AudioCircle
Audio/Video Gear and Systems => Cheap and Cheerful HiFi => Topic started by: Folsom on 15 Dec 2013, 09:27 pm
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Alright guys, here it is! First the parts you need. *C4 amended.
From Mouser.
Input caps, order 10x because it's cheaper than 4x (yes you'll need 4x)
647-UES1H010MDM
UES1H010MDM
50volts 1uF
Power cap 1x
661-EKZH250E222MK30S
EKZH250ELL222MK30S
25Volts 2200uF
Shunt/Mute Power cap
661-EKY500ETC220ME1
EKY-500ETC220ME11D
50volts 22uF
Building
Ok, so first I recommend getting to this point, the naked board of all the parts you don't need. That is unless you want the volume pot, but I wouldn't recommend it.
Here's a clear board, I've labeled the R and L inputs, and their grounds. R1, D1, D2, C1, C2, C3, C4 (not shown removed) C5, CN4, and RP 50k have been removed.
(http://www.audiocircle.com/image.php?id=91508)
Install a wire for the bypass of the diode (D2), I did this on the bottom.
(http://www.audiocircle.com/image.php?id=91511)
Install the Shunt/Mute cap (C3) 22uf, negative side (short lead) goes to the striped pattern on the board.
(http://www.audiocircle.com/image.php?id=91521)
Install the upside C1 and C2 capacitors, 1uf Nichicon Muse. Long leads go toward the input (as circled)
(http://www.audiocircle.com/image.php?id=91515)
Install on the bottom 1uf capacitors with the reverse orientation of the first two (long leads towards the chip), on C1 and C2. This is very important, and can only be done with non-polar caps. Without doing this your amplifier won't be that great unless you got some very nice film caps for the inputs.
(http://www.audiocircle.com/image.php?id=91519)
Install C5, the big 2200uf cap, again stripe to stripes.
(http://www.audiocircle.com/image.php?id=91520)
That's it! My next post here will be about advanced options, this is the simple, but very good build.
Use only DC power supply after removing the diode.
*do not replace C4, it's a worthless snubber that causes ringing.
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Advanced options
Adding capacitance to the DC input, multiple capacitors. You can use whatever size you want 470-2,200uf. I think 1,500uf, 1000uf, are decent sizes. Panasonic FC's are good, but I'm really into the low impedance ones offered from Mouser now, the United Chemi-con, KZH and others. whatever low impedance one. For an amplifier of this size 9000-12000uf is as much as you'll probably need. That's for 15w amplifier.
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Burn in time isn't too short with these mods. Expect much sweeter sound somewhere after 20 hours or so...
as in don't judge it too fast!
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Your first amp stopped making sound--presumably from using an SMPS that might have triggered a fault or something in the TDA7297 chip. Now that you've modded another unit, do you still support the idea of removing the polarity protection diode and replacing it with the jumper wire between the Vcc input and the rest of the amp's power supply path? You mentioned before that do this increased soundstage depth. Also, which power supply are you now using in terms of DC voltage and current?
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I switched to a 12v. This is probably the smart way to go. I can guarantee my chip failed for a particular reason even, but this new one has been playing for a few days. Besides that if it was a voltage problem the diode wouldn't stop it.
All the datasheets don't indicate any need for a diode. The diode is purely so you can use AC power. But it probably sounds like poop with AC.
Do I support it? I wouldn't use it with it, literally, because my different amplifiers I've previously used were better before removing the diode. But I was in a little bit of a panic when the first one failed since I didn't bother to order two or more, ha! They take awhile to arrive.
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I have a little bit of bad news for everyone... I tried listening to this amplifier without it being plugged into my power conditioner... It loses the magic. But that's true with all amplifiers. Trouble is it loses too much.
Looks like I might have to develop a linear supply that can provide comparable results without a conditioner (have it built in). Such as it goes... not a big surprise since I've never heard an SMPS sound very good in anything non-constant current supplied; baring a good power conditioner.
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Why not skip the power supply and just go straight to a big amp/hour battery?
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Maybe. I haven't been totally convinced of them. The sound is usually good, but their's an edge I don't always get. Not the bad one, a good one.
Plus it's not unusual that I want to listen longer than 6 hours or whatever.
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I have a little bit of bad news for everyone... I tried listening to this amplifier without it being plugged into my power conditioner... It loses the magic. But that's true with all amplifiers. Trouble is it loses too much.
Looks like I might have to develop a linear supply that can provide comparable results without a conditioner (have it built in). Such as it goes... not a big surprise since I've never heard an SMPS sound very good in anything non-constant current supplied; baring a good power conditioner.
Or just get a TPA3116 instead. Can't believe you're going all on the TDA without having heard the 3116.
yep, hijack! :D
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I'll give it a try, but I'll be very surprised if it's too much better. I can tell you the 3875 amplifier can't come even close with a nice linear PSU and power conditioning.
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I'll give it a try, but I'll be very surprised if it's too much better. I can tell you the 3875 amplifier can't come even close with a nice linear PSU and power conditioning.
3875 is totally unrelated to the TI TPA3116. The 3116 is Class D sibling chip to the one used in the TBI Millenia.
More here:
http://www.ti.com/lit/ds/symlink/tpa3116d2.pdf (http://www.ti.com/lit/ds/symlink/tpa3116d2.pdf)
one of many versions here:
http://www.ebay.com/itm/Assembled-TPA3116-store-Power-amplifier-board-50W-50W-/400560249079?pt=US_Amplifier_Parts_Components&hash=item5d434058f7 (http://www.ebay.com/itm/Assembled-TPA3116-store-Power-amplifier-board-50W-50W-/400560249079?pt=US_Amplifier_Parts_Components&hash=item5d434058f7)
So far from comparisons the general feedback is the 7297 has a more impressive soundstage but the 3116 sounds more refined to some with better top end. Granted the TPA3116 boards are a whopping $20-28 compared to the $6 7297, but it's certainly worth comparing.
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3875 was just for referance of overall. You could buy $1200 3875 monoblocks that sound like a dead dog fart compared to the TDA7297, if you ask me.
Perhaps someone should let me try theirs. I am fooling around with TDA7297 deciding if I want to make it a product, because I am so impressed. Unfortunately it appears it needs extra care in the power arena.
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... You could buy $1200 3875 monoblocks that sound like a dead dog fart compared to the TDA7297,
Hmmmm, now I know what was in that old NAD amp I used to have. :thumb: It did a great job creating realistic dead dog farts with a super soundstage.
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So far from comparisons the general feedback is the 7297 has a more impressive soundstage but the 3116 sounds more refined to some with better top end. Granted the TPA3116 boards are a whopping $20-28 compared to the $6 7297, but it's certainly worth comparing.
Just returned home from a business trip, and discovered that my Sure Electronics TPA3110D2 amp module arrived from Parts Express. I will make the connections in my system tomorrow and begin some comparisons between the TI Class D amp and the TDA7297. I have big expectations for the TPA3110D2.
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Oh good, maybe I'll just wait for word from you. The surface mount parts don't look as fun to work with, but who knows on sound. rhing are you going to try battery?
I'm skeptical given how good the TDA7297 sounds with conditioned power. I might have to try an experiment plugging it into another socket not near my conditioner. It sounds pretty darn good at a friends house without a conditioner. But... well, we'll see.
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Oh good, maybe I'll just wait for word from you. The surface mount parts don't look as fun to work with, but who knows on sound. rhing are you going to try battery?
After listening to this amp, I have to say I am very impressed with this Sure TPA3110D2 amp board. I have to qualify this statement with the fact that I connected this amp to my Audio Research LS7 vacuum tube line stage preamp, since I do not have any spare 50kohm volume pots except the cheap stock volume pots that came with my two TDA7297 amps. I used the Audio Research preamp to handle volume control duties. At this point, I cannot make a direct apples-to-apples comparison between the Sure Class D amp and the TDA7297 Class A/B amp, but I will say that the combination I have been listening to sounds better, overall, than the TDA7297 in stock or modified form.
- More detailed or articulate
- Deeper and cleaner bass--less boomy
- Higher frequency extension
- More natural tonality
- Soundstage is comparable with a large, deep soundstage
- Greater dynamic range
I feel like I'm splitting hairs with this, but I do hear the difference with careful listening with music material that I am very familiar with. Using my Alan Parson's "Sound Check 2" test CD which has a series of 1/2 octave tones from 20Hz up to 20kHz, I could verify that the bass response is lower with the TPA3110D2 than with the TDA7297. With the TPA3110D2, I could hear down to 31.5Hz in my room. I don't hear this with the TDA7297. In fact, the bass seems to roll off around 45Hz. What the TDA7297 does do is it seems to have a stronger bass output between 80 and 120Hz, which can give the impression that the bass is stronger.
I still have to sort this out, but I do hear some low level background noise with the TPA3110D2. The noise disappears when I engage the MUTE on my LS7, which indicates that the output filter-less TPA3110D2 amp may be emitting some RFI that's affecting my preamp. I never hear this noise, or any for that matter, from the TDA7297 or my Dynakit Stereo 35 tube amp. If this is something that cannot be reduced/eliminated, than an amp module such as the Yuan Jing TPA3116D2 2.0 amp might be a better solution since it does have the LC output filter to minimize RFI.
I still have more testing and listening to do, but the Texas Instruments Class D-proponents like wushuliu are probably onto something really good with these Class D amps.
(http://www.audiocircle.com/image.php?id=91738)
(http://www.audiocircle.com/image.php?id=91739)
(http://www.audiocircle.com/image.php?id=91740)
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Interesting. Do you have any power conditioning on your smps?
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I am getting some noise with TPA 3110 also when I connect it to a pre-amp. It is dead silent when it is connected to an Apple AirportExpress. I have not been able to figure it out yet.
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I am getting some noise with TPA 3110 also when I connect it to a pre-amp. It is dead silent when it is connected to an Apple AirportExpress. I have not been able to figure it out yet.
Thanks for pointing that out MLS. I just connected my iPhone to the amp, and it's quiet just as you described.
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Here's a clear board, I've labeled the R and L inputs, and their grounds. R1, D1, D2, C1, C2, C3, C5, CN4, and RP 50k have been removed.
(http://www.audiocircle.com/image.php?id=91508)
Install a wire for the bypass of the diode (D2), I did this on the bottom.
(http://www.audiocircle.com/image.php?id=91511)
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Use only DC power supply after removing the diode.
I removed the diodes and installed solid core Copper wire jumpers in their place. The improvements in frequency extension, better dynamic response and detail were subtle, but worth the effort. If anyone has this amp and has a decent DC power supply, this is a worthwhile mod.
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Use only DC power supply after removing the diode.
Firstly, thanks so much for taking the time to put this together.
Secondly, when it comes to removing the diode - do you mean that we need to use only a standalone dc power source (12v battery), or can we use a 12v dc switching supply like a laptop brick, or Meanwell?
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Anything that doesn't get near 18v and is DC will work.
With the diode you can run AC, but it's not going to sound great.
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Looks like there's another revision running around. Note the "-002" label on the left side. Looks like some components are in different places. Is there any way to verify that replacing by using the labels (C2, C3, etc) will still work? Or do we need to come up with a separate guide?
(http://i.imgur.com/EAGnXRb.jpg?1)
(http://i.imgur.com/nymrfN5.jpg?1)
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Looks like they removed the LED and it's current limiting resistor. Is there still a diode behind the big power capacitor?
Seems like the mustard colored caps are the coupling capacitors, but a view from the bottom (to see the traces) would help.
Mike
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Looks like they removed the LED and it's current limiting resistor. Is there still a diode behind the big power capacitor?
Seems like the mustard colored caps are the coupling capacitors, but a view from the bottom (to see the traces) would help.
Mike
View from the bottom added above to post #22.
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Judging by the traces, the diode must still be there (hidden behing the big capacitor). But, WOW! Looks like they beefed up the power and speaker traces with a silver (?) coating.
The coupling caps (the mustard ones connected to the middle pins of the volume control) could be easily replaced, but removing/replacing any other component will be tricky. Anyone else agree?
Mike
Edit: Google "conductive ink pen".
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You are correct, the capacitor names did change.
Remove C2, the little yellow bypass cap. You can wiggle it off if you want.
C3 and C5 appear to be the input caps, replace those with the 4 Nichicon ES or anything .47uf-2.2uf in size (.22uf rolls off prematurely in the 20-30hz range, when a larger cap allows -3db at 20hz)
C1 looks like the big power cap, replace with the other big 2,200uf of choice.
C4 can be changed if you please, it doesn't matter.
The resistors are fine how they are, they're insignificant to sound.
Also, yeah, I'd remove the diode and bridge it still.
The inputs are identical if you want to remove the 1/8th jack.
I don't know why it has tinned tracing... Silver solder wouldn't really do anything. But I've been skeptical as to whether or not these have copper or steel tracing. Maybe cutting tracings for signal and just running wire would be better.
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I bought this fantastic amplifier and did all the suggested Salis mods.
Only one issue,when I touch the case that I mounted the amp in I get a hum through the speakers.
All input & output sockets are isolated from the case.
At this stage I am using a volume pot,not the one supplied but an Alps.
Mounted on the front face of the case and connected via wire to the pcb.
Suggestions would be most welcome.
Thank you in advance.
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At this stage I am using a volume pot,not the one supplied but an Alps.
Mounted on the front face of the case and connected via wire to the pcb.
If this is a metal case, it may help to solder a thin wire from the volume pot case to the chassis.
Mike
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Hi mboxler,
I was thinking of doing that but dismissed the idea because the front panel is wood.
Thank you.
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I'd connect the ground of the amplifier to the case via a .1uf and 100-150ohm resistor (in parallel). Also maybe try connecting the case to earth ground at the same time. You might have to play a bit for this, as I can't predict what'll work for certain, because I don't know your other equipment.
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Problem solved.
I put in 2.2 uF Janzten superior z caps for the inputs.
Because I had to mount them off the board I extend the leads,insulated wire.
Talk about a hum magnet.
I replaced the Jantzen caps with 1.0 uF Wima's that fitted nicely on the board.
They were the only caps I had on hand.
Once again,Thank you.
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Problem solved.
I put in 2.2 uF Janzten superior z caps for the inputs.
Because I had to mount them off the board I extend the leads,insulated wire.
Talk about a hum magnet.
I replaced the Jantzen caps with 1.0 uF Wima's that fitted nicely on the board.
They were the only caps I had on hand.
Once again,Thank you.
Glad you were able to fix the problem, but I have Mundorf Supreme film caps off board on my amp too with an Alps Blue Velvet volume pot in an Aluminum case, and I did not have have any grounding or hum issues. I always check to insure there is no continuity between connectors and the case before I wire everything up. Sometimes, I use Teflon plumbers tape around the connector bodies to insure there is no ground path through the chassis. Are you sure the ground connections were properly wired and soldered between the RCA jacks, volume pot and PCB?
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The case has served duties for other amplifier experiments without issues.
Good point about using Teflon tape,I do this as a matter of course.
Thank you.
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The cap and resistor I recommended makes your case less of an inductor, and not an antenna. But also doing this can match ground potential through your power strip, through safety ground, if your source has safety ground connected (to signal in some way, phono preamps usually do if they run on AC).
When you touch parts and get noise you are often inducting a change in ground potential. As you know induction doesn't explicitly require connectivity.
Well anyway, glad you like it.
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I just love Audiocircle,lots of good people so generous with advice.Not like that other forum(diy*****)where some people,not all, derive pleasure from treating people like fools.
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As often a fool myself, I love it too :green:
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So since you are so friendly, I would like to ask a stupid question. Could this amp be used in a car to boost the signal from a DAC to a headphone 3.5mm aux input on the vehicles head unit? I assume that these amps are too powerful, but wanted to see what you think. Maybe what I need is just a small headphone amp. I am intrigued by a simple DIY and cost effective solution, but don't want to damage my existing vehicle head unit.
Thanks,
Dan
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It's much too powerful. You be putting in lots of resistance to get it down. I think a headphone amp is a great idea. They also often have a form factor that fits in convient cases too.
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Speaking of the car - I think an awesome application for these could be tweeter or midrange amplifiers for an active setup. Wondering if direct power from the car battery/alternator would be clean enough for these amps or if it'd have to be filtered.
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Any suggestions for a good headphone amp. I would love a nice DIY project?
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One more question Mouser and Digikey are out of this cap until mid March:
EKY-500ETC220ME11D
Any suggestions on where I can buy a couple of them?
Thanks,
Dan
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What is this cap for? No one has recommended it for the TDA7297.
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rhing,
I copied it and pasted it from the first post in this build guide. Is there a typo...its the third cap listed in the parts list.
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Is it okay to use an unregulated DC power supply with this?
This one in particular - http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_2102094_-1
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Is it okay to use an unregulated DC power supply with this?
This one in particular - http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_2102094_-1
Yes. You just don't want to use things too close to 18v, because if you get too much of a spike it might fry it.
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Is it okay to use an unregulated DC power supply with this?
This one in particular - http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_2102094_-1
Hmmm...that looks like a 2.1 x 5.5 mm plug. I think you want a 2.5 x 5.5 mm.
I go this one...works very well.
http://www.ebay.com/itm/290727815800?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649 (http://www.ebay.com/itm/290727815800?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649)
Mike
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Took the TDA7297 over to a friends place today. This has a Panasonic and two Sprague orange drops, but still has the rectifier, the led, and the pot- powered by a 7AH battery. I blindfolded him and we went back and forth with his Rogue integrated. We agreed that the Rogue had more musical vocals with greater depth, but gave the nod to the 7297 on imaging. Bass accuracy and quickness were deemed a tie. Needless to say, he was stunned when he saw what was competing so closely with his $1200 amp- and not exactly pleased. I've got another one that I've still got to mod and compare again. Fun, fun, fun.
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So far they do better with non-phono sources as far as I can tell.
I am going to swap in an Elna Silmic 11 for next to chip duty. Might have to be smaller, so more off board or mounted under.
When comparing mine to a Bryston 3BSTT, it was pretty shocking. And thats before yanking a series cap, MOV, and replacing the tinsel cable on the SMPS that was used. The bass was slightly shy, and overall lacked a little authority, but it was more accurate with some stuff. The highs on the Bryston lack some timbre that small circuits seem to keep a bit better. (Or higher voltage)
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I just completed the mods - Holy moley, night and day difference.
Bass is MUCH more present, and tighter. The amp runs much cooler as well. I didn't notice any large change to mid/high clarity personally, but it really feels like it's extending 2 octaves lower than it did at stock configuration. I really feel like we're cheating the system with this little guy. Unbelievable value.
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Hello all,
just an update.
waiting for Nichicon Muse BP 1 uF to arrive,in the meantime I have reinstated the Jantzen Superior Z caps.(no hum issues this time)
Removed the volume pot.The volume is now controlled with a Silk TVC.
Just a personal observation.
when people report on modifications to this amp and indeed all other types of cheap ebay amps,the first comment is usually on how the bass has improved.
Sure bass is important but what about the whole spectrum.To my old ears the mids and highs remain the same,no improvement to be had.
One more thing,I have added an off board power supply capacitor bank.
Thank you.
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Sure bass is important but what about the whole spectrum.To my old ears the mids and highs remain the same,no improvement to be had.
I agree with you. The bass improvement to me was important because I felt that it was rolling off too early in the stock configuration. By improving the bass, the mods help bring it to sound more "flat".
The mids/highs remaining the same isn't a bad thing - in the stock config, they're pretty darn good - everyone (myself included) praises the imaging of the amp, which is mainly a function of the mids/highs.
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Don't forget that input caps take a minute (or 20hrs) to burn in.
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Just ordered a stepped attenuator with surface mount resistors, I don't think it comes with through pins, so I'll have to mount it off board.
What do you guys recommend for hookup wire? I'm really trying to avoid any inducted noise or loops.
Thanks!
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For signal go small, 28ga.
Rhing likes some shielded stuff, check the 3116 topic for info.
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Thanks salis - have you ever tried using reclaimed cat5 cable? That's the only stuff I have on hand that approaches 28 ga.
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For signal go small, 28ga.
Rhing likes some shielded stuff, check the 3116 topic for info.
On one of my TDA7297 amps, I used 0.5mm (24AWG) Mundorf Silver-Gold wire twisted in a pair from the RCAs to the Alps Blue Velvet volume pot. I have also used Mil Spec 22AWG Teflon-insulated solid core Copper wire twisted in a pair in my other TDA7297 amp with good results. My runs are short, so I'm not too concerned about inductance.
I've used shielded hookup cables in my Class D amps to avoid any RFI. This is not a concern with the TDA7297 chip amp.
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Cat5 is great if you can keep it short.
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Cat5 is great if you can keep it short.
Cool, this is going in a VERY small enclosure that will also house the capacitor buffer that you outlined in one of your previous posts. All internal wire runs will be very short.
Should be a real giant killer. I still think that there could be a good application for these in an active car audio setup as well.
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What are you going to power it with? It has basically no filtration. Sure the Power cap is very low ESR, but unlike big giants in AB world, there is no filtration, or RF rejection of any sort.
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What are you going to power it with? It has basically no filtration. Sure the Power cap is very low ESR, but unlike big giants in AB world, there is no filtration, or RF rejection of any sort.
Not determined yet. Obvious choices are the normal switching power supplies (Meanwell), or a battery. I'm curious, what are your thoughts? I'm trying to keep it as small as possible.
I've been doing my testing with a regulated 3amp 12v power supply, and the results have been stellar. I also tested with a larger 50amp 12v power supply and I couldn't hear a difference (post mods).
I've said it before, but thanks again for all your advice and guidance re: this amp! I'm having tons of fun with it.
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I'm all about linear :D .
3A is plenty.
But you should clean up power with some form of noise control. Can you get Teddy regs in 3a?
I just made a mock PSU with MSR860's and a Coilcraft CMC with 1uf X2 cap on transformer secondaries. My SMPS can't compete. In fact I intend to play around a bit with it, considering different voltage regulators and such.
You can also make boxes with linear that act as a better shield.
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Just now really taking a look at this amp. The lit says it is a dual bridge amplifier. Is this implying that it can be bridged?
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Just now really taking a look at this amp. The lit says it is a dual bridge amplifier. Is this implying that it can be bridged?
No, it is saying that it only runs as a bridged amp. The stereo module has 4 amplifiers, 2 for each channel, with the 2 amps for each channel running antiphase and bridged.
(http://www.audiocircle.com/image.php?id=95564)
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No, it is saying that it only runs as a bridged amp. The stereo module has 4 amplifiers, 2 for each channel, with the 2 amps for each channel running antiphase and bridged.
(http://www.audiocircle.com/image.php?id=95564)
Ah, I see that now.
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I'm all about linear :D .
3A is plenty.
But you should clean up power with some form of noise control. Can you get Teddy regs in 3a?
I just made a mock PSU with MSR860's and a Coilcraft CMC with 1uf X2 cap on transformer secondaries. My SMPS can't compete. In fact I intend to play around a bit with it, considering different voltage regulators and such.
You can also make boxes with linear that act as a better shield.
Woah - I'm just a beginner when it comes to PSUs, take it easy on me! :) Much of that went WOOSH over my head.
So you say linear PSUs are much better than SMPS. Gotcha - Where can I start researching/purchasing linear PSUs?
As far as noise control - In another thread, you mentioned that a mini capacitor bank could help with noise control, is that what you're referring to here, or an actual regulator like the Teddy Pardo product (http://www.teddypardo.com/resources/superteddyreg.html)?
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Teddies do work for some noise.
You want low ESR caps on 7297, or multiple ones, to reduce some noise. Basically everytime you double how many caps you use, you half the ESR so the capacitors look like a better conductor for noise compared to say the chip and your speakers.
You can use capacitors on AC side but it's another ball game. For a beginer, well, caution is adviced.
Linear PSU usually consists of a transformer to bring 115v from wall down to something else. But it's still AC until it goes to the diodes, where rectification occurs. Then you have something close to DC, and capacitors fill in the rest to have DC. I know it's a bunch of stuff to know... You just have to look it up and dig in. Someone else will have to link a website for you, I'm just on iphone atm. Diagrams and what not will be helpful, as they'll help you get it faster than me typing a small book of only text.
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I just completed the mods - Holy moley, night and day difference.
I ordered the 3 parts as recomended here and plan to use my 12V2A, wallwart. What kind of power supply did u use?
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Anyone tried paralleling the inputs and outputs to use both channels together making it a mono amp?
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Perhaps with a preamp that has some gain this would work. But I'm not certain the amplifier has any current deficiencies. I've had it hooked up to speakers that otherwise usually have a 250w Bryston (AB, constant current), and with a really cheap power supply was very close. I haven't re-tested it with a linear, but I suspect it will hold it's own maybe evenly until ear blistering volumes.
I'm not certain, but you may need 1uf caps (or two 2.2uf caps using my configuration) on each channel to retain frequency response, with this parallel layout.
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Perhaps with a preamp that has some gain this would work. But I'm not certain the amplifier has any current deficiencies. I've had it hooked up to speakers that otherwise usually have a 250w Bryston (AB, constant current), and with a really cheap power supply was very close. I haven't re-tested it with a linear, but I suspect it will hold it's own maybe evenly until ear blistering volumes.
I'm not certain, but you may need 1uf caps (or two 2.2uf caps using my configuration) on each channel to retain frequency response, with this parallel layout.
My thought is why not turn them into little mono-blocks. They are only $6 a piece. And there maybe something there to gain as well.
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Well it'd be nice to have the same power source not doing dealing with two channels. It might be just as smart to only use one channel. Sure it seems silly, but it'd work. As is this thing works on 87db speakers just fine.
I think alternatively you could just use one cap, .47uf, (or two 1uf) if you wire the channels together after it, instead of before, if you want to use both for sure. Then there wouldn't be any concern. (.22uf is too small, unless you want premature roll-off)
I'd be interested in building a sort of reference version, possibly.
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Yeah, my thoughts were that with both channels sharing one power supply cap that it might limit stereo separation.
My first thought was to just use one channel from each amp. Sure it seems wasteful, but it doesn't really cost anything.
Then I got to thinking about paralleling the two channels after a buddy suggested it. Output would be the same. Current capability would double. Damping factor would double. The input impedance will drop in half though. What was it to start with 47k ohms? Correct me if I'm wrong here.
I am not sure if I even want to use any coupling caps on the input. I have coupling caps on the output of my pre-amp.
And all of those cheesy connectors are going bye-bye too. I think those things are steel.
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Input resistance is 25-30kohm. 12.5-15kohm is drivable, but not as good as would be preferred. I guess the whole situation makes this preamp/source dependent to not drop current by splitting and being able to drive it as the input resistance. What's your pre put out? You could always use some Lundel input transformers :thumb: .
Yes, you can skip the input capacitor if you know there's no DC on the line.
I haven't found any problem with stereo separation. The imaging is ridiculously good. But better is better!
I sent you a PM about this and a few things, but it's best to not order these from China. I'm not even certain the tracings are copper given how solder doesn't stick to them as well as I'd like. Plus the chips are second rate, so getting two to match is much harder with these. It'd be better to order them from Mouser and just P2P, for one build anyways. Then again, I suppose you could have PCB made. Yes the cost starts to go up, but this little thing can certainly be worth it.
What kind of power supply you thinking Danny? This little guy has some timbre; it's interesting.
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Yes, I got your e-mail. Thank you.
My tube amp is a Dodd Audio. Mine has three outputs. Couple caps on two of them are Jupiter cap 3.3's by-pass by a .01uF Sonicap Platinum. On the third one it just uses a .047uF Sonicap Platinum to roll off the lows. I can drive tube mono-blocks and four servo amps off of it without issue.
My first listen was surprising. It definitely gave a lot up to my little mono-block tube amps, but then again I was using a cheap RCA to 1/8 plug that came from who knows what. And I was just using some cheap speaker cables since it had no binding posts or anyway to hook up any good cables. So I know there is a lot of improvement ahead from the get go and it wasn't that bad to begin with.
Right away I removed the pot and that was a nice improvement.
Oh, and I plugged it into the 100 amp hour Power Sonic batter that I run my tube amps with. So I have that part covered.
I was thinking this would make a really nice amp to burn things in with. It uses almost nothing for power consumption and it sounds pretty good to boot. And if I can make it sound even better with a little tweak or two then all the better.
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I'm still under the impression it can be anyone's main amp. You have some beautiful tube amps we've seen in pictures that I'm sure will be preferred, however.
If you still have the diode in, you got to get rid of that, and the film bypass cap on it! You really haven't scraped the ice on the windshield if all you've done is remove the pot :icon_lol: ; just removed the snow.
I actually prefer this things minimalist component layout, as it can out class more expensive amps that don't maintain the higher frequencies as well through the horde of components that some equipment happens to have (quality vs. watts and features, usually). But it comes at the cost of having to do all the work for noise rejection in the power area. Some would call it "crisis" design, but whatever.
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I'm still under the impression it can be anyone's main amp. You have some beautiful tube amps we've seen in pictures that I'm sure will be preferred, however.
I think for a lot of people it could. A real tricked out version of this thing might embarrass some high dollar amps. So long as you don't need a lot of power.
If you still have the diode in, you got to get rid of that, and the film bypass cap on it! You really haven't scraped the ice on the windshield if all you've done is remove the pot :icon_lol: ; just removed the snow.
Little yellow cap right over the diode? I thought you left that.
Yeah, I know there is a lot of improvement ahead. I just had to get a feel for it and see if it had potential. It clearly does. Now I am trying to figure out what all I might do to it.
I actually prefer this things minimalist component layout, as it can out class more expensive amps that don't maintain the higher frequencies as well through the horde of components that some equipment happens to have (quality vs. watts and features, usually). But it comes at the cost of having to do all the work for noise rejection in the power area. Some would call it "crisis" design, but whatever.
I like the minimalist approach as well. My Dodd pre-amp is along those same lines.
No worries here on the power supply. That big 100 amp hour battery is dead quiet. And it's cheaper than a decent power cable.
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My pictures show he little yellow cap because I thought it was an bypass to ground from a different point within the chip. You can do that easily on a 3875 and other chip amps, but on this one it's just bypass cap that causes ringing (you'll hear it not ringing when you pull it, no joke, and you can wiggle it off if you're feeling lazy). I edited to show the removal of that capacitor later. Sorry about that. Perhaps with the original junk capacitor it was helpful, but with a better one it's just a nuisance.
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My pictures show he little yellow cap because I thought it was an bypass to ground from a different point within the chip. You can do that easily on a 3875 and other chip amps, but on this one it's just bypass cap that causes ringing (you'll hear it not ringing when you pull it, no joke, and you can wiggle it off if you're feeling lazy). I edited to show the removal of that capacitor later. Sorry about that. Perhaps with the original junk capacitor it was helpful, but with a better one it's just a nuisance.
I just looked at it. Yeah, it just by-passes the main cap.
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These amps have got to be one of "those" finds.
I talked to Danny this morning about all of the ins and outs of them and just ordered two of them. What great low $$$ fun.
In the past I have had great success using one channel of stereo amps. Every time there was better sound and headroom.
Battery power is a no brainer when properly done.
Thanks for the tutorial and this thread. :thumb:
Dave
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Battery power is a no brainer when properly done.
My ears pricked up - can you provide a bit more detail about your thoughts re: battery power and applying it here? I'm researching different power strategies for these little guys and would love to hear any input you have.
Thanks!
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My ears pricked up - can you provide a bit more detail about your thoughts re: battery power and applying it here? I'm researching different power strategies for these little guys and would love to hear any input you have.
Thanks!
Batteries are easy... or hard, depending on your POV.
Batteries are weird animals. Oddly enough there are good and bad sounding batteries. It has to do with the purity of the plates and their internal connections.
Never use a battery (lead type) that is not an AGM. As far as I am concerend the care and feeding of lithium derivatives are just too much of a PITA to use. They sound good, but are like that cute sister-in-law that is a _itch (pick your letter).
I use and recommend Power Sonic batteries. They are consistent and they SOUND GOOD. I use and recommend Ctek chargers. I have 3 different versions. The 3300 will be just fine for this application, if you turn it off when listening. The 7002 is pretty much silent when used with a big battery. I have a 26AH, 55AH and a 100AH. The 100 has the best sonics, but is very pricey. Thanks to Trung for hooking me up a few years ago. That ship has sailed, but I got on JIT :D I recommend the 55 for most applications.
Batteries have high output impedances. In my BatteryBUSS there is 34,000+ufd of very low impedance capacitors to reduce that impedance. Other things, too, but I will not divuldge that info. I am a capitalist after all. Mouths to feed and all of that.
DO NOT use one of those 1 farad car audio caps. Again: the output impedance is too high. They may be fine to use in conjunction with smaller, very low impedance caps as mentioned here in this thread.
Once you hear battery audio you will never go back. That is why my preamp and power amp are DODD Audio designs. Gary believes, as I do, that the simplest circuit topology, properly implemented sounds the best. My DAC is DC powered. My Mac Mini is DC powered. The only AC powered components in my system are the GR Research subs that startle every one that hears them.
To me, the secret to audio (if there is one) is low noise, VERY high current power supplies with extremely low output impedance. I have taken crappy gear and made it sing with power supply mods. The power supplies in gear are the most expensive parts. Bean counters cut the $$$ there, first.
Remember: voltage is horsepower and current is torque.
The thoughts of a totally unbiased (Bwaha!) audiophool.
PM me if you want more info.
Dave
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Dave, have you played with LiFePO4? They're a safe alternative to LiPO (fire bombs).
I'm going to agree with you, it's all in the power! But as far as impedance, well it's all a matter of perspective not only between us, but the gear too. DC is great for having relatively no noise going into a system, but not very good for getting it out.
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My pictures show he little yellow cap because I thought it was an bypass to ground from a different point within the chip. You can do that easily on a 3875 and other chip amps, but on this one it's just bypass cap that causes ringing (you'll hear it not ringing when you pull it, no joke, ...
ARGGGHH!!! I pulled those by mistake when taking out the rectifier, and then put them back!!! If you don't like the Chinese boards, who do you recommend? Don't just tell Danny in a PM, we all want to know!
And you're right about imaging. If the stereo can get better then it's going to top my Moscode 401HR with just under a thousand $ worth of mods... Hard to believe I just typed that.
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:lol: Sorry.
I happened to realize that after, and amended my build guide, but without pictures during process.
The boards are not ideal, but I'll point out the big problem, there aren't any other ones!
I DO NOT like 3875 chips by comparison. They're ok, but not a show stopper. I'm just saying it's easier to unload some RF with them.
The question now is, would people like boards/kits instead? The price changes significantly, if you can imagine it. But kit's will have more closely matched capacitors, etc.
You can do what Danny was talking about pretty easily. Get an extra board, and only install one channel input capacitor. Then connect right and left channel after the capacitor. Then also do the same thing with the speaker outs. Then report back for the rest of us that haven't actually done it! Could also try just running one channel on each board.
*Don't connect one channel to both input caps, only connect channels post capacitors.
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Dave, have you played with LiFePO4? They're a safe alternative to LiPO (fire bombs).
I'm going to agree with you, it's all in the power! But as far as impedance, well it's all a matter of perspective not only between us, but the gear too. DC is great for having relatively no noise going into a system, but not very good for getting it out.
Yep, I have played with every battery known and some that are not available to general consumption. Cool living where I live, knowing the people that I know.
Anyway, The AGM battery is the best compromise for most people IMO. They are cheap, have NO isue when they are properly implemented and sound great. One of the things that EVERY battery needs is a stout capacitive buffer. Even the LiFePo4 batteries. If there is not a buffer, the sound of the battery is prevalent. Of course, some people may prefer the SOUND of things, but that is purely a YMMV situation. Me, I like a 64 year old grey headed woman that I have 47 years invested in. Know what I mean?
Anyway, all of this is great fun and I may have an entirely different take when I get the amps I ordered today. After all, the proof is in the pudding.
Dave
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I'm not even going to use the coupling caps with mine. I have output coupling caps on my pre-amp that should do the job.
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I liked it and said I didn't think I'd mod it, but I did. Finished the E-A-S-Y mods as indicated and now have 20 or so hours on it. Will wait a bit more before rendering an opinion. BUT ... it does sound nice.
Curious, though. The mods, as suggested, are essentially better quality replacement components, right? Or, is there something else going on with the recommended replacements?
Any insight would be appreciated.
SamA
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I liked it and said I didn't think I'd mod it, but I did. Finished the E-A-S-Y mods as indicated and now have 20 or so hours on it. Will wait a bit more before rendering an opinion. BUT ... it does sound nice.
Curious, though. The mods, as suggested, are essentially better quality replacement components, right? Or, is there something else going on with the recommended replacements?
Any insight would be appreciated.
SamA
There isn't anything to change really. Most of everything is built into the chip, and basically every part I recommended replacing it has to have under almost every circumstance. The ones I recommended pulling can all be pulled.
Inside the chip there's a bunch of stuff, all of which you'd have in a regular discrete amplifier, but it's TINY.
If you want somewhere to do some changes, I'd recommend the power supply. You can do all sorts of things, switchers, linear, regulators, filtration, etc. You can even get two of them, or four of them if you run two boards with inputs and outputs paralleled. You'd have to cut some traces in order to separate the power, and attach a wire in a VERY careful manner, but there's options.
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One of the things I like about the TDA7297 amp is how it combines The Lab, The Starting Block, and The Cheap & Cheerful HiFi
circles into one place.
For $6, you can buy one and leave it alone....or
You follow the traces to and from the IC...learn how to use a multi-meter.
You buy a soldering iron and a better capacitor, replace the stock one, and smile ear to ear when it still works!
You learn about AC, DC, coupling caps, resistors, diodes, LED's.
Batteries vs Power Supplies.
"I wonder What does this part does?"
Google some more. Volume controls, RCA's, binding posts.
Call over your husband or wife..."listen to this!". "Nice dear"...eyes rolling.
Ask questions, make mistakes, correct mistakes. Next thing you know, you are helping someone else
with things you yourself knew nothing about before you started.
You can even buy these unassembled (5 for $22). Again, a rewarding experience.
I hope others are learning as much as I have.
Mike
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There isn't anything to change really. Most of everything is built into the chip, and basically every part I recommended replacing it has to have under almost every circumstance. The ones I recommended pulling can all be pulled.
Inside the chip there's a bunch of stuff, all of which you'd have in a regular discrete amplifier, but it's TINY.
If you want somewhere to do some changes, I'd recommend the power supply. You can do all sorts of things, switchers, linear, regulators, filtration, etc. You can even get two of them, or four of them if you run two boards with inputs and outputs paralleled. You'd have to cut some traces in order to separate the power, and attach a wire in a VERY careful manner, but there's options.
Are you still a believer in using several diodes at the dc to clean up noise?
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No, one can reduce ripple. More has too much leakage, ultimately hurting the output. I probably jumped the gun a bit too much. :lol:
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I posted some pics and info on my amp build in my circle: http://www.audiocircle.com/index.php?topic=124981.msg1317309#msg1317309
(http://gr-research.com/amps/TDAside.jpg)
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Very nice builds Danny. Being a professional speaker designer/builder, have you found the TDA7297 to roll off the bass? In my experience, the bass is nice down to 50-60Hz, but no deeper. I'm not a really big bass hound, but I find this one area to be a shortcoming. It was enough to drive me toward the TI TPA3110D2 and TPA3116D2 Class D amps, which go lower.
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Very nice builds Danny. Being a professional speaker designer/builder, have you found the TDA7297 to roll off the bass? In my experience, the bass is nice down to 50-60Hz, but no deeper. I'm not a really big bass hound, but I find this one area to be a shortcoming. It was enough to drive me toward the TI TPA3110D2 and TPA3116D2 Class D amps, which go lower.
I'll have to try them with a full range speaker to see. I have been using them on some Super-7's with in-line filters to roll off the lower ranges.
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Very nice builds Danny. Being a professional speaker designer/builder, have you found the TDA7297 to roll off the bass? In my experience, the bass is nice down to 50-60Hz, but no deeper. I'm not a really big bass hound, but I find this one area to be a shortcoming. It was enough to drive me toward the TI TPA3110D2 and TPA3116D2 Class D amps, which go lower.
Ya but you use the wrong sized capacitors to reach lower anyway. .22uf isn't big enough to reach 20hz even if the amp is capable. You can calculate the corner frequency, and basically at .47uf or larger you're able to hit 20hz. .47uf is a common size anyhow.
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Ya but you use the wrong sized capacitors to reach lower anyway. .22uf isn't big enough to reach 20hz even if the amp is capable. You can calculate the corner frequency, and basically at .47uf or larger you're able to hit 20hz. .47uf is a common size anyhow.
If you look at the STM TDA7297 datasheet, the frequency response graph shows a roll-off above 20Hz. This has nothing to do with capacitors outside of the amplifier IC.
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Data sheet is -3db at 20hz for the chip. The roll off for a given build with improperly sized capacitors for hifi instead of TV or portable boxes is of no real concern to me.
It's physics, .22uf is incorrect for low bass. It's not an arguement, it's simple math to describe a physical relationship.
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I recently bought a TPA3116 (YJ blue board)
Applied all the the tricks(Wurth coils,silmic caps etc.)
My personal opinion,The Sallis modded TDA7297 kills it.YMMV
Best regards.
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I recently bought a TPA3116 (YJ blue board)
Applied all the the tricks(Wurth coils,silmic caps etc.)
My personal opinion,The Sallis modded TDA7297 kills it.YMMV
Best regards.
Your review aside, I'm surprised that the TDA7297 doesn't blow the TPA away in general given how few parts it uses. Unfortunately it looks only suitable for 8 ohms so it would not be suitable for my speakers to test.
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Your review aside, I'm surprised that the TDA7297 doesn't blow the TPA away in general given how few parts it uses. Unfortunately it looks only suitable for 8 ohms so it would not be suitable for my speakers to test.
I drove it into some 4 ohm loads and it was very stable and played well with no issues.
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I drove it into some 4 ohm loads and it was very stable and played well with no issues.
OK good to know. I've got one sitting in a drawer I'll do the usual mods and give it a whirl.
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Your review aside, I'm surprised that the TDA7297 doesn't blow the TPA away in general given how few parts it uses. Unfortunately it looks only suitable for 8 ohms so it would not be suitable for my speakers to test.
My speakers are M.J .King H frames with Eminence Alpha 15/L-Cao 8 inch.
Started out with the Alpha/Fostex FE103en combination,tried Visaton B200 and Mark Audio Alpair 12.
The present set up is best for me.
Regards.
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Alright guys, here it is! First the parts you need. *C4 amended.
From Mouser.
Input caps, order 10x because it's cheaper than 4x (yes you'll need 4x)
647-UES1H010MDM
UES1H010MDM
50volts 1uF
Power cap 1x
661-EKZH250E222MK30S
EKZH250ELL222MK30S
25Volts 2200uF
Shunt/Mute Power cap
661-EKY500ETC220ME1
EKY-500ETC220ME11D
50volts 22uF
Building
Ok, so first I recommend getting to this point, the naked board of all the parts you don't need. That is unless you want the volume pot, but I wouldn't recommend it.
Here's a clear board, I've labeled the R and L inputs, and their grounds. R1, D1, D2, C1, C2, C3, C4 (not shown removed) C5, CN4, and RP 50k have been removed.
(http://www.audiocircle.com/image.php?id=91508)
Install a wire for the bypass of the diode (D2), I did this on the bottom.
(http://www.audiocircle.com/image.php?id=91511)
Install the Shunt/Mute cap (C3) 22uf, negative side (short lead) goes to the striped pattern on the board.
(http://www.audiocircle.com/image.php?id=91521)
Install the upside C1 and C2 capacitors, 1uf Nichicon Muse. Long leads go toward the input (as circled)
(http://www.audiocircle.com/image.php?id=91515)
Install on the bottom 1uf capacitors with the reverse orientation of the first two (long leads towards the chip), on C1 and C2. This is very important, and can only be done with non-polar caps. Without doing this your amplifier won't be that great unless you got some very nice film caps for the inputs.
(http://www.audiocircle.com/image.php?id=91519)
Install C5, the big 2200uf cap, again stripe to stripes.
(http://www.audiocircle.com/image.php?id=91520)
That's it! My next post here will be about advanced options, this is the simple, but very good build.
Use only DC power supply after removing the diode.
*do not replace C4, it's a worthless snubber that causes ringing.
this is great, thanks for putting this together with pictures even I was able to get this done and listening to sweet quartet as I am writing this. Your instructions are excellent, since I did not listen to nonmod version extensively I can not tell, but as I am listening in garage sounds nice.
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Hey I'm glad it's working.
I recommended a few other potential changes to another guy. The biggest issue is the board is the OPPOSITE of compatible of using different power caps. The input caps are going to remain as a very transparent, balanced, recommendation. You can spend $480 on V-cap input caps if you want... a piece!
Bang for buck, I'd like to know how far my input capacitor method can go.
What PSU are you using? An Astron like the guys with the TPA3116 guys are using would be a great choice. They do well with minor capacitor mods too.
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Hey I'm glad it's working.
I recommended a few other potential changes to another guy. The biggest issue is the board is the OPPOSITE of compatible of using different power caps. The input caps are going to remain as a very transparent, balanced, recommendation. You can spend $480 on V-cap input caps if you want... a piece!
Bang for buck, I'd like to know how far my input capacitor method can go.
What PSU are you using? An Astron like the guys with the TPA3116 guys are using would be a great choice. They do well with minor capacitor mods too.
I was using a cheap 2A, 12V wallwart.
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You have so much more amp to enjoy when you switch that out (http://www.ebay.com/sch/i.html?_from=R40&_trksid=p2050601.m570.l1313.TR12.TRC2.A0.H0.Xastron+power+supply&_nkw=astron+power+supply&_sacat=0)!
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Alright guys, here it is!
is there any chance on continuing the pictorial steps in putting the modded unit in the case with power connector, pot/volume, DC connector etc? This tutorial has been very helpful.
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I'd have to get all that stuff :lol: .
I've been mounting all these little amps on a piece of plywood for testing.
There's some decent guides to volume (http://m.wikihow.com/Wire-a-Potentiometer=) out there. Generally any DC jack uses the center pin for power.
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I am confused about the proper soldering of signal inputs, original suggestion was the common ground is the single hole in the front as pictured. There are 4 holes (2 for R/L). Can either hole be used for each channel? or is the ground the outer holes and each signal must be soldered on inner holes?
(http://www.audiocircle.com/image.php?id=104310)
(http://www.audiocircle.com/image.php?id=104311)
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Just flip the board over and look at the back side of the traces. The ones that are ground will be apparent.
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Just flip the board over and look at the back side of the traces. The ones that are ground will be apparent.
Yes, and they connect to the same plane. You can connect both ground wires to the board, or make a Y shaped cable so that only one wire runs away from the RCA jacks.
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can someone verify whether this is correct connection of audio input after ridding of the volume pot?
(http://www.audiocircle.com/image.php?id=104416)
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We need to see the underside, it appears to be a different board.
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Hi! I'm in India and getting the caps that Salis Audio recommends is near impossible here. Shipping from Mouser/Farnell is prohibitively expensive so that is ruled out. I have put in some links of the caps that are available here and would like to request someone to be so kind as to check them out and see what would fit best for the Input caps and for the Shunt/Mute Power cap.
Input caps [50V 1uF]: Choices are:
http://theaudiocrafts.com/index.php?route=product/product&path=79_80_154&product_id=263 (http://theaudiocrafts.com/index.php?route=product/product&path=79_80_154&product_id=263)
http://www.diycomponents.in/ProductDetails.xhtml?current_SKU=1209 (http://www.diycomponents.in/ProductDetails.xhtml?current_SKU=1209)
http://www.diycomponents.in/ProductDetails.xhtml?current_SKU=1197 (http://www.diycomponents.in/ProductDetails.xhtml?current_SKU=1197)
http://www.diycomponents.in/ProductDetails.xhtml?current_SKU=1198 (http://www.diycomponents.in/ProductDetails.xhtml?current_SKU=1198)
Shunt/Mute Power cap [50volts 22uF]: Choices are:
http://www.diycomponents.in/ProductDetails.xhtml?current_SKU=1226 (http://www.diycomponents.in/ProductDetails.xhtml?current_SKU=1226)
http://www.diycomponents.in/ProductDetails.xhtml?current_SKU=1196 (http://www.diycomponents.in/ProductDetails.xhtml?current_SKU=1196)
http://www.diycomponents.in/ProductDetails.xhtml?current_SKU=1144 (http://www.diycomponents.in/ProductDetails.xhtml?current_SKU=1144)
http://www.diycomponents.in/ProductDetails.xhtml?current_SKU=1173 (http://www.diycomponents.in/ProductDetails.xhtml?current_SKU=1173)
http://www.diycomponents.in/ProductDetails.xhtml?current_SKU=1132 (http://www.diycomponents.in/ProductDetails.xhtml?current_SKU=1132)
http://theaudiocrafts.com/index.php?route=product/product&product_id=288 (http://theaudiocrafts.com/index.php?route=product/product&product_id=288)
http://theaudiocrafts.com/index.php?route=product/product&product_id=299 (http://theaudiocrafts.com/index.php?route=product/product&product_id=299)
I haven't found a suitable Power cap [25V 2200uF] yet and will keep looking.
Thanks in advance!!!
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I have a audio input signal that intermittenly cuts out on one channel, corrects if I wiggle the input line at the terminal. I want to solder lines on the bottom to bypass the loose connection but I am little confused about the orientation.
a: I am guessing is the R input, but 2 solder teminals are connected, looks like it is shorted? (on picture does not show well since angle is not correct)
b: likely ground
c: prob L input, but 2 solder terminals are not shorted.
I like to take the input jack out but not clear on exactly which holes I should solder to. Can anyone explain
(http://www.audiocircle.com/image.php?id=104658)
(http://www.audiocircle.com/image.php?id=104659)
?
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I think these caps (http://www.diycomponents.in/ProductDetails.xhtml?current_SKU=1209) would work well for the inputs, two of them, keith. Don't worry about the 22uf cap, you can leave it as is if you want. Two of these (http://www.diycomponents.in/ProductDetails.xhtml?current_SKU=1178) will work great for replacing the 2200uf.
gychange, you're correct that they are the input signals. They're not bypassed, that's just the cheap 1/8 jack's way of mounting. First try re-touching the solder joints with a tiny bit of lead solder. It's most likely either a cold solder or a jack that's too cheap.
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I think these caps (http://www.diycomponents.in/ProductDetails.xhtml?current_SKU=1209) would work well for the inputs, two of them, keith. Don't worry about the 22uf cap, you can leave it as is if you want. Two of these (http://www.diycomponents.in/ProductDetails.xhtml?current_SKU=1178) will work great for replacing the 2200uf.
Thank you! Are you sure about this (http://www.diycomponents.in/ProductDetails.xhtml?current_SKU=1178) to replace the 2200uF cap? It is only 100uF. Won't even 2 of them paralleled be inadequate?
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Darn, you are right. I thought they were 1000uf.
I'm not sure how to search sites for your location so I was just looking on those two.
http://theaudiocrafts.com/index.php?route=product/product&path=124_146&product_id=278
Those will work if you can't find Nichicon KG or FG.
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Darn, you are right. I thought they were 1000uf.
I'm not sure how to search sites for your location so I was just looking on those two.
http://theaudiocrafts.com/index.php?route=product/product&path=124_146&product_id=278
Those will work if you can't find Nichicon KG or FG.
Thank you!
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I drove it into some 4 ohm loads and it was very stable and played well with no issues.
does this mean, the amp is also good with "4ohm" speakers? Had been hesitant on getting 4ohm driver for the amp...
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Curious, though. The mods, as suggested, are essentially better quality replacement components, right? Or, is there something else going on with the recommended replacements?
Any insight would be appreciated.
SamA
I also have the same question, mods sound nice I noticed the "specs" of the original and replacement parts are pretty much same, is it the name of the brand that make the difference?
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can anyone direct me to source a low profile so I can put it in a slimmer case?, like the modded amp a lot.
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does this mean, the amp is also good with "4ohm" speakers? Had been hesitant on getting 4ohm driver for the amp...
Yes, it is stable into 4 ohm loads.
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I dusted off my last TDA7297 amp in my garage storage, and connected it to some speaker binding post connectors from Lowes and a pair of Vampire CM1F RCA connectors. Previously, I had been toying with a Sure TPA3116 amp, and decided it was time to give the TDA7297 another try again.
(http://www.audiocircle.com/image.php?id=114538)
Per Salis Audio's recommendation and based on some of my own experience with these amps, I did the following:
- Replaced stock volume pot with 50k log taper, 21-position SMD resistor stepped attenuator
- Replaced stock .22uF metallized Polyester film caps with 1uF/25V Black Gate N non-polar electrolytic capacitors
- Replaced large stock DC decoupling electrolytic cap with 2,200uF/25V Panasonic FM cap
- Replaced DC polarity protection diode with a small jumper wire (Kimber Kable TCSS, 19AWG)
- Removed 3.2mm mini stereo plug and directly wired inputs to RCA connectors
- Wired signal inputs with Kimber Kable TCSS, 19AWG Teflon-insulated Copper hook-up wire
- Wired DC power input with 16AWG Teflon-insulated Silver-plated Copper Mil Spec wire
I connected the TDA7297 amp to my Audio Research LS7 line stage and ARC PH5 phono stage, and my modified Klipsch Forte II speakers to see how good this amp can be. For power, I used my modified Astron RS-12A regulated linear power supply.
Well, it sounds really good. In fact, I think it sounds better than my original TDA7297 amp with the .22uF Mundorf Supreme film caps. The Black Gate N caps take a long time to break in, but once they do they really open up nicely with a warm midrange and deep soundstage. I really liked the tonality of this amp with the exception that the bass doesn't go deeper. What bass is there seems solid and well-defined down to 45-50Hz, but nothing ground-shaking.
I've been experimenting with the Texas Instruments TPA3116 Class D amps and even replaced the input coupling caps with CineMag CMLI-15/15B input transformers to take full advantage of the differential inputs. I am quite pleased with my efforts with the TPA3116 Class D amp, but I have to admit that the TDA7297 isn't far behind, and it's considerably easier and cheaper to modify. I'll do some more critical listening. Comparing amps can be very difficult, but with listening to very familiar material, I can start drawing some comparisons.
I have yet to take that little yellow ceramic cap off the board. Perhaps I'll try experimenting with the Nichicon ES bipolar caps once I get a solid feel for the Black Gate N caps. I wouldn't mind trying some 1uF Polypropylene film and foil caps either.
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You still have some upside potential there. The speaker wire connectors on the board are ferromagnetic. The screws are steel. You can remove those connectors and solder the speaker wire straight to the board. So there is one improvement for you that won't cost you a dime.
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Certainly try a 1uf film cap. I'm using around .7uf, and Lorde's album makes my Encore X-LS play like their is a small subwoofer or something. Try two .47uf Sprague Orange Drop 716p capacitors on the input. They're pretty damn good for the $.
The amp tends to polarize electrolytic capacitors, so you can lose bass with them. The ES caps works for pennies, but can't top film.
The amp seems to love Belden 8412 brilliance from Parts Express. You use the two inside wires as one conductor, and the shield as the other.
I've tried without input caps and the amp tends to trial off into something undesirable. There's a few notable things it does better without, but the 716p caps aren't that far off.
This sounds funny but it hates Dale resistors prior to it. The SMT from China stepped attenuators work very well with it.
The real bread and butter is a capacitor multiplier on the DC input. My kit (delayed due to theft) features one. But it works well in conjunction with some high end OSCON caps like the 3116 uses.
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One thing that hasn't been discussed much is the TDA7297 chip itself.
Would it be worth replacing the chips supplied with the amps with ones purchased from Mouser?
I purchased a 5-pack of unassembled amps (I don't have to un-solder anything).
Mike
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You still have some upside potential there. The speaker wire connectors on the board are ferromagnetic. The screws are steel. You can remove those connectors and solder the speaker wire straight to the board. So there is one improvement for you that won't cost you a dime.
Excellent point. I want to use connectors to play around with this amp. I have some Weidmuller 2-position terminal blocks that use Tin-plated Copper alloy contacts. I bought these from Digikey for this very purpose. Eventually, direct wired connections are the way to go.
Certainly try a 1uf film cap. I'm using around .7uf, and Lorde's album makes my Encore X-LS play like their is a small subwoofer or something. Try two .47uf Sprague Orange Drop 716p capacitors on the input. They're pretty damn good for the $.
The amp tends to polarize electrolytic capacitors, so you can lose bass with them. The ES caps works for pennies, but can't top film.
I'll try the Sprague Orange Drop 716p Propylene film and foil caps. You are recommending two caps wired in parallel per channel, correct? A long time ago when I first tried the TDA7297, I threw in a pair of NOS .22uF/400V Panasonic ECQP Propylene film and foil caps, and the sound was impressive, except I wasn't getting deep bass extension. I then tried the Mundorf Supremes thinking they would be an improvement, but I haven't found that to be the case with these amps. Since the Panasonic ECQP caps are near-unobtainium, I'll try the Sprague 716p Orange Drops, which are very similar in construction.
I have to say though that these Black Gate N non-polar caps are sounding very sweet. I also like the fact that they fit on the board. By the way, I had bought Lorde's "Pure Heroine" on vinyl for my son for Christmas, and it really does sound great.
(http://www.audiocircle.com/image.php?id=114554)
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The amp seems to love Belden 8412 brilliance from Parts Express. You use the two inside wires as one conductor, and the shield as the other.
Let me know when you are putting another one of these together and I'll send you some of my wire (for free). It is a four 9's pure Copper in polyethylene. I think you'll like it a lot better.
Get rid of those binding posts and try some tube connectors and you'll be real surprised too.
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Considerable more capacitance will help with bass too. There's no way to mount more on the board, but just off of it will help.
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The real bread and butter is a capacitor multiplier on the DC input. My kit (delayed due to theft) features one. But it works well in conjunction with some high end OSCON caps like the 3116 uses.
Hello, can you please post more details on the capacitance multiplier?
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It's a variation on this (http://www.diyaudio.com/forums/power-supplies/177516-keantokens-cfp-cap-multiplier.html).
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I like the modded 7297, is there a simple changing of resistor that will increase sensitivity of this amp?
when I play from my PC, I have to turn up the volume to max to hear in my small bedroom. When I play from my desktop CD player it is loud enough half way turned up. Can any of the electronic guru suggest replacement part etc?
I will attach datasheet, thanks, oops can't attach a .pdf file...
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The amp will be at full volume at 1.1v or so... there's nothing to change on it besides removing the potentiometer. I suggest checking computer settings. You can also increase the voltage to the amplifier for a bit more power.
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The amp will be at full volume at 1.1v or so... there's nothing to change on it besides removing the potentiometer. I suggest checking computer settings. You can also increase the voltage to the amplifier for a bit more power.
got it, thanks.
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Hi Salis,
What would you suggest the maximum voltage be set to?
I love this little amp. and have applied most of your modifications to date.
Thank you in advance.
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If you have a unit from China then I'd be wary about 17v. Even then some say 12v.
However the chips I ordered from Mouser take a lot more. In fact I had one run at 23v for a week and half. I turned it back down, but it seemed fine. Maybe it wouldn't last forever, but it sounded real nice.
The PDF says 18v top of the range, and 20v max in another location. That's a bit confusing. I guess I'd run 18v on a Mouser bought chip, and 20v if I wasn't worried about soldering in another/made a socket. The ones from china, well, 17v tops I recommend. I had two stop working by hitting just a smidge over 18v spikes from bad power.
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What's the recommended volume control impedance? I think the chip is like 30k right...so something south of that, ideally? Like 10-20k?
Thanks,
Jim
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10kohm is about as low as you can get. Alternatively you can use a buffer between them.
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10kohm is about as low as you can get. Alternatively you can use a buffer between them.
Yeah, 10k is as low as I've seen to...but is it the ideal value here (I've got one on hand, that's why I ask)? No buffer in between.
-Jim
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Hello, I would like to ask for some help.
I bought a TDA7297 amplifier (http://www.banggood.com/ACDC-12V-2-x-15W-TDA7297-Version-B-Digital-Audio-Amplifier-Board-p-917242.html (http://www.banggood.com/ACDC-12V-2-x-15W-TDA7297-Version-B-Digital-Audio-Amplifier-Board-p-917242.html)) and I tried 3 different power source (DC) and I got no bass.
I tried with
5V DC 1A (USB), no noise, but no bass
12V DC 12A (XBOX360 PSU), big noise, no bass
8.5V DC 1.5A (Camera charger), big noise, no bass.
Could you help me Guys why I have a crap sound quality? I read everywhere this amplifier have good sound quality , but not for me. :(
Thanks!
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You need bigger input capacitors. Try 1uf film caps. 12v will the better.
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Hello, I would like to ask for some help.
I bought a TDA7297 amplifier (http://www.banggood.com/ACDC-12V-2-x-15W-TDA7297-Version-B-Digital-Audio-Amplifier-Board-p-917242.html (http://www.banggood.com/ACDC-12V-2-x-15W-TDA7297-Version-B-Digital-Audio-Amplifier-Board-p-917242.html)) and I tried 3 different power source (DC) and I got no bass.
I tried with
5V DC 1A (USB), no noise, but no bass
12V DC 12A (XBOX360 PSU), big noise, no bass
8.5V DC 1.5A (Camera charger), big noise, no bass.
Could you help me Guys why I have a crap sound quality? I read everywhere this amplifier have good sound quality , but not for me. :(
Thanks!
Had a similar prob, cured with astron linear power supply.
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Had a similar prob, cured with astron linear power supply.
That's a great solution, but the input capacitors will give you bass down to 20hz, as opposed starting to roll over prematurely. The stats say it can do -3db at 20hz, but not with .22uf capacitors on the input.
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I've read that TDA7297 is balanced, as opposed to single-ended. I've also read that the inputs share a common ground. This seems to be contradictory, unless I understand "balanced" even less than I thought.
My Pono player plays modified (no common ground) headphones in balanced mode. I'm concerned that using Pono as a balanced source for this amp might harm the Pono player. Any insights are appreciated.
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(http://www.audiocircle.com/image.php?id=144723)
I removed the diodes and installed solid core Copper wire jumpers in their place. The improvements in frequency extension, better dynamic response and detail were subtle, but worth the effort. If anyone has this amp and has a decent DC power supply, this is a worthwhile mod.
I have removed the pot and will like to use just as a power amp (always at maximal gain), I plan to use it with moode audio software which include a volume control. What connection or mod is needed?
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I would check build guide V.2
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I would check build guide V.2
checked the V.2 but did not catch how to fix the gain... I still have some parts from the first version..., plan to try V.2 in near future. Good stuff.
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The gain is always fixed. The pot is just volume.
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The gain is always fixed. The pot is just volume.
with the pot removed will it function at full volume, and allow the input device, i.e. iphone to lower volume?
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Yes
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Thanks, Jeremy. I think you broke the record for speedy shipping. I'm looking forward to building this out semi-deluxe, or at least slowly.
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Alright guys, here it is! First the parts you need. *C4 amended.
From Mouser.
Input caps, order 10x because it's cheaper than 4x (yes you'll need 4x)
647-UES1H010MDM
UES1H010MDM
50volts 1uF
Power cap 1x
661-EKZH250E222MK30S
EKZH250ELL222MK30S
25Volts 2200uF
Shunt/Mute Power cap
661-EKY500ETC220ME1
EKY-500ETC220ME11D
50volts 22uF
Building
Ok, so first I recommend getting to this point, the naked board of all the parts you don't need. That is unless you want the volume pot, but I wouldn't recommend it.
Here's a clear board, I've labeled the R and L inputs, and their grounds. R1, D1, D2, C1, C2, C3, C4 (not shown removed) C5, CN4, and RP 50k have been removed.
(http://www.audiocircle.com/image.php?id=91508)
Install a wire for the bypass of the diode (D2), I did this on the bottom.
(http://www.audiocircle.com/image.php?id=91511)
Install the Shunt/Mute cap (C3) 22uf, negative side (short lead) goes to the striped pattern on the board.
(http://www.audiocircle.com/image.php?id=91521)
Install the upside C1 and C2 capacitors, 1uf Nichicon Muse. Long leads go toward the input (as circled)
(http://www.audiocircle.com/image.php?id=91515)
Install on the bottom 1uf capacitors with the reverse orientation of the first two (long leads towards the chip), on C1 and C2. This is very important, and can only be done with non-polar caps. Without doing this your amplifier won't be that great unless you got some very nice film caps for the inputs.
(http://www.audiocircle.com/image.php?id=91519)
Install C5, the big 2200uf cap, again stripe to stripes.
(http://www.audiocircle.com/image.php?id=91520)
That's it! My next post here will be about advanced options, this is the simple, but very good build.
Use only DC power supply after removing the diode.
*do not replace C4, it's a worthless snubber that causes ringing.
So I've removed the pot and the input block and now I dont understand how I can feed it audio signal. I tried to hook up L/R to the corresponding holes on the first picture but no sound would come out, plus im very confused by the terminals you put in the last picture at the pot and line in. Please help.
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The holes marked L/R are inputs to the pot from what was the input jack. The middle holes are outputs from the pot/inputs to the amp. The left holes are ground.
I would not use the terminal blocks, and solder + to the middle holes and - to the left most holes (ground).
If you want to use terminal blocks, the connections will be more involved.
I assume you have a way to control volume; otherwise, you will be going from no sound to full volume after this connection.
Mike
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You should be following Ver. 2 also
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The holes marked L/R are inputs to the pot from what was the input jack. The middle holes are outputs from the pot/inputs to the amp. The left holes are ground.
I would not use the terminal blocks, and solder + to the middle holes and - to the left most holes (ground).
If you want to use terminal blocks, the connections will be more involved.
I assume you have a way to control volume; otherwise, you will be going from no sound to full volume after this connection.
Mike
Ok thanks, I'll try this later on.
You should be following Ver. 2 also
I would but it has to wait since there are no reasonable priced part shop in Norway, I have to gather up a chunky list for mouser.com and order everything in one go. I've also ordered 5 more of these amps plus I have a bunch of salvaged caps from old sony mini hifi system/cd walkman etc which I want to compare to the non modded ver.
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I have successfully modded version 1 in past without removing the pot and input source socket. This time I wanted to remove the pot and input socket, otherwise standard mod of version 1.
I get no audio output, replacing the amp works fine, when I turn off the power source to the amp, I get a soft click and LED indicated getting power. I have attached the input socket as pictured. Can someone spot where my mistake may be?
thanks
(http://www.audiocircle.com/image.php?id=167224)
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Picture makes it a little hard to tell. It appears like you need to jumper where the pot was for left and right channels.
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Picture makes it a little hard to tell. It appears like you need to jumper where the pot was for left and right channels.
is this correct, to jump the red line?
thanks
(http://www.audiocircle.com/image.php?id=167254)
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Yes.
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The Muse caps are bipolar. AFAIK, orientation is irrelevant and the different leg lengths simply aids in insertion.
Alright guys, here it is! First the parts you need. *C4 amended.
From Mouser.
Input caps, order 10x because it's cheaper than 4x (yes you'll need 4x)
647-UES1H010MDM
UES1H010MDM
50volts 1uF
Power cap 1x
661-EKZH250E222MK30S
EKZH250ELL222MK30S
25Volts 2200uF
Shunt/Mute Power cap
661-EKY500ETC220ME1
EKY-500ETC220ME11D
50volts 22uF
Building
Ok, so first I recommend getting to this point, the naked board of all the parts you don't need. That is unless you want the volume pot, but I wouldn't recommend it.
Here's a clear board, I've labeled the R and L inputs, and their grounds. R1, D1, D2, C1, C2, C3, C4 (not shown removed) C5, CN4, and RP 50k have been removed.
(http://www.audiocircle.com/image.php?id=91508)
Install a wire for the bypass of the diode (D2), I did this on the bottom.
(http://www.audiocircle.com/image.php?id=91511)
Install the Shunt/Mute cap (C3) 22uf, negative side (short lead) goes to the striped pattern on the board.
(http://www.audiocircle.com/image.php?id=91521)
Install the upside C1 and C2 capacitors, 1uf Nichicon Muse. Long leads go toward the input (as circled)
(http://www.audiocircle.com/image.php?id=91515)
Install on the bottom 1uf capacitors with the reverse orientation of the first two (long leads towards the chip), on C1 and C2. This is very important, and can only be done with non-polar caps. Without doing this your amplifier won't be that great unless you got some very nice film caps for the inputs.
(http://www.audiocircle.com/image.php?id=91519)
Install C5, the big 2200uf cap, again stripe to stripes.
(http://www.audiocircle.com/image.php?id=91520)
That's it! My next post here will be about advanced options, this is the simple, but very good build.
Use only DC power supply after removing the diode.
*do not replace C4, it's a worthless snubber that causes ringing.
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Yes.
But I would only run a film cap on the 7297 anymore. There's problems with electrolytic input caps on them.
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Is there a way to connect a balanced XLR source to these little amps? That would be a big deal for me.
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Are these amps still well regarded or has there time passed? looking for amps for a two way active system.
TIA
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Well, I've killed one of these already, so I thought I would reach out and see if I could get some advice from users on this thread before I abandon this board and start over. Midway through this project, it stopped producing sound.
Here's what I've done. I took one of these amps with the intention of stripping them down to get all the junk components off the board, in an attempt to upgrade to the best quality parts I could. I am running this off of battery power, and I figured for now, I would leave the power connector connected with some basic crimp terminals.
https://www.amazon.com/gp/product/B00LOG51EE/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1
First step, I removed the speaker connectors, drilled out the holes ever so slightly, and soldered wires directly to the board, which will eventially connect to some binding posts. But for now, I just literally soldered speaker wires directly. Just doing that was a noticeable improvement in sound quality, so I know I didn't kill the amp at that point.
The next thing I did was removed the 1/8" jack and the volume POT, then removed the one diode on the board and soldered a bypass wire for it on the underside, and finally, I removed the rest of the caps, (Some parts were desoldered, others were just cut because it was a little too hard to desolder, given the space on the board).
At that point, the amp stopped working producing any sound at all. Additionally I noticed that the LED stopped working as well. I'm pretty sure the amp isn't working right now because I removed too much from the board. Yes, I got a little carried away. My issue is I have no sound, which isn't exactly how you want your amp to work, unless you're listening to 4:33 by John Cage (google it for some fun trivia).
As you can see in the photos, I've connected the RCA plugs to the wires soldered where the POT was. But no combination of those worked (I'm pretty sure the left most leads are ground, but I tried the left most and middle connectors and got nothing). Now, before you just tell me, I'm fully aware the board is a little bit of a mess, but I'm confident all solder connections are good enough to not be the problem. But I'm at a loss for what the problem or problems with this board could be at this point. I'm 50% confident I fried the chip, but since they are almost free I have another I can start working on, with another 2 on their way by the weekend.
I thought, before I just start doing the same things again, hoping for different results, I would reach out and see if anybody could guide me as to what I'm doing wrong in this upgrade project. Honestly, all I want to do is replace the big CAP with a good Sonicap, dump the volume pot in favor of letting the source control volume, and hard wire my speaker connectors to the board. Those are my goals. So the first question is: what do I need to leave on the board, and what can I safely remove? There are 2 big caps, 3 small caps, 2 resistors and a lone diode. I would like to keep the LED so I know its got power, and I'm pretty sure the resistors have to stay.
Working from the assumption I jumped the gun removing the smaller of the two larger capacitors, I've replaced said capacitor, but its entirely possibly I was too hard on the cap when I removed it, and it may be dead. Still not producing any sound.
So, again, to repeat myself, my goal for this project is to see how much better this amp can sound: pull everything unnecessary from the amp (including the volume pot and the Diode that allows it to connect to AC power, as I will run this off battery power full time), and thats about it. I'd greatly appreciate any advice people have. I am already growing impatient, and want to start working on the second board, but maybe I need to slow down, and get more advice. The biggest problem Im having with this project is the original post for this thread had instructions that may not apply to both my goals, and the board Im working with, as its a newer board from a different manufacturer, but using the same chip. So, the implimentation may be a little different. I've included several images of the board, and included an unaltered version of that same board for comparison.
(https://www.audiocircle.com/image.php?id=209811)
(https://www.audiocircle.com/image.php?id=209812)
(https://www.audiocircle.com/image.php?id=209813)
(https://www.audiocircle.com/image.php?id=209814)
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Instead of wasting time and money on trying to improve the cheap import boards with the suspected counterfeit or sub par chips, why not build the tried and true Folsom amp using the same TDA7297 chip along with quality parts from Mouser?
https://www.audiocircle.com/index.php?topic=138229.0
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I appreciate the feedback, but I already own these boards. But while the folsom board looks interesting, where can you get the board? Does anybody sell it in kit form? I did some searching and couldnt find much info. That link you sent talks about indigogos from 2015 which are long expired.
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It looks like you connected your input wires to the input of the pot, but needed to connect them to the ouput of the pot (center holes).
I don't know if that'll fix exactly what's going on, but that's the first step. You also need signal capacitors. (don't want DC going to speakers)
It looks like you replaced the electrolytic with a film cap? The electrolytic, big one, is for power not signal.
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Folsom, thanks for all that. I was basically making some guesses as to what I was supposed to do here. I did eventually wire it to the middle input, but that didn't solve it.
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Drilling can ruin the holes for connection sometimes. If you figure out how the traces are connected to the holes you'll see why.
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I appreciate the feedback, but I already own these boards. But while the folsom board looks interesting, where can you get the board? Does anybody sell it in kit form? I did some searching and couldnt find much info. That link you sent talks about indigogos from 2015 which are long expired.
There's nothing wrong with continuing with the boards you have, but I wouldn't throw much money at the project knowing there's a better implementation using the same chip.
The availability of the Folsom amp and power supply boards are from Folsom when he has them. Send him an e-mail for availability. Also, post a request on the Folsom amp thread looking for boards. there are people that bought boards and never built the amp, and may sell. There is a BOM for all the parts to order from Mouser, but no kits.
See reply 1265 for Folsom contact info:
https://www.audiocircle.com/index.php?topic=138229.msg1789054#msg1789054
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I must say for the amount paid + mods its one of the Best investments I've ever made.
(https://www.audiocircle.com/image.php?id=211868)
(https://www.audiocircle.com/image.php?id=211869)
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It really is remarkable how good those cheap amps can sound. Years back, I put one in a large cardboard box and took it to a friends record store, where he sells lots of vintage receivers. We did a comparison to all the Pioneers, Marantz, Sonys that he had on display to demonstrate how the "mystery" amp was better. When I opened the box, he was dumbfounded-- and opened a whole side branch to his business, putting Chinese amps in old radios. That demo has probably made him >$25K over the next several years. He sells every old radio he can get his hands on.
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It really is remarkable how good those cheap amps can sound. Years back, I put one in a large cardboard box and took it to a friends record store, where he sells lots of vintage receivers. We did a comparison to all the Pioneers, Marantz, Sonys that he had on display to demonstrate how the "mystery" amp was better. When I opened the box, he was dumbfounded-- and opened a whole side branch to his business, putting Chinese amps in old radios. That demo has probably made him >$25K over the next several years. He sells every old radio he can get his hands on.
Nice! That's pretty cool.
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Yes.
But I would only run a film cap on the 7297 anymore. There's problems with electrolytic input caps on them.
I just got one of these amps and was going to play around with the mods. Are you saying not to use the original electrolytic caps you suggested in your original post and use film caps instead?
Thanks for sharing.
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I just got one of these amps and was going to play around with the mods. Are you saying not to use the original electrolytic caps you suggested in your original post and use film caps instead?
Thanks for sharing.
Yes. I made build guide 2 for a reason.
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. I found it :duh:
Thank You
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I got bored.
The heat sink cost many times more than the amp :lol:
(https://www.audiocircle.com/image.php?id=212604)
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Yes. I made build guide 2 for a reason.
Hi, I am new in this topic. I did the Ver 1 mod and can i just use 2 x 1.5uF to replace the C1 and C2 capacitors ? What is the reason to use 2 caps in same location with reverse orientation (bottom and up side)? Wish to use some Siemens MKL axial cap for C1 and C2. :D
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Another quick question about replacement - Shunt/Mute Power cap . Can i use 100uF instead of 22uF as stated ? Does this make any different? Appreciate anyone advise. :)