$6 TDA7297 Chip Amp

randytsuch · « **Reply #80 on:** 12 Dec 2013, 12:07 am »

Quote from: Salis Audio on 11 Dec 2013, 07:56 pm

Put your meter on it, ripple, leakage, inducted, doesn't matter, it's there.

The output inductors on SMPS's can generate AC by the way. It's low, and ideally shouldn't except under heavy load, but.....

OK, I get what you're talking about. You set the meter to measure AC voltage, and measure across the supply voltage.

I would not call that AC, I would call it ripple or noise, but that's a semantics thing. I just wasn't sure what you meant, but I get it now.

Except your diode theory is not really correct. Since this is truly not AC, the voltage and current are not really changing directions, and the diode is not really blocking any reverse current. You would need a scope to see this, but the scope would show that the voltage never goes negative, so the current never reverses direction. Just because the meter says it measures AC, it doesn't really make it a true AC signal.

If I drew a picture, I would draw a small ac signal that is offset 12 or 15 volts or whatever above ground. A meter will measure the magnitude of that small ac signal, but since the signal is offset above ground there is no AC current.

Randy

Folsom · « **Reply #81 on:** 12 Dec 2013, 05:09 am »

I have no idea what you are talking about for blocking reverse current since I'm not suggesting a series device. You're not making sense. Series diodes destroy the quality of the sound is my finding with this amp.

Try it and tell me you can't obviously hear the difference.

The measurement you get is in mv, not v, by the way.

randytsuch · « **Reply #82 on:** 12 Dec 2013, 05:58 am »

Quote from: Salis Audio on 12 Dec 2013, 05:09 am

I have no idea what you are talking about for blocking reverse current since I'm not suggesting a series device. You're not making sense. Series diodes destroy the quality of the sound is my finding with this amp.

Try it and tell me you can't obviously hear the difference.

The measurement you get is in mv, not v, by the way.

Sorry, I misunderstood what you were doing and I obviously am misunderstanding your explanation of what you are doing, so nevermind.

Folsom · « **Reply #83 on:** 12 Dec 2013, 06:09 am »

No worries.

I'm still waiting on some fresh capacitors so I can post some pictures for everyone, for just doing the simple mods.

S Clark · « **Reply #84 on:** 15 Dec 2013, 01:50 am »

Took my TDA7297 to the local record store, set it under a box, and hooked up a pair of Klipsch speakers to it. The store owner was stunned. It was clearly superior to the old Kenwood receiver that it replaced. I swapped it to him for a couple of Oscar Peterson's and a T. Monk lp. I already had two more coming from China anyway, and may order a couple more for grins.
Helluva note- swapping a decent amp for three lp's and getting a good deal.

rhing · « **Reply #85 on:** 15 Dec 2013, 01:48 pm »

Quote from: S Clark on 15 Dec 2013, 01:50 am

Took my TDA7297 to the local record store, set it under a box, and hooked up a pair of Klipsch speakers to it. The store owner was stunned. It was clearly superior to the old Kenwood receiver that it replaced. I swapped it to him for a couple of Oscar Peterson's and a T. Monk lp. I already had two more coming from China anyway, and may order a couple more for grins.
Helluva note- swapping a decent amp for three lp's and getting a good deal.

S Clark, that's a great swap, and a lot of creative thinking for a win-win situation. The store owner has a better amp, and you have three great jazz LPs.

I had a holiday audio get together at my home yesterday comparing the TDA7297 chip amp to my restored and EFB-modified Dynakit Stereo 35 6BQ5/EL84 push-pull amp. Actually, it was a comparison between the TDA7297 and the combination of my Audio Research LS7 tube line stage and Dynakit Stereo 35. I ran the TDA7297 as an integrated amp. I kind of had my Stereo 35 and TDA7297 amps tucked away behind the Klispch Forte II speaker on the right hand side.

My friend John has been applying some system set-up tips from Jim Smith's "Get Better Sound" (Quarter Note Press) to speaker placement and room treatments, so he brought over his book and we played around with speaker placement and throwing large, thick beach towels over my LCD TV and glass-top coffee table in my living room. These tweaks made profound improvements, and I encourage anyone who cares about great sound quality to invest in this book.

My friends and I enjoyed quite a few nice LPs:

Paul Motian Trio, Le Voyage, ECM
Kenny Drew, Freddie Hubbard, Hank Mobley et al, Undercurrent, Blue Note (Music Matters reissue)
Tina Brooks, True Blue, Blue Note (Music Matters reissue)
Muddy Waters, Folk Singer, Chess (Classic Recordings reissue)
Pink Floyd, Wish You Were Here, EMI (reissue)

Not surprisingly, the vacuum tube amp combination won out, but not by much. The tube amps were slightly more detailed and created a slightly more three dimensional presentation. My friends liked the ability to hear the better defined separation of performers in the soundstage. Interestingly, the tube amps had a more forward presentation than the TDA7297.

My friends knew nothing about the TD7297 chip amp before the get together, so they were quite astonished by the small size of the amp and the big sounds they heard from it. They all agreed that the TDA7297 has a warm tube-like presentation, impressive dynamic response and a well defined low end. The imaging was bit more diffused compared to the tube amps. It is analogous to using a diffuser in film.

Anyway, everyone really liked the TDA7297 and I get the feeling that my friends will placing orders on eBay soon.

Folsom · « **Reply #86 on:** 15 Dec 2013, 09:43 pm »

Chang 10uf and 2200uf capacitors are within spec, believe it or not.

shadowlight · « **Reply #87 on:** 29 Dec 2013, 08:54 pm »

Do I need to install another pot or can I use it straight as amp?

Folsom · « **Reply #88 on:** 29 Dec 2013, 09:17 pm »

It's good for up to about 3kohm output impedance of your source. Not that I have any idea of what your volume device is... But that's the general 1 to 10 rule.

In other-words, straight should be fine since the chip has enough internal resistance for the average source.

SamA · « **Reply #89 on:** 4 Jan 2014, 03:16 pm »

Tracking info tells me my TDA7297 chip amp kit should be on my doorstep this afternoon. I'm looking forward to heating up the soldering iron and getting this project going. I'll report back on my progress.

rhing · « **Reply #90 on:** 4 Jan 2014, 03:35 pm »

Quote from: SamA on 4 Jan 2014, 03:16 pm

Tracking info tells me my TDA7297 chip amp kit should be on my doorstep this afternoon. I'm looking forward to heating up the soldering iron and getting this project going. I'll report back on my progress.

SamA, You'll be pleasantly surprised. Some people say that the stock amp is fine. You may want to give it an audition first depending on how anxious you are in getting started with mods.

In post #35, Salis Audio removed the polarity protection diode from the Vcc path and replaced it with a wire. I didn't do this mod until after I hosted my audio get together. The diffused, "soft" presentation that I mentioned before disappeared and the notes now have more strike and decay characteristics now. To me, the difference is like putting a higher quality power cable in the system.

Looking forward to your listening impressions.

raysracing · « **Reply #91 on:** 5 Jan 2014, 01:46 am »

My 3116 is so noisy (but sounds good in other ways) I may buy one of these too. I even added the 47Kohm resistors and the hiss is still easily heard.

SamA · « **Reply #92 on:** 5 Jan 2014, 05:42 pm »

OK, I admit it. This TDA7297 chip amp is amazing. After fiddling with it for a couple hours, I'm ga-ga at what this thing does. What it does with soundstage is inspiring, having listened to a pile of Apple lossless tracks from my iPod. I mean, this thing was $5.99 (shipping included and it arrived at 17 days via China Post) and I'm looking at my $800+ main rig wondering. Really.

I've tried two wall warts - one at six volts DC and another at 15 volts AC - and both are rated at less than 2 amps. I can't tell the difference, although I hear a bit of static when touching the bare pot knob when using the AC wall wart.

And it's driving my Odyssey Nightingale speakers with total ease. I have as yet to still crank the TDA7297 at full volume.

More listening time is required (with pleasure) before I decide about modding it with some of the suggestions posted here. This could be a keeper as built.

Folsom · « **Reply #93 on:** 5 Jan 2014, 08:10 pm »

If you're impressed now wait till you mod one... (but you'd want to find another DC source at 12v or so)

Do you have any form of power conditioning? That's when it gets really good.

shadowlight · « **Reply #94 on:** 5 Jan 2014, 11:19 pm »

I tried modding the tda7297 and sure 3110 board today. I got smoke from the Sure board while the tda7297 lights up but no sound. I think I know what the problem is with tda board. The capacitor that I tried to replace in c4 (Wima MKP4 Film Capacitors 250V .1uF 10% ) the leads were too far apart and I tried to stuff it in there and it came off. I do have a question on the tda if you remove the mini input jack. is the ground wire shared between both left and right input?

Folsom · « **Reply #95 on:** 6 Jan 2014, 12:22 am »

Yeah it's shared.

Did you see my build guide?

shadowlight · « **Reply #96 on:** 6 Jan 2014, 12:36 am »

Salis,

What did you replace c4 capacitor with?

Folsom · « **Reply #97 on:** 6 Jan 2014, 12:46 am »

I didn't, it's a bypass that needs removed.

rhing · « **Reply #98 on:** 6 Jan 2014, 02:15 am »

shadowlight, what are you using for a power supply, and have you measured the actual voltage output? I think the TDA7297 chip can only take 17-18V DC max.

shadowlight · « **Reply #99 on:** 6 Jan 2014, 02:26 am »

I am using a 12 volt battery which was what I was using before the mods for both amp.