Folsom amp .
Not really any improvement and clicking sounds when turning the DACT so ...test over . Out it comes
The Little Dot does improve the sound of my modded Audio Source Amp 100 though !
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 26 Apr 2017, 10:20 pm
Just tried putting my Little Dot MkII+ tube headphone/preamp in front of the Folsom amp .
Not really any improvement and clicking sounds when turning the DACT so ...test over . Out it comes
The Little Dot does improve the sound of my modded Audio Source Amp 100 though !

KR500,

What do you normally use to control the volume on your Folsom?

Brad
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 27 Apr 2017, 12:39 am
The DACT that Jeremy initially recommended. It works well .
I Just got clicking sounds with each detent of the knob being turned using the Little Dot as a preamp .
This is in my exercise room on the same circuit as the HVAC and I've had clicking issues there with the Little Dot before .
But the LD didn't really make the chip amp sound any better anyway which I was curious about .
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 27 Apr 2017, 03:45 am
I tried to put the Little bear P3 6N3 6Z4 tube preamp in front of the Folsom amp. This is a cheap preamp that used to be popular choice for the the TPA 3116 amps. I liked it a lot with my TPA amps since it added some tube character to the sound, but it didn't work well at all with the Folsom amp. It really degraded the sound (noise), so out it went after just a couple of minutes, and it's been collecting dust since. Perhaps I could swap out the tubes for better ones, but don't think it will help much.

I have tried to add a cheap buffer between my source and the Folsom amp and that made a nice positive difference. I still need to get around to buy the parts for the buffer recommended earlier in the thread. It's my understanding that it will take it to the next level.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 27 Apr 2017, 11:53 am
I use the PASS B1 buffer in front of the 7297.
The B1 board and matched jfets are at PASS audio for $40 .
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 27 Apr 2017, 01:55 pm
I still need to get around to buy the parts for the buffer recommended earlier in the thread. It's my understanding that it will take it to the next level.

That's the Kuartlotron Simple Error Correction Super Buffer: http://www.diyaudio.com/forums/analog-line-level/251413-kuartlotron-keantokens-simple-error-correction-superbuffer-70.html#post4834519

It definitely does take the Folsom amp to the next level. Highly recommend it. I am currently using a passive shunt type (Haler style) volume control with a 10K Alps Blue Valvet pot, and 2 resistors that works very well. I do have one of the DACT pots that Folsom recommended, but haven't tried it yet.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: S Clark on 27 Apr 2017, 02:03 pm
I've been running the Folsom amp from a Dodd battery pre from the beginning of this thread (wow, 41 pages ago!).  It's a great pre driving an excellent amp.  What's not to like?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 27 Apr 2017, 03:54 pm
I'm running a BH battery powered Quickie with my Folsom. I also have all the parts to build a new Kuartlotron buffer for it.

I had a Kuartlotron buffer, but sold it, but want to give it another try, because I made a build mistake wiht the first that could have affected the sound. Going to take my time and triple check everything this time.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 1 May 2017, 07:14 pm
Finally got some time and brought the 7297 amp up out of the basement to my listening room where I have a dedicated electrical circuit for audio .

sources are  TASCAM CD player > Schitt Uber DAC > quality IC's > PASS B1 > Folsom 7297 > Seas 8 inch full range speakers with the Seas  contour circuit , no crossover.

Listening material is Paul Desmond and Gerry Mulligan on "Out Of Nowhere" RCA CD , ( The Desmond/Mulligan CD is really well recorded and the Folsom amp just reproduces each instrument beautifully , turning the volume up just sounds even better. )
Simon & Garfunkel "Bookends" CD , Juan Esquivel "Space Age Bachelor Pad Music" RCA CD and Colosseums' " Walking In The Park " from the Sanctuary CD of their debut album.

The amp has nice low end and treble extension , upright bass and drums sound really nice, the top end is not etched,but gets right up there on brassy material . If your room or speakers are bright sounding, this might not be the amp for you.
The amplifier really puts out some good sound.  I wish my construction skills were past the beginner level to give the amp it's due when I was putting it together .
The transformer hum is an issue I'll have to address although it isn't audible when music is playing . It is about as much of an issue as the refrigerator cycling on or traffic sounds from outside . The NABU case I used just doesn't have enough clearance to really use much dampening on the transformer . I have some room on the case top to add a thin layer of something above the transformer but that's about it .
The soundstage on the amp just isn't as good as my tube SET amp though . The sound seems pretty directional and narrow although I didn't try toeing the speakers in or using different speakers so ......YMMV.
My tube amp doesn't reproduce the low or high end as well as the 7297 though and it seems a tad less focused although pleasing in it's own way . Tradeoffs .

The Folsom 7297 is a winner , holding it's own compared to an amp that costs much more.
Thanks to the designer for  sharing it with us
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 1 May 2017, 09:15 pm
How many hours do you have on that amp?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 1 May 2017, 09:48 pm
not a lot yet , with fall classes and work Jan through late April this year unfortunately I didn't have much listening time.
Probably 20 hours max so far on the 7297 amp
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 1 May 2017, 09:56 pm
It'll sound better with more time than that! You've got the basic amount that's needed for the OSCON's to shine, but not nearly enough for the input caps.

Maybe now with summer coming up you'll have some free time? I'm excited for trails and such to turn from mud to dirt.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 2 May 2017, 10:44 pm
Would it speed up the cap hours burn in by putting a CD on repeat for a couple of days playing through the amp with the volume down ?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 2 May 2017, 11:25 pm
Yes. Anything helps.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 3 May 2017, 05:11 pm
I need an 8 hour governor before my posts are posted , there's no such thing as a dumb question until I ask one .
I have  a cd playing on continuous repeat into the amp with the volume down until Saturday or Sunday.
It will help get the input caps on the PASs B1 buffer I just built get broken in too.
I'll give it a re-listen on Monday
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 11 May 2017, 02:43 pm
just an update after 150 hours continous CD repeat play of my 7297 amp .
The soundstage is not as directional and has gotten wider and deeper
Listening to Paul Desmond and Segovia sounds fine as wine, really draws you in to the music .
I'll have to listen to some more Pop music on it, but with that material it is not quite as engaging as my SET amp.
The amp is on the workbench so I can add some sound damping material to the area the transformer is in .
Title: Re: Folsom's great little 7297 Chip Amp
Post by: indosmokejon on 12 May 2017, 06:13 pm
So I got my first of two Folsom's built out and so far I am very impressed. I am not completely finished as I don't even have an on/off switch yet, and no faceplate but it will get there. I got tired of waiting for my heat sinks to come in from China and just sandwiched the two that came with the Nabu cases with some thermal grease and it seems to work fine with the heat. The nabu case is unfortunately a little large for my tastes but it has a lot of positives as well, like the built in divider as well as the power cord, it's also very heavy duty. I used the Antek As-1215 toroidal and I am very happy with it, no buzzing or noise of any kind, the amp is dead quiet. I will update my thoughts after some break in time. So far I find it bright, but in a very revealing way, not shrilly or with simblance.  It was easy build too, with great instructions and BOM.  Maybe not recommended, but I did no quality or DMM checks, just plugged it in and it fired right up.  I am currently listening on some modded DCM time window 1A's and once broken in a bit I can't wait to see how it pushes around my Vandersten sig 2ce's. Eventually I will finish the second and try vertically biamping with the pair to increase power delivery.

(http://www.audiocircle.com/image.php?id=162168)

(http://www.audiocircle.com/image.php?id=162169[/
[img]http://www.audiocircle.com/image.php?id=162170)

Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 19 May 2017, 10:46 pm
I opened the NABU case up and noticed I had installed 4 rubber washers between the transformer and chassis base, but only 2 on the tops of the 4 transformer legs before the nuts .
There must have been only  6 rubber washers on hand when I originally finished assembling the case .
A quick trip to Lowe's to get 2 more rubber washers to install and the hum is definitely diminished . Yay !
The vinyl damping material arrived from PE so I placed a layer on the case top panel above the transformer side.
The little stepped DACT volume Control is nice for making small adjustments and works well .
Title: Re: Folsom's great little 7297 Chip Amp
Post by: indosmokejon on 11 Jun 2017, 04:41 am
So I finished up my second Folsom, first one was fine, worked right out of the gate, this one unfortunately doesn't, so I am hoping for a little help. I am getting 16V AC to the antipole, but when I fire it up, the 300v 16A rectifiers start smoking?  The antipole is pretty simple, everything on it is non polarity besides the capacitors. Any suggestions?
(http://www.audiocircle.com/image.php?id=163744)


(http://www.audiocircle.com/image.php?id=163745)

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 11 Jun 2017, 05:19 am
It looks like you drilled out the PCB board holes, probably causing a dead short.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 11 Jun 2017, 05:41 am
The transformer might cook and weld itself before you trip the breaker, I guess... but something else should be failing before long if you leave it on. Sooo you need to use insulated mounts, basically, and replace diodes; maybe transformer if it is having heat issues, hopefully you didn't get that far.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: indosmokejon on 11 Jun 2017, 06:04 am
I didn't get that far.  I hope!  Transformer is working properly, and I definitely didn't drill anything out. Rectifiers are definitely shot, as they are no longer one way by testing with my dmm. The 7297 chip may have been contacting the heat sink when I first fired it up?  Would this fry the rectifiers?  I will order new rectifiers and install and see if I get a repeat performance. I did not install insulated mounts on my last build as it does not seem that the mounts make any contact with anything else on the board?  As long as I did not drill them out this would be the case, yes?  Thanks for the quick reply Folsom.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 11 Jun 2017, 06:13 am
Heatsink to chip doesnt matter.

The holez for the Antipole look drilled on the capacitor side for mounting locations.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: indosmokejon on 11 Jun 2017, 06:18 am
Yeah definitely no drilling of any kind into any holes. I know that's a no-no. Well now I am thinking if I replace all the rectifiers they may just pop again as I may have some other problem?  Guess I could always try and see. I checked for any type of continuity between the mounting holes and anything else on the board and I wasn't getting any readings from all four corners, so that's def not the problem. 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 11 Jun 2017, 08:08 am
Ok, well something is probably shorting out somewhere, otherwise that much current simply wouldn't be drawn. The speaker outputs are isolated from chassis, right?

This image shows the hole that looked odd to me, but I guess it's just an optical illusion.

(http://www.audiocircle.com/image.php?id=163746)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 11 Jun 2017, 01:16 pm
How about trying a different PS to see if the Folsom board is working?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: indosmokejon on 11 Jun 2017, 06:23 pm
I just hooked it up to just under 24v of battery power and everything works just fine. Good to know that I'm not completely dead in the water. I will order 4 new rectifiers and see what happens with the antipole once they are installed. Any way to check the antipole before putting 120v to it and possibly having a repeat?  Could I put 12-20VAC to it and test it?  Folsom, the pic you are questioning is some sort of cell phone anomoly, here's a better one.
(http://www.audiocircle.com/image.php?id=163756)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: indosmokejon on 11 Jun 2017, 06:25 pm
And obviously, thank you so much for the help!!!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 12 Jun 2017, 12:55 am
120v? I hope not directly to the Antipole!

The Antipole is only need 16-18VAC for the amp to get what it needs.

Have you checked the output on the transformer?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: indosmokejon on 12 Jun 2017, 06:34 pm
Yeah sorry. Slip of the keyboard. Antipole only sees 16V AC. My toroidal is functioning perfectly. I could try finding a transformer in my pile that steps 120 down to 5 or so and try it first?  Not sure it will make a difference.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 12 Jun 2017, 11:55 pm
No it won't. Just check for dead shorts.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: indosmokejon on 16 Jun 2017, 06:52 pm
Happy to report that with new rectifiers installed all is well and working perfectly. Not sure what the original problem was?  Maybe a bad rectifier in the first batch?  That's kinda hard to imagine but I changed nothing on the antipole. A couple pics of my finished build with the Nabu case.
(http://www.audiocircle.com/image.php?id=164032[/img

[img]http://www.audiocircle.com/image.php?id=164033)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: indosmokejon on 16 Jun 2017, 06:55 pm
Pics didn't load the first time.
(http://www.audiocircle.com/image.php?id=164034)

(http://www.audiocircle.com/image.php?id=164035)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 16 Jun 2017, 11:04 pm
Oh good! I'm glad it wasnt so hard to solve  :wink:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: errcl65 on 17 Jun 2017, 12:18 am
Where does one get Folsom's amp board or kit?  I would like to build it to replace an old car amp
2 x 40W.     Is there is PSU which can run off the car's 12-14.2 VDC?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 17 Jun 2017, 02:59 am
Where does one get Folsom's amp board or kit?  I would like to build it to replace an old car amp
2 x 40W.     Is there is PSU which can run off the car's 12-14.2 VDC?

I cant find it any where as well, I am interested, itching for a project
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 17 Jun 2017, 03:02 am
Pics didn't load the first time.
(http://www.audiocircle.com/image.php?id=164034)

(http://www.audiocircle.com/image.php?id=164035)

Nice looking build.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 17 Jun 2017, 03:37 am
Im out of boards.

A PSU for a car? Depends on how much voltage you need. If 12v is enough then its some capacitors. If you need more you need a buck booster.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: ebag4 on 8 Jul 2017, 07:14 pm
Just a note about the Folsom amp. 

My son is moving to a house where he now has room to take the GR Research V1s so I thought I would go ahead and set him up with a few other components to get them playing rather than have them use a reciever.  He and his housemates are all in their early 20s so they all use their phones as a source. To make this work I have picked up the iFi iOne for Bluetooth duty, this will run into the original iFi iTube preamp buffer which will drive the Folsom Amp.

To ensure the amp is is running correctly, I pulled it out of the closet and checked it over.  Afterwards I plugged it into my big system, this is truly an excellent amp.  It sounds great running my big system and as an added benefit allows me to break in speakers I just completed without burning up the tubes in my regular amp (Bottlehead Kaiju). 

I may need to find another set of boards to build myself a summer amp, it sounds great and does not heat up the room like the Bottlehead.

One thing I would like to change on the amp is the transformer, I am using the recommended Hammond and it has a slight mechanical hum.  What other currently available transformers have any of you used that have given quiet operation?

Best,
Ed
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 8 Jul 2017, 09:50 pm
If you don't have DC on your line Antek and others offer toroids that hum less. But hum can often be prevented too, with a little isolation work.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 10 Jul 2017, 10:54 pm
In case anyone wants some boards, this just started (http://www.diyaudio.com/forums/group-buys/309860-folsom-diy7297-amp-antipole-psu.html#post5128286).
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 10 Jul 2017, 11:50 pm
In case anyone wants some boards, this just started (http://www.diyaudio.com/forums/group-buys/309860-folsom-diy7297-amp-antipole-psu.html#post5128286).

That's great news! Anybody that has been interested in building one of these great amps, better jump on the group buy.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: jmc207 on 11 Jul 2017, 11:25 pm
That's great news! Anybody that has been interested in building one of these great amps, better jump on the group buy.


I'll second this great news!  http://www.diyaudio.com/forums/group-buys/309860-folsom-diy7297-amp-antipole-psu.html#post5128286
Title: Re: Folsom's great little 7297 Chip Amp
Post by: WC on 12 Jul 2017, 03:26 am
Haven't even finished mine current amp build, but I put in for another set of boards. I bought two of the amp chips, so I guess I should be able to use them both now.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 12 Jul 2017, 09:17 pm
Pro tip:

The 7297 can be light in the bass if a speaker is ported/vented with too low of QES (too much physical dampening is bad too). The simple solution is to take the speaker impedance (4 , 6 , 8 ohm) and divide by 5.45 and get a resistor of that value to insert in series with the speaker. At least as of so far that's the conclusion. If you know the spec's on the driver, and QES is in the .30's range, try a resistor and less stuffing for ported/vented.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 12 Jul 2017, 09:36 pm
Great to see that you have a group buy going.  :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: indosmokejon on 13 Jul 2017, 06:31 pm
For ebag4. The antek toroidal transformers that I bought and used for my two builds work flawlessly and produce not the slightest hum. I am pretty sure I used the as-1215 I believe???  Here is a link.
http://www.antekinc.com/as-1215/

Also, I think it was KR500 that complimented me on my finished build a page or two back, thanks for the praise!!!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: ebag4 on 14 Jul 2017, 12:29 am
For ebag4. The antek toroidal transformers that I bought and used for my two builds work flawlessly and produce not the slightest hum. I am pretty sure I used the as-1215 I believe???  Here is a link.
http://www.antekinc.com/as-1215/

Also, I think it was KR500 that complimented me on my finished build a page or two back, thanks for the praise!!!
Thanks for that, much appreciated.  I see they have a 15v and 20v, I wonder if there is any reason to go above the recommended 16v since it appears he is taking it to 23 V:

Battery power use 24v, SMPS can be as low as 21v, and transformer should be 16v to get rectified around 23-24v.

Best,
Ed
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 14 Jul 2017, 07:17 pm
Thanks for that, much appreciated.  I see they have a 15v and 20v, I wonder if there is any reason to go above the recommended 16v since it appears he is taking it to 23 V:

Best,
Ed
You need to be careful about how much voltage you are providing the amp, because the regulators my not be able to handle the higher voltage.

indosmokejon,

Thanks for the link to the power tansformer. I think that I will use it for my next build. From my calculation it should provide over 21.7VDC.

Brad
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Plund on 16 Jul 2017, 01:36 pm
Lacro,  earlier you posted about completing your fourth Folsom amp and how noticeably better sounding it was compared to the previous three.  What do you attribute most of the improvement to...the large Lundahl xformer?  ...the Clarity input caps?

Looking forward to my 1st Folsom amp build,
Pete
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 16 Jul 2017, 02:24 pm
Lacro,  earlier you posted about completing your fourth Folsom amp and how noticeably better sounding it was compared to the previous three.  What do you attribute most of the improvement to...the large Lundahl xformer?  ...the Clarity input caps?

Looking forward to my 1st Folsom amp build,
Pete

Pete,
If you read my post, you will see that ALL previous builds were powered by SMPS's, not the Antipole PS. I feel the single greatest improvement is the Antipole PS, but powering it with the overkill Lundahl transformer has to be working some magic too. The input caps upgrade  are probably adding something as well. There are dozens of choices for the input and bypass caps to experiment with, limited only by your wallet.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Plund on 16 Jul 2017, 10:35 pm
Thanks Lacro...so, the Antipole is the magic.  Good to hear that the "cheap and cheerful" version of the Antipole is also magical.   I am not sure my ears are golden enough to hear or appreciate any added benefit that the rolls royce-esque components might add anyway.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: ebag4 on 22 Jul 2017, 10:29 pm
For ebag4. The antek toroidal transformers that I bought and used for my two builds work flawlessly and produce not the slightest hum. I am pretty sure I used the as-1215 I believe???  Here is a link.
http://www.antekinc.com/as-1215/
Thanks again indosmokejon/BRN, I recieved the Antek as-1215, it is now installed.  It is dead quiet, the amp is completely quiet .  This one is for my son but I have another set of the boards on order from Folsom.  Happy camper!

Best,
Ed

Quick question for anyone, the LED in my switch is rated at 12VDC, it is the automotive type. I put the recommended 680 ohms resistor in  series  with the positive lead, I am picking up the power to the switch from the output of the Antipole.  The LED is incredibly bright, what are my options to reduce the brightness?

(http://www.audiocircle.com/image.php?id=165887)

Switch Specs
Specifications:
Head diameter: 7/8" (22mm)
Mounting hole size: 3/4" (19mm)
Depth inc contacts: 1.5" (38mm)
Switch combination: 1NO1NC
Operation types: Latching
Switch rating: 5A/250VAC
LED voltage: 12V DC
LED color: Red
Head shape: Flat
Enclosure material: Stainless Steel
Protection level: IP67, IK10
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 23 Jul 2017, 12:04 am


Quick question for anyone, the LED in my switch is rated at 12VDC, it is the automotive type. I put the recommended 680 ohms resistor in  series  with the positive lead, I am picking up the power to the switch from the output of the Antipole.  The LED is incredibly bright, what are my options to reduce the brightness?


Switch Specs
Specifications:
Head diameter: 7/8" (22mm)
Mounting hole size: 3/4" (19mm)
Depth inc contacts: 1.5" (38mm)
Switch combination: 1NO1NC
Operation types: Latching
Switch rating: 5A/250VAC
LED voltage: 12V DC
LED color: Red
Head shape: Flat
Enclosure material: Stainless Steel
Protection level: IP67, IK10

Ed,
 I have the same or similar switch, and I used a 10 or 15K trim pot (variable resistor) to fine tune the illumination I liked, then checked the pot's resistance with my DMM. I ended up with 8k resistance needed, and I didn't have that value resistor so I used 2 resistors in series to get to 8K. Also, I wired my push button switch so power ON is with the switch out, and OFF is in. I liked the way the light looks when it's in the out position. Hope this helps....
Title: Re: Folsom's great little 7297 Chip Amp
Post by: ebag4 on 23 Jul 2017, 12:09 am
Thanks Lacro, exactly the info I needed.

Best,
Ed
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 16 Aug 2017, 03:52 pm
Hi Folsom:

Remarkably quiet around here lately...everyone must be building up their new boards  :D

I had a couple questions about changes you made in the BOM from the first run of boards to the current round:

1) The OSCON cap bank change from 330 to 560 uf--does this affect the sound of the amp at all, or does it simply provide a little more headroom/reserve capacitance to the 7297?

2) In the DIY Audio thread (announcing the new batch of boards http://www.diyaudio.com/forums/group-buys/309860-folsom-diy7297-amp-antipole-psu.html#post5128286) you wrote:
'These next print of boards will feature a BOM with an updated TL431 that's even lower noise. The old TI one sounds a little warmer for who's ever interested.' I ended up ordering both the old TI part and the ON part, and am not sure which one I will use...I know you described the change in the BOM pretty well, just wondering if you have any further insight into this change?

3) For my second Folsom 7297 build (with the new boards), I am going to use a different transformer (Antek AS-2215) and incorporate a Felix line conditioner in the amp case in front of the primaries of the transformer. The ones I have built in the past did not use the 1.8 kOhm 3 watt resistor bypassing the coils of the CMC, which you mention in your construction notes. What is the function of adding this resistor?

Thanks for any insight you may have on my ramblings  :lol:

limits
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 17 Aug 2017, 05:43 pm
1. Not sure anyone will hear the difference, just a little more headroom.

2. TL431.. one sounds a little warmer, one sounds a little more clear. Thats it.

3. Don't put any caps post CMC. What size CMC are you going to use? 1.8k may not be a good value. The resistors stop the CMC from struggling with capacitence on the AC mostly, but help it with other problematic stuff riding on it that can filthy up the CMC too much.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 17 Aug 2017, 06:28 pm
Hi Folsom:

Thanks for the response. I was planning on using the Bourns 8120 RC. Do you think the 1.8kOhm/3 watt resistor would be suitable with this CMC? I was planning on using 1 uf, 0.1 uf, and 0.01 uf x-caps in front of the CMC.

So...kind of a half Felix (no caps past the CMC)? Interesting. Most of the examples I have seen where people have incorporated a felix into a case have used the audiocircle pcb's and have caps after the choke, but I could certainly leave these out.

Thanks again;
limits
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 17 Aug 2017, 09:07 pm
Those are good R values for that CMC.

I know about having the following caps on the CMC's, seems like a good idea on the 115v AC side, but really isn't.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 18 Aug 2017, 04:22 am
(http://www.audiocircle.com/image.php?id=165887)

Ed,

The chassis looks nice. Where did you get it?

Thanks,
Brad
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rtate on 18 Aug 2017, 10:59 am
Got my boards here in Canada yesterday , thanks Jeremy !!   :green:
I have a couple of decisions on parts selection and would like some opinions if I may.

1) for the antipole transformer, some have used a toroid with 18V secondary's, is there any advantage to this or any risk with the higher voltage ? Is there a performance loss with the 15V secondary's instead of the spec'd 16V ?

2)In pictures I have noticed 2 different styles of chokes, one more square and one round. Is one better than the other?

3)I would like to hear from those who have upgraded their caps to see what people are using.
I realize that it's a personal/subjective thing only limited to ones wallet...  :wink:

Keep those build pictures coming, they are really helpful and inspiring !!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 18 Aug 2017, 05:03 pm
1. 18v>15v. 15v might be cut out under load from providing enough power. 18v will produce a little more heat is all.

2. The square one was saturating a tiny bit. It had a warmish sound but the round one has dynamics and stuff that are more accurate.

Title: Re: Folsom's great little 7297 Chip Amp
Post by: ebag4 on 18 Aug 2017, 05:11 pm
Ed,

The chassis looks nice. Where did you get it?

Thanks,
Brad
Thanks Brad.  I would like to tell you but I honestly don't recall.  This case has housed several amp kits throughout the years, I have had it for more than 10 years.  They are still available I believe, I see others using the same or similar case every so often.

Best,
Ed

Edit: I also received my new boards, thanks Jeremy.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 19 Aug 2017, 12:51 am
Ed,

No problem. Does your chassis have a divider that separates the PS from the amp?

Thanks,
Brad
Title: Re: Folsom's great little 7297 Chip Amp
Post by: ebag4 on 19 Aug 2017, 01:13 am
Ed,

No problem. Does your chassis have a divider that separates the PS from the amp?

Thanks,
Brad
Hey Brad, no it does not although I did consider fabricating something.  In the end I just put it together, the end result sounds very good.  It's not my best work so I didn't post any pics, but here it is with the Antec transformer (which made a great improvement over the Hammond):

(http://www.audiocircle.com/image.php?id=167207)

Best,
Ed
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 19 Aug 2017, 02:16 am
How would you compare the hammond to antek in a little more descriptive language?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rtate on 19 Aug 2017, 03:37 am
@ ebag4 , also is it 18v or 15v secondary's ?

Edit , I saw an earlier post that had the model #  (15y)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Voncarlos on 19 Aug 2017, 12:56 pm

(http://www.audiocircle.com/image.php?id=167207)


Hi eBag4

If I could, I would like to make a suggestion tip that was given to me by Rick Schultz, and to which I implemented in my own SS amps.
Remove that large ferrous metal bolt and nut running up through the transformer and replace them with a plastic bolt.
This made a very obvious difference to me for the better.
If I recall correctly, it brought out more clarity and detail in my system.
I should also add that I got rid of the large metal plate on top and substituted a piece of 1/8th inch plywood.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: ebag4 on 19 Aug 2017, 02:45 pm
How would you compare the hammond to antek in a little more descriptive language?
Hi Jeremy, no audiophile terminology required to describe the difference, the Hammond had a constant low level mechanical and electrical hum, I had it mounted on rubber in a separate enclosure and still had the problem. The antec has no self noise that I can hear.

@ ebag4 , also is it 18v or 15v secondary's ?

Edit , I saw an earlier post that had the model #  (15y)
Hi rtate, I am using the 15V secondary as recommended earlier in this thread.  I will use it again for my next amp.

Hi eBag4

If I could, I would like to make a suggestion tip that was given to me by Rick Schultz, and to which I implemented in my own SS amps.
Remove that large ferrous metal bolt and nut running up through the transformer and replace them with a plastic bolt.
This made a very obvious difference to me for the better.
If I recall correctly, it brought out more clarity and detail in my system.
I should also add that I got rid of the large metal plate on top and substituted a piece of 1/8th inch plywood.
Hi Voncarlos, thanks for the recommendation, that's an easy change to try,

Best,
Ed
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 27 Aug 2017, 05:23 pm
Hi everyone--I got my second Folsom 7297 amp, which uses the current version of both the antipole and amp boards, finished on Friday! Once again, I would like to thank Jeremy for offering them again, and also for tweaking the design of both boards.

After a rough set of mistakes I made on the first build, I wanted to challenge myself to have an easier time putting together another one and possibly improve on a thing or two over amp #1. Maybe even have some fun in the process...  :lol: I probably wouldn't have bothered taking on another one, except, despite all the uphill battles at getting the first one to work, it sounds damn good. So...Onward...

This one uses Folsom's updated BOM, with the exception of the under-board bypass caps and I also went with the original TI transistor instead of the ON part. The biggest substitution I made was using the Antek 200 VA transformer instead of the Hammond on my first build...Try as I might, I could never eliminate the hum completely  from it, which was annoying because otherwise the amp was so good. Imaging and detail are just scary good...

I also incorporated  a Felix line filter in front of the transformer primaries. I don't know how great of difference, good or bad, it made, but man, I will say the 3d imaging I am getting--even early on--from this amp is amazing!!


It has been playing almost continually since Friday night, and has really smoothed out since then, with the bonus of an absolutely black, silent background when music isn't playing  :thumb:

So here are some pics...

(http://www.audiocircle.com/image.php?id=167618)


(http://www.audiocircle.com/image.php?id=167617)

(http://www.audiocircle.com/image.php?id=167616)

(http://www.audiocircle.com/image.php?id=167619)

Title: Re: Folsom's great little 7297 Chip Amp
Post by: pocomo on 27 Aug 2017, 09:50 pm
Looks awesome, congrats lims! 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 28 Aug 2017, 01:03 am
 :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: xsb7244 on 28 Aug 2017, 08:26 pm
Folsom,

Do you have a website?  Facebook?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 29 Aug 2017, 12:21 am
Neither. A website will come at some point.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 29 Aug 2017, 01:21 am
Hi everyone--I got my second Folsom 7297 amp, which uses the current version of both the antipole and amp boards, finished on Friday! Once again, I would like to thank Jeremy for offering them again, and also for tweaking the design of both boards.

After a rough set of mistakes I made on the first build, I wanted to challenge myself to have an easier time putting together another one and possibly improve on a thing or two over amp #1. Maybe even have some fun in the process...  :lol: I probably wouldn't have bothered taking on another one, except, despite all the uphill battles at getting the first one to work, it sounds damn good. So...Onward...

This one uses Folsom's updated BOM, with the exception of the under-board bypass caps and I also went with the original TI transistor instead of the ON part. The biggest substitution I made was using the Antek 200 VA transformer instead of the Hammond on my first build...Try as I might, I could never eliminate the hum completely  from it, which was annoying because otherwise the amp was so good. Imaging and detail are just scary good...

I also incorporated  a Felix line filter in front of the transformer primaries. I don't know how great of difference, good or bad, it made, but man, I will say the 3d imaging I am getting--even early on--from this amp is amazing!!


It has been playing almost continually since Friday night, and has really smoothed out since then, with the bonus of an absolutely black, silent background when music isn't playing  :thumb:

So here are some pics...


limits, what size enclose did you go with, L / W / H ? and Brand?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 29 Aug 2017, 02:56 am
Limits,

You build looks great. I can't wait to start my next Folsom amp.

Brad
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 29 Aug 2017, 02:04 pm
Thanks, guys!  :)

Can't wait to see your next build, Brad--you always do great work!

limits, what size enclose did you go with, L / W / H ? and Brand?


undertowotg1--I went with a chassis from the diyaudio store:

 1 x Pesante 3U - Quantity 1 / 300mm / 10mm Silver for $117.00 each
Rear Panel IEC Socket Option:Without IEC Socket
Handles:None
Baseplate:I'd like a baseplate
Baseplate Depth (Match your chassis depth):300mm
How many 300mm deep baseplates?:1 x 300mm deep baseplate [Add $12.00]
Feet:Anti-Vibration Feet
Feet Quantity:1 set (4 pieces) of Anti-Vibration feet [Add $16.00]
Customization:None

Kind of expensive but it looks nice. I would highly recommend getting the baseplate. It makes assembly a lot easier, as you have open access to everything, and once you get everything built (except soldering the input/output connections) you can just drop in the baseplate and complete the build.

limits
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 29 Aug 2017, 07:33 pm
thank you for the detailed respone Limits
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 7 Sep 2017, 02:16 am
I am in the process of ordering my parts for the Folsom AMP.... I am a total newbie at this :scratch:, I have built other audio related things but nothing like an amplifier. I may be relying on this thread a little to much during my build, only time will tell. I went ahead and splurged on the case and got the same case limits used, they do look nice.

For my second question.....As far as the heat sink is concerned what size should I be aiming for? Whats the deal with this aspect of the build?

Thanks.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 9 Sep 2017, 01:31 am
I am in the process of ordering my parts for the Folsom AMP.... I am a total newbie at this :scratch:, I have built other audio related things but nothing like an amplifier. I may be relying on this thread a little to much during my build, only time will tell. I went ahead and splurged on the case and got the same case limits used, they do look nice.

For my second question.....As far as the heat sink is concerned what size should I be aiming for? Whats the deal with this aspect of the build?

Thanks.
I have been looking on Mouser and some pics of other members builds. Would a HALF BRICK designed for adhesive work? So many choices on Mouser! :o
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 15 Sep 2017, 03:29 am
So I have started my build, I did the antipole first to get in the groove again. I was pretty straight forward. Now I guess I am on the harder part, mounting the chip and soldering the chip. The solder holes are pretty close in this area. I assume it is an issue if the legs on the chip touch other legs. Anyone have some tips for this area of the build.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 15 Sep 2017, 04:00 am
Well you certainly need a thin tip for the iron.

(http://img.dxcdn.com/productimages/sku_156152_1.jpg)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 15 Sep 2017, 04:36 am
OK, I will have to pick one up, mine is a little too big I guess. Thanks Folsom, this amp is already a blast to build.

Another question, why do I have 5 INSUL SHOULDER WASHERS?  I know 1 is for the Chip and bolt, where do the other 4 go (or are they not needed)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 15 Sep 2017, 05:42 am
Oh, I guess I could reduce those. For awhile they were useful for the mountain screws, on the old boards.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: drmike on 16 Sep 2017, 04:44 pm
hello,
where can the epcos 2.2 uf caps be bought?
thannks,
drmike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 16 Sep 2017, 05:28 pm
http://www.mouser.com/ProductDetail/EPCOS-TDK/B32560J1225K/?qs=%2fha2pyFadui2wUXthMXfNAix%252baxXKxYxqvjE9tkd0sVFEXD4CLkiBw%3d%3d

Did you not get the BOM?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: pocomo on 18 Sep 2017, 01:01 pm
New Build working :)

(http://www.audiocircle.com/image.php?id=168660)


(http://www.audiocircle.com/image.php?id=168661)

Build is basic, using the standard BOM (++ Jantzen input caps) in a Galaxy 3U case from the DIYAudio store.

This was to be my first amp building project, but when I actually looked at the soldering skills required I was not up to the task. I researched a bit and found Radu Tarta of CT who usually builds very nice DHT amps who did a great job for me.  You can reach him through his project blog: https://simplepleasuretubeamps.wordpress.com/projects/.

Still breaking in, but so far the sound is very, very good. Especially at low levels where you can still hear detail and dynamics which I really enjoy. Bottom end is full, tight and detailed; top end is shimmery yet sibilance is perfectly controlled (pet peeve of mine).  Great job Jeremy.

Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 18 Sep 2017, 02:35 pm
Look very nice pocomo.

Thanks for the pics. What is that "extra" piece above the PSU?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: pocomo on 18 Sep 2017, 02:47 pm
Thanks!

That's a thermistor-controlled chassis ground connection, which can be easily removed if there are problems with ground loops. This was Radu's little innovation.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 18 Sep 2017, 03:59 pm
Looking good, pocomo  :thumb: enjoy!!

limits
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 19 Sep 2017, 03:14 pm
So I discovered I made a small error when ordering the heat Sink for my amp. The heat sink "fins" will be running horizontally when I attach it to the chip (due to chassis height) . I realize now that I should have ordered a size allowing me to have the fins running vertically. I was planing on having he heat sink inside the case and NOT mounted to the back of my chassis but I can always change that idea or cut the heat sink

So overall is this an issue if the fins are running horizontally? or should I cut to size?

Here is the link to the one I have now
http://ca.mouser.com/ProductDetail/Wakefield-Vette/557-140AB/?qs=%2fha2pyFaduiG2q9R1p1wFwcJKjK4nkUZWllLfOfAWOG%252bC6PYgLkYRQ%3d%3d
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 19 Sep 2017, 03:44 pm
Verticle works much better if it has airflow on top and bottom. You could use a silent fan.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 19 Sep 2017, 03:54 pm
Verticle works much better if it has airflow on too and bottom. You could use a silent fan.

I figured vertical is the way to do it properly. Will it work as needed horizontally, I will have airflow side to side?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 19 Sep 2017, 04:25 pm
No air really flows side to side unless you force it. Up and down is convection.

It'll work but you may want to monitor it because if it gets hot you lose power.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: S Clark on 19 Sep 2017, 04:28 pm
Why not take a Dremel and a cutoff disc or a hacksaw and cut vertical slots?  It will reduce mass a bit, but increase air flow. 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 19 Sep 2017, 05:13 pm
pocomo,

That is a very nice build. I'm going to build my second amp, when I can find the time, with the new boards and was looking at a chassis and like the one you used. What are the dimensions and did you have to cutout the opening for the IEC inlet?

By the way my original build was with the stock BOM with the exception of Nichicon caps. The amp sounds great and I still never feel the need to change it like I do with other gear in my system.

Thanks,
Brad
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 19 Sep 2017, 05:18 pm
I am really new at this, but wouldn't the easiest solution be to cut the heat sink to fit my case, then rotate it. I did a crazy paint drawing to illustrate what I would do so there is not confusion ( I hope) :? OR after cutting would the heat sink be too small to be useful?

(http://www.audiocircle.com/image.php?id=168705)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: pocomo on 19 Sep 2017, 05:50 pm
@BRN

Hi Brad -

There are a lot of choices on the DIYAudio store https://diyaudiostore.com/collections/chassis;  we chose the biggest Galaxy 3U at 330mm x 280mm which gives plenty of room for layout plus height for heatsink clearance with a still pretty reasonable overall footprint (~ 13"w x 11"d).  Radu did punch openings for connectors and the power switch but I believe you can order them pre-cut.

Good luck with your next build!

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Hirst on 19 Sep 2017, 10:09 pm
This is an excellent and easy build for those with "hobby" level skills.  My soldering station crapped out on me and I had to use an old and abused 30 watt soldering iron without any special tips.  No, it was not pretty but there is ample room on the board.  The PSU is even easier.   I would not recommend the iron that I used.  The layout is very accommodating so do not be intimidated and grab this amp/psu, order the parts and have some fun. 
For those like me that have to be careful where their funds go I ended up using an old computer case.  No pictures as this is version 1 and I still have to replace the face.
The sound is incredible and the power is more than ample.  I have the gr research X-LS speakers in a 13' x 15' room and the volume adjustment is at 12% for casual listening and I anything over 25% is uncomfortable.  I did have to buy an inexpensive DAC as my music is played through an old "business" PC with on board sound.   
Buy two kits and give one as a Christmas gift.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 21 Sep 2017, 03:46 pm
Why not take a Dremel and a cutoff disc or a hacksaw and cut vertical slots?  It will reduce mass a bit, but increase air flow.

I took your advice SClark. Man is my arm tired
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 22 Sep 2017, 06:09 pm
Hi All,

Another question from the newbie. I am in the process of wiring the RCA signal input to the amp board. Looking at the board I see L SG R by the input section. How do I know which holes to use for the ring and the tip of each RCA jack?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 22 Sep 2017, 06:42 pm
The L and R are signal, which is the center of the RCA jack. SG is signal ground, the outside of the RCA jack.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: zek on 22 Sep 2017, 06:46 pm
.. SG is signal ground, the outside of the RCA jack.
Common for the L and R input signal.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 22 Sep 2017, 09:25 pm
Thank you so much.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 22 Sep 2017, 09:26 pm
The L and R are signal, which is the center of the RCA jack. SG is signal ground, the outside of the RCA jack.

Thank you so much. This amp is so fun to built even though I have very little knowledge about electronics  :lol:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 3 Oct 2017, 03:38 am
Thank you so much. This amp is so fun to built even though I have very little knowledge about electronics  :lol:

Well, I am not surprised (see above comment by myself). I finished my amp a few nights ago, plugged it in, turned it on................and it doesn't work  :?

I took it to my father in laws place; he is an electrical engineer; and we looked it over. I am using an ANTEK Transformer  http://www.antekinc.com/as-1215/
We measured the power. I am getting 16 V AC on the Input of the PSU and 20.5 out of the PSU to the Aamp Board. Right now it seems like there is not power getting to the Amp Board but a multi meter says its there.

Everything else seems to be fine coming off the of the amp to the RCA Jacks and Binding post.. So what could be wrong, any help is appreciated. I can post more pictures later. I can always use it as a door stop I guess. I am going to go cry myself to sleep now, goodnight.

(http://www.audiocircle.com/image.php?id=169286)

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 3 Oct 2017, 05:55 am
Can I get a higher res photo of the amp board? Top and bottom.

What voltage do you get off of one of the OsCON's?

It is probably something simple. It happens.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 3 Oct 2017, 08:00 pm
Can I get a higher res photo of the amp board? Top and bottom.

What voltage do you get off of one of the OsCON's?

It is probably something simple. It happens.

I will post some tonight, hope it is a small thing.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 4 Oct 2017, 02:17 am
Here are some Hi Res pics hope the are useful. I am not the best solderer in the world that's for sure. I cannot measure the OsCONs right now, need batteries for my meter. I will grab some ASAP to check.

notice the part I circled. the through hole filled with solder by accident.

(http://www.audiocircle.com/image.php?id=169326)

(http://www.audiocircle.com/image.php?id=169327)


(http://www.audiocircle.com/image.php?id=169329)

(http://www.audiocircle.com/image.php?id=169330)

(http://www.audiocircle.com/image.php?id=169331)

(http://www.audiocircle.com/image.php?id=169332)

Title: Re: Folsom's great little 7297 Chip Amp
Post by: srb on 4 Oct 2017, 02:31 am
notice the part I circled. I through hole filled with solder by accident.

It could be a problem with 4-layer boards by shorting out ground or power layers, but because I'm not seeing any circuit traces on the bottom of the board, it looks like it's probably a single layer board.

Steve
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 4 Oct 2017, 05:39 am
I'll keep looking but I can't tell anything obvious from these photos atm, maybe there is... Knowing the voltage of the OSCON's will tell us more.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 4 Oct 2017, 03:13 pm
I'll keep looking but I can't tell anything obvious from these photos atm, maybe there is... Knowing the voltage of the OSCON's will tell us more.

Just measured the OSCON's With my meter. The voltage coming into the AMP Board is 20.5 and the OSCON's are -17.5    ------ I set the meter on 200 V range.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 4 Oct 2017, 03:27 pm
undertowogt1--measure from an oscon positive leg (underside of board) to negative power input to the amp board. If you have the red probe of your multimeter on the positive leg of an oscon, you should see 17.5-17.7 vdc. Also, based on your pictures, you might want to flow some more solder on the chip legs. Good luck!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 4 Oct 2017, 03:33 pm
OK did it. I got 17.71
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 4 Oct 2017, 03:56 pm
So the problem is in the chip area, mute/stby, or inputs.

Reflowing solder and making sure none of the chip pins are connecting through solder is a good idea.

What temo do you solder at?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 4 Oct 2017, 04:32 pm
Just looked at the chip with my magnify glass. looks good, no solder is touching other legs. I do see that the middle pin on the first row (closest to the chip) is

soldered on the bottom only. The top potion of the hole is not full of solder. What is that leg for? Maybe thats the isue? I will fix this tonight and see what happens. My Iron is a Weller Soldering station, its a fixed temp. not sure of the temperature.


(http://www.audiocircle.com/image.php?id=169344)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 6 Oct 2017, 01:17 am
Just looked at the chip with my magnify glass. looks good, no solder is touching other legs. I do see that the middle pin on the first row (closest to the chip) is

soldered on the bottom only. The top potion of the hole is not full of solder. What is that leg for? Maybe thats the isue? I will fix this tonight and see what happens. My Iron is a Weller Soldering station, its a fixed temp. not sure of the temperature.


(http://www.audiocircle.com/image.php?id=169344)

Hi Folsom,

I was just looking at the chip soldered legs. The hole that I circled in the above image is soldered fine on the bottom of the board. What I do notice is the solder from that circled hole is just slightly touching the copper of the hole above it. It is the solder hole all by itself under the chip. Would this be an issue? Where do I look to trouble shoot the mute standby
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 6 Oct 2017, 04:17 am
That little hole above it isn't a concern. The closest chip hole to it is the same thing, they're connected.

The Mute/stby is the two 47kohm resistors and 100uf cap near the chip.

Maybe make sure that there is no continuity between the chassis and the negative or positive output binding posts?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 6 Oct 2017, 04:40 pm
I checked continuity of all my inputs and outputs, between the binding post and chassis. I have looked at all my solder points , nothing is touching. I am getting power to the AMP Board with the proper values. I am pretty stumped now :?. Any other recommendations. What would an experienced AMP makers next move be.
Any recommendations are appreciated.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 6 Oct 2017, 04:57 pm
Usually it involves looking at it forever ever and ever, thinking about it a lot... feeling insane. Doing something stupid like replacing the chip and it still not working.  :lol:

At this point you may want someone to take a look. But you already had that one engineer take a peak? Think he's up for soldering in a new chip?

Before you do that, plz double check the codes on the resistors for mute/standby. You can find resistor code things online where you can put in the colors.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 6 Oct 2017, 05:15 pm
Usually it involves looking at it forever ever and ever, thinking about it a lot... feeling insane. Doing something stupid like replacing the chip and it still not working.  :lol:

At this point you may want someone to take a look. But you already had that one engineer take a peak? Think he's up for soldering in a new chip?

Before you do that, plz double check the codes on the resistors for mute/standby. You can find resistor code things online where you can put in the colors.

 :o I thought they were the same resistor. Must look at this ASAP. Feeling kinda dumb, but that ok with me..........ok I looked and did the a calculator online. They are the 47k Resistors.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 6 Oct 2017, 05:54 pm
On one of the amp boards I built, I inadvertently swapped polarity on the power inputs which immediately fried the chip. You didn't possibly do that did you? Another thought: could a static discharge from you handling the chip or from your soldering iron have zapped the chip? If you have to go that route, the chip is only $4 but kind of a pain to remove. I cut all the leads from the chip, and desoldered them one at a time which wasn't that difficult. Hope you solve your problem soon.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 6 Oct 2017, 06:45 pm
On one of the amp boards I built, I inadvertently swapped polarity on the power inputs which immediately fried the chip. You didn't possibly do that did you? Another thought: could a static discharge from you handling the chip or from your soldering iron have zapped the chip? If you have to go that route, the chip is only $4 but kind of a pain to remove. I cut all the leads from the chip, and desoldered them one at a time which wasn't that difficult. Hope you solve your problem soon.

thanks for your thought. I did not have the polarities wrong at any time from the PSU to the AMP Board so that would not fry the chip. Maybe a static discharge, but I really dont know. All I can conclude is that the chip is broken.  maybe I will desolder in redo it to see what happens.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 6 Oct 2017, 07:21 pm
Quote
Any other recommendations. What would an experienced AMP makers next move be.

I'm far from an experienced AMP maker and would put myself at the other side of the spectrum...so pay more attention to the experts. The only thing I would add is before going through the painful process of desoldering is to make sure to triple check the obvious. For example, when I built my amp board I spent an evening trouble shooting why I didn't get any sound - in the end it turned out to be a faulty RCA cable... :duh:

It's probably not what you have problem with, but at least a lesson I learned is to always make sure to check the easy things first. Hope you will get it sorted soon!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 6 Oct 2017, 07:28 pm
Odal, that is pricesly why I said going insane and doing something unnecessary is part of the standard process.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Odal3 on 6 Oct 2017, 08:18 pm
 :lol:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 7 Oct 2017, 04:07 am
Is there any way to test the transistor with multi meter. The transistor that can be fried if the PSU is plugged in if the capacitors are charged. I don't think I did that but I want to be positive I didn't.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 7 Oct 2017, 05:09 am
Only if you take it out first.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 7 Oct 2017, 01:33 pm
Ok I will take it out. Am I then just checking continuity between the legs.................EDIT> I contacted my Father In Law and apparently Transistors are I little more complicate to test
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 7 Oct 2017, 04:41 pm
Oh my Gosh :o, I am on my way to solving this. Something silly of course , its working will update when it is 100 percent :icon_lol:

UPDATE: So it has something to do with the binding post. When I was trouble shooting I tested continuity from inputs to the board and from the board outputs to the binding post, ALL was good. Also when trouble shooting I attached my speaker wire directly to the output wire, BUT the output wire was ALSO attached to the binding post at the same time. When I finally solved the issue I de soldered the binding post and went direct to Speaker wire.  Bingo, it worked. I didnt a little dance and ran around the house telling everyone I think I solved it. The were like......oh.

So I guess the binding post were shorting out the single somehow. I need to figure that out now. Currently listen direct from the outputs and it sounds great so far.
(http://www.audiocircle.com/image.php?id=169495)



UPDATE: Since I am such a newbie at this I made s silly mistake. Hopefully another newbie can learn from it reading this thread. When I drilled the binding post holes I did them to the size of the binding post  POST. So my Binding post were touching the chassis The were shorting out the binding post. So even when I was trouble shooting it was shorting out my signal.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: uncola on 7 Oct 2017, 06:38 pm
Congrats undertow!  You’re the second person in this thread where it turned out his problem was the binding posts..  odd
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 8 Oct 2017, 01:32 am
Finished and working, so far it sounds better than my other AMP, Yamaha CR1020. The build was pretty easy for a newbie like me until I ran into my rough patch after it didn't work :lol:. Ultimately it was a simple, silly issue with a simple fix. Thank you Jeremy and others on the forum for their time and help with my built. I am very happy with it.
(http://www.audiocircle.com/image.php?id=169509)

(http://www.audiocircle.com/image.php?id=169510)

(http://www.audiocircle.com/image.php?id=169511)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: S Clark on 8 Oct 2017, 01:40 am
Glad you got it working.  They are very high quality amps if a dozen watts will suffice- and for not much cash. 
Mine does a great job with 91 dB efficient speakers.   
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 8 Oct 2017, 01:59 pm
Glad you were able to figure out the problem. I think we have all had to deal with making mistakes when doing diy, I know I’ve had my share.

It is a great sounding amp. I really enjoy mine and have plans to put another one together.

By the way, what are you using to separate the sections between the transformer, power supply, and amp?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 8 Oct 2017, 02:24 pm
Glad you got it solved. This seems to be a common mistake. See my comment at post 696 http://www.audiocircle.com/index.php?topic=138229.msg1565604#msg1565604
The holes drilled in the chassis have to be the diameter of the step on the plastic washer which prevents the post from shorting to chassis. The common mistake is to drill the holes the size of the threaded post which can allow it to contact the chassis. See the drawing in the link I posted in the above post.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 8 Oct 2017, 03:33 pm
Quote

By the way, what are you using to separate the sections between the transformer, power supply, and amp?


Between the amp and psu and transformer I am using some metal I had kicking around. It was perfect because it was already bent at the bottom for mounting. I painted it a funky yellow and drilled holes to accommodate and mount MDF on each side. I wanted to dampen the metal walls and it worked out well. The MDF made everything a little more solid for mounting.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 8 Oct 2017, 04:32 pm

The holes drilled in the chassis have to be the diameter of the step on the plastic washer which prevents the post from shorting to chassis. The common mistake is to drill the holes the size of the threaded post which can allow it to contact the chassis. See the drawing in the link I posted in the above post.

Ya this is exactly what I did. The holes I drilled initially where the size of the threaded pole. It all made sense once I figured it out. Rookie mistake right :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 8 Oct 2017, 06:40 pm
I did actually mention to check for that.

Many binding posts have a tiny lip to prevent it, easy to miss.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 8 Oct 2017, 08:24 pm
Nice, undertowogt1!! :thumb: Am glad you got it working! Enjoy!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 8 Oct 2017, 11:25 pm
I did actually mention to check for that

Yes Folsom, I remember. I am too inexperience and only checked for continuity between the board and binding posts. I am learning as I go with my multi meter as well. I learned a lot of basic things with this build.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: absolutk on 10 Oct 2017, 03:03 am
I'm relieved that the issue is resolved, undertowogt1! You will not be disappointed in what you hear.

TL;DR: This amplifier is incredible... IF your speakers are not insanely hard to drive. If you've been debating, do it now.

I've traveled quite a bit in my audio journey, and practically all of it has been in the same apartment. I've had a Parasound A21, Simaudio i5.3, Vinnie Rossi LIO, and Devialet 400 among solid state equipment (a handful of tube gear here and there), paired over the years with Zu Superfly, Harbeth C7, Martin Logan Vantage, and finally tired of the constant chase, a locally made pair of speakers using Focal drivers which are basically illiquid.

I'd bought Jeremy's boards (DIY7297 + Antipole) a while ago, but never got around to ordering the parts because life got in the way, and the Devialet combination was working so well. Still there were some quirks, and I always thought that I could eliminate those with a raspberry pi. So I finally bit the bullet and ordered the standard BOM from Mouser, a DAC from the good guys at Allo, a chassis off of Amazon and connectors and wire from around the web. I expected assembly to take the whole weekend, but put it all together in four hours! The chassis was being a bit troublesome but finally hooked it all up, got Spotify Connect working and... sound!

And not just sound - a sound that got me close enough to the Devialets to make me sell them.

Here are the characteristics that stand out the most:

* Impeccable control on the sub-100 Hz range
* I'm not sure if I'm using this correctly, but the 'dynamic range' is fantastic. Its ability to deliver a bass punch to the gut and simultaneously rustling leaves in your ears is pretty neat.
* The background is black as ink. Though, when I get closer there's a mild 120 Hz hum that I need to trace down.
* The soundstage was wide when I used the standard Kemet + Vishay caps in the input stage. When I replaced those with Jantzen Superior, it became W I D E. The Jantzen took about 3-4 days to break in.
* Micro details/voice texture could be more pronounced, but then again, the entire source is <$150, so that's likely the bottleneck

This weekend I took the amp to my friend's place who also has a Devialet 400, but with a pair of Magico Q1 (4~5 Ohms, 86 dB/w/m). Listening to it at medium volume (baby was sleeping), we couldn't hear any bass from 5-6 ft away. Swapped back to the Devialet and more music seemed to emanate at the same listening level. My speakers are supposedly 91 db/w/m sensitive, and simply rock at all volumes.

The boards are really thoughtfully laid out and their quality is fantastic. As you can see, Jeremy is enthusiastic about helping and teaching. Super kudos to him. This is a wonderful and simple opportunity for one to create something of beauty *and* value.

Thankfully he had a few more boards remaining from the last run and I managed to get another 2x DIY7297 + Antipole boards from him. I'm considering a dual mono design. I really have no reason to do so apart from curiosity. Does anyone have thoughts on how to approach bridging? I have 3 pairs of binding posts on each speaker (2 in the bookshelf, 1 in the LFE), if that affects the direction.

 
(http://www.audiocircle.com/image.php?id=169671)

(http://www.audiocircle.com/image.php?id=169672)

(http://www.audiocircle.com/image.php?id=169673)

Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 10 Oct 2017, 01:13 pm
 Looks like you were able to stuff a bunch of  parts into that smallish chassis. interesting how you did the top :thumb: Curious what the single gang electrical box is for?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: absolutk on 10 Oct 2017, 04:30 pm
Yeah, the top is just a piece of maple plywood that I had stained a few years ago, sitting on top! The electrical box was intended to include an outlet so I could easily mess around with various sources (The Raspberry Pi and the isolator HAT both need 5v, for example). I didn't do it because then the components would be too tall to put a cover on top. 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 10 Oct 2017, 11:45 pm
I'm relieved that the issue is resolved, undertowogt1! You will not be disappointed in what you hear.

TL;DR: This amplifier is incredible... IF your speakers are not insanely hard to drive. If you've been debating, do it now.

And not just sound - a sound that got me close enough to the Devialets to make me sell them.

Here are the characteristics that stand out the most:

* Impeccable control on the sub-100 Hz range
* I'm not sure if I'm using this correctly, but the 'dynamic range' is fantastic. Its ability to deliver a bass punch to the gut and simultaneously rustling leaves in your ears is pretty neat.
* The background is black as ink. Though, when I get closer there's a mild 120 Hz hum that I need to trace down.
* The soundstage was wide when I used the standard Kemet + Vishay caps in the input stage. When I replaced those with Jantzen Superior, it became W I D E. The Jantzen took about 3-4 days to break in.
* Micro details/voice texture could be more pronounced, but then again, the entire source is <$150, so that's likely the bottleneck

This weekend I took the amp to my friend's place who also has a Devialet 400, but with a pair of Magico Q1 (4~5 Ohms, 86 dB/w/m). Listening to it at medium volume (baby was sleeping), we couldn't hear any bass from 5-6 ft away. Swapped back to the Devialet and more music seemed to emanate at the same listening level. My speakers are supposedly 91 db/w/m sensitive, and simply rock at all volumes.

The boards are really thoughtfully laid out and their quality is fantastic. As you can see, Jeremy is enthusiastic about helping and teaching. Super kudos to him. This is a wonderful and simple opportunity for one to create something of beauty *and* value.


Thank you for kind words.

The Magico speakers have elliptical filters and without very special treatment that, frankly, Magico and 99.999% of speaker makers are unfamiliar with, they drain current and have a bigger reactive load in general. Basically even in a two way speaker or theirs the crossovers have at least a dozen more parts than the average speaker. That combination with low efficiency simply is going to need more power.



Btw, I really like that the chip has such awesome protection that it won't turn on unless the speaker binding posts are not shorted.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 13 Oct 2017, 05:21 pm
Hi AC members and Folsom Builders,

After almost a week with my DIY Folsom Amp I just wanted to share my impressions of the amp.

A little background. I used to listen with mediocre powered monitors so I really have no listening experience with Hi quality "audiophile" amps. Once I purchased my Spatial M3 Turbos S' I moved on and started using an old integrated amp that my father did not want any more, it is a YAMAHA CR 1020. I was bypassing the preamp in the Yamaha and using my Promitheus Audio TVC  before the amp. Over all this combo worked pretty good. The sound stage was deep, the sound formed a deep "U" behind the speakers, very laid back listening actually. I did lack slam in the bass department. Even though it sounded pretty good and the bass was ok it was not very detailed. This is why I was wanting another amp option. 

So now with the Folsom Audio Amp I am completely satisfied (for now :D). I have all the Bass I need with "slam" as well as the detail I want. I am hearing more air around instruments, more reverb within tracks. I have noticed that instruments are more dynamic, especially with drums and strings.  The sound stage is not as deep as my last amp, but I now have more sound infront and side to side of my speakers .  The timbre of all the instruments has improved. Everything sounds great so far with this amp

So thank Folsom for a great sounding amp and your help during my build.

(http://www.audiocircle.com/image.php?id=169787)




Title: Re: Folsom's great little 7297 Chip Amp
Post by: rtate on 17 Oct 2017, 01:24 pm
Hi Folsom, I plan on using a Felix conditioner on my amplifier and in your "construction recommendations"
you say to use x-caps on both sides of the cmc but earlier in this thread you stated to use the caps only in front of the cmc and not post.
I am just looking for some clarification before I order the parts for the pcb.

Also are the values stated : 1.8k/3watt resistors , 1uf.,.1uf., and .01uf. x-caps and Bourns 8120 cmc optimized for the 7297 amplifier
For the resistors would you use wire wound or metal film ?

Thanks
Robert
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 17 Oct 2017, 02:01 pm
Hi Folsom, I plan on using a Felix conditioner on my amplifier and in your "construction recommendations"
you say to use x-caps on both sides of the cmc but earlier in this thread you stated to use the caps only in front of the cmc and not post.
I am just looking for some clarification before I order the parts for the pcb.

Also are the values stated : 1.8k/3watt resistors , 1uf.,.1uf., and .01uf. x-caps and Bourns 8120 cmc optimized for the 7297 amplifier
For the resistors would you use wire wound or metal film ?

Thanks
Robert

Hi Robert:

On my latest build, I wired a felix inside the case of the amp. For the resistor that bypasses each coil winding on the CMC, I used http://www.mouser.com/search/ProductDetail.aspx?r=588-23J1K8E. You can kind-of see the resistor, shiny brown at the base of the CMC. The other values you list (for the X caps and the Bourns CMC) are also what I used --> 1 uf .1 uf .01 uf CMC .01 uf .1 uf 1 uf. I put the felix in front of the transformer primaries. This picture is a little busy, but might give you an idea of what I did. I really love this amp! I should hook up my other build and compare, but haven't yet...

limits


(http://www.audiocircle.com/image.php?id=170008)

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 17 Oct 2017, 04:13 pm
Hi Folsom, I plan on using a Felix conditioner on my amplifier and in your "construction recommendations"
you say to use x-caps on both sides of the cmc but earlier in this thread you stated to use the caps only in front of the cmc and not post.
I am just looking for some clarification before I order the parts for the pcb.

Also are the values stated : 1.8k/3watt resistors , 1uf.,.1uf., and .01uf. x-caps and Bourns 8120 cmc optimized for the 7297 amplifier
For the resistors would you use wire wound or metal film ?

Thanks
Robert

I guess I better look at construction notes. I do prefer only on the side away from the amp.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: uncola on 19 Oct 2017, 09:55 pm
I, too had Radu Tarta at simpletubepleasures construct my amp from parts I had collected.. since I chickened out on making this my first diy amp build.  Just arrived an hour ago, sounds incredible with scary big and realistic soundstage
I'm using it with new philharmonitors 85db sensitive in near field at my computer setup with a ps audio gain cell dac/pre with 12db gain and it's working out great.. I was worried I'd have to switch to my other preamp with 0/6/12/db gain settings or that I'd get hiss but nope!


(http://www.audiocircle.com/image.php?id=170098)

(http://www.audiocircle.com/image.php?id=170099)

(http://www.audiocircle.com/image.php?id=170100)

(http://www.audiocircle.com/image.php?id=170101)

(http://www.audiocircle.com/image.php?id=170102)

(http://www.audiocircle.com/image.php?id=170103)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: shadowlight on 19 Oct 2017, 10:56 pm
@uncola, any pointers on where you got your case from?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: uncola on 20 Oct 2017, 09:48 am
this is the case I have, Radu said he had to flip the EI core transformer sideways so it would fit.  it's 80mm tall
https://www.modushop.biz/site/index.php?route=product/product&product_id=449&search=1NGXA388

this one is 120mm tall but otherwise the same, might allow you to use a giant transformer :)
https://www.modushop.biz/site/index.php?route=product/product&path=67_195_200&product_id=642

in other news..  this amp hasn't even been burned in more than 24 hours but it's sounding amazeballs..  I have firstwatt f7, odyssey kismet monoblocks, digital amplifier company inline maraschinos..  and this amp holds it's own with all of them in my near field setup
I did end up switching to my preamp with gain settings so I could use 0db gain..  the 12db gain preamp was useable but not good for very quiet listening, got loud fast

Is there an official name for this amp other than Folsom TDA7297?  I'm thinking about having my friend create an applique sticker thing for the frontplate of the amp with the name
Title: Re: Folsom's great little 7297 Chip Amp
Post by: pocomo on 20 Oct 2017, 01:20 pm
Looks great @uncola.  I too am quite taken with the sound.  The value prop on this amp (even using a hired gun) is out of this world.

Glad you had a good experience with Radu.  He is a truly nice guy who does quality work at very reasonable prices.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rtate on 20 Oct 2017, 02:01 pm
@ uncola, what is the varistor used for in your set up ?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: pocomo on 20 Oct 2017, 02:18 pm
@rtate - I think you are referring to the little standalone black disk in the photos? 

My amp has the same thing - it's a PTC thermistor in the chassis ground connection.  It serves as a secondary fuse and an easily removable connection when debugging ground loops.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 20 Oct 2017, 05:04 pm
I bet it's an NTC, because that would conduct very little until it needs to be wide open. Basically you can reduce ground noise with it, but when the juice starts to move it'll heat up and act like an open wire. That would be much safer than a PTC... which conducts all the time but would trigger like a fuse and leave you with a deadly hot chassis.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: pocomo on 21 Oct 2017, 12:26 am
I stand corrected  :oops:

Thanks Jeremy, and congratulations on such a successful project.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: drew_t on 21 Oct 2017, 09:01 pm
What is the little part between the thermistor and the AC connector/switch unit?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: uncola on 21 Oct 2017, 09:15 pm
I believe that's just a chassis ground screw.  When I asked radu for more information about the thermistor he said it's commonly used in many nelson pass amps to break signal ground from earth ground.  This amp is insanely good.. I can't believe how cool it runs.. it's literally cold to the touch but sounds so powerful.  The soundstage is massive

Theory:  you know how in GI Joe, Cobra create their ultimate evil leader by combining the dna of hitler, ghenghis khan, atilla the hun, alexander the great, stalin and hannibal of carthage into one ultimate guy?  I think Harmon International must have done something similar using the dna of Nelson Pass, John Curl, Douglas Self and Bruno Putzy to create Jeremy Folsom
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 21 Oct 2017, 09:55 pm
Theory:  you know how in GI Joe, Cobra create their ultimate evil leader by combining the dna of hitler, ghenghis khan, atilla the hun, alexander the great, stalin and hannibal of carthage into one ultimate guy?  I think Harmon International must have done something similar using the dna of Nelson Pass, John Curl, Douglas Self and Bruno Putzy to create Jeremy Folsom

 +1  :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: uncola on 22 Oct 2017, 07:04 pm
I have some leftover 1 amp slow blow fuses, is that rating ok for this amp?  They are fancy ceramic not glass
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 22 Oct 2017, 10:23 pm
What size is the PSU/transformer? There is no reason why you can't use whatever fuse you wish, so long as it is sized right.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: uncola on 22 Oct 2017, 10:37 pm
it's the hammond ei core transformer from the BoM..  I'm asking because I don't have the math to calculate the right fuse size :P 
is the formula..  80VA  so 80 divided by 120volts.. is 0.66666?   so I need a 666mA fuse or bigger?
Edit:. Oops 80va divided by 16V secondary winding equals 5 so with safety margin use a 6 amp fuse?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Abszero on 23 Oct 2017, 03:32 am
I bet it's an NTC, because that would conduct very little until it needs to be wide open. Basically you can reduce ground noise with it, but when the juice starts to move it'll heat up and act like an open wire. That would be much safer than a PTC... which conducts all the time but would trigger like a fuse and leave you with a deadly hot chassis.
Hi Jeremy,
Yes, it is a NTC CL60 10 ohms @ 25C, and it is used to provide ground loop isolation between the
chassis, which is hardwired to the AC outlet ground, and the circuit ground. So the chassis is always grounded.
Radu
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Abszero on 23 Oct 2017, 05:21 pm
it's the hammond ei core transformer from the BoM..  I'm asking because I don't have the math to calculate the right fuse size :P 
is the formula..  80VA  so 80 divided by 120volts.. is 0.66666?   so I need a 666mA fuse or bigger?
Edit:. Oops 80va divided by 16V secondary winding equals 5 so with safety margin use a 6 amp fuse?
Hi James,
Choosing the right fuse is a tricky thing. You'll need a slow blow on the primary. This will protect the downstream of the transformer too. However, the sensitive solid state devices will not be protected.
See this : http://www.emerson.com/documents/automation/1276316.pdf for reference.

In your case, a 120VA transformer needs a 300% In primary which will be 3A. However, this transformer will never be loaded more than 50% anytime and has less inrush compared with toroidal, so you'll be fine with a 1.6A fuse.
Cheers,
Radu
Title: Re: Folsom's great little 7297 Chip Amp
Post by: drew_t on 24 Oct 2017, 09:01 pm
Radu, what fuse would you recommend for a toroidal like this: http://www.antekinc.com/as-1215/ ?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: uncola on 29 Oct 2017, 09:22 am
Vinyl decals are easy!  and much cheaper than mailing your frontplate to get cnc routed or laser etched hehe
Yes I realize now it's slightly crooked.  but hey that is part of the charm of diy or custom builds :P
I'm telling people that it's not crooked it's a dutch angle and my tribute to lars von trier ;)
(http://www.audiocircle.com/image.php?id=170450)

(http://www.audiocircle.com/image.php?id=170451)


(http://www.audiocircle.com/image.php?id=170452)

got it from this vinyl service, very low prices
https://www.facebook.com/ambervinylallthethings


Title: Re: Folsom's great little 7297 Chip Amp
Post by: poseidonsvoice on 29 Oct 2017, 12:53 pm
Uncola,

You totally get an A for effort man! :thumb:

Best,
Anand.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Abszero on 29 Oct 2017, 01:55 pm
Radu, what fuse would you recommend for a toroidal like this: http://www.antekinc.com/as-1215/ ?
3A should work just fine. With toroidal transformers , most likely over 200VA, it'll exhibit up to 5x nominal at start up and will need NTCs to make it start soft. Not your case though.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Abszero on 29 Oct 2017, 01:55 pm
Vinyl decals are easy!  and much cheaper than mailing your frontplate to get cnc routed or laser etched hehe
Yes I realize now it's slightly crooked.  but hey that is part of the charm of diy or custom builds :P
I'm telling people that it's not crooked it's a dutch angle and my tribute to lars von trier ;)
(http://www.audiocircle.com/image.php?id=170450)

(http://www.audiocircle.com/image.php?id=170451)
Awesome job.


(http://www.audiocircle.com/image.php?id=170452)

got it from this vinyl service, very low prices
https://www.facebook.com/ambervinylallthethings
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 29 Oct 2017, 02:47 pm
Vinyl decals are easy!  and much cheaper than mailing your frontplate to get cnc routed or laser etched hehe
Yes I realize now it's slightly crooked.  but hey that is part of the charm of diy or custom builds :P
I'm telling people that it's not crooked it's a dutch angle and my tribute to lars von trier ;)
got it from this vinyl service, very low prices
https://www.facebook.com/ambervinylallthethings

Nice! I will have to save the link for future builds. I made my own decals on my first Folsom amp build.

(http://www.audiocircle.com/image.php?id=170457)

Title: Re: Folsom's great little 7297 Chip Amp
Post by: mresseguie on 18 Nov 2017, 08:28 am
Hi, everyone.

Before I flew off to Taiwan, I managed to power two very different pairs of speakers with this amp. In the first effort I paired an old pair of AV123 two-way speakers (5.25"  midwoofers, ~86 dB) and a Nuprime DAC-9. The result was really ice sounding music that was a little on the warm side- almost tube-like sound. The next pairing was with my Daedalus Apollos (three-way, 96.5 dB). These are very resolving speakers. The resulting sound is very different. There's a noticeable brightness in female vocals, violin, and other higher frequency sounds. It's not a big issue but very noticeable after listening to the other speakers.

Now, let me point out that different rooms were used. The brighter room is nearly square and there are few soft surfaces. The Apollos are mere inches from the front wall whereas the small two-ways were placed in the middle of a large room.

Have any of you experienced brightness with your speaker pairings?
Do you think the room is generating some/much of the brightness?
Could it be that the amp had but a few hours' use and really just needs a solid 100 hours of burn in?

I welcome your thoughts.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 18 Nov 2017, 10:28 am
What input caps are you using? Different ones take different amounts of time.

The amp takes at least a half hour before it really is up and going.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mresseguie on 18 Nov 2017, 10:34 am
It's got the Jantzen caps.

Title: Re: Folsom's great little 7297 Chip Amp
Post by: maty on 18 Nov 2017, 10:37 am
Hi, everyone.

Before I flew off to Taiwan, I managed to power two very different pairs of speakers with this amp. In the first effort I paired an old pair of AV123 two-way speakers (5.25"  midwoofers, ~86 dB) and a Nuprime DAC-9...

AV123 ELT525M Monitors

http://www.highfidelityreview.com/av123-elt525m.html

Quote
    System: 2-way, 2-driver direct radiating vented enclosure with rear-firing flared ports.
    Drivers: One (1) custom 5.25″ woofer and one (1) 1″ tweeter
    Frequency Response: ± 3dB to 20KHz with -3dB at 60Hz
    Crossover Point: 2200Hz Slope: 2nd order acoustic Impedance: 8 ohms Efficiency: 83dB @ 1w/1m Video Shielding: Yes

Other very data is the minimum impedance but few manufacturers tend to indicate it. In the rest of the speakers, through the measurements of frequency response, impedance and phase.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: maty on 18 Nov 2017, 10:43 am
https://www.guru3d.com/articles-pages/av123-elt-525m-2-speaker-kit-review,3.html

Only the frequency and spectral graph.

ELT525M -> Mini monitors. Are there ELT525 monitors?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: uncola on 18 Nov 2017, 10:54 am
hmm I just tested it with the anne akiko meyers vivaldi four seasons and my max richter Leftovers soundtrack and the violin sounds very realistic and not unnaturally harsh..  this amp has totally replaced all my other amps for my "serious listening" 2 channel bedroom setup.. I really love it.  Folsom if you ever come out with some commercial stuff I'll definitely be interested!
edit:  I've got the jantzen z-superior input caps too..  mine is fully burned in by now though.  using philharmonic audio new philharmonitors bookshelf speakers
Title: Re: Folsom's great little 7297 Chip Amp
Post by: maty on 18 Nov 2017, 11:08 am
It was a good idea the RF/EMI inlect input filter. With this amp only you need the 1 A. I have a lot of Schaffner RF/EMI FN 9244B in my house, 3 A (and one 8 A).

And I use fuses + varistors in my DC blockers. Recently one fuse and the varistor burned down after joining phase and neutral and the old electric company cables was burned. 230 volts -> 400 volts.

I put one as you can find them in air conditioners.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: maty on 18 Nov 2017, 11:13 am
I believe that's just a chassis ground screw.  When I asked radu for more information about the thermistor he said it's commonly used in many nelson pass amps to break signal ground from earth ground.  This amp is insanely good.. I can't believe how cool it runs.. it's literally cold to the touch but sounds so powerful.  The soundstage is massive

Earth loop-breaker boards

-> https://hoppesbrain.com/2017/05/26/earth-loop-breaker-boards/

[IMG] http://hoppesbrain.files.wordpress.com/2017/05/diode-shunt-loop-breaker.png


The ARTICLE, by Rod Elliott (1999)

Earthing Your Hi-Fi – Tricks and Techniques

-> http://sound.whsites.net/earthing.htm

[IMG] http://sound.whsites.net/earth-f4.gif
Title: Re: Folsom's great little 7297 Chip Amp
Post by: uncola on 18 Nov 2017, 11:29 am
Maty oh yes, since I said that Radu my builder corrected me and told me it Breaks earth ground from signal ground.  I have a delta 6A iec with emi/rfi filter in mine..  and I have it behind an atl hifi  dc blocker that you recommended.  But I understand EI core transformers such as the recommended Hammond in the BOM are not vulnerable to DC the way toroidal are
Title: Re: Folsom's great little 7297 Chip Amp
Post by: maty on 18 Nov 2017, 11:40 am
Maty oh yes, since I said that Radu my builder corrected me and told me it Breaks earth ground from signal ground.  I have a delta 6A iec with emi/rfi filter in mine..  and I have it behind an atl hifi  dc blocker that you recommended.  But I understand EI core transformers such as the recommended Hammond in the BOM are not vulnerable to DC the way toroidal are

6A is too much with only 15 watts amp!!!! It is better idea to use the lowest possible amperage because they attenuate much more.

Schaffner F2244B:

[IMG] http://maty.galeon.com/WP-imagenes/hard/IEC-inlet-filter-Schaffner-FN_9244-specs.png

The graphs: [IMG] http://maty.galeon.com/WP-imagenes/hard/IEC-inlet-filter-Schaffner-FN_9244-typical-filter-attenuation.png

[IMG] http://maty.galeon.com/WP-imagenes/hard/IEC-inlet-filter-Schaffner-FN_9244-cicuit.png

I can use Würth 150 kHz ferrites with the power cables (besides the RF/EMI filters). The usual problem in audio is in the RF < 1 MHz.

The ferrites (and very cheap) that are usually seen there are for EMI ( > 1 Mhz), so they are not very useful in audio. They are useful with video.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: maty on 18 Nov 2017, 11:41 am
But I understand EI core transformers such as the recommended Hammond in the BOM are not vulnerable to DC the way toroidal are

EI and toroidals are vulnerable with more 10-15 mV at AC, specially the BIG toroidals (400 VA). Your EI 80 AV is very small. I have problems -distorsion- with DC and the almost 400 VA of the EI transformer, but I do not have mVolts!

The small continuous not only may vibrates the toroids and the consequent noise, it also causes the ALL transformers (EI and toroidal) to stop working in the linear zone of the hysteresis curve, with which they add distortion.


The ARTICLE, by Rod Elliot (1989)

Blocking Mains DC Offset

http://sound.whsites.net/articles/xfmr-dc.htm


With amplifiers of such low power I do not think there will be problems with the small continuous at mains.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mresseguie on 18 Nov 2017, 12:07 pm
AV123 ELT525M Monitors

http://www.highfidelityreview.com/av123-elt525m.html

Other very data is the minimum impedance but few manufacturers tend to indicate it. In the rest of the speakers, through the measurements of frequency response, impedance and phase.

Maty,

Yes. You are correct.

I hadn't realized they were 83dB. All the more impressive, I think.  Good job, Folsom!

I'm certain the amp needs more time to burn in. I'd like to point out that I wasn't complaining. I'm just curious if the amp might not pair so well with really resolving or really efficient speakers. I'll hear them again on/about January 31, so the amp will be very well burned in. I'll return to this thread with my thoughts then.

Michael
Title: Re: Folsom's great little 7297 Chip Amp
Post by: uncola on 18 Nov 2017, 01:24 pm
if you want to borrow a dac and preamp when you get back let me know, I have a tiny cheap dual sabre chip dac that has surprising synergy with my small hattor active preamp and the folsom amp.  by then my ric schultz modded sonica dac with volume control should be here so the pair will be stored in my closet by then :P
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 18 Nov 2017, 06:24 pm
It's got the Jantzen caps.

200 hrs burn in for completeness, the first hours will be a little rough.

The Daedalus speakers lean towards a slight natural brightness, so it'll take a bit of time on the burn in.

Personally with Daedalus speakers I might seek a warmer sounding source component of some kind, the midrange benefits from it. I'm pretty familiar with the non-modified version of the midrange and that is my general opinion.

I've had my amp hooked up to the Daedalus DA-1.1 ver. 2 and it sounded great.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rtate on 18 Nov 2017, 06:59 pm
I have a question regarding hooking up my antek 2215 transformer.
I think that I need to hook up the input in parallel (red and black) and then hook up the output in parallel as well (green and blue).
Is this correct ?
also what do I do with the purple wire ? is this a shield ?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 18 Nov 2017, 07:35 pm
Antek 2215 looks like

115v Primary, tie the red and red, black and black together.

Purple goes to ground (safety, earth).

15v Secondary, tie the green and green, blue and blue together.

That's cool that they offer a shield! That makes it a viable alternative to the Hammond.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rtate on 18 Nov 2017, 07:43 pm
Thanks Jeremy , I am getting close to the power on stage !
A few more hours !!   
Title: Re: Folsom's great little 7297 Chip Amp
Post by: 1108 on 30 Nov 2017, 08:26 pm
Anyone have a board they'd like to sell?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rtate on 3 Dec 2017, 10:25 pm
I have got one of my amps running and sounds really good but I have a little problem.
Music was playing fine and I lifted the chassis to move it slightly and all of a sudden I got a loud hum through the speakers.
I put the amp down and the hum went away however when I touch the input capacitors I also get a hum as well as the input jacks.
I measure them with my meter and they are not grounded to the chassis.  Any ideas what it could be ?
I am having trouble inserting pictures but have a few in my gallery if that helps...
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 3 Dec 2017, 11:05 pm
Well it sounds like somehow you are shorting the inputs. (signal and ground touching)

Perhaps you have a cold solder on a cap or wire that has to do with the input?

It's not abnormal for the human touch to make a ground loop induce, btw. What is strange is when you lift it and it occurs.

Maybe you have a broken IC cable?

Title: Re: Folsom's great little 7297 Chip Amp
Post by: rtate on 3 Dec 2017, 11:41 pm
I removed the ic's and also lifted the earth ground from the chassis and the hum is there.
Should the heat sink be isolated from the chassis ?
Mine is anchored to and sitting on the bottom of the chassis.
The hum is loudest at the output caps even touching the paper and even louder if I touch the leads.
I can make it hum by touching other things like the heat sink and even the mounting screws from the felix.
The amp is dead quiet until I touch it and sometimes remains even after I let go...
So I isolated the heat sink from the chassis and removed the input wires from the jacks and the hum is still there and amplifies when I touch the input wires on the insulation.
When the amp was hooked up to the pre amp it was quiet until I touched the amp and would go quiet again when I let goof the amp.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 5 Dec 2017, 01:40 am
Well, some pics may be helpful.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rtate on 5 Dec 2017, 03:13 am
sorry , I have a bunch of pics in my gallery.
I can't get them to upload.
As a update: With the amp hooked up to the preamp the Hum is gone (completely silent) even when I touch components on the amp.
If I disconnect the amp from the pre amp the hum is there loud and clear.
I completely disconnected the input wires from the chassis as well as the speaker wires so I think I can rule the chassis out , it must be on the amp board.
When the amp is connected to the preamp (pass B1) the music sounds great ! Less than 8 MV offset at the speakers.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: S Clark on 5 Dec 2017, 03:17 am
(http://www.audiocircle.com/index.php?action-gallery;area=browse;image=172277)
Yep, I tried to upload one from your gallery and failed...  :dunno:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 5 Dec 2017, 06:13 am
Well then I don't see any problems.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: uncola on 5 Dec 2017, 07:04 am
*ba dum psssh*
(https://thumbs.gfycat.com/SlushySimplisticAracari-max-1mb.gif)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rtate on 5 Dec 2017, 11:38 am
 Thanks Jeremy ,so it's normal for the amp to create speaker hum on both channels with nothing connected to the inputs ?  Or because you can't see the pictures ?

How does the pre-amp stop the hum ?   :scratch:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 5 Dec 2017, 01:51 pm
http://www.audiocircle.com/image.php?id=172282&size=xlarge

http://www.audiocircle.com/image.php?id=172277&size=xlarge

http://www.audiocircle.com/image.php?id=172279&size=xlarge

http://www.audiocircle.com/image.php?id=172280&size=xlarge
Title: Re: Folsom's great little 7297 Chip Amp
Post by: zek on 5 Dec 2017, 02:50 pm
....so it's normal for the amp to create speaker hum on both channels with nothing connected to the inputs ?
No it's not normal to be eny hum.
Carefully check the isolation of the chip and heatsink.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rtate on 5 Dec 2017, 06:28 pm
Thanks lacro for uploading the pictures !
@ zek if the chip was shorted to the heatsink would it still make music and be quiet while hooked up to the pre-amp ? I did isolate the heatsink from the chassis by sliding a piece of rubber between the heatsink and chassis with no improvement.
I'm guessing that it has to be something on the input side but I have gone over all the solder joints and component values and can't find any problems. I even unsoldered the input wires from the circuit board but still humming.
I was thinking of removing the by pass caps from under the board even though I don't think there is a problem with them    :scratch:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 5 Dec 2017, 09:06 pm
I was say it is normal. Have you ever heard a guitar amp without a guitar? A fair amount of audiophile amps have a shut-off feature for events without a source connected. But this is one of the reasons why you turn on your preamp/source before the amp, as not only does it make complete circuit but it prevents loud thumps.

When the amp is connected to something it can make a complete circuit.

The pics look good. That is a pretty good sized heatsink, do you have any hole above and below it? If it gets hot that would be about the only thing you could have to do. Otherwise nice job.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rtate on 6 Dec 2017, 12:31 am
Yes , there are slots below and the cove is completely vented as well.
I built 2 identical amps just because they were not very expensive and I just like to build stuff.
I have lined the inside of the chassis with duct seal just to deaden it a bit. I will take more pictures later.

I repurposed the heatsinks from some equipment at work. I have had the amp on for about 6 hours and the heat sink still feels like room temperature. Although I am in the garage and it is cooler out here.

Is there a circuit drawing of the amp out there that I could look at ?
I really would like to see what is causing the hum.

Once again  a Big Thanks to Folsom for putting this out there for us !!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 6 Dec 2017, 01:16 am
It's just from an incomplete circuit. At that point it is very vulnerable to outside fields like 60hz. With interconnects attached you just have bigger antennas when the circuit isn't complete. Don't worry about it.

Check out the TDA7297 data sheet. There just isn't anything in particular. As long as you followed my instructions for isolation, you're all good.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 17 Jan 2018, 01:15 am
The BOM calls for .022uF by-pass caps on the input caps. Would other values like .01 or .047 work? If so, what would the trade offs be?

Mike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 17 Jan 2018, 11:01 pm
Any will work. I wouldn't call any a "trade off" exactly. The value of the capacitance only ultimately matter in the sense that the total amount needs to be high enough to not cut off bass. Once you're there it doens't matter if you have 2 million uf or just 2 uf.

But what you can do is calculate the corner frequency (http://www.learningaboutelectronics.com/Articles/Cut-off-frequency-calculator.php) to see where the bypass capacitor will effect. The R value is 25k - 30k, you can try both. The 7297 chip lands somewhere in that range.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 17 Jan 2018, 11:58 pm
I’m wondering about the value of the by-pass caps that go under the board.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 18 Jan 2018, 10:01 am
They are in parallel to the ones on top. The capacitance is cumulative. Signal will be split between the two except where one has rolled off and the other has not.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mlundy57 on 18 Jan 2018, 01:48 pm
Ok. Thanks
Title: Re: Folsom's great little 7297 Chip Amp
Post by: WC on 21 Jan 2018, 06:01 pm
Is there an issue with only using the 7297 to power one of the two channels? I am building way more amps than I have speakers to power, so I was thinking of using only one channel of a stereo amp to power my center channel. Wasn’t sure if the amp would have an issue with it.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 21 Jan 2018, 07:07 pm
That's fine. You can also connect it so both channels provide their current, to the single signal.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: zek on 21 Jan 2018, 08:26 pm
That's fine. You can also connect it so both channels provide their current, to the single signal.
And how to connect speaker terminals - in parallel (L+ and R+, L- and R-)? :?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: WC on 21 Jan 2018, 09:07 pm
Ok, can you send the + and - from a balanced signal to the amp and combine the speaker outputs to get a single channel output to the speaker?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 21 Jan 2018, 10:15 pm
Yes the speaker outputs go in parallel. The inputs would be too, but you can use only one set of caps if you tie the channels together after the caps. (look carefully, may not be the holes your think)

 Not sure what you mean balanced signal to the amp, it cannot take balanced inputs.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 23 Feb 2018, 08:31 pm
http://www.diyaudio.com/forums/group-buys/309860-folsom-diy7297-amp-antipole-psu-16.html#post5351397
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 5 Mar 2018, 04:28 am
Finally finished my second Folsom. It only took me 5 months. That’s what happens you have a young child in the house. It takes longer to put things together.

This time I used a Galaxy 4U chasis and an AnTek 18v 200va transformer. I would have purchased the 100va transformer but they were not in stock at the time. I also, ordered the transformer with the steel case.

Everything came together nicely and the amp fired up the first time. I had no mechanical noise like I got with Hammond transformer. The chassis was nice, but not the quality of Landfall Systems.

I really missed having this amp in my system. Even without break in it sounds good.


(http://www.audiocircle.com/image.php?id=177109)

(http://www.audiocircle.com/image.php?id=177110)

(http://www.audiocircle.com/image.php?id=177111)


Title: Re: Folsom's great little 7297 Chip Amp
Post by: TrungT on 5 Mar 2018, 04:54 am
Very nice and clean build :thumb:
Thanks for sharing.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 5 Mar 2018, 06:00 am
Very nice! I have one small suggestions that is a minor upgrade. It shouldn't take you 5 month...  :icon_lol:

Between the binding posts of each channel, cut out either a slot between them, or drill a hole large enough between them that there is a clear opening between them. The idea is not to open it up far enough to sacrifice the integrity of the hole, but just enough to stop a turn in the grounding from the balanced outputs by allowing the two fields to touch.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 5 Mar 2018, 02:53 pm
Finally finished my second Folsom.

Looks really well done... congrats! :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 5 Mar 2018, 02:55 pm
Between the binding posts of each channel, cut out either a slot between them, or drill a hole large enough between them that there is a clear opening between them. The idea is not to open it up far enough to sacrifice the integrity of the hole, but just enough to stop a turn in the grounding from the balanced outputs by allowing the two fields to touch.

Huh?  :scratch:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 5 Mar 2018, 03:04 pm
 :thumb: Nice job, Brad--really well done!

Before using this amp, I was never much of a believer in 'improving your source gear'. I was in the 'but they're just ones and zeros' camp, pass the digits and let the DAC do its thing. Well, not anymore! I hear a huge difference when using a usb attached hard drive loaded with flac files/raspberry pi 2/volumio/allo DigiOne/BNC SPDIF/iFi 5 volt SMPS versus spinning discs through my Oppo BluRay (coax SPDIF) to the Folsom 7297. Sorry for the aside, but this is quite a testament to this amp, I think!

Enjoy, Brad  :D
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 5 Mar 2018, 08:54 pm
:thumb: Nice job, Brad--really well done!

Before using this amp, I was never much of a believer in 'improving your source gear'. I was in the 'but they're just ones and zeros' camp, pass the digits and let the DAC do its thing. Well, not anymore! I hear a huge difference when using a usb attached hard drive loaded with flac files/raspberry pi 2/volumio/allo DigiOne/BNC SPDIF/iFi 5 volt SMPS versus spinning discs through my Oppo BluRay (coax SPDIF) to the Folsom 7297. Sorry for the aside, but this is quite a testament to this amp, I think!

Enjoy, Brad  :D

Limits,

Yes a good amp does put other components in a system under the microscope. The amp I was using is a very nice sounding Decware ZKIT1 with some upgrades. It does have a very clean and sweat midrange sound, but does not have the extension of the Folsom or the imaging. I use a BH Quickie preamp that is very clean. I find that I like a preamp that has gain, as opposed to a buffer or passive control, even though I can't move the volume control much. It adds just a little more in dynamics to the sound. My next is a new preamp kit.
 
Very nice! I have one small suggestions that is a minor upgrade. It shouldn't take you 5 month...  :icon_lol:

Between the binding posts of each channel, cut out either a slot between them, or drill a hole large enough between them that there is a clear opening between them. The idea is not to open it up far enough to sacrifice the integrity of the hole, but just enough to stop a turn in the grounding from the balanced outputs by allowing the two fields to touch.

Jeremy,

What is the purpose of cutting a space between each binding post? I assume you mean between the plus and minus of each post.

Thanks,
Brad
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 5 Mar 2018, 09:01 pm
Huh?  :scratch:

(https://image.ibb.co/iv7807/bindpost.png)

It's an upgrade to do this, I found, with how it sounds.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 5 Mar 2018, 09:06 pm
Jeremy,

What is the purpose of cutting a space between each binding post? I assume you mean between the plus and minus of each post.

Thanks,
Brad

Well the short is, it makes it sound better. And yes between + and - of one channel.

Not doing it forms a turn around the panel and causes skinning RF currents to be inducted into the amplifier.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: pocomo on 5 Mar 2018, 09:38 pm
Only one channel?  Would it be considered harmful to modify both?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 5 Mar 2018, 09:51 pm
Huh?

If you do it, do it to both... I just mean that there is no hole between the channels.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: BRN on 6 Mar 2018, 12:17 am
(https://image.ibb.co/iv7807/bindpost.png)

It's an upgrade to do this, I found, with how it sounds.

When I get a chance I will breakout the Dremmel and make the cuts and see if there is an improvement.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 6 Mar 2018, 12:25 am
I heard it. Just had to get around to trying it... did, and now I recommend it.

Hopefully it'll be as obvious to everyone else.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Danny Richie on 6 Mar 2018, 08:54 pm
I just put one of these together and posted some information about it in our circle.

http://www.audiocircle.com/index.php?topic=156151.msg1671062
Title: Re: Folsom's great little 7297 Chip Amp
Post by: slefley on 24 Mar 2018, 03:00 pm
I have an new & unused set of circuit boards (1 amp board and 1 antipole board) plus the electronic parts (resistors, caps, etc) that I will sell for what I paid - $122.  I can send the BOM for the electronic parts if requested.  The parts and circuit boards are unopened in their original packaging.  I have permission to forward all assembly documentation as well.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: fredcassidy on 30 Mar 2018, 04:36 am
Hi Slefley, I may be interested, what additional parts would be necessary to get the amp fully operational, Transformer and what else? Thanks, Fred
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mresseguie on 17 Jun 2018, 08:09 pm
What damage occurs when a clever fool powers on the amp with just the right channel speaker connected?

I don't know if the left speaker cable leads were touching. As soon as I discovered the mistake, I powered down the amp. Then, I connected the leads to the left speaker. Then, I powered the amp on. Right speaker sounds great, but nothing is coming out of the left speaker.

Is there an internal fuse? Did I fry the left-side portion of the amp?

Any help would be greatly appreciated.

Humbly,

Michael
Title: Re: Folsom's great little 7297 Chip Amp
Post by: S Clark on 17 Jun 2018, 09:04 pm
What damage occurs when a clever fool powers on the amp with just the right channel speaker connected?

I don't know if the left speaker cable leads were touching. As soon as I discovered the mistake, I powered down the amp. Then, I connected the leads to the left speaker. Then, I powered the amp on. Right speaker sounds great, but nothing is coming out of the left speaker.

Is there an internal fuse? Did I fry the left-side portion of the amp?

Any help would be greatly appreciated.

Humbly,

Michael
Michael, know that you are not the first to fry one of these.  The very first amp that this thread is based on fried the chip, then was repaired, then got fried again when I tried to put it in a metal case.  That was fatal.  So, these are not idiot proof, as I can attest.  Hopefully Jeremy will give you some clues where to begin repair... I'd guess the chip.  Good luck.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 17 Jun 2018, 10:04 pm
It would be the chip. But I haven't had any problems running single channels. Try leaving it off for a bit and try again, the internal protection may reset.

The chips can die, but they are pretty hardy, typically.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mresseguie on 18 Jun 2018, 06:23 am
I opened a bottle of Ordinance Brewing Blackfisk Imperial Stout 9.5% alc. as an offering to the amplifier gods. After allowing them a couple minutes to absorb the vapors, I drank a toast. Then, I reconnected the amp; turned everything on and played some Marc Cohn. All is well.  :banana piano: :bowdown: :beer:

I'll do my best to make sure that clever fool doesn't blow it again. Thanks, Scott and Jeremy.  :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Plund on 16 Sep 2018, 02:12 am
Well, a few months ago I decided it was time to blow the dust off my Folsom amp and Antipole boards and get to building. Last night I reached "first-sound"... a few frustrations aside, building these two boards was a kick in the britches! 

Jeremy, thanks for designing and making these jewells available! I decided to up-cycle a salvaged case...I am pleased with how the project turned out.  ...I am still trying to figure were to land the winchester drive ribbon cable.  :?

(https://www.audiocircle.com/image.php?id=184469)


(https://www.audiocircle.com/image.php?id=184470)

In comparing the Folsom Amp, with Antipole, to a Sure itteration of a TPA3116 (an amp I like), I found the Folsom to carry more weight in the bass and to sound "cleaner".  The Folsom simply sounds a step or two closer to sounding "real".  The speakers used here were some 3" Peerless full-rangers in a small labrynth enclosure.  This TPA3116 is powered with a 5A laptop brick... makes me wonder how it might sound powered with the Antipole or a nice regulated supply.

In comparing the Folsom Amp, with Antipole, to my Pioneer VSX-D912 (also an amp i like), the Folsom made my Pioneer sound a bit rolled-off or even a bit muffled.  Again, the Folsom has a "clean", balanced sound.  The speakers connected here were MA 7.3 in Frugal Horns.

Jeremy, thanks again.  I will keep my eye out for another available Folsom amp board... I think to integrate with a battery supply.

Pete



Title: Re: Folsom's great little 7297 Chip Amp
Post by: mzbrahce on 26 Sep 2018, 09:00 pm
Folsom--Didn't read your notes carefully enough before starting work on the Antipole and mounted all 6 2.2 uf film caps with the same orientation.  Couldn't remove the odd 3 without damaging them.  Identical caps are back-ordered util January.  I'm hoping you can recommend a replacement......
Thanks----------Mark
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 26 Sep 2018, 11:56 pm
Show me a picture, you probably did it right.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mzbrahce on 28 Sep 2018, 06:05 pm
Too late.  I've already removed every other capacitor in the line.  They were all oriented with the printed side facing the top of the Antipole board, with the board oriented so you can properly read "Folsom Audio."
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 28 Sep 2018, 08:04 pm
Those capacitor orientations of the writing, the little gray ones, dont matter, on the Antipole.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: WireNut on 29 Sep 2018, 01:50 am
Hi Jeremy,

I'm interested in building your amp in the future. Hopefully it will be around for awhile.
I currently working on 2 of you other projects.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 29 Sep 2018, 03:15 am
I will update it before I retire it. Updates will just be more refined congruency oh mounting holes or what not.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: skrstc on 21 Nov 2018, 07:35 pm
My left channel is not working. There is 17.6V DC. Is TDA7297 died or something else?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 21 Nov 2018, 08:18 pm
Make sure the binding posts are isolated from chassis. Check continuity on RCA cables and check wires for cold solderes. Turn it off for a bit and back on if everything seems ok. The internal protection can take a turn on and off or two to come back.

No drilling in PCB, right?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: skrstc on 22 Nov 2018, 07:48 am
Binding posts and RCA are OK. When I get back from work, I'll check soldering again. Thanks.

On Saturday I soldered beater wire on RCA and binding posts and the amplifier worked until yesterday.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: skrstc on 23 Nov 2018, 04:44 pm
Everything looks OK.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 23 Nov 2018, 05:04 pm
Well if everything is OK then chip replacement makes the most sense. But I will say that most of the time it isn't the chip.

If you are going to replace the chip I recommend cutting the old one off first. You need some small side cutters to do it. You don't have to be accurate or cut close to the board. Hell, if you have some big ones you can cut directly through the chip. Then touch the solder and pull each leg out with tweezers/needle nose. After that give each hole a spot of solder and then use solder wick to suck up the solder and you'll have holes that a new chip will easily go into.

It's not super easy, and some care is needed, but in general it's not too bad.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: skrstc on 23 Nov 2018, 07:35 pm
Thanks.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: 1108 on 30 Nov 2018, 01:19 pm
Will there be another run of boards?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 30 Nov 2018, 06:40 pm
I still have some.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: yardbird on 21 Dec 2018, 10:37 pm
The BOM now has 2 options for the 12 caps on the 7297 board. One is for 560uf 20v Panasonics and he other is for 330uf 25 v Nichicons.


Want to make to sure the 2 different values are OK and to see if folks have noted any differences.


Thanks,
Jeff
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 21 Dec 2018, 11:58 pm
They just sound different. Nichicons sound slightly more open. Obviously, since I put them both in, nothing is wrong with either.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: WC on 30 Dec 2018, 01:52 am
Jeremy,

On the Antipole, is there a certain orientation that the Bourns choke has to go? All your photos had the coilcraft choke.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 30 Dec 2018, 02:01 am
Nope
Title: Re: Folsom's great little 7297 Chip Amp
Post by: WireNut on 30 Dec 2018, 02:28 am
I can't wait to build your amp :bounce:.
In the long run I will most likely be driving your amp with a Mesmerized DCB1, I can't afford to build the Pass BA-3 preamp.

The gain of the DCB1 is 1.
I don't know if zero (1) gain will work with the 7297 amp or not :scratch:

Currently I'm using an old Pioneer SA8500mk2 integrated amp as my preamp (pre-outs) and it never gets pass 10 o'clock.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 30 Dec 2018, 02:42 am
no gain is good for it, generally
Title: Re: Folsom's great little 7297 Chip Amp
Post by: WireNut on 30 Dec 2018, 03:06 am
no gain is good for it, generally

Awesome, That's what I was hoping for. My system doesn't seem to need any gain from a preamp.
BTW, your Fo-Felix is working perfectly. I'm extremely happy with it :thumb:.

Oh, and your instructions on the 7297 amp and Antipole are fantastic  :rules:

(https://www.audiocircle.com/image.php?id=188472)

(https://www.audiocircle.com/image.php?id=188473)

(https://www.audiocircle.com/image.php?id=188474)

(https://www.audiocircle.com/image.php?id=188475)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: WC on 30 Dec 2018, 03:49 am
How would it work being driven from a DAC directly? My DAC is a Soekris Dam 1021 with 1.4V, 625R output. I am putting them together in a single enclosure.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 30 Dec 2018, 05:21 am
Does it have volume control?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: WC on 30 Dec 2018, 01:46 pm
Yes, it has a volume control.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 30 Dec 2018, 06:25 pm
That sounds fairly ideal then, as long as your speakers aren't very low efficiency. For example Magnapans sensitivity isn't super low, but they're so inefficient that there's no way to power them.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: WC on 30 Dec 2018, 07:57 pm
It will be powering the shop speakers. Most likely they will be JBL G100 bookshelf speakers at 86 dB and 6ohm or BA HD9 speakers at 90 db and 8 ohms. Don’t think it should be an issue.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 30 Dec 2018, 11:33 pm
For the shop it'd probably be fine, but I'm not sure why you'd build it when you can get something real cheap.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: WC on 31 Dec 2018, 04:47 am
If I wanted something cheap (no additional cost) I would keep using my 25 year old Denon receiver. Well I have all variety of DIY amps (about 14 channels) that I have boards for and I have the parts for most of them. The Folsom amp is actually the least expensive amp build. Need to find a place for all my amps.  :)

The Soekris DAC will also be feeding my main 2 channel system, when I get my preamp built, so it is pulling double duty.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: yardbird on 16 Jan 2019, 02:10 am

(https://www.audiocircle.com/image.php?id=189147)

hey guys. tested my anti pole and got about 19.8 volts. I have a blue 3.3 watt led on the aux with a 1.0k 1/2 watt resistor. using the antek AS-1215 trafo. does that voltage sound ok?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: yardbird on 19 Jan 2019, 02:47 am
Little amp is up and running. Sounds phenomenal! Only an hour or two on it yet. Thanks so much for the great project. Really nice build directions. The amp really transformed the Elac 6.2s. Very fun to build. I ordered a Furutech IEC out to change out for the cheapo one that came with my case. Will wait a bit to see how it evolves.

Thanks again!
Jeff
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 19 Jan 2019, 04:33 am
Sorry, I missed it. That transformer is lower voltage than you should use.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: yardbird on 19 Jan 2019, 11:47 am
Not a big deal to swap out to the Antek 1218. I assume the 1215 is not enough to activate the Infinite Capacitor? The 1218 transformer is only $21 (plus shipping). I need to change out the IEC connector as well. Bought a Furutech to replace the one that came with the case.

Is the 1/2 watt resistor on the LED adequate? I have 3 watts that could work or I guess I could use 2, 1/2 watts in parallel.

Thanks again for the project. It really sounds nice.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 19 Jan 2019, 07:09 pm
You're correct on the voltage.

What LED?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: yardbird on 19 Jan 2019, 11:58 pm
I added an LED to the auxiliary outputs on the Antipole. It is a 3.3 watt blue. I was calculating the resistor value projecting a 17 v output from the Antipole. in actuality it is 19.8 and will be more once I add the new 100 VA 18v transformer. I will likely need to change the resistor. Wasn't sure if a 1/2 watt resistor is sufficient and was curious if having an LED reduced the output of the Antipole.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 20 Jan 2019, 03:58 am
http://www.ohmslawcalculator.com/led-resistor-calculator
Title: Re: Folsom's great little 7297 Chip Amp
Post by: drew_t on 22 Jan 2019, 10:53 pm
Sorry, I missed it. That transformer is lower voltage than you should use.

I thought you said that one was OK?
https://www.audiocircle.com/index.php?topic=138229.msg1553726;topicseen#msg1553726
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 22 Jan 2019, 11:01 pm
I thought you said that one was OK?
https://www.audiocircle.com/index.php?topic=138229.msg1553726;topicseen#msg1553726

I must have only been looking at the VA rating, sorry.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: yardbird on 26 Jan 2019, 10:45 pm
Replaced the IEC receptacle and the transformer, Fired it up and only have one channel working. Moved around cables and isolated it to the L channel of the amp. Opened up the amp and power is good going into the Antipole but only has one side coming out (the + side has 24v and the - is really low ~0.2v). Turned on the variac to about 70v and started measuring. Power is consistent across all 4 legs of the choke and across all 6 of the 2.2uf capacitors. Two of the diodes have ~6v on one leg and 12v on the other (with variac at 70v). The other 2 have ~6v on one leg and 0v on the other. All 4 of the big caps have about 12v on one leg. I can include pics if helpful. Am guessing I have trashed 2 of the diodes. The 2 "bad" ones are not adjacent. If you are looking at the top of the board with choke end close to you, it is the left diode and second from the right.

Any other measurements you recommend or just replace the 2 diodes?
Thanks for any input!
Jeff
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 26 Jan 2019, 11:52 pm
Your left channel probably has a binding post touching chassis or something.

There is no center tap, so you are suppose to be just getting 24v.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: yardbird on 27 Jan 2019, 12:31 am
Antipole is fine. Cold solder joint on an RCA. Stereo has returned!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 27 Jan 2019, 01:33 am
 :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: DougD on 28 Jan 2019, 02:19 am
Finally started after having the boards for a year (or so). I seem to have lost the BC337-40 transistor that Folsom sent with the boards, can I get a suggested part# for a replacement. There seem to be a lot of options at Mouser and I barely know what I'm working with. Also, on the D45H11G, I've noticed that in pictures of populated boards some have a heat sink attached to the black metal clip. Is the black metal clip sufficient heat sink, or does the transistor need more?
Thanks,
Doug

(https://www.audiocircle.com/image.php?id=189621)


(https://www.audiocircle.com/image.php?id=189622)

Title: Re: Folsom's great little 7297 Chip Amp
Post by: DougD on 6 Feb 2019, 09:33 pm
Found that little bugger and soldered it in. Finished the anti-pole board. Start working on the case now
(https://www.audiocircle.com/image.php?id=190056)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 6 Feb 2019, 10:04 pm
Oh , good. Nothing on mouser will work. I have back stock for awhile and can get more.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rockdrummer on 13 Feb 2019, 03:51 pm
Hi everyone.  Got my boards for this amp last week!  I'm so excited to start on this build.

I have come to the decision that I will order a chassis from DIYAudio Store.  I have done lots of reading on this thread, and I know some have hired out companies to drill out of the chassis for parts installation.  Is that the way to go if I haven't ever drilled through metal before? 

Am I wrong in thinking that it just takes having the right bit to drill through aluminum? 

Also, I will need to get the parts ahead of ordering the chassis because I will need lots of planning to know where I want to put things. 

Any advice?  I have built bottlehead products before, several pairs of GR Research speakers/subs before, but I have never had to plan a layout for an amp and needed to drill myself.


I have many more questions but I will have to wait to start spewing them out.
Thanks.
Ben
Title: Re: Folsom's great little 7297 Chip Amp
Post by: S Clark on 13 Feb 2019, 04:50 pm
Drilling aluminum is like going through butter. You don't need anything special, just a drill and a bit. 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rockdrummer on 13 Feb 2019, 04:53 pm
Great!  Just what I needed to hear.
Thanks,
Ben
Title: Re: Folsom's great little 7297 Chip Amp
Post by: RoadTripper on 13 Feb 2019, 05:24 pm
I've read through this valuable thread and I came to the clear realization that there are several items that are needed to finish the job that are not listed in the BOM. This is what I have so far:

1. Anti vibration pads/material
2. Enclosure
3. Transformer
4. Wire
5. Switch
6. LED
7. Rubber washers
8. Thermal grease
9. Rubber standoffs
10. IEC connector - fuse

Can anyone add to this list? I suspect it isn't complete.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 13 Feb 2019, 07:34 pm
There is a transformer on the BOM, but maybe it's out of stock?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: RoadTripper on 14 Feb 2019, 04:19 pm
I must be dense. I don't see a transformer on the BOM. What's its part number?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: bentconvert on 14 Feb 2019, 07:24 pm
Mouser #546-185F16    Hammond #185F16   Hammond   Power Transformers Global/Chassis Mount 130VA, 16V CT @8.1A
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 14 Feb 2019, 07:58 pm
Mouser #546-185F16    Hammond #185F16   Hammond   Power Transformers Global/Chassis Mount 130VA, 16V CT @8.1A

Yes, it's in the upload file.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: RoadTripper on 14 Feb 2019, 08:17 pm
Ah. There it is in the Antipole BOM. I was looking in the wrong one.

So, back to my question, then, is my list of parts/items incomplete?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 14 Feb 2019, 08:34 pm
I've read through this valuable thread and I came to the clear realization that there are several items that are needed to finish the job that are not listed in the BOM. This is what I have so far:

1. Anti vibration pads/material
2. Enclosure
3. Transformer
4. Wire
5. Switch
6. LED
7. Rubber washers
8. Thermal grease
9. Rubber standoffs
10. IEC connector - fuse

Can anyone add to this list? I suspect it isn't complete.

Board stand offs.
Automatic center punch for marking holes in aluminum.
Step drill for drilling holes in aluminum.
Hand counter sink tool with handle for deburring drilled holes.
T-handle reamer for enlarging holes (not essential, but handy)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 14 Feb 2019, 09:48 pm
The BOMs are for board population only, and transformer. The rest is up to you, but I did note lots of possible things in the notes.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: borism on 18 Feb 2019, 03:45 pm
Hi Jeremy,
I received my boards and am waiting for the various ordered components to arrive before starting my build. One question I have is about the input capacitors. My understanding is that a 1.5 uf capacitor or higher helps extend the lower frequency. The film bypass cap is 0.022 uf. What is the function and what effect would a slightly higher 0.056 - 0.1 uf rating as bypass have? I am asking because I have a few high quality 0.056 and 0.1 uf film caps from prior projects.
Thanks
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 18 Feb 2019, 07:07 pm
They'll do basically the same thing. They just cost more so I didn't spec them as getting bigger with the bypass doesn't benefit you really. But if you have them, use them! You can also not use bypass cap, totally up to you. The input caps are a fun place to explore differences, you just need 1.5uf (total) or more is the only requirement.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mzbrahce on 22 Feb 2019, 03:07 pm
Hi Jeremy--

I'm finally in the process of completing my 7297 and have a few questions.  I have decided that I need 3 inputs, so I am planning to add a rotary switch.  I'm also using the 10K DACT.  Should the switch come after the DACT or before it?  I also want to use headphones with it.  What is the best way to do that?  Just use a  3x switching jack?  https://www.mouser.com/Connectors/Audio-Video-Connectors/Phone-Connectors/_/N-778cv?P=1yzvc3fZ1z0yy6bZ1yvsm2eZ1yzvpvdZ1yzowym

Thanks for all of this!  It is a lot of fun building this out, and I'm looking forward to countless hours of great sounds.

------------------Mark

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 22 Feb 2019, 05:12 pm
I would go before.

I wouldn't use this amp to power headphones. If you did try it, you need headphones that can accept 4 wire, balanced output (and a bunch of resistance probably to get the power down, on separate switched outputs)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mzbrahce on 22 Feb 2019, 06:23 pm
Thanks for the quick response. 
I'll get a separate headphone amp.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 22 Feb 2019, 06:29 pm
I don't get it, How does the DACT go before the input selector? Please explain. I put the DACT on the output of the selector.


(https://www.audiocircle.com/image.php?id=191005)

(https://www.audiocircle.com/image.php?id=191009)

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 22 Feb 2019, 07:22 pm
I meant selector before DACT.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: WireNut on 22 Feb 2019, 08:33 pm
Hi lacro,

This looks interesting. Can you tell me how it hooks up?
If I only have 1 input on an existing preamp will this add more inputs?

What are the rear RCA's, inputs/outputs?
Why 2 dials?


I don't get it, How does the DACT go before the input selector? Please explain. I put the DACT on the output of the selector.

(https://www.audiocircle.com/image.php?id=191005)

(https://www.audiocircle.com/image.php?id=191009)



Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 22 Feb 2019, 09:10 pm
It's a Glassware audio 3 input selector with one output. Yes it would allow you to have multiple inputs to your preamp. The reason for the 2 knobs is one is for the selector, and the other is the DACT volume control. I originally made it as an input selector, but recently added the DACT pot making it a great sounding passive preamp with 3 inputs. If i did it again, I would add one more output for a powered sub.

https://glass-ware.stores.yahoo.net/inseswandpcb.html


(https://www.audiocircle.com/image.php?id=191012)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 22 Feb 2019, 09:18 pm
Also, check out this thread for more options: https://www.audiocircle.com/index.php?topic=161437.180
Title: Re: Folsom's great little 7297 Chip Amp
Post by: borism on 15 Mar 2019, 12:44 am
It's alive! Sounds very nice on initial listen.


(https://www.audiocircle.com/image.php?id=192046)

(https://www.audiocircle.com/image.php?id=192047)

(https://www.audiocircle.com/image.php?id=192048)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 15 Mar 2019, 12:57 am
Nice build!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 16 Mar 2019, 03:02 pm
What's the current consensus on transformers that will work? The 16V Hammond in the BOM is really tall (85.6mm) which requires a pretty tall chassis with limited choices available. The 1218 Antec 100VA, 18V and is much shorter in height allowing for many more chassis choices. Is the 18V Antec a viable choice even though the recommended input voltage for the Antipole is 16V?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 16 Mar 2019, 04:18 pm
Its fine
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 16 Mar 2019, 04:29 pm
What's the current consensus on transformers that will work? The 16V Hammond in the BOM is really tall (85.6mm) which requires a pretty tall chassis with limited choices available. The 1218 Antec 100VA, 18V and is much shorter in height allowing for many more chassis choices. Is the 18V Antec a viable choice even though the recommended input voltage for the Antipole is 16V?

Nice build, indeed borism :thumb:

Larry, I had the 15 volt Antek (200 VA, an2215)  in one of my Folsom amps that I recently replaced with their an2218 transformer, and prefer the 18 volt one in there. I also drilled out most of the metal between the binding post for each channel when I had everything apart. I'm liking my 'new' amp...it doesn't seem like having the higher Vout transformer is doing anything detrimental. In fact, there were a few times with the 15 volt transformer in the amp that my speakers bottomed on me, which hasn't happened after the replacement.

I wonder if the 100 VA version would be adequate, as the Hammond is spec.'ed at 130 VA, I believe?

limits
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 16 Mar 2019, 06:03 pm
Nice build, indeed borism :thumb:

Larry, I had the 15 volt Antek (200 VA, an2215)  in one of my Folsom amps that I recently replaced with their an2218 transformer, and prefer the 18 volt one in there. I also drilled out most of the metal between the binding post for each channel when I had everything apart. I'm liking my 'new' amp...it doesn't seem like having the higher Vout transformer is doing anything detrimental. In fact, there were a few times with the 15 volt transformer in the amp that my speakers bottomed on me, which hasn't happened after the replacement.

I wonder if the 100 VA version would be adequate, as the Hammond is spec.'ed at 130 VA, I believe?

limits

Limits, thanks for the heads up. The reason for needing the 1218 over the higher VA 2218 is the size. The 2218 would't fit with the planned chassis. The BOM lists that the trans must be a minimum of 80VA. My concern was whether 18V was too high.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: borism on 16 Mar 2019, 09:14 pm
For what it's worth, I measured my wall outlet voltage at 118V, the Antek 1218 out was 18.5V and the Antipole out was 23.8V DC. It seems to be working just fine.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rockdrummer on 17 Mar 2019, 02:27 pm
Hi everyone. Happy St Patty's Day!

Couple rookie questions today.
I imported the bom into mouser last night. I would like to replace the caps. Question 1, those would be the input caps correct? The 1.5uF ones?
My  2nd question is related to the first one. Eventually this amp will run mains with servo subs having the bass duty. If I was to give this amp only input signal the subs won't be playing, is that the bypass caps job? Not even sure that those caps in this amp function that way...see? Rookie.

I guess it makes sense to run this amp full signal because i dont even know what my mains will be yet anyway.

And finally, are the power socket cutouts usually the same dimensions if I was to have the enclosure company cut the opening for me? (May save some work by having the diystore cut the back panel for me.)

This thread has been so helpful, but I have bounced around reading it so much, I have defaulted to just asking...

Thanks for any advice.
Ben
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 17 Mar 2019, 04:46 pm
1.5uf are the input caps.

You could use smaller ones to limit low frequency extension. You would calculate what you need basedxon 25-30k resistance for the corner frequency with a capacitor.

You want to get the white paper with dimensions to give to the machinest for whatever IEC socket you use.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 17 Mar 2019, 05:15 pm
I like to use Neutrik Powercons for AC input instead of the standard IEC connector. The hole for the chassis connector is an easy to make 15/16" round hole. You will have to make your own cord for the power plug. The Powercon offers a very secure connection compared to IEC connectors.

https://www.mouser.com/ProductDetail/Neutrik/NAC3FCA?qs=sGAEpiMZZMtiRBiUbHlRZXrdchW6pJUT93uYqN%2FSFGw%3D

https://www.mouser.com/ProductDetail/Neutrik/NAC3MPA-1?qs=sGAEpiMZZMtiRBiUbHlRZaspORIhCQLubgktMdJEqK0%3D

Here's the hole(s) cut layout for the chassis connector:


(https://www.audiocircle.com/image.php?id=192177)




Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 17 Mar 2019, 06:44 pm
For what it's worth, I measured my wall outlet voltage at 118V, the Antek 1218 out was 18.5V and the Antipole out was 23.8V DC. It seems to be working just fine.

Would you please measure the exact diameter of your Antek 1218. I know the data sheet states 3.9" Just want to know if it's actually larger.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 17 Mar 2019, 08:59 pm
Jeremy,
 In your build photos I see you used shorter capacitors for the big ones on the Antipole PS. Are they something that you would recommend? They would help gain a lot of room in the chassis. If so part # please.


(https://www.audiocircle.com/image.php?id=192184)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 18 Mar 2019, 03:49 pm
No, they're too small. I painfully added more to that amp after the fact.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rockdrummer on 18 Mar 2019, 10:57 pm
Hey there, I'm still coming up with questions.

Taking the neutrik connector approach.
I see the ratings on those connectors is 20A and 250v. I can't find an AC plug for the other end of the power cable with those same ratings. I need to stay affordable. I see lots of 15A and 125v, and I'm sure the answer is obvious but not to me. Also any advice for the actual cable brand some use would be great.
Thanks
Ben

Also, I certainly am likely over-thinking some of this. I appreciate it.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 18 Mar 2019, 11:10 pm
15A plug is all you need. I used 14ga wire for my cord.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rockdrummer on 18 Mar 2019, 11:12 pm
Terrific, thank you lacro!
Ben
Title: Re: Folsom's great little 7297 Chip Amp
Post by: borism on 18 Mar 2019, 11:46 pm
Lacro, I measured the diameter of my Antek 1218 to be between 3 3/4 and 3 7/8".

Here is my amp with vinyl lettering.


(https://www.audiocircle.com/image.php?id=192252)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 19 Mar 2019, 04:22 pm
Thanks for getting back. Tell me more about the vinyl lettering. When I built my first Folsom amp I printed my front panel lettering on tissue paper, and buried it in varnish, but the vinyl letters look good on aluminum.



(https://www.audiocircle.com/image.php?id=192263)






Title: Re: Folsom's great little 7297 Chip Amp
Post by: borism on 19 Mar 2019, 05:37 pm
Lacro, I was looking for a quick and inexpensive solution. The vinyl letters come in different sizes and colors. I chose 1/4" black and white.
Here is a link:
https://www.amazon.com/gp/product/B000GP08K6/ref=ppx_yo_dt_b_asin_title_o06_s00?ie=UTF8&psc=1


(https://www.audiocircle.com/image.php?id=192251)

Title: Re: Folsom's great little 7297 Chip Amp
Post by: rockdrummer on 25 Mar 2019, 05:13 pm
Hey everyone.  I am waiting on some parts to be delivered, and will need to start layout planning soon.  But I am still asking questions.

Up front, I appreciate all the help. 

1. Can my divider wall have holes in it?  I was going to order a chassis from DIYstore, and use the riser walls to separate the boards.  They have a grid of holes pre drilled in them.  Will those play the role of divider or do I need a solid sheet of metal for it to do it's job?

2. I see some people are using terminal blocks inside the amp to connect transformers to the boards.  Also, I think that maybe where some switches are attached.  I wasn't aware of those and wonder if I need to try to use one.

3.  Can I use solid core 16 gauge wire everywhere in the amp?  Or do i need to use signal wire and power supply wire that is different gauges?  Also, I wouldn't know how to choose since I don't know if it matters or not.

Antek transformer wiring and switch/LED questions to come later :oops:

Thanks for any advice,
Ben
Title: Re: Folsom's great little 7297 Chip Amp
Post by: WireNut on 25 Mar 2019, 06:55 pm
Hi Jeremy,

Just wondering what the 2 black looking parts are that are connected to the RCA's?  Bleed resistors maybe? :scratch:
I didn't see them in the BOM.

See Pic.

Thanks.

(https://www.audiocircle.com/image.php?id=192521)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 25 Mar 2019, 07:31 pm
Sockets I think? Something I was playing with.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 25 Mar 2019, 07:33 pm
Hey everyone.  I am waiting on some parts to be delivered, and will need to start layout planning soon.  But I am still asking questions.

Up front, I appreciate all the help. 

1. Can my divider wall have holes in it?  I was going to order a chassis from DIYstore, and use the riser walls to separate the boards.  They have a grid of holes pre drilled in them.  Will those play the role of divider or do I need a solid sheet of metal for it to do it's job?

2. I see some people are using terminal blocks inside the amp to connect transformers to the boards.  Also, I think that maybe where some switches are attached.  I wasn't aware of those and wonder if I need to try to use one.

3.  Can I use solid core 16 gauge wire everywhere in the amp?  Or do i need to use signal wire and power supply wire that is different gauges?  Also, I wouldn't know how to choose since I don't know if it matters or not.

Antek transformer wiring and switch/LED questions to come later :oops:

Thanks for any advice,
Ben

1. Don't worry about it. Just use what you got and drill when you need.

2. I'm not sure what ones people are using.

3. I'm pretty sure I have the sized that work written in the guide.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: KR500 on 26 Mar 2019, 07:35 pm
Recently I moved my Folsom chip amp up to my dormer room and have been using it for vinyl playback
It is  a good match to my ears.   :thumb:

Source is Rega P3 with Elys cart
Bellari tube phono preamp ( with Sovtek 12LPS tube )
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rockdrummer on 29 Mar 2019, 07:05 pm
I'm really liking this project. I have learned a lot from all of your posts, and responses.  Also, thanks to ebag4 for his help with my transformer wiring.

I'm ordering resistors from Mouser today for the LED and the capacitor bleeder resistor on the power board. 

Does it matter what kind of resistor I order for the cap bleeder application?  The large film resistor looks so much different from the metal film ones, as long as the numbers are 10K ohms and 1 watt, does it matter which one i order?

Ben
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 29 Mar 2019, 07:32 pm
Doesn't matter
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rockdrummer on 31 Mar 2019, 11:44 pm
Hey, I have capacitors that were replacements for backordered ones on the power board.

They are not lining up for what I think are the proper places for the circles Folsom indicated. They are supposed to alternate sides where the circles are, right?

I am posting a picture because I think it is easier to see than explaining. I circled the same spots that are indicated in the info from Jeremy. And I put a yellow dot where I have leads from capacitors. They are too wide to get them any closer together.


(https://www.audiocircle.com/image.php?id=192776)
Thanks for any advice.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 1 Apr 2019, 12:00 am
Yellow dots look good.

You can check with a DMM. The dots shouldn't connect with nothing no the board that you're using for the capacitors. If they connect then the holes are wrong.

The spacing is meant to fit those capacitors, so the yellow ones are correct.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rockdrummer on 1 Apr 2019, 12:10 am
Okay, then I clearly dont understand the circles. I appreciate how many times you have helped me, Jeremy.

Ben
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rockdrummer on 1 Apr 2019, 01:02 am
Every yellow dot on the right has a circle and connects to each other on the right. The ones on the left are all connected but don't have circles. I'm sorry, I don't get it.

Each capacitor end doesn't connect with its other end.

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 1 Apr 2019, 01:46 am
I don't follow. Put them in the holes that make them parallel on the board and solder.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rockdrummer on 1 Apr 2019, 01:51 am
Okay. I must be making this harder than it really is :oops:

I was trying to make each capacitor not have a circle on the same end as it's neighbor.
I will go with it.
Ben
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Peter J on 1 Apr 2019, 02:27 am
Hi all. Man, am I ever late to this party! Was fired up and rarin' to go in the beginning, but lost my steam somewhere along the line.  Lacro has been checking in with me from time to time and we've agreed to cooperate on finally getting this done. I'll prep the case and then send his way for completion.


Some time ago I purchased these on eBay. I believe this is the one:

 https://www.ebay.com/itm/2109-Aluminum-Preamplifier-enclosure-case-amplifier-chassis-BOX-with-heatsink/252933969731?hash=item3ae40a1743:g:kysAAOSwjI5at24A



(https://www.audiocircle.com/image.php?id=192777)



Me being me, of course I can't just leave it alone, gotta put my spin on it! I modeled the faceplate in V Carve so I'll have a cut file. Been thinking wood or solid surface or maybe just engrave the one it came with, which I've never done. Could look like this:



(https://www.audiocircle.com/image.php?id=192778)


Cut one from scrap ply to make sure hole spacing was right


(https://www.audiocircle.com/image.php?id=192779)


Parts are on order, we'll update as things progress.

Title: Re: Folsom's great little 7297 Chip Amp
Post by: slefley on 4 Apr 2019, 08:50 pm
Are the power supply boards and BOM still available?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Peter J on 8 Apr 2019, 01:24 am
Moving along a bit since collecting all the bits and pieces. Lacro and I have been emailing back and forth figuring a way to get all in this into an almost-too-small chassis. I'm using a combo IEC/switch.

Here are some rudimentary layouts done in SketchUp. Weird dimensions are a result of some metric conversions. There'll be yet another conversion as I'm going to try cutting back panel on router which likes decimals.


Here's "floorplan"



(https://www.audiocircle.com/image.php?id=193008)


And back panel cutouts. RCAs down low on left, speaker binding posts up high and IEC on right. Bulkhead drawn in for reference.


(https://www.audiocircle.com/image.php?id=193009)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 8 Apr 2019, 01:27 am
Add the slots between the speaker binding posts, and the RCA posts.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Peter J on 8 Apr 2019, 01:37 am
Add the slots between the speaker binding posts, and the RCA posts.


Will do. I'll post CAD file once done that will show more detail, including slots. Slots between RCAs as well, huh?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 8 Apr 2019, 01:44 am
YES. The grounds on the RCA sockets need to be able to "see" each other electrically. The results are very nice.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 8 Apr 2019, 04:14 pm
YES. The grounds on the RCA sockets need to be able to "see" each other electrically. The results are very nice.

Hi Folsom,

What does this mean exactly. Are you cutting slots in the metal between the binding post? Do I have that right?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 8 Apr 2019, 06:01 pm
Yes. Just each channel, and each pair of RCA's. The slot can be relatively small.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 8 Apr 2019, 08:18 pm
Yes. Just each channel, and each pair of RCA's. The slot can be relatively small.

Can you point to any discussion or reference material regarding this slot. I am intrigued/curious about the science of it, even though it's probably way over my head.

Is 1mm too narrow for a slot?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 8 Apr 2019, 08:25 pm
I'd go for like 3mm.

I can't find the thread again. It's buried in DIYa. It's something that I just didn't get around to forever, turns out that was a mistake.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rockdrummer on 10 Apr 2019, 11:20 pm
Hey, I am wondering, I have 5 of the shoulder washers. Are there 5 on the bom in case one breaks while attaching the chip to the heatsink? Or is there another place to use them and I don't know where?
Ben
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 10 Apr 2019, 11:50 pm
Just an extra
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Peter J on 12 Apr 2019, 08:22 pm
We move along some.

Drill and tap left side for power supply


(https://www.audiocircle.com/image.php?id=193202)



(https://www.audiocircle.com/image.php?id=193203)



It's tight but looks good for clearance so far



(https://www.audiocircle.com/image.php?id=193204)



First time cutting aluminum on CNC router. I learned a few things...and broke two 1/8" bits.

Here's toolpaths and cut preview:


(https://www.audiocircle.com/image.php?id=193205)


(https://www.audiocircle.com/image.php?id=193206)


Some frustration and three bits later:


(https://www.audiocircle.com/image.php?id=193207)




A potential problem. I cut hole for RCAs 5/16" and binding posts 3/8", not realizing that there's a tiny little lip on plastic washer for RCAs. Oops. Do I need to open that up to 3/8"?


(https://www.audiocircle.com/image.php?id=193208)


Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 12 Apr 2019, 08:36 pm
Not if you can still get isolation (good luck). That lip stops conducting between chassis and RCA barrel.

Great job so far.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Peter J on 12 Apr 2019, 08:49 pm
Not if you can still get isolation (good luck). That lip stops conducting between chassis and RCA barrel.

Great job so far.


I'll just goop a bunch of caulk in there...


or


I'll see if I can ream it out. Slots will make it harder, but I'm stubborn.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: WireNut on 12 Apr 2019, 09:50 pm
(https://www.audiocircle.com/image.php?id=192778)



Looks like there's another CNC machinist / Cadcam Programmer working on the Folsom amp. Love that drawing Peter J  :wave:.
I haven't started mine yet.

Couple pics from a project I was playing around with a few years back.........Not as cool as yours but I was just messin..........

(https://www.audiocircle.com/image.php?id=86780)
(https://www.audiocircle.com/image.php?id=86749)

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Peter J on 13 Apr 2019, 01:48 am


Yeow, I'm cringing at the thought of Twisting My Nutz  :o You be my guest!



CAD programmer? Wannabe would be more accurate, methinks, but am having fun learning.



Unlikely the dragonfly will be engraved in the existing front. My practice piece was a dismal failure. I may work on something else while Lacro is doing his thing on the amp...we'll see.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: WireNut on 13 Apr 2019, 02:30 am
Yeow, I'm cringing at the thought of Twisting My Nutz  :o You be my guest!

CAD programmer? Wannabe would be more accurate, methinks, but am having fun learning.

Unlikely the dragonfly will be engraved in the existing front. My practice piece was a dismal failure. I may work on something else while Lacro is doing his thing on the amp...we'll see.


I'll pass on twisting anyone's nutz. I'm a retired CNC machinist/Cadcam programmer. Aerospace / Military, just about anything any costumer wants, Job shop machinist.

Anyway, it's nice to find someone that does DIY, and is a machinist/programmer. Not very many of use out there.
Being retired I know longer have access to machines but if I need something done my employer will machine it.
I can still program like a bitch and make G-code programs which I pass along to my old employers.

Again, glad to meet you and I'd love to play with your Dragonfly cad file :D.

Jeremy, continue on with your awesome amp thread, :popcorn:.
Sorry if I derailed.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: WireNut on 13 Apr 2019, 03:40 am
Peter J.
I built one of Jeremy's projects including three Fo-Felix filters, along with a DC Blocker into a single enclosure and I absolutely love it.
My plan is to build 4 of them given time.
 
Being retired, my old employer was nice enough to shear up enough pieces of aluminum sheet metal to build 4 enclosure's per my specs.
Thank you Roger Hasler.

With that sheet metal and aluminum angle iron purchased from Lowes I built my first unit pictured below.
Many audio purest won't like all the screws but I think they look pretty cool.
I didn't want to ask them to weld it together for me.

FWIW, If you can get scrap aluminum sheet metal for free and bolt it together with alum angle iron it will save you a lot of money and it's rewarding to do.
To me, the screw's look pretty cool but I'll try and keep them to a min on my next build.
Jeremy is a very good designer and I can't wait to build his amp.

Sorry Jeremy, didn't mean to derail. On with the thread.


(https://www.audiocircle.com/image.php?id=193223)

(https://www.audiocircle.com/image.php?id=193224)

(https://www.audiocircle.com/image.php?id=193227)


(https://www.audiocircle.com/image.php?id=193228)

(https://www.audiocircle.com/image.php?id=193229)


Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 13 Apr 2019, 02:17 pm



A potential problem. I cut hole for RCAs 5/16" and binding posts 3/8", not realizing that there's a tiny little lip on plastic washer for RCAs. Oops. Do I need to open that up to 3/8"?


(https://www.audiocircle.com/image.php?id=193208)

Peter, Looking good! I would definitely open up the holes to 10mm (3/8") In one of my e-mails to you, I mentioned the step washer, and included the Mfg. parts drawing which shows the 10mm hole to accommodate the step on the plastic washer.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Peter J on 13 Apr 2019, 03:30 pm
Yeah, somehow I got it in my head that was only for speaker binding posts. They're more obvious and I should have looked closer. Not to worry, I fixed it with a reamer. Photo makes them look off-center, but they're not.


(https://www.audiocircle.com/image.php?id=193241)


I somewhat remember you posting that stuff Wirenut, having haunted here a long time. Cool.

 I'm happy to send CAD file if you want to eyeball. Drawn in VCarve Pro, so it's a .crv file. I'm slowly learning more about G Code, but depend on software to generate it at this point.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rockdrummer on 14 Apr 2019, 06:18 pm
Peter j and wirenut, looking great!

I installed my neutrik input and switch.


(https://www.audiocircle.com/image.php?id=193283)


Really enjoying the build. I do have another question.
The bleeder resistor I got from mouser is 10kohm and 1 watt, but it is tiny compared to others I see in this thread. I tried to research the kind of resistor, and maybe I ordered the right specs but the wrong kind. Does the resistor in this pic look okay?

(https://www.audiocircle.com/image.php?id=193284)

Thanks for any advice.
Ben
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 14 Apr 2019, 07:43 pm
If the specs are right, it's fine.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Peter J on 15 Apr 2019, 06:44 pm
Bulkhead complete. Time to get it Lacro-ized!



(https://www.audiocircle.com/image.php?id=193360)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Peter J on 16 Apr 2019, 02:13 am
Since engraving looks like a dud for now, I've been messing with V Carving the dragonfly in black solid surface.  I can leave the carving as is, color and fill with clear epoxy, or fill with tinted epoxy which is mostly opaque. What do y'all like?


(https://www.audiocircle.com/image.php?id=193384)


(https://www.audiocircle.com/image.php?id=193383)
 

(https://www.audiocircle.com/image.php?id=193385)


(https://www.audiocircle.com/image.php?id=193386)

Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 16 Apr 2019, 09:54 am
Since engraving looks like a dud for now, I've been messing with V Carving the dragonfly in black solid surface.  I can leave the carving as is, color and fill with clear epoxy, or fill with tinted epoxy which is mostly opaque. What d


I like the tinted Orange first, because it looks more unique. The blue comes in a close second. You do great work
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Peter J on 16 Apr 2019, 02:21 pm
I like the tinted Orange first, because it looks more unique. The blue comes in a close second. You do great work


Orange was a (lame) attempt at copper with a limited palette available. But orange is a possibilty as well.


For anyone  reading, had I not cut the back panel on router, I would have used a Rotabroach. They cut on their rim and leave a cleaner, more concentric hole than a twist drill. I've had this little set for years. You can get new cutters when they're dull.


(https://www.audiocircle.com/image.php?id=193408)


https://www.nationaltoolwarehouse.com/Rotabroach-Cutter-Kit-Fractional-P44942.aspx?gclid=Cj0KCQjw-tXlBRDWARIsAGYQAmeiJ-C8f_4Y_14lOTMJS3NoeNa61QHkbiiYzUj4Y3nnBXc-wwMKu-4aAkLuEALw_wcB



Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 16 Apr 2019, 03:01 pm
I vote for all black. I like it's subtle (KISS) statement. However, I would add 1-1.5 mm holes (eyes) on both sides of the head with the rear of the panel counter-bored to 3mm to receive 2 red LED's. When powered on the red  eyes will draw attention to the subtle black image.  :drool:


(https://www.audiocircle.com/image.php?id=193413)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: uncola on 16 Apr 2019, 03:22 pm
thanks for mentioned those rotobroch, seems like it's better than a stepped bit for rca sockets etc and not more expensive
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Peter J on 16 Apr 2019, 07:13 pm
I vote for all black. I like it's subtle (KISS) statement. However, I would add 1-1.5 mm holes (eyes) on both sides of the head with the rear of the panel counter-bored to 3mm to receive 2 red LED's. When powered on the red  eyes will draw attention to the subtle black image.  :drool:


(https://www.audiocircle.com/image.php?id=193413)

Your wish is my command...almost. I redrew "the bug" to keep more with original concept...the head just got too busy. Eye holes will cut as cones about 1/8" deep and I'd drill hole diameter of LED in bottom. Would sort of illuminate the pocket.

If you give me thru hole diameter and depth so I can cut backside pocket, I'll give it a go.


(https://www.audiocircle.com/image.php?id=193417)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 16 Apr 2019, 11:03 pm
I love it! But it's your build, and if a colored bug is your choice, go for it. PM sent for suggested dimensions.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Peter J on 18 Apr 2019, 01:36 am
I just can't leave stuff alone, I guess. Seems one thing always leads to another. Today I made this. Black Corian and a makeshift lighting arrangement for demo.



(https://www.audiocircle.com/image.php?id=193457)



(https://www.audiocircle.com/image.php?id=193458)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mzbrahce on 22 Apr 2019, 06:19 pm
Folsom--

If I'm running your amp with the Antipole, is there any benefit in also using your Fo-Felix?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 22 Apr 2019, 07:28 pm
Yes, it does help clean up the sound a bit more. It stops some noise from getting into the enclosure, for example.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rockdrummer on 23 Apr 2019, 05:25 am
I have made lots of progress, not without a couple snags.

I spend most of my build time double checking design ideas so I don't overlook anything.

I have the binding posts wired, started the rca inputs. I am using the cardas inputs and they were really challenging to solder the ground as they have a goofy collar instead of a tab. Tomorrow I hope to finish connecting input wires, install the mica and heatsink, and get a finalized plan for the LED wired off the aux output of the power board.


(https://www.audiocircle.com/image.php?id=193793)

Ben
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 23 Apr 2019, 05:29 am
You have a heatsink for the chip, right?

Also, I hope you didn't drill the board for the speaker binding posts wire.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rockdrummer on 23 Apr 2019, 05:38 am
Folsom, thanks for the reply. Yup, I have a heatsink, and no I didn't drill the board. I went back and forth trying to plan steps to best install the wires and heatsink.

I tapped the sink last week and I will get that installed tomorrow, I hope.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 23 Apr 2019, 07:46 am
 :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rockdrummer on 24 Apr 2019, 12:21 pm
Hi, here is my layout. I went back and forth with the psu position. I originally had the antipole backed up the same way but with the capacitors on the front side of the chassis.  This ran the ac wires as far away from the amp board as possible. But I decided to change it. Adding the LED and testing are left.


(https://www.audiocircle.com/image.php?id=193832)

Ben
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 24 Apr 2019, 05:16 pm
Looking good. People will probably think it's a much more powerful amp than it is, purely by size!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Hirst on 24 Apr 2019, 09:36 pm
If you have not done so already, remember to cut a slot between the posts, see pictures in previous page. 

Paul
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 24 Apr 2019, 09:47 pm
If you have not done so already, remember to cut a slot between the posts, see pictures in previous page. 

Paul

It's not required, but it sure is a cheap and effective upgrade.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rockdrummer on 24 Apr 2019, 09:54 pm
Yes, the size is totally overkill isn't it?

I'm regretting not cutting those slots. I didn't do it. To be totally honest, I was so focused on cutting out the large neutrik cutout for the power cord, and cutting for all the holes, I completely forgot. Head slap after I was going back and looking through the thread.

Ben
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rockdrummer on 27 Apr 2019, 07:27 pm
Hello, okay, this is the toughest part for me. Troubleshooting. I finished my amp, and since I'm very uninformed about testing circuits and basic knowledge to navigate such subjects, I opted to fully build then power on.

Did that, and my led didn't light up. No pop, or smoke, but no sound either. When measuring the ac into the psu, I get .003 volts on my meters auto range. So, I suspect I didn't hook up the transformer correctly.

I am using an Antek as 1215 which has been used by others in this thread.
Ben
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rockdrummer on 27 Apr 2019, 07:36 pm
I have a feeling I don't have the correct blue and green wires out of the transformer.
Ben
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 27 Apr 2019, 07:52 pm
I have a feeling I don't have the correct blue and green wires out of the transformer.
Ben

The AS1215 is a 15V transformer. You need 16V to power the Antipole. You should have got the AS1218. I don't know how well it will work with the lower voltage transformer.

To wire it for 120v: For the primary side, use the 2 red wires for one leg, and the 2 black wires for the other
leg. The purple wire goes to chassis ground. On the secondary side do the same, tie the 2 green together, and tie the 2 blue together.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rockdrummer on 27 Apr 2019, 08:13 pm
Okay, I was under the impression that I should only use one green and one blue. I do have the black and red combined correctly. I was trying to follow some other builders who have used the 15v.

Thanks for the response. I will resolder the combined blue and green.

Again, I appreciate it.
Ben
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 27 Apr 2019, 08:17 pm
15v will turn on but bass and gumption in general may be a bit (or lot) more limited.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: borism on 27 Apr 2019, 08:18 pm
Yardbird (p54) used an AS 1215 and got about 20V from the power supply board. He later changed to the 1218 transformer.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rockdrummer on 27 Apr 2019, 08:23 pm
Okay, what does that mean? I'm lost.
I want more than 20v?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rockdrummer on 27 Apr 2019, 08:36 pm
Undertowogt1 is also using one on page 47.

Not sure what to do now. I will wire this up, see if it sounds okay. I will eventually be using servo subs on both sides and amps for bass, but I certainly want the best out of this amp.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 27 Apr 2019, 08:41 pm
Give it a try. What sensitivity are the speakers?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rockdrummer on 27 Apr 2019, 08:47 pm
91db. Today, my test speakers are definitive technology bp8. I will hopefully have some open baffle monitors around 93 db in the next couple months.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 27 Apr 2019, 09:07 pm
Give it go. You can swap transformers later.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: WireNut on 27 Apr 2019, 10:06 pm
Add the slots between the speaker binding posts, and the RCA posts.

I'm late to this thread. Please help me understand "Add the slots between the speaker binding posts, and the RCA posts."

Title: Re: Folsom's great little 7297 Chip Amp
Post by: zek on 27 Apr 2019, 10:45 pm
I'm late to this thread. Please help me understand "Add the slots between the speaker binding posts, and the RCA posts."
See two pages back. :thumb:
https://www.audiocircle.com/image.php?id=193206
Title: Re: Folsom's great little 7297 Chip Amp
Post by: WireNut on 27 Apr 2019, 10:53 pm
See two pages back. :thumb:
https://www.audiocircle.com/image.php?id=193206

I see that It's a thru slot between the RCA's and also the binding post. But Y, what does it accomplish?

Is it to separate the grounds?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rockdrummer on 27 Apr 2019, 10:54 pm
Alright. Bountiful sound out of the left channel, and no right channel. Both interconnects work into the left channel, but not the right. Also, the right speaker works out of the left binding post. So it's either the right rca input or somewhere between it and the right binding post.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: WireNut on 27 Apr 2019, 11:20 pm
Add the slots between the speaker binding posts, and the RCA posts.

Will do. I'll post CAD file once done that will show more detail, including slots. Slots between RCAs as well, huh?

YES. The grounds on the RCA sockets need to be able to "see" each other electrically. The results are very nice.


Got It  :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: WireNut on 27 Apr 2019, 11:22 pm
Alright. Bountiful sound out of the left channel, and no right channel. Both interconnects work into the left channel, but not the right. Also, the right speaker works out of the left binding post. So it's either the right rca input or somewhere between it and the right binding post.

rockdrummer needs help.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rockdrummer on 27 Apr 2019, 11:53 pm
GOT IT!

I gave the heatsink attached to the chip a tiny bit of a wiggle, and the right channel flickered. Reflowed all the chip tabs and I'm making music!

Thanks wirenut, I'm good now.
Ben
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rockdrummer on 28 Apr 2019, 12:15 am
Going to dinner, mostly to celebrate! Haha

Then put the top on and do some burning in. I got 16.07v at the psu input.


(https://www.audiocircle.com/image.php?id=193986)
Thanks for the help everyone.
Ben
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 28 Apr 2019, 12:58 am
15v will turn on but bass and gumption in general may be a bit (or lot) more limited.
Rockdrummer is correct, I did use a AS 1215. Should I be swapping it out for a AS 1218? The amp sounds really nice to my ears, am I missing out? I am getting 16 V AC on the Input of the PSU and 20.5 out of the PSU to the Aamp Board.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 28 Apr 2019, 01:27 am
With your speakers you may not notice. But it's an easy and fairly inexpensive thing you can try if you get the itch.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 28 Apr 2019, 03:00 pm
Folsom:

If undertowogt1 is getting 20.5V out of the Antipole PS without load what happens when the volume is cranked, and the current load increases (voltage drops)? Is there enough voltage to activate the infinite capacitor?

From your original Indiegogo info about this amp:

-*Requires 21-25v to operate correctly, which is regulated down to 17.8-18v by Kmultiplier to meet amplifier chip voltage safety. This can be attained with batteries, SMPS, or to match the performance of the demo the Antipole also by Folsom.

From your post#4:

Yup, the "infinite capacitor" only activates with enough voltage (listed on my IndieGoGo). S Clark is going to get a very nice improvement soon switching to 24v input (gets regulated to 17.8-18v on amplifier board).


This AS1215 transformer chart shows the output voltage drop as load increases:

(https://www.audiocircle.com/image.php?id=194012)

My question: If current load is decreasing the the transformer output voltage, does this have a detrimental affect on the chip when using the AS1215 transformer?



Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 28 Apr 2019, 05:15 pm
Voltage does drop, and I just don't know if it can maintain the infinite capacitor, I suspect not but I'd have to be on his power testing it. It's cutting it so close that I would just say "I doubt it".

I prefer above 21v for a transformer. SMPS doesn't waver so down to 21v on them is just fine.

S. Clark was on 12v before switching to 24v battery.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 28 Apr 2019, 07:24 pm
Bulkhead complete. Time to get it Lacro-ized!



(https://www.audiocircle.com/image.php?id=193360)

It has now been "lacro-ized" It fired right up first try, and it sounds great!


(https://www.audiocircle.com/image.php?id=194040)


(https://www.audiocircle.com/image.php?id=194041)



Title: Re: Folsom's great little 7297 Chip Amp
Post by: S Clark on 28 Apr 2019, 07:38 pm
Voltage does drop, and I just don't know if it can maintain the infinite capacitor, I suspect not but I'd have to be on his power testing it. It's cutting it so close that I would just say "I doubt it".

I prefer above 21v for a transformer. SMPS doesn't waver so down to 21v on them is just fine.

S. Clark was on 12v before switching to 24v battery.
Only for a short while, until using a variable power supply up to 18V. 
But 24V has clearly been a better option. 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Peter J on 29 Apr 2019, 02:43 pm
It has now been "lacro-ized" It fired right up first try, and it sounds great!


(https://www.audiocircle.com/image.php?id=194040)


(https://www.audiocircle.com/image.php?id=194041)


I'd say lacro is being a little modest here, this compact and clean layout was mostly his brainchild. Between us, we managed to put "twelve pounds of potatoes in a ten pound sack".

While doing this he also checked fit for most recent amp board which I understand is longer. It would indeed fit, but I'll let him speak to the details should someone else decide to use this particular case.


Should be plenty of heat sinking there, no? 8)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 29 Apr 2019, 05:39 pm

I'd say lacro is being a little modest here, this compact and clean layout was mostly his brainchild. Between us, we managed to put "twelve pounds of potatoes in a ten pound sack".

While doing this he also checked fit for most recent amp board which I understand is longer. It would indeed fit, but I'll let him speak to the details should someone else decide to use this particular case.


Should be plenty of heat sinking there, no? 8)

The Chinese 2109 case really is a great choice for the Folsom amp. I did check the fit with the latest, longer Folsom amp board, and it will work with the transformer shoved into the front corner. I checked with Antek, and was told it's OK to have the transformer touch the sides. The fact that the case already has a heat sink, there is no need to buy the one listed in the BOM which comes to about $16 total for the heat sink, cutting charge, and shipping.

The case is easy to work with as front, back, sides, top, and bottom are all separate pieces making for easy interior access by removing one or more pieces.

Can't wait to see Peter's custom front panel installed.

https://www.ebay.com/itm/2109-Aluminum-Preamplifier-enclosure-case-amplifier-chassis-BOX-with-heatsink/252933969731?hash=item3ae40a1743:g:kysAAOSwjI5at24A
Title: Re: Folsom's great little 7297 Chip Amp
Post by: WireNut on 29 Apr 2019, 11:10 pm
Hi Jeremy,

I was looking at the BOM and noticed the two options for the 12 aluminum polymer caps are 560uF or 330uF.
The Panasonic's are 560uF, 20 volt, while the Nichicon's are 330uF, 25V.
Are they suppose to be the same uF value, typo maybe?

Thanks.

https://www.mouser.com/ProductDetail/Panasonic/20SEPF560M%2bT?qs=%2Fha2pyFaduhzHJzzPX6Io3y3EIFd0mSHh3UAKFhbYh3cwIQ7io48SQ%3D%3D

https://www.mouser.com/ProductDetail/Nichicon/RNU1E331MDN1PH?qs=%2Fha2pyFadujVIAFfwoA35%252B2IYhgmyzi0EJJlJz5ifHvhjFt2xEOB3w%3D%3D
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 30 Apr 2019, 12:51 am
No. Nichicon doesn't offer as big of value, but they have a different sound.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: drew_t on 2 May 2019, 12:26 am
I was about to order the rest of the parts I need to finally finish my Folsom amp, but the six film caps for the power board -- https://www.mouser.com/ProductDetail/871-B32560J1225K -- are out of stock.  (This is the part # I had in my project list on mouser.com; not sure if they're the ones originally specified or a substitute which at some point was suggested.)

I did a search for a part with the same specs, but it doesn't look like they have anything.

Is there anything that will work that is currently in stock at Mouser?

EDIT:
Would the version of the part rated for 40VAC/63VDC work?
https://www.mouser.com/ProductDetail/EPCOS-TDK/B32520C0225J000?qs=Xovllr2ZOuYQ7EvLeHnsdg%3D%3D



Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 2 May 2019, 01:46 am
There are alternative part numbers in the Antipole build notes.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Peter J on 5 May 2019, 11:36 pm
The following is minutia that has little to do with the actual amp, but it's fun for me because I learned some new things about LEDs and light fiber. I thought y'all might like it too.

 What I was after was to illuminate the eye sockets but not have piercing little LEDs staring back at me. Conclusion is no matter how much I dimmed the tower LEDs in the 2mm holes it was still more intense than I wanted. It seem to me it needed not just dimming but diffusion. Next step was 2mm light fiber which I've never worked with either.


The setup


(https://www.audiocircle.com/image.php?id=194270)


The result. Still not what I'm after



(https://www.audiocircle.com/image.php?id=194271)


I filed ends of fiber, stuck in holes from rear and ground flush



(https://www.audiocircle.com/image.php?id=194272)

(https://www.audiocircle.com/image.php?id=194273)



After more experimenting, I cut a little piece of clear acrylic and stuck LED into side.



(https://www.audiocircle.com/image.php?id=194274)


Applied black out tape :)

 
(https://www.audiocircle.com/image.php?id=194275)


To end up here.


(https://www.audiocircle.com/image.php?id=194276)


I'll tidy things up, but it looks like I wanted now. I'll probably have nightmares about bright eyed dragonflies...











Title: Re: Folsom's great little 7297 Chip Amp
Post by: WireNut on 6 May 2019, 12:41 am
That is wicked, I love it  :idea: :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: WireNut on 6 May 2019, 12:45 am
Looks like you went with a simpler toolpath with a small ballmill. Looks great.

Peter J. You are very talented. Not many have your skills. Keep up the good work.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Peter J on 6 May 2019, 07:19 pm
Thanks Wirenut. I actually used a 60° V cutter, but did spray with conversion varnish which probably makes the bottom of carving look rounded.

Made a mo' betta acrylic block, sprayed all but bottom side with texture black, glued in place, cleaned up wiring and Bob's your uncle. Lacro left a connector for me to plug LED into. I need to get a preamp figured out so I can listen to it!



(https://www.audiocircle.com/image.php?id=194316)

(https://www.audiocircle.com/image.php?id=194317)

(https://www.audiocircle.com/image.php?id=194318)


Forgot to mention two people who were instrumental in getting this done. Lacro, take a bow.


Also Nick at          https://lighthouseleds.com/    who answered my many LED questions and supplied the LEDs and fiber optics.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 6 May 2019, 07:22 pm
Definitely build Keantoken’s buffers with a chinese DACT for volume.  :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 6 May 2019, 07:29 pm
Looking good, Peter J!!

What Folsom said...or...https://www.diyaudio.com/forums/pass-labs/313612-b1-korg-triode.html --I have both, and they are both great solutions.

Either way, use the exact same case for the pre, etch a mosquito on the faceplate, and stack the pre on the amp. Then Bob really is your uncle!  :lol:

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Peter J on 6 May 2019, 07:31 pm
Definitely build Keantoken’s buffers with a chinese DACT for volume.  :thumb:


Jeremy, give me clue man. Where will I find Keantoken and his buffers?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 6 May 2019, 07:37 pm
https://www.diyaudio.com/forums/analog-line-level/251413-kuartlotron-keantokens-simple-error-correction-superbuffer.html

I haven’t heard the Triode B1, but I have a board and NuTube.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 6 May 2019, 07:38 pm
Looking good, Peter J!!

What Folsom said...or...https://www.diyaudio.com/forums/pass-labs/313612-b1-korg-triode.html --I have both, and they are both great solutions.

Either way, use the exact same case for the pre, etch a mosquito on the faceplate, and stack the pre on the amp. Then Bob really is your uncle!  :lol:

Or a lizard?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 6 May 2019, 07:53 pm
Or a lizard?

Ooohh, I like it...the hunter becomes the hunted...

I live in northern MN, where in the spring we have a literal armada of dragonflies patrolling the forest clearings for those pesky mosquitoes. So, from my perspective, the dragonflies are on the prowl.

You should build it, Folsom (the Korg B1). I just used the stock parts and it sounds great. My NuTube is very microphonic (high pitched ringing), but once isolated, it is great. Really easy build, too...


limits
Title: Re: Folsom's great little 7297 Chip Amp
Post by: WireNut on 7 May 2019, 07:12 pm
Is this what you guy's are talking about?

B1 Buffer with Korg Triode PCB + Fairchild JFETs

https://diyaudiostore.com/collections/kits/products/b1-buffer-with-korg-triode-pcb-and-jfets
Title: Re: Folsom's great little 7297 Chip Amp
Post by: limits on 7 May 2019, 07:35 pm
Is this what you guy's are talking about?

B1 Buffer with Korg Triode PCB + Fairchild JFETs

https://diyaudiostore.com/collections/kits/products/b1-buffer-with-korg-triode-pcb-and-jfets

Yep, that's it, WireNut.  :thumb:

limits
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Danny23 on 2 Jun 2019, 05:41 pm
Or a lizard?

@ Folsom - Would you mind providing a comparison between this 7297 chip amp, and your new 7293 chip amp?  How are they similar, and how are they different?  Will the new 7293 have a battery option?

I haven’t seen much about the 7293, other than the GB on the other site.  Thanks!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 2 Jun 2019, 06:43 pm
It's better. It does everything better. It's a lot more power. You can't battery power it because it needs +, PG, - power supply. It also needs a higher minimum voltage for the regulator to work that provides power to the LED board (that shines on the PVI cells and powers the feedback much more stable than the PSU and any regulator can). We provide a BOM that includes PSU stuff that's tuned for the Antek transformer that's a great fit. The Antek is nice because at 200/300VA they have a shield between the primary and secondary that keeps RF down.

This amp is kind of special given that the front end is totally discrete. OPAMP front ends have clamps, protections, compensators, etc. They are the type of things a lot of people want to avoid (even when they're benign) in audio. You can also tune it by swapping around a couple of the caps that deal with signal.

Overall it employees a lot of the same PCB stuff we did with the 7297, but it's even better. It's got CFC, copper pours, tracing for signal that reduces field sizes, etc.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: zek on 2 Jun 2019, 07:38 pm
Some link for new 7293 amp, please.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Danny23 on 2 Jun 2019, 07:43 pm
Some link for new 7293 amp, please.

It looks to be pretty spectacular.  See here:
https://www.diyaudio.com/forums/group-buys/338275-folsom-ec7293-pvi-powered-frontend-60-120w-8-4ohm.html
Title: Re: Folsom's great little 7297 Chip Amp
Post by: zek on 2 Jun 2019, 10:54 pm
Thanks. :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: HT cOz on 3 Jun 2019, 06:34 am
 I think you guys are going to be in for a surprise with this new one. 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: annamarykahn on 3 Jun 2019, 02:52 pm
waiting with anticipation :-)

how do we order/pre-order?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Danny23 on 3 Jun 2019, 02:56 pm
waiting with anticipation :-)

how do we order/pre-order?

See the link in my post above.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: annamarykahn on 3 Jun 2019, 03:09 pm
thx danny, i've inquired in getting the amp
Title: Re: Folsom's great little 7297 Chip Amp
Post by: SuperXRSSeattle on 8 Jun 2019, 08:34 am
Any possibility of purchasing pre-built of the new Folsom amp? If not, how long until all the parts can be acquired? Chancing the question as I'm not registered at DIY.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Hirst on 8 Jun 2019, 12:15 pm
Quote
Any possibility of purchasing pre-built of the new Folsom amp? If not, how long until all the parts can be acquired? Chancing the question as I'm not registered at DIY.

You can contact Folsom on this board.  He lives in the PNW and can most likely work something out for you.

Paul
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mresseguie on 8 Jun 2019, 02:40 pm
Any possibility of purchasing pre-built of the new Folsom amp? If not, how long until all the parts can be acquired? Chancing the question as I'm not registered at DIY.

There is a fellow named Radu Tarta who builds and sells tube amps and preamps. He will also build an amp such as Folsom's Little Chip amp. I know this because he built mine for me. He's very easy to communicate with and he did an excellent job on my little amp. His contact email is simplepleasuretubeampsrct@gmail.com .

His website:  https://simplepleasuretubeamps.wordpress.com/

Jeremy's little amp sounds great in my home office system. Mac Mini => Gustard X20u DAC => Folsom's amp => Wild Burro 8" OB FR drivers in Caintuck Audio's Betsy baffles = Happy me!

Michael
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 8 Jun 2019, 04:56 pm
Radu is a great suggestion!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: SuperXRSSeattle on 8 Jun 2019, 06:27 pm
Hirst, mresseguie, Folsom - thanks!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Rivalaudio on 15 Jul 2019, 02:33 pm
Has anyone tried these caps with their Folsom amp?

http://www.soniccraft.com/product_info.php/miflex-kpal-15uf-600vdc-aluminum-foil-polypaper-in-oil-p-5278
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 15 Jul 2019, 04:28 pm
Has anyone tried these caps with their Folsom amp?

http://www.soniccraft.com/product_info.php/miflex-kpal-15uf-600vdc-aluminum-foil-polypaper-in-oil-p-5278

I have not, but I was going to upgrade mine to the Jantzen Superior Z-Cap, 1.50µF 800VDC. These "look" nice. Do you think the Thru Hole is big enough on the boards? It say s it needs to be larger than .065
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 15 Jul 2019, 05:35 pm
I have not, but I was going to upgrade mine to the Jantzen Superior Z-Cap, 1.50µF 800VDC. These "look" nice. Do you think the Thru Hole is big enough on the boards? It say s it needs to be larger than .065

The thru holes for the caps are smaller than .065" More like .030" IMO/ chasing the "best" sounding caps for this amp is probably not worth the expense. I have heard different boutique caps, with this amp, and find the caps from the original BOM are all you really need for this great little chip amp! 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 15 Jul 2019, 09:16 pm
The thru holes for the caps are smaller than .065" More like .030" IMO/ chasing the "best" sounding caps for this amp is probably not worth the expense. I have heard different boutique caps, with this amp, and find the caps from the original BOM are all you really need for this great little chip amp!
Good to know, really not worth it? So in your experience do you even hear a difference at all?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 16 Jul 2019, 03:27 pm
Good to know, really not worth it? So in your experience do you even hear a difference at all?

I don't think there is enough difference if any to justify the price of admission. Everybody has a different system and set of ears. You may hear a significant difference using expensive boutique capacitors, where I may not. Maybe others that have tried different caps can chime in.

This sweet sounding little amp is designed around a $4 chip using good parts, and design. At the price point of this amp, and how easy it is to build, it's hard to beat without spending a lot more for something better. Trying to get a lot more out of it by changing 2 caps is probably not going to happen. If you do go that route, I wouldn't spend over $25 total for a pair of boutique caps. YMMV....
Title: Re: Folsom's great little 7297 Chip Amp
Post by: DeeJayBump on 23 Sep 2019, 05:30 pm
What size screws/bolts should be used for mounting the PCB? And what kind + size board standoffs?

Thanks.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: wushuliu on 23 Sep 2019, 08:42 pm
I think Folsom has a new amp out that's supposed to be better.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: S Clark on 23 Sep 2019, 09:13 pm
I took the sonicap platinums out of my LS9 speakers, and Folsom used them in another version of his amp.  Improvements, but modest.  Those caps are about detail, which is something that that amp does well to start with. 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: undertowogt1 on 23 Sep 2019, 10:17 pm
I took the sonicap platinums out of my LS9 speakers, and Folsom used them in another version of his amp.  Improvements, but modest.  Those caps are about detail, which is something that that amp does well to start with.
Thanks for the info. I think I have decided it is not worth any amount of money to change the caps in the amp for improvements. Just based on this forum.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 23 Sep 2019, 10:23 pm
What size screws/bolts should be used for mounting the PCB? And what kind + size board standoffs?

Thanks.

I use M3 for everything.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: DeeJayBump on 24 Sep 2019, 12:22 am
I use M3 for everything.

Thanks.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: jonny5 on 18 Oct 2019, 06:24 pm
I'm a longtime tinkerer with electronics and audio gear, but this is my first full solid state build.

Everything is still burning in, but to echo prior comments, it sounds fantastic.

#4 screws work just fine as an alternative to M3 screws - I used #4 for little stuff and larger screws for any part of the build that didn't require screws that small. 

The cheap W226.5×H70×D271mm case on eBay makes a fantastic case for the build:
https://www.ebay.com/itm/252579253474

Pics with the build in that case are below.

(https://www.audiocircle.com/image.php?id=199779)

(https://www.audiocircle.com/image.php?id=199780)

(https://www.audiocircle.com/image.php?id=199781)

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 19 Oct 2019, 02:52 am
Very nice.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: uncola on 19 Oct 2019, 07:32 am
That’s an awesome looking amp...  so compact yet neat
Title: Re: Folsom's great little 7297 Chip Amp
Post by: jmc207 on 19 Oct 2019, 12:28 pm
That’s an awesome looking amp...  so compact yet neat

Yes, awesome, and almost like it's been vacuum-packed.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 19 Oct 2019, 04:32 pm
Very nice work!! The case you used is similar to the one we used to build Peter's amp, but different dimensions. The price is right for either one especially considering you don't need to buy a heat sink. BTW/ what input caps/bypass caps did you use?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rollo on 19 Oct 2019, 05:42 pm
  Looking good. Yet to hear one however people who have liked it.

charles
Title: Re: Folsom's great little 7297 Chip Amp
Post by: jonny5 on 19 Oct 2019, 10:29 pm
Jantzen Z-Superior caps with Miflex KPCU copper foil bypass caps was what I decided.  With the layout, size of capacitors was potentially limited, haha.

I originally had doubts that I could find a cover that could fit the Antek 1218 transformer yet had adequate clearance for the layout in the case. Once I had all the parts in hand, it looked like a 120x57mm toroidal transformer cover would just barely fit and do the job.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Peter J on 20 Oct 2019, 03:24 am
Well done!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mresseguie on 20 Oct 2019, 06:42 am
Jonny5,

That internal shot sure is nice looking!

Question: Is there an advantage to using a toroidal transformer over another transformer? My Folsom's chip amp uses 'another', but I don't know what to call it.

Michael

Title: Re: Folsom's great little 7297 Chip Amp
Post by: poseidonsvoice on 20 Oct 2019, 02:09 pm
Jonny5,

Great work  :green:. I like the shielded toroid as well. The stainless steel shielding minimizes noise from the toroid. Hopefully it came with electrostatic shielding to minimize capacitative coupling from the primary to secondary which you should connect to chassis ground.

Nearly all my builds use a stainless steel toroid cover plus electrostatic shielding. Antek supplies them. For my super high end builds I custom order from Toroidy.

In my experience, less noise = more low level detail, and a smoother sound to boot.

Best,
Anand.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: jonny5 on 20 Oct 2019, 03:42 pm
Yeah - you can’t see it in the picture, but the transformer shield wire is grounded to to the chassis ground.

Antek’s own transformer cover wouldn’t fit in that case without grinding it down to be several millimeters shorter.  The cheap Chinese cover from eBay cost considerably less, didn’t require modification, and had a mounting setup that was easier to tuck wire under the cover.

Aluminum provides no magnetic shielding, so if you want to go crazy like I did with that build, a bit of steel sheet to cover the underside of the transformer to complete a more complete box to shield the external magnetic field of the transformer more thoroughly.

Other people can answer the question about trade-offs between transformer types better than me - I went with the toroidal transformer to fit in the case because I was trying to make the build as compact as possible.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: drew_t on 21 Oct 2019, 12:28 am

The cheap W226.5×H70×D271mm case on eBay makes a fantastic case for the build:
https://www.ebay.com/itm/252579253474


Why is it that Chinese vendors will sell you almost anything you can think of with free shipping, but if you want an empty, presumably unassembled and flat-packed aluminum box, they invariably quote very high shipping charges?

Very nice build, jonny5.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: DeeJayBump on 24 Oct 2019, 01:54 pm
Excellent build, jonny5, thanks for sharing.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: AKLegal on 30 Oct 2019, 07:02 pm
Are the boards for these still available?  I read through the thread but I cant really tell.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: DeeJayBump on 30 Oct 2019, 11:11 pm
Are the boards for these still available?  I read through the thread but I cant really tell.

Yes :

https://www.diyaudio.com/forums/group-buys/309860-folsom-diy7297-amp-antipole-psu.html
Title: Re: Folsom's great little 7297 Chip Amp
Post by: AKLegal on 31 Oct 2019, 10:02 pm
^^^Much Appreciated
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Wind Chaser on 1 Nov 2019, 05:28 pm
Rather than digging through this gigantic thread is there a website with all the essential information like specs, power supply requirements etc that is easily accessible all on one page?  TIA :D
Title: Re: Folsom's great little 7297 Chip Amp
Post by: AKLegal on 1 Nov 2019, 05:56 pm
Rather than digging through this gigantic thread is there a website with all the essential information like specs, power supply requirements etc that is easily accessible all on one page?  TIA :D

I ended up getting the newer ec7293 amp instead of the 7297.  The specs for the 7293 are here https://www.diyaudio.com/forums/group-buys/338275-folsom-ec7293-pvi-powered-frontend-60-120w-8-4ohm.html
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 2 Nov 2019, 10:04 pm
TDA7297 specs (https://www.st.com/resource/en/datasheet/tda7297.pdf)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: uncola on 15 Mar 2020, 02:52 pm
Might be a dumb question, but if I build active 3 way speakers with a DSP crossover, will this amp handle a chinese clone bg  neo3 pdr?  it's 4 ohms nominal and I know this amp is for 8 ohm speakers.. but tweeters don't use much power right?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 15 Mar 2020, 03:13 pm
Incorrect, it works fine with 4 and 8ohm. 4ohm gets 120w!

Tweeters do not use as much power as woofer.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Dhananjeyan on 16 Mar 2020, 04:16 pm
Hey I was just wondering where can I buy all the parts from or is there a kit I can just buy?
Thank you
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 16 Mar 2020, 07:23 pm
Email me at folsom.jeremyh@gmail.com. The parts are all in the BOM, easy to order off of Mouser.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: uncola on 13 Apr 2020, 06:20 am
another dumb question about the 7297.. if I only connect one speaker because I'm only testing one speaker.. it doesn't break the amp does it?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: pocomo on 13 Apr 2020, 01:04 pm
another dumb question about the 7297.. if I only connect one speaker because I'm only testing one speaker.. it doesn't break the amp does it?

Not in my experience, you should be fine.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 13 Apr 2020, 04:15 pm
Not in my experience, you should be fine.

Correct
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rajacat on 13 Apr 2020, 05:24 pm
Hi Folsum,

I'd like to order one kit.

...Roy
Title: Re: Folsom's great little 7297 Chip Amp
Post by: feelswatt on 11 May 2020, 03:05 pm
These look awesome, is anyone offering a build service for those of us who aren't amp builders?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: ksbruce on 11 May 2020, 04:20 pm
These look awesome, is anyone offering a build service for those of us who aren't amp builders?

I'd be interested too!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Batman Basmati on 11 May 2020, 04:36 pm
Correct
Sometimes I wonder if people are hired by advertising firms to post.
That was a quote too. 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 11 May 2020, 05:00 pm
I literally have no idea what you're talking about.

But if you think Folsom has an advertising firm I think you're confused, very.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: rajacat on 11 May 2020, 05:15 pm
Sometimes I wonder if people are hired by advertising firms to post.
That was a quote too.
:roll:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: vilding on 11 May 2020, 09:57 pm

(https://www.audiocircle.com/image.php?id=208756)

(https://www.audiocircle.com/image.php?id=208757)

Prepped this little aluminium box on my kitchen table using a drill, handsaw and some sand paper.  :P
Now just waiting for the boards and off we go!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: S Clark on 11 May 2020, 10:02 pm
Cool looking box.  I started this thread 64 pages ago, and my Folsom amp is still sitting in a cigar box.   :oops:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: vilding on 11 May 2020, 10:17 pm
Cool looking box.  I started this thread 64 pages ago, and my Folsom amp is still sitting in a cigar box.   :oops:

 :lol: I'd say you started in the right end, though... Great sound from a cigar box beats no sound out of any box. Bought the BOM so just waiting for the mail man to slide some green magic through my mail slot.  8) And this thread is a really nice read!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 11 May 2020, 11:55 pm
(https://www.audiocircle.com/image.php?id=208756)

(https://www.audiocircle.com/image.php?id=208757)

Prepped this little aluminium box on my kitchen table using a drill, handsaw and some sand paper.  :P
Now just waiting for the boards and off we go!

If you cut a small slot between the binding posts + and - for each channel you'll get better sound.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Batman Basmati on 11 May 2020, 11:56 pm
I literally have no idea what you're talking about.

But if you think Folsom has an advertising firm I think you're confused, very.

Uh :popcorn:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mresseguie on 12 May 2020, 12:43 am
My Radu Tarta built amp:
[Please note that Radu no longer builds SS amps. He's a tube guy.]


(https://www.audiocircle.com/image.php?id=208767)


(https://www.audiocircle.com/image.php?id=208768)


(https://www.audiocircle.com/image.php?id=208769)

(https://www.audiocircle.com/image.php?id=208769)



(https://www.audiocircle.com/image.php?id=208771)
Premium Jantzen Superior Audio caps

It seems I've sold it!  8)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 12 May 2020, 01:23 pm
(https://www.audiocircle.com/image.php?id=208756)

(https://www.audiocircle.com/image.php?id=208757)

Prepped this little aluminium box on my kitchen table using a drill, handsaw and some sand paper.  :P
Now just waiting for the boards and off we go!

Have a link to the chassis you used?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: vilding on 12 May 2020, 06:56 pm
Have a link to the chassis you used?

Sure! From a European vendor but I'm pretty sure you could find it in the US pretty easily. I know Hammond and few others make similar boxes. And it's dirt cheap (But takes a little bit of work)! Also comes in black. What I really like about it is that there are no seems/gaps, just smooth. And you just mount everything on the lid making it your bottom plate.

https://www.elfa.se/sv/metallskap-275x175x65-5mm-aluminiumlegering-aluminium-rnd-components-rnd-455-00702/p/30096020
Title: Re: Folsom's great little 7297 Chip Amp
Post by: vilding on 12 May 2020, 06:57 pm
If you cut a small slot between the binding posts + and - for each channel you'll get better sound.

Done, good sir! :)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mresseguie on 18 May 2020, 02:57 am
Question for any and all chip amp owners/builders:

What might be responsible for a humming sound coming out of one of these amps? It hums without a preamp connected. It hums with a preamp connected. It doesn't hum when it's off. [Obviously.]

I'm trying to help someone trouble shoot their chip amp.

Thank you in advance.

Michael
Title: Re: Folsom's great little 7297 Chip Amp
Post by: navi on 18 May 2020, 03:29 am
Question for any and all chip amp owners/builders:

What might be responsible for a humming sound coming out of one of these amps? It hums without a preamp connected. It hums with a preamp connected. It doesn't hum when it's off. [Obviously.]

I'm trying to help someone trouble shoot their chip amp.

Thank you in advance.

Michael


I had this issue with a chip amp once- someone told me to put a Zobel network between amp and speakers
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 18 May 2020, 03:30 am
Michael, you didn't have that ever did you?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mresseguie on 18 May 2020, 03:55 am
Michael, you didn't have that ever did you?

Well, I don't recall that I had that issue with mine. I used it in February with my Schiit Lyr3 and full range single driver speakers. It wasn't a good match because the speakers sounded a bit bright, but I don't recall a hum. [That may have been because of the Lyr3 though.] :scratch:

I'm just trying to help the guy who bought mine, so I figured putting the question to other owners might prove helpful. I hope you don't mind - I'm not trying to stir up a hornets nest.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: uncola on 18 May 2020, 08:04 pm
mine has a hum from the transformer inside physically vibrating.. mine uses the hammond EI from the BOM.  but you can only hear it from close up with the music off.. I remember a lot of people using this transformer mentioned it.. it's within specs imo
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 19 May 2020, 04:47 am
I think Michael's is using a toroid, which may be less hum prone. I'd like to try to help solve the problem.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: mresseguie on 19 May 2020, 05:54 am
The fellow who bought mine repositioned his amp onto a different rack. This apparently reduced the hum considerably. He hasn't texted me today, so it is possible the issue is fixed.

Jeremy,

I'm pretty certain the transformer is not toroidal, but I can no longer peer into it to be sure.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 19 May 2020, 04:18 pm
Well I'm always open to help - as long he knows that everything is ok for now.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: vilding on 13 Jun 2020, 11:56 am

(https://www.audiocircle.com/image.php?id=210327)
(https://www.audiocircle.com/image.php?id=210326)


Aaaarrrghhh! How do I connect it to just turn on when pushed in, turn off when released..? Lights are separate 12v.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: AKLegal on 13 Jun 2020, 12:13 pm
(https://www.audiocircle.com/image.php?id=210326)


Aaaarrrghhh! How do I connect it to just turn on when pushed in, turn off when released..? Lights are separate 12v.

I'm pretty sure you can just use GND and either NC or NO to operate the switch. 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: vilding on 13 Jun 2020, 12:39 pm

(https://www.audiocircle.com/image.php?id=210335)

Yeah.. I just don't get in which order... Shouldn't the 12v go gnd to 5, 12v+ to 4? Then the L goes to common (nr2), and out from...
Don't the get the wiring diagram.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: ostvald on 13 Jun 2020, 01:13 pm
Hi guys,

I'm thinking of building the amp with SMPS..
Doesn't it really ruins the sound much?..

I was looking at this one: WX-DC2416 (http://www.aliexpress.com/item/32839383217.html) - will it fit?

Thanks!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 13 Jun 2020, 01:37 pm
(https://www.audiocircle.com/image.php?id=210335)

Yeah.. I just don't get in which order... Shouldn't the 12v go gnd to 5, 12v+ to 4? Then the L goes to common (nr2), and out from...
Don't the get the wiring diagram.

It is a little confusing with led in the switch. Here's how I think I did it with the same switch:
Send + from PS to 3 (com), Connect 3 and 4 together and send to + power input on amp, Connect the - from the PS to a wire from 5 and send to the - side of the amp power input. Beware the led is 12v only! If you are powering with 21V from PS you will need a resistor to reduce the voltage to 12v or it will burn out the LED.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: vilding on 13 Jun 2020, 01:48 pm
Hi guys,

I'm thinking of building the amp with SMPS..
Doesn't it really ruins the sound much?..

I was looking at this one: WX-DC2416 (http://www.aliexpress.com/item/32839383217.html) - will it fit?

Thanks!

I went with this one. :) Hoping it'll turn out well. Seems well enough built and the specs are good.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: vilding on 13 Jun 2020, 01:56 pm
It is a little confusing with led in the switch. Here's how I think I did it with the same switch:
Send + from PS to 3 (com), Connect 3 and 4 together and send to + power input on amp, Connect the - from the PS to a wire from 5 and send to the - side of the amp power input. Beware the led is 12v only! If you are powering with 21V from PS you will need a resistor to reduce the voltage to 12v or it will burn out the LED.

Thanks man! :) The thing is I have a separate 12v out from the smps. And when you say Com (3), you mean 2? I'm thinking I can just take the 12v out from the ps straight to gnd (5) and 12v+ (4), connect + from ps (or wall?) to Com (3). And from there..?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: vilding on 13 Jun 2020, 02:22 pm
Is it just:  PS 12v+ -> 4, PS gnd -> 5 for led.

For switch: Live (+)to 2, 2 to 3, 1 to smps +in. N to smps n in, gnd to star ground from wall socket and smps.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 13 Jun 2020, 09:03 pm
Is it just:  PS 12v+ -> 4, PS gnd -> 5 for led.

For switch: Live (+)to 2, 2 to 3, 1 to smps +in. N to smps n in, gnd to star ground from wall socket and smps.

My head is spinning! You are using this labeled 12v (per diagram) switch with 120v mains power. The + switch action is from 2 to 3. 3 when energized with button push 120v power is sent to the smps +. Mains N is direct to PS N in. 1 (NC) on switch is not used. 12v output from smps + goes to 4.  - goes to 5. No other connections needed. I think I have this correct this time.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 14 Jun 2020, 12:46 am
12v isn't enough for the amp. But I also wouldn't want to use a switch between PSU and amp because the voltage spike is dangerous to transistors.

If you had a hard switch that allowed 120v, and had a mini 12v power supply to run a relay for 120v to the amplifier transformer you'd be fine. That's kinda what amplifier companies do.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: vilding on 14 Jun 2020, 11:48 am
Ok....
I'll try to to push past my technical and linguistic shortcomings.... ;)
The switch is rated at 240VAC, the led at 12V(suppose DC since theres a battery in the wiring diagram).

I think this is might be it:
12vdc+ from smps to 4, 12vgnd from smsps to 5 for led.
230vac from wall via fuse to 2, 3 to smps +in.
Neutral from wall to neutral in smps.
Earth from wall to star ground
Earth from smps to star ground.
Done!
:)

The other output of the smps is rated at 24VDC, but is adjustable some. Do I need to trim it down to 21? Will it hurt the amp if I run it higher?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 14 Jun 2020, 05:41 pm
No it won't hurt it at 24v but it'll make extra heat.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: vilding on 15 Jun 2020, 09:47 pm
Ok, so I worked it out, and now it makes music. It sounds freakin fantastic!

It has a pleasing, almost soft sound, without losing an ounce of clarity. Kurt Rosenwinkel's guitar solo on "Return of the prodigal son" with Brian Blade & the Fellowship band i so clear and precise. I hear all the little stuff he does and the decay of every note. And at the same time everything the band plays behind him is crisp, dynamic and incredibly well separated. And the bass is deep and strong with great body.
So far, maybe two hours in, at reasonable listening levels, it runs very cool. And it seems, as said by many before me, so much more powerful than 15 measly watts.

It's soon midnight in Stockholm, but I think I'll open a beer and make it a late night... 

/Hilding
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 16 Jun 2020, 02:17 am
 :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: vilding on 16 Jun 2020, 09:14 am
(https://www.audiocircle.com/image.php?id=210470)


(https://www.audiocircle.com/image.php?id=210472)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: uncola on 17 Jun 2020, 04:43 am
hehe your amp looks so teeny on that giant amp platform.  I'm always impressed when I put my folsom amp back in the system, I even used it to replace my IceEdge 1200as2 600 watt per channel amp in my small home theater temporarily and it had enough power to get as loud as I normally listen without strain.  But I do use a sub at 80hz with high pass filter on the mains so that might help slightly
Title: Re: Folsom's great little 7297 Chip Amp
Post by: drmike on 17 Jun 2020, 11:28 am
hello, are there any boards left?
thanks,drmike
Title: Re: Folsom's great little 7297 Chip Amp
Post by: vilding on 17 Jun 2020, 01:25 pm
hehe your amp looks so teeny on that giant amp platform.  I'm always impressed when I put my folsom amp back in the system, I even used it to replace my IceEdge 1200as2 600 watt per channel amp in my small home theater temporarily and it had enough power to get as loud as I normally listen without strain.  But I do use a sub at 80hz with high pass filter on the mains so that might help slightly

Haha yeah, it was a tight fit, and a hellish job to put together and solder up, since it's just a two piece. Finicky, I think is the appropriate word. The amp itself on the other hand was a delight to put together.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: WC on 17 Jun 2020, 05:35 pm
hello, are there any boards left?
thanks,drmike

I have a set I could sell you.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: sarora9 on 11 Jul 2020, 12:01 am
I now have Folsom's newer 7293 amp, assembled by amp afficionado pinocchio who hangs out at diyaudio forum. (NB:  pinocchio does not normally assemble amps for others. He did it for me because he was intrigued by the design and wanted to hear it for himself.)

The 7293 is freakin' amazing. In my system I have had over the years a Sim Audio moon entry level (back in the aughts), a decent EL34, an audio GD integrated, and most recently AVA hifi's SET120 (same circuit as their SET 400). The Folsom 7293 is from another planet, combining fantastic soundstage/prat/clarity with a very nonfatiguing sound. Another builder at diyaudio forum  finds it superior to Cherry Maraschino and Hegel 360. The thread is here https://www.diyaudio.com/forums/group-buys/338275-folsom-ec7293-pvi-powered-frontend-60-120w-8-4ohm.html

My system: Roon Rock -> Bricasti M5 streamer -> Bricasti M1 SE dac -> Folsom 7293 -> Spatial X3.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 11 Jul 2020, 02:22 pm
Thank you for the kind words!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: vilding on 17 Jul 2020, 02:34 pm
Newbie problems....

Haven't run mine in a while, and when I started it, it has a nasty ground hum. It is somewhat under control when playing music from my macbook pro unconnected, but gets worse if I touch the metal of the computer and much worse if I plug it in to the wall.
Where do I search and what do I search for..?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: HT cOz on 17 Jul 2020, 07:37 pm
I now have Folsom's newer 7293 amp, assembled by amp afficionado pinocchio who hangs out at diyaudio forum. (NB:  pinocchio does not normally assemble amps for others. He did it for me because he was intrigued by the design and wanted to hear it for himself.)

The 7293 is freakin' amazing. In my system I have had over the years a Sim Audio moon entry level (back in the aughts), a decent EL34, an audio GD integrated, and most recently AVA hifi's SET120 (same circuit as their SET 400). The Folsom 7293 is from another planet, combining fantastic soundstage/prat/clarity with a very nonfatiguing sound. Another builder at diyaudio forum  finds it superior to Cherry Maraschino and Hegel 360. The thread is here https://www.diyaudio.com/forums/group-buys/338275-folsom-ec7293-pvi-powered-frontend-60-120w-8-4ohm.html

My system: Roon Rock -> Bricasti M5 streamer -> Bricasti M1 SE dac -> Folsom 7293 -> Spatial X3.

Pinocchio builds are amazing, do you have pics of your amp? 

Thanks,
Robert
Title: Re: Folsom's great little 7297 Chip Amp
Post by: sarora9 on 17 Jul 2020, 07:46 pm
Pinocchio builds are amazing, do you have pics of your amp? 
--Robert
Pinocchio posted pics on the diyaudio thread starting page 15. Yeah, I am lucky he agreed to build it. :D

Title: Re: Folsom's great little 7297 Chip Amp
Post by: ctviggen on 17 Jul 2020, 08:04 pm
Pinocchio posted pics on the diyaudio thread starting page 15. Yeah, I am lucky he agreed to build it. :D

That guy has real oscilloscopes and signal generators, and a nice lab.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: ostvald on 18 Jul 2020, 10:29 am
I've started my 7297 build.
Will post here some photos, comments are welcomed and appreciated!  :)


(https://www.audiocircle.com/image.php?id=211978)
2109 chineese case

(https://www.audiocircle.com/image.php?id=211979)
almost done with the PSU board

(https://www.audiocircle.com/image.php?id=211980)
Should bend chip pins 180 degrees cos the board is to be mounted on the chassis side

(https://www.audiocircle.com/image.php?id=211981)
Almost populated amp board

(https://www.audiocircle.com/image.php?id=211982)
Amp board mounting

(https://www.audiocircle.com/image.php?id=211983)
The workplace on the kitchen table
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 18 Jul 2020, 01:59 pm
Good job on the implementation of the chip on the bottom of the amp pcb. That will make it a lot easier to fit everything in that case  :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 18 Jul 2020, 02:08 pm
I truly wish they sold chips like that...
Title: Re: Folsom's great little 7297 Chip Amp
Post by: ostvald on 18 Jul 2020, 02:22 pm
Good job on the implementation of the chip on the bottom of the amp pcb. That will make it a lot easier to fit everything in that case  :thumb:

lacro, was inspired by your builds  :thumb: :thumb:
it's gonna be pretty tight even with the board on the side. Doesn't fit otherwise if using 200VA transformer.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: drew_t on 20 Jul 2020, 01:36 am
Newbie problems....

Haven't run mine in a while, and when I started it, it has a nasty ground hum. It is somewhat under control when playing music from my macbook pro unconnected, but gets worse if I touch the metal of the computer and much worse if I plug it in to the wall.
Where do I search and what do I search for..?

Since it worked OK previously, I would suspect it's just something simple like a plug or jack that isn't making good contact, or a flaky cable.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 20 Jul 2020, 02:03 am
Since it worked OK previously, I would suspect it's just something simple like a plug or jack that isn't making good contact, or a flaky cable.

That's pretty typical. A bad connection somewhere is very commonly behind such noise.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: vilding on 20 Jul 2020, 09:04 am
You guys have any good tips on searching for it? Where to measure and what to look for? :) Can't find any cold joints or visually flaky cables.

Title: Re: Folsom's great little 7297 Chip Amp
Post by: ostvald on 23 Jul 2020, 05:21 am
Hi guys, I have some build-related questions.

First, I have these type of RCA connectors:
(https://www.audiocircle.com/image.php?id=212226).
Does it still make any sense to drill a hole in the chassis between them, as was advised to do here in this thread?

Another thing is - what would be your recommended way of mounting the pcb to the chassis, specifically the type of stand-offs?
Is it OK to use metal standoffs and bolts ("grounding" the pcb to the chassis, is there any grounding layer in the pcb connected to mounting holes?), or
is it better to isolate the PCB from chassis with plastic (shoulder) washers, or mount on plastic stand-offs? Both PSU and the AMP PCBs are the subject.

Thanks!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 24 Jul 2020, 03:40 am
You'd have to cut through the connector housing as well all the way to the plastic.

7297 and psu holes don't connect to ground.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: ostvald on 24 Jul 2020, 10:11 am
You'd have to cut through the connector housing as well all the way to the plastic.

7297 and psu holes don't connect to ground.

Ouch.. Don't have suitable tools, will probably just destroy them, so will leave it like this for the build
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 25 Jul 2020, 03:10 am
Use different RCA’s?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: ostvald on 25 Jul 2020, 11:09 am
Use different RCA’s?

Neutriks where kind of one of your recomendations from the Construction Notes, Furutechs were a bit more expensive and not supplied by Mouser.
Could you please maybe recommend any other RCAs (to be ordered from Mouser)?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: HT cOz on 25 Jul 2020, 03:39 pm
Hi guys, I have some build-related questions.

First, I have these type of RCA connectors:
(https://www.audiocircle.com/image.php?id=212226).
Does it still make any sense to drill a hole in the chassis between them, as was advised to do here in this thread?

Another thing is - what would be your recommended way of mounting the pcb to the chassis, specifically the type of stand-offs?
Is it OK to use metal standoffs and bolts ("grounding" the pcb to the chassis, is there any grounding layer in the pcb connected to mounting holes?), or
is it better to isolate the PCB from chassis with plastic (shoulder) washers, or mount on plastic stand-offs? Both PSU and the AMP PCBs are the subject.

Thanks!

We might be able to help but it's hard to understand your question.  Why not use these as designed?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 25 Jul 2020, 05:16 pm
Neutriks where kind of one of your recomendations from the Construction Notes, Furutechs were a bit more expensive and not supplied by Mouser.
Could you please maybe recommend any other RCAs (to be ordered from Mouser)?

I admit it needs an update. You'll still be happy with those. But if you were wanting to go for the slots, I wanted to help.

NYS367-2
and
NYS367-9

would be compatible with a slot/hole.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: ostvald on 8 Aug 2020, 10:19 am
More photos from my build!

(https://www.audiocircle.com/image.php?id=212925)
24 mm hole for a push button switch

(https://www.audiocircle.com/image.php?id=212926)
PSU board power up

(https://www.audiocircle.com/image.php?id=212927)
Packed

(https://www.audiocircle.com/image.php?id=212928)
Bottom up


(https://www.audiocircle.com/image.php?id=212930)
Front view, still no decals. On the background:
NORD NC500 SE MKII mono block,
RME ADI-2 DAC,
DIY Discowery-12W speakers

It turned up I messed 100uF cap polarity and I need to re-assemble / resolder the amp board (thanks 2 Jeremy for instant reply with the solution!) -
currently the amp plays for several minutes and then goes to mute, so no listening impressions yet.
I am to compare it vs my NC500 mono blocks, btw  :roll:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: ostvald on 9 Aug 2020, 08:47 pm
Ok, so it's a hi-fidelity quality, that's for sure :icon_surprised:

Compared to the NCore, it's more musical - with its downsides, but pleasant to listen to :)
Continuing the burning-in - it gets better.

Jeremy, could you give an idea what are the burning in timings for the amp?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 10 Aug 2020, 05:44 pm
At 20 hours it'll sound a lot like it will continue to sound but the input capacitors might take a fair bit more like 80hrs to really finish.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: ostvald on 16 Aug 2020, 09:23 am
As I promised before, I feel like ready to share my listening impressions of Folsom's 7297 chip amp.

First, let's clarify the costs. I reside in Israel, so the following table includes shipment and tax prices for Israel. The overhead is basically costs which are not directly related to the build (like tools, additional parts that were not needed, or solder tin that I bought a lot, cos you can't buy just a bit), or additional costs that could have been avoided, like additional boards components being sent. Here is the table:

(https://www.audiocircle.com/image.php?id=213261)

Let's say, it's a $600 amp for me in parts (shipped to IL, $440 - no shipment, no tax) + my labor, which was about ~60 hours, as far as I can estimate it.
60 hours is a lot, but this is basically my first amp build, and it was a pleasure to do.

It's about 50 hours of burn-in passed now, and I'm mainly talking about 10-15 last hours of listening. You really need to burn it in at least 20 hours like Jeremy already wrote here, don't even listen to it before that.

SO, what does it sound like?
Well, in short, it's very nice, especially for the price! For me it sounds "sweet", with pretty much apparent solid state signature I was looking for.

My listening setup is DIY Troels Gravesen Discovery-12W speakers: http://www.troelsgravesen.dk/Discovery-12W_Ilia.htm (http://www.troelsgravesen.dk/Discovery-12W_Ilia.htm) which are very nice 800 EUR alone in parts (no shipment no tax no cabinet no labor) desktop monitors
The source is digital - RME ADI-2 DAC https://www.rme-audio.de/adi-2-dac.html (https://www.rme-audio.de/adi-2-dac.html) (about $1150)
I also own Audeze LCD-X headphones to "verify" what I hear. Together with the DAC's headphone amp, these are analytical monsters - https://www.audeze.com/products/lcd-x (https://www.audeze.com/products/lcd-x) (about $1200)
I'm mainly comparing the build with my Nord ONE SE NC500MB MKII mono blocks, which are class D NCore 500 based power amps - https://www.nordacoustics.co.uk/product-page/nord-one-se-up-nc500mb-mkii-mono-block-single (https://www.nordacoustics.co.uk/product-page/nord-one-se-up-nc500mb-mkii-mono-block-single)  (~$1000 each - ~$2000 for stereo)

I basically have a desktop setup, so I intend to use the 7297 on my desktop, and the amp has way enough power for this application.

So what do I mean by "sweet"?
I will do measurements later, but it looks like compared to my monoblocks it has those higher 2-nd and 3-rd harmonics, which make the sound rich, pretty dense hence still clear. It has very nice layering. Because of the presentation it's much easier to perceive it, as opposed to my monoblocks, which are sharper. Generally, my monoblocks are much more "analytical", while 7297 is more "musical", so it is pleasant to listen to. It sounds super great with soft rock, jazz, blues. Vocals are also great.

The downsides, well.. There are some. First, highs are (juuuust a bit rolled off?) not that crisp as on NCores. On the Ncores I even put an "SD Slow" filter on my DAC when I want a longer listening and not analytical session. On the 7297 amp I put "SD Sharp", otherwise it starts to be a bit "muddy". The base is not that tight as on NCores, it sounds a bit relaxed, that especially noticed with electronic music tracks. Though, it's not distorted, even on a decent volume. Few times while I was listening to some not thoroughly known tracks I heard a distortion and was like "Ahaa!", but after rechecking with my headphones it always turned out the distortion was in the record itself (and I was able to hear it "as is" with the amp!). I must also say the base improved a lot while the burn in. I was even setting +1.5 Db on the DAC to match my regular base expectation in the beginning, but now it is set back to 0Db, so I kind of expect it to improve a bit more, but the gap is still big. NCores are holding those D12s by the throat. Looks like the NCores have a sharper step response and a greater damping factor. I'm not really talking about the lower lower base cos my speakers don't really produce it. Still, the base is nice.

Summing up again, it's a very decent amp for the money! It sounds sweet on the midrange midbass, which was my main goal, the presentation I lacked with my NCores.
It's clear, the highs are precise hence not analytically bright, the base is pretty strong and also sweet and natural which adds up to the space perception and "drive" when is appropriate.
It's not a loud deep house party amp, but it was not meant to. In general, I'm indeed pretty much satisfied.

I'm looking forward to building Folsoms 7293 chip amp - https://www.diyaudio.com/forums/group-buys/357577-gb-2-folsom-ec7293-pvi-powered-frontend-amplifier-60-120w-8-4ohm-0-0005-thd.html (https://www.diyaudio.com/forums/group-buys/357577-gb-2-folsom-ec7293-pvi-powered-frontend-amplifier-60-120w-8-4ohm-0-0005-thd.html)
It was told to be "better in every single way" and I have no reason not to believe it. I suppose I would be able to drive floor standing speakers with inarguable base authority.

Jeremy, thank you very much for everything - your guidance, assistance, responsiveness and a great design!
Also, thanks everybody for the help and a great community we have.
I was very helped and inspired by other people's builds.

Thank you!

 
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Ambio on 8 Oct 2020, 08:54 pm
Hi all, I have been having fun learning about this amp via the eBay version, preliminary to build folsoms amp. This thread helping enormously so thanks everyone! Here is a handy tool if you can obtain them. There perfect for cutting circular holes in metal neatly and quickly.
(https://www.audiocircle.com/image.php?id=215592)

(https://www.audiocircle.com/image.php?id=215593)

I have my work cut-out for me :lol:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: vilding on 15 Oct 2020, 08:41 pm
Ok. So i put the amp on a board, went over all joints and connections and all seemed fine and it made the music. Happy moment! :)

I then moved the amp to a new case, connected everything and started listening. It held up fine and sounded great at low levels for maybe two hours. At that point I turned it up a bit, maybe halfway on the pre, and it started to distort badly, then flail back and forth between distorted and quiet music and after maybe ten seconds of this going silent. No more music... The chip was cool to the touch. One of the resistors (big one) was a little warm but nothing bad. I measure 22.4 vdc in to the amp, zero volts at speaker output. No speaker posts or connectors touch the chassi.
I'm starting to give up on this DIY thing at this point... :´(
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 15 Oct 2020, 09:31 pm
Ok. So i put the amp on a board, went over all joints and connections and all seemed fine and it made the music. Happy moment! :)

I then moved the amp to a new case, connected everything and started listening. It held up fine and sounded great at low levels for maybe two hours. At that point I turned it up a bit, maybe halfway on the pre, and it started to distort badly, then flail back and forth between distorted and quiet music and after maybe ten seconds of this going silent. No more music... The chip was cool to the touch. One of the resistors (big one) was a little warm but nothing bad. I measure 22.4 vdc in to the amp, zero volts at speaker output. No speaker posts or connectors touch the chassi.
I'm starting to give up on this DIY thing at this point... :´(


Maybe some hi-res photos would help see what's up.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: WC on 19 Dec 2020, 02:42 am
Yes the speaker outputs go in parallel. The inputs would be too, but you can use only one set of caps if you tie the channels together after the caps. (look carefully, may not be the holes your think)

 Not sure what you mean balanced signal to the amp, it cannot take balanced inputs.

Jeremy,

I have two sets of boards, but I am trying to determine how to put the amp together. All my other amps only accept balanced inputs. So couldn’t I take my two stereo 7297 builds in one chassis and send the positive signal from the XLR to the right channel on one of the amps and the negative signal from the XLR  to the left channel of the  same amp. Then I could parallel the speaker outputs together. Would that work?

If using a 300VA torrid transformer with separate secondaries would I need to send both secondaries to each antipole board or can I split the secondaries so I have one to each secondary?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Fredericksburg on 20 Dec 2020, 05:24 pm
This looks very doable, I've got to start somewhere this may it the thing.

Robert
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 21 Dec 2020, 03:31 pm
Jeremy,

I have two sets of boards, but I am trying to determine how to put the amp together. All my other amps only accept balanced inputs. So couldn’t I take my two stereo 7297 builds in one chassis and send the positive signal from the XLR to the right channel on one of the amps and the negative signal from the XLR  to the left channel of the  same amp. Then I could parallel the speaker outputs together. Would that work?

If using a 300VA torrid transformer with separate secondaries would I need to send both secondaries to each antipole board or can I split the secondaries so I have one to each secondary?

That will not work because the outputs are balanced of the 7297. You can't combine them.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: AKLegal on 21 Dec 2020, 06:06 pm
That will not work because the outputs are balanced of the 7297. You can't combine them.

One could do this with four of your 7293 boards correct?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 21 Dec 2020, 08:44 pm
I would not go as far as to make a claim that something could be possible that is untested thus far... (and if possible how much modification it would take)

The easier thing to do is just use an input transformer that turns balanced to single ended, and eliminates the need for an input capacitor.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: AKLegal on 21 Dec 2020, 11:02 pm
Thanks.  I'm not really interested in further modding my amp anyway.  Just trying to learn a bit more.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: vilding on 23 Feb 2021, 04:16 pm
Ok. So i put the amp on a board, went over all joints and connections and all seemed fine and it made the music. Happy moment! :)

I then moved the amp to a new case, connected everything and started listening. It held up fine and sounded great at low levels for maybe two hours. At that point I turned it up a bit, maybe halfway on the pre, and it started to distort badly, then flail back and forth between distorted and quiet music and after maybe ten seconds of this going silent. No more music... The chip was cool to the touch. One of the resistors (big one) was a little warm but nothing bad. I measure 22.4 vdc in to the amp, zero volts at speaker output. No speaker posts or connectors touch the chassi.
I'm starting to give up on this DIY thing at this point... :´(


So I almost gave up and did other stuff for a while, after being quite discouraged by the struggles of amp building. I still have the big EC7293 waiting for me as well...  :o

I´m posting a few pics. My suspicion is that I might have fried a transistor or so, but I´m not sure how to measure for it. My biggest scare is that I somehow damaged the chip, which would really, really suck. I'm hoping for you guys experience and patience to help med put this together. :)
Cheers!

(https://www.audiocircle.com/image.php?id=221197)


(https://www.audiocircle.com/image.php?id=221198)

(https://www.audiocircle.com/image.php?id=221199)

Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 23 Feb 2021, 04:50 pm
Where are the two capacitors that go next to the DC input?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: vilding on 23 Feb 2021, 05:33 pm
Feeling stupid now, but were they not optional for rf screening, or have I burnt my chip to crisp....  :|
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 23 Feb 2021, 05:37 pm
Sorry, what are symptoms again?

They are not optional.

Can you see a gap between all the chip pins? It's pretty hard from the pictures to tell.

BTW I can't reply to noreply emails. My email is folsom.jeremyh@gmail.com
Title: Re: Folsom's great little 7297 Chip Amp
Post by: vilding on 23 Feb 2021, 05:42 pm
Ok. I'll mail you. :)
No, there are no solder bridges. It looks a little messy but thats mostly flux... It played for a few hours on low volume, and when I turned it up, it started to distort badly and then went real quiet fo a few secs before it went silent.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: vilding on 10 Mar 2021, 05:42 pm
It's alive!
Thank you Jeremy!
Now time for listening...
Title: Re: Folsom's great little 7297 Chip Amp
Post by: S Clark on 10 Mar 2021, 06:11 pm
That's good news.  It's a very nice little amp, and you're going to enjoy it.   :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 10 Mar 2021, 06:39 pm
It's alive!
Thank you Jeremy!
Now time for listening...

Awesome, I'm glad it wasn't too difficult.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: vilding on 10 Mar 2021, 09:24 pm
Awesome, I'm glad it wasn't too difficult.
That's good news.  It's a very nice little amp, and you're going to enjoy it.   :thumb:

Listening through it right now. So glad I finally fixed it. Deep soundstage, tight bass, sweet top end.  Planted in the chair... :thumb: :thumb: :thumb:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Yatsushiro on 12 Mar 2021, 07:26 am
What was the fix?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: vilding on 12 Mar 2021, 10:21 am
What was the fix?

Stupid noob misunderstanding of instructions.... Omitted the 220Uf caps at the DC intake and fried the big transistor. Very easy fix, very happy noob. Strange thing is that the transistor held up pretty well earlier. It died after I had changed chassis to sort out a ground loop issue (after lying in the closet for a few months).
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Nahuelitsn on 15 Mar 2021, 03:17 am

(https://www.audiocircle.com/image.php?id=222001)

(https://www.audiocircle.com/image.php?id=222002)
Hi guys. I don’t know if this is the place and you can help me. I make all the changes to the Chinese tda7297. First build  guide 1 amazing sound. Put to Shame some vintage amplifiers of friends. And  now build guide v2. I have big problems. I put more capacitance off the board (8500uf ) and bypass the 1.5uf dc input caps. But when i connect my amp to 12v battery i see a spark and the amp stays mute. Then if i connect again start playing only in left  channel and the right doesnt produce sound at all but i can see the speaker stay stuck forward like if receive DC power. Please help!!

Thanks for your time and sorry for my english. Best regards.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 15 Mar 2021, 05:56 pm
Pretty hard to tell from pictures. You didn't put a switch for turn on?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Nahuelitsn on 15 Mar 2021, 07:17 pm
I did not install a switch because I am an anxious person  :duh: :duh: and wanted to test if it worked before continuing to assemble the rest of the things. I have a switch to install that would allow me in its on state to connect the battery to the amplifier and when I turn it off, connect the battery to its charger, leaving the amplifier without power.

I recently discovered that between the ground and the left channel I have a very low impedance and sometimes the tester beeps indicating continuity. In the right channel I have about 1200ohms of impedance between ground and R Line In But I can't find the problem on the board. Could the chip be damaged by turning it on without a switch? Prior to these problems the amplifier was working on the battery correctly but it started to distort easily if I increased the signal from my DAC. Before that with the potentiometer this did not happen and it achieved higher SPL without distortion and with a very bad and precarious power supply. The battery is a 12v 7ah SLA.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 17 Mar 2021, 10:52 pm
I think you might be on your own little quest here to figure out what's going given the amount of variables. The input impedance is suppose to be 25-30k I believe in the spec sheet. You can test by removing cables and checking with multi-meter on each channel. When everything is attached there's no way to really know.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Nahuelitsn on 17 Mar 2021, 11:08 pm
Thanks Folsom. I desolder everything except the chip and happen exactly the same. Between R and ground Líne in have  :duh:5 ohms and between L and ground 1200ohm. If i put a 1k resistance between the R in and ground  nothing change. I think that i screw it up the chip.  :duh:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 18 Mar 2021, 12:37 am
Well order a couple this time  :lol:
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Nahuelitsn on 20 Mar 2021, 03:48 am
I will Folsom!!I will !!! :lol: :lol: :lol: :lol:

Thanks for everything!!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: vilding on 22 Mar 2021, 03:19 pm
Hi again!
The amp is running smoothly and keeps remarkably cool with the 86-87db 6ohm speakers that are plugged in at the moment.
However, I have a slight ground hum.  You hear it when you're within a little over a foot from the speaker. Would you guys look at my layout and see if there are any obvious mistakes there? Or other ideas?
(https://www.audiocircle.com/image.php?id=222266)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 22 Mar 2021, 06:23 pm
Wiggle all your IC's to make sure there is not change. A disconnected ground is a sure way to get a hum.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: vilding on 22 Mar 2021, 10:58 pm
Ok, so I've been crawling around on the floor, wiggling, reconnecting, changing cables and swearing  :lol:
With just the phone plugged in to the amp, it's dead silent. The biggest cause of noise seem to be the dac, or it's power supply. When everything else is plugged in (dacs ic's still connected to preamp) and I pull the wallwart for the dac, almost all noise disappear. This kinda sucks since my listening is probably 75% through that thing.  :cry: Any ideas..? Been trying to read up some on grounding but don't really know what to make of it.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 23 Mar 2021, 12:17 am
So a loop is forming through the DAC.

Does the DAC have a 3 prong?
Title: Re: Folsom's great little 7297 Chip Amp
Post by: vilding on 23 Mar 2021, 10:27 am
No, it's a two prong double insulated little wallwart.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 23 Mar 2021, 12:13 pm
You could try this (https://www.mouser.com/ProductDetail/Schurter/DENO-25-0001?qs=A5k8bsa1loDfpdVSyZOXZg%3D%3D) on the amp's ground between the socket and chassis. It'll reduce common mode noise, and ground noise.

You can test if it'll work by disconnecting the ground temporarily.

Title: Re: Folsom's great little 7297 Chip Amp
Post by: vilding on 24 Mar 2021, 09:52 am
Thanks! Will try but it'll have to wait until I need some more stuff from Mouser, or it will be one expensive little coil.  :icon_lol: I'm gonna try and troubleshoot using the guide from DIYA-member Bonsai. Simple enough even for me...  :P Listening to some Chris Potter on vinyl rn and the amp is dead quiet between tracks and sounds scary good.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: SGI on 30 May 2021, 07:04 pm
Anyone has another 7297 amp board / antipole board for sale?  My friend just built mine and he was testing it out w/o even fully broken in and now wants one!  :)  Please PM me or email me if you do have one.  Thanks!
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Terry U on 10 Jun 2021, 09:09 pm
I have a kit for a complete 7297 amp minus the case that I am looking to move on.  I do not want to separate the boards however.  Might you be interested in this.   terryu55@comcast.net
Title: Re: Folsom's great little 7297 Chip Amp
Post by: drew_t on 7 Apr 2022, 02:56 am
I finished my build a couple of years ago at least. It's alternated between sitting on a shelf unused and being hooked up to one of my computers -- most recently the latter,  powered up for at least a few months 24/7. I noticed that the power LED was off yesterday. I checked the fuse, saw that it was blown, put in another one, turned it on, the power LED lit up, but I immediately heard a "zzzzttt" sound that lasted about a second, and the LED slowly faded out. 

I have never pushed this amp even remotely hard; it has not been exposed to power surges; it has not been dropped, gotten wet, or anything like that.  There are no scorched wires, burned components, leaking caps, bad smells, or anything else obviously amiss.  The power transformer is one of whichever Antek toroids were recommended. The fuse (same one that has been in it from the start) is a 1.6 amp one. I used one of the combination IEC socket/power switch/fuse holder deals (I know, I know, it's not a boutique audio-type part) and built the amp in an old computer case. 

Any ideas what the issue might be?  Could the Antek have just crapped out?  Should leaving the unit powered up for an extended period of time with the sound source (computer) asleep have done any harm?
(https://www.audiocircle.com/image.php?id=239301)
Title: Re: Folsom's great little 7297 Chip Amp
Post by: lacro on 7 Apr 2022, 10:09 pm
I suspect the IEC socket/power switch/fuse holder. Try disconnecting the Antec toroid from it's primary and secondary and power the primary with a different 120v source power cord, then check it's secondary output voltage (16-18v).
Title: Re: Folsom's great little 7297 Chip Amp
Post by: ctviggen on 23 Apr 2022, 07:30 pm
Are these still for sale?  If so, where?
Title: Re: Folsom's great little 7297 Chip Amp - Where can I buy the circuit boards?
Post by: EJHickert on 13 May 2022, 11:20 pm
Hi there! I have just joined Audiocircle and heard about this great little chip amplifier from GR research. I have searched on google for the circuit designed by Folsom with no success.

I would really appreciate it if someone could point me to the right location where I can purchase the circuit board and a really good power supply to run it.

Thank you in advance!

Eric
Title: Re: Folsom's great little 7297 Chip Amp
Post by: Folsom on 14 May 2022, 10:11 pm
Sorry I don't have any boards.
Title: Re: Folsom's great little 7297 Chip Amp
Post by: pbzepplin on 19 Dec 2022, 12:03 am
Hey everyone,

I am new here just got a pair of XLS encores built up. They are pretty exciting speakers and I was looking for DIY an amp to get the most out of the speaker. I hear these chip amp's might be a good pairing. Any idea on where to find a board or recommendations for a different DIY AMP that would pair with the XLS encore?

Thanks,

Steve
Title: Re: Folsom's great little 7297 Chip Amp
Post by: PeterC on 8 May 2023, 07:28 pm
Can someone let me know where I can find the parts list and instructions to build the amp and power supply?

I have both circuit boards and have decided I should do something about it.

Thanks...