[gychang]

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...

[gychang]

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?

[gychang]

can anyone direct me to source a low profile so I can put it in a slimmer case?, like the modded amp a lot.

[Danny Richie]

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.

[rhing]

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.



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.

[Danny Richie]

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.

[Folsom]

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.

[mboxler]

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

[rhing]

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.

[Danny Richie]

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.

[Folsom]

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.

[keith_correa]

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?

[Folsom]

It's a variation on this.

[gychang]

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...

[Folsom]

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.

[gychang]

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.

[elb]

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.

[Folsom]

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.

[JDUBS]

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

[Folsom]

10kohm is about as low as you can get. Alternatively you can use a buffer between them.