TDA7297 Build Guide

Dunk_c · « **Reply #161 on:** 11 Apr 2020, 09:52 pm »

The Muse caps are bipolar. AFAIK, orientation is irrelevant and the different leg lengths simply aids in insertion.

Quote from: Folsom on 15 Dec 2013, 09:27 pm

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.

Install a wire for the bypass of the diode (D2), I did this on the bottom.

Install the Shunt/Mute cap (C3) 22uf, negative side (short lead) goes to the striped pattern on the board.

Install the upside C1 and C2 capacitors, 1uf Nichicon Muse. Long leads go toward the input (as circled)

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.

Install C5, the big 2200uf cap, again stripe to stripes.

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.

Folsom · « **Reply #162 on:** 11 Apr 2020, 11:59 pm »

Yes.

But I would only run a film cap on the 7297 anymore. There's problems with electrolytic input caps on them.

patricksalter · « **Reply #163 on:** 13 May 2020, 05:51 am »

Is there a way to connect a balanced XLR source to these little amps? That would be a big deal for me.

Pookie_ears · « **Reply #164 on:** 29 May 2020, 07:29 am »

Are these amps still well regarded or has there time passed? looking for amps for a two way active system.

TIA

patricksalter · « **Reply #165 on:** 1 Jun 2020, 10:04 pm »

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.

lacro · « **Reply #166 on:** 2 Jun 2020, 09:05 pm »

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

patricksalter · « **Reply #167 on:** 2 Jun 2020, 09:36 pm »

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.

Folsom · « **Reply #168 on:** 2 Jun 2020, 09:39 pm »

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.

patricksalter · « **Reply #169 on:** 2 Jun 2020, 11:12 pm »

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.

Folsom · « **Reply #170 on:** 3 Jun 2020, 01:27 am »

Drilling can ruin the holes for connection sometimes. If you figure out how the traces are connected to the holes you'll see why.

lacro · « **Reply #171 on:** 3 Jun 2020, 03:01 pm »

Quote from: patricksalter on 2 Jun 2020, 09:36 pm

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

devious17 · « **Reply #172 on:** 15 Jul 2020, 01:22 pm »

I must say for the amount paid + mods its one of the Best investments I've ever made.

S Clark · « **Reply #173 on:** 15 Jul 2020, 02:10 pm »

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.

Folsom · « **Reply #174 on:** 15 Jul 2020, 02:30 pm »

Quote from: S Clark on 15 Jul 2020, 02:10 pm

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.

AlexH · « **Reply #175 on:** 24 Jul 2020, 09:45 pm »

Quote from: Folsom on 11 Apr 2020, 11:59 pm

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.

Folsom · « **Reply #176 on:** 25 Jul 2020, 03:09 am »

Quote from: AlexH on 24 Jul 2020, 09:45 pm

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.

AlexH · « **Reply #177 on:** 25 Jul 2020, 03:41 am »

. I found it

Thank You

devious17 · « **Reply #178 on:** 1 Aug 2020, 04:32 am »

I got bored.

The heat sink cost many times more than the amp

ycliew79 · « **Reply #179 on:** 26 Aug 2023, 12:13 pm »

Quote from: Folsom on 25 Jul 2020, 03:09 am

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.