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
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.
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:
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.
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?
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.
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.
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.
How do I order an antipole board?
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)
Is there a pcb available for power supply?
What's the excitation of the board requirement?
?Power requirement.
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.
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)
Actually I did try finding the number at Mouser, but no luck? Is that the transistor you are supplying?
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?
OK, so if battery power is 24Vdc what is the current requirement?
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?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.
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.
I'm selfishly bumping this in an effort to draw attention and $$ to the power supply which needs some more neophytes like me to support it. Or anyone, I guess...newbie or not! I'd just like to see it come to fruition.
https://www.indiegogo.com/projects/antipole-pcb-filtered-psu#/
I'm selfishly bumping this in an effort to draw attention and $$ 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.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.
https://www.indiegogo.com/projects/antipole-pcb-filtered-psu#/
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?
So like 2.5A @ 24Vdc?
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?
So a buffer in front of it helps such as a Pass B1...
Buffered means it doesn't have trouble driving the amplifier due to impedance mismatch.Standard 10k pot is exactly that at maximum 2500 ohm ????
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.
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...
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").
Anyone have an approximate Mouser BOM cost yet?
Also, Folsom, you're just selling boards right, not complete kits?
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
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
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 ?
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.
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.
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.
Don't know about the Cardas being worth the money, but it is easier to work with than Kester 60/40.
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)
Surely someone here has got the amp running? :lol:
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.
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)
Why would you use thermal paste during the fitting process on the chip? I don't follow.
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.
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
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
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
How many PCB boards for two of those Larco? :green:
Lacro - I want one of those board holders too. That looks great :thumb:
I already built your Volume Control Device into a Hammond,
Is there a thread (link) for building this Volume Control?
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 ?
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.
Is the heat sink supposed to just hang off the chip?
Lacro - that looks nice!
Btw - Where do you buy those nylon (?) standoffs?
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?
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.
What is everyone using for case? Are there in pre-drilled cases available?
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.
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 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
Does a fuse ruin the sound and that's why you've omitted that? :o
It is only one stage filter.
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?
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.
So are you saying that in your opinion it's not a requirement to have a fuse?
Hypex (SMPS) has a good RFI/EMI filter inside. Maybe a Schaffner filter ruin the sound.
What RFI/EMI filter incorporates your design?
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)
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!
The main is increasingly dirty by the cheap switched transformer connecting.
The main is increasingly dirty by the cheap switched transformer connecting.
Anyway, everyone decides for himself that enough information has been provided.
i'm in the process of building/planning an enclosure ... i was thinking of using wood ... is that a bad idea?
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)
Also it's best to have some distance from transformer and amplifier board.
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...
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.
I didn't get the email about adding the two additional caps. What are the values for each location?
Here's the chassis layout I'm thinking about...
(http://www.audiocircle.com/image.php?id=139917)
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!
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:
@lacro, where did you get the case from?
: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!
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.
Certainly...not pretty, I know...
Thanks for the kind words guys.....
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.
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?
I have the Bourns 8120 for the Antipole. Does it need to be oriented in any particular way?
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.
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.)
Matt, Did you bypass the existing cap on the bottom as Jeremy suggested or removed/replaced it?
Matt has skills.
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.
There are still some boards available.
Found some mods on another forum that worked well for bass......Can you post the link please?
Nice clean work, looks great :thumb: No ventilation holes?
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.
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)
Reported to have great mids on up, which it does. The thing that surprised me most was the bass, which is also excellent.
Anyone interested in soldering the parts on the board for me?
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:
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
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.radiotechnika.hu/images/TDA7297.pdf
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
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
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.
Should work good. The attenuator impedance won't matter with the buffer following it.
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?
What are some good sources for wire? What different gauges would you recommend?
(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.
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.
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?
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
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
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 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.
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.
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.
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.
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.
Twin 12V 18AH connected in series. They are about $35 each from Amazon w free shipping.
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???
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
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.
Yes. Careful not to crush them.
(http://www.audiocircle.com/image.php?id=148395)
Mike, Looks like you will be making sound (or smoke :icon_twisted:) pretty soon.
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.
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.
1w is fine. Higher just means it's slower. It wont hurt anything.
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.
The light is 12VDC
Mike, it goes near the PSU caps where there's a symbol for a resistor. I wouldn't add a switch.Almost certainly. It was late, I was tired, ... But now I get to start over and upgrade parts!
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...
Mike, it goes near the PSU caps where there's a symbol for a resistor. I wouldn't add a switch.
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?
Almost certainly. It was late, I was tired, ... But now I get to start over and upgrade parts!
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.
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
Larry,
The light is built into the rocker switch, I guess it is an LED.
Mike
More info @ Wikipedia.
Best,
Anand.
Lots of local stores closed, but no, they are not online or locally to me (yet).
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)
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.
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
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.
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
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)
How does it compare to yours with different caps?
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
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
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
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
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.
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.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).
jay
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)I may have those parts in my collection. Where exactly should it be mounted?
See if you can tell the difference after that.
I'm not sure how to explain it any more...How about pointing out the CMC.
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.The choke, now I know what you are referencing.
CMC is the common mode choke. It's big, has wires around a core.
Thanks Folsom !
I will drill in the top also
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...
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.
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.
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 really didn't want to bend the chip or de/re solder to match the chip up against the heat sink.
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.
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
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
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
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
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.
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 ?
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
(http://www.audiocircle.com/image.php?id=152427)Is this correct way to wire it? My DACT type pot pops with each turn.
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)
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
... 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:
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.
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?
Hey--What's up with those fancy input caps?
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?
Question to Lacro: where did you buy the LL2728 transformer? It is not listed on the Lundalh site?
Thanks,
Vlad
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!
One.
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.
I'm out of boards again.
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.
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?
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 .
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 !
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.
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?
Pics didn't load the first time.
(http://www.audiocircle.com/image.php?id=164034)
(http://www.audiocircle.com/image.php?id=164035)
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.
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.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:
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!!!
Battery power use 24v, SMPS can be as low as 21v, and transformer should be 16v to get rectified around 23-24v.
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: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.
Best,
Ed
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
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.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!
http://www.antekinc.com/as-1215/
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
(http://www.audiocircle.com/image.php?id=165887)
Ed,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.
The chassis looks nice. Where did you get it?
Thanks,
Brad
Ed,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):
No problem. Does your chassis have a divider that separates the PS from the amp?
Thanks,
Brad
(http://www.audiocircle.com/image.php?id=167207)
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 ?Hi rtate, I am using the 15V secondary as recommended earlier in this thread. I will use it again for my next amp.
Edit , I saw an earlier post that had the model # (15y)
Hi eBag4Hi Voncarlos, thanks for the recommendation, that's an easy change to try,
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 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?
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.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
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.
Verticle works much better if it has airflow on too and bottom. You could use a silent fan.
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.
.. SG is signal ground, the outside of the RCA jack.Common for the L and R input signal.
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:
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.
notice the part I circled. I through hole filled with solder by accident.
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 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)
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.
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.
Any other recommendations. What would an experienced AMP makers next move be.
By the way, what are you using to separate the sections between the transformer, power supply, and amp?
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.
I did actually mention to check for that
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.
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 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
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
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,
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 :PHi James,
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?
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.
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
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
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...
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
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
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
But I understand EI core transformers such as the recommended Hammond in the BOM are not vulnerable to DC the way toroidal are
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.
It's got the Jantzen caps.
....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.
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-)? :?
Finally finished my second Folsom.
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.
: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
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.
Huh? :scratch:
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
(https://image.ibb.co/iv7807/bindpost.png)
It's an upgrade to do this, I found, with how it sounds.
What damage occurs when a clever fool powers on the amp with just the right channel speaker connected?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.
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
no gain is good for it, generally
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
Mouser #546-185F16 Hammond #185F16 Hammond Power Transformers Global/Chassis Mount 130VA, 16V CT @8.1A
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.
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)
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
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.
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
Add the slots between the speaker binding posts, and the RCA posts.
YES. The grounds on the RCA sockets need to be able to "see" each other electrically. The results are very nice.
Yes. Just each channel, and each pair of RCA's. The slot can be relatively small.
Not if you can still get isolation (good luck). That lip stops conducting between chassis and RCA barrel.
Great job so far.
(https://www.audiocircle.com/image.php?id=192778)
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.
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)
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
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)
If you have not done so already, remember to cut a slot between the posts, see pictures in previous page.
Paul
I have a feeling I don't have the correct blue and green wires out of the transformer.
Ben
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."See two pages back. :thumb:
See two pages back. :thumb:
https://www.audiocircle.com/image.php?id=193206
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.
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.
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.
Bulkhead complete. Time to get it Lacro-ized!
(https://www.audiocircle.com/image.php?id=193360)
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".Only for a short while, until using a variable power supply up to 18V.
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.
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)
Definitely build Keantoken’s buffers with a chinese DACT for volume. :thumb:
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?
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
Or a lizard?
Some link for new 7293 amp, please.
waiting with anticipation :-)
how do we order/pre-order?
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.
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.
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
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?
Good to know, really not worth it? So in your experience do you even hear a difference at all?
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.
What size screws/bolts should be used for mounting the PCB? And what kind + size board standoffs?
Thanks.
I use M3 for everything.
That’s an awesome looking amp... so compact yet neat
The cheap W226.5×H70×D271mm case on eBay makes a fantastic case for the build:
https://www.ebay.com/itm/252579253474
Are the boards for these still available? I read through the thread but I cant really tell.
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
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.
These look awesome, is anyone offering a build service for those of us who aren't amp builders?
CorrectSometimes I wonder if people are hired by advertising firms to post.
Sometimes I wonder if people are hired by advertising firms to post.:roll:
That was a quote too.
Cool looking box. I started this thread 64 pages ago, and my Folsom amp is still sitting in a cigar box. :oops:
(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!
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.
(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?
If you cut a small slot between the binding posts + and - for each channel you'll get better sound.
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
Michael, you didn't have that ever did you?
(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.
(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.
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!
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.
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.
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
hello, are there any boards left?
thanks,drmike
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?Pinocchio posted pics on the diyaudio thread starting page 15. Yeah, I am lucky he agreed to build it. :D
--Robert
Pinocchio posted pics on the diyaudio thread starting page 15. Yeah, I am lucky he agreed to build it. :D
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:
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.
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.
Use different RCA’s?
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!
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)?
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... :´(
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?
That will not work because the outputs are balanced of the 7297. You can't combine them.
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... :´(
It's alive!
Thank you Jeremy!
Now time for listening...
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:
What was the fix?