I built out some TDA7297 amps

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Danny Richie

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I built out some TDA7297 amps
« on: 2 Apr 2014, 10:52 pm »
Thanks to Scott Clark for sending me these little amps to play with.

There is a big thread on these in the Cheap and Cheerful circle. http://www.audiocircle.com/index.php?topic=122152.0

When I first listened to a stock amp I knew it had potential. It did sound really good considering how cheap the volume pot was and all the cheap connectors with steel screws, etc. I knew there was a lot of upside potential as it was easy to see a lot holding them back. I really didn't need more amps, but these would be ideal for burning stuff in. And they are so efficient that they could probably play for weeks on my 100 amp hour battery that typically power my little tube amps.

I pretty much stripped these things and got rid of almost all of the parts on them. And since my Dodd pre-amp has coupling caps in the output I really didn't need additional coupling caps for the input of the amp. I used two of them to make some mono-blocks using just one channel on each amp. This improved stereo separation. And why not. They're dirt cheap.

Just getting rid of the junk on the board and using good quality wire and connectors really went a long way. I used a Cardas RCA input and connected it to the board with Vampire's continuous caste Copper wire. For power in I used a Neutrix connector and our 16 gauge solid core OFC wire with the polyethylene jacket. It is the same stuff I use for internal speaker wire. I used the same wire on the outputs to tube connectors. I had to drill out the holes on the board for the bigger wire and then scraped the varnish off of the back side of the board exposing the bare Copper underneath. So the larger wire was inserted through the holes then bent over against the Copper trace and soldered on. I then doctored the top side with some hot glue to help hold the wires in place. 

And I made some neat little wood boxes for them and veneered them in some scrap I had left over from an old project. The box has holes drilled in the bottom right under the heat sink that the chip is mounted to and matching holes drilled into the lid. So air can flow in and out of the box.

I made some little amp stands for them too.



And yes the veneer is book matched. So the amps match on all sides.





The tube connectors are on the outer facing sides.



I have to also thank Dave Elledge for the mini-battery buss for each amp. That has to be really helping as well.







Okay, how do they sound? So far pretty stunning, and they are still burning in and opening up. I also had Electra Cable make me a new set of speaker cables with the tube connectors on both ends. The speaker cables are still burning in too... So more on the sound after some more time on them. Right now they are just about 40 hours in.

I think I need to add tube connectors to all of my amps now.

And I didn't put an on/off switch on the amps. I have one on my big battery. So one switch turns them both on or off.

No, they are not for sale and I am not building any more of them. They doesn't cost anything to buy the little amp to start with and you can copy what I did for next to nothing. I'll sell you some tube connectors and wire.  :green:


Folsom

Re: I built out some TDA7297 amps
« Reply #1 on: 2 Apr 2014, 11:13 pm »
I wouldn't use the bypass cap of the coupling/psu caps. There's nothing to damp resonances. Do you have 3 sizes?

If you're dari g you could cut the trace to one VCC leg, and add a second set of capacitors  8)

Folsom

Re: I built out some TDA7297 amps
« Reply #2 on: 2 Apr 2014, 11:14 pm »
Oh, they look great btw  :thumb:

S Clark

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Re: I built out some TDA7297 amps
« Reply #3 on: 2 Apr 2014, 11:15 pm »
You're more than welcome, Danny.  They really are a good sounding amp, not just a good amp for the money.
That's some nice veneer on those boxes.  :thumb:

dBe

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Re: I built out some TDA7297 amps
« Reply #4 on: 2 Apr 2014, 11:39 pm »
Pretty cool, sir  8)

I got 4 of them to make two vertical 2 channel mono amps.... someday.  That way I can parallel the inputs/outputs on each amp and have enclosures to house each side and do a true dual mono double vertical amp thing for 60W/channel.  With a little work I can just barely cram two of them into the enclosures I use for the BatteryBUSS.

How much fun.

D

dBe

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Re: I built out some TDA7297 amps
« Reply #5 on: 2 Apr 2014, 11:44 pm »
Do you have 3 sizes?
Yes, he does.  There is one that is 6800ufd, one 2200UFD MUSE and two 100ufd Rubycons with a .1ufd PP bypass.  I know that the textbooks all say not to do that, but these work... in that configuration only.  Don't know why they do, they just do. :dunno:

Dave

Captainhemo

Re: I built out some TDA7297 amps
« Reply #6 on: 3 Apr 2014, 01:37 am »

I've been following the threads over in the C&C circle, lots of high praise for these amps, both these as well as the TPA 3110 and 3116. . Have been  curioous about  trying something similar to this myself   My limited eye sight has me a bit  hesitant about   jumping in and playing with  these little guys.  Also wish I  already had a decent battery /  charger or PS on hand ....
Anxious to hear your impresions Danny once you have  some more time  on them

I agree with  Salis,  they look great , nice job  :thumb:

-jay

OzarkTom

Re: I built out some TDA7297 amps
« Reply #7 on: 6 Apr 2014, 06:14 pm »
I've been following the threads over in the C&C circle, lots of high praise for these amps, both these as well as the TPA 3110 and 3116. . Have been  curioous about  trying something similar to this myself   My limited eye sight has me a bit  hesitant about   jumping in and playing with  these little guys.  Also wish I  already had a decent battery /  charger or PS on hand ....
Anxious to hear your impresions Danny once you have  some more time  on them

I agree with  Salis,  they look great , nice job  :thumb:

-jay


With the TPA amps, I found that the Astron SL-11A linear power supply sounds even better than the SLA battery. These are about $100 brand new, 40-50 used on Craigslist and Ebay.

corndog71

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Re: I built out some TDA7297 amps
« Reply #8 on: 7 Apr 2014, 11:28 pm »
I think I need to add tube connectors to all of my amps now.

I put them on my latest project, the VTA ST120.  It was a little tricky getting them to stay put but I figured it out.




Does anyone have a recommended seller of the TDA amps?  I've seen them at varying prices but not too sure of the sellers.  Looks like a fun project.  These look like they might go well with the LGK 1.0.
« Last Edit: 8 Apr 2014, 12:03 pm by corndog71 »

Danny Richie

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Re: I built out some TDA7297 amps
« Reply #9 on: 8 Apr 2014, 12:06 am »
I put them on my latest project, the VTA ST120.  It was a little tricky getting them to stay put but I figured it out.

Looks good. Did you notice any change in how it sounds?

Oscillate

Re: I built out some TDA7297 amps
« Reply #10 on: 8 Apr 2014, 12:17 am »
"... on my 100 amp hour battery that typically power my little tube amps."

Danny, could you please link to the battery(ies) you use ...or perhaps make
a battery recommendation? Thanks.

Are those "my little tube amps" the blue monoblock Dodds?  :green:

Danny Richie

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Re: I built out some TDA7297 amps
« Reply #11 on: 8 Apr 2014, 12:41 am »
"... on my 100 amp hour battery that typically power my little tube amps."

Danny, could you please link to the battery(ies) you use ...or perhaps make
a battery recommendation? Thanks.

Are those "my little tube amps" the blue monoblock Dodds?  :green:

These are the amps (and pre-amp) that I run on the 100 amp hour battery.



And having a big battery on this type of gear really makes a big difference. The bigger batteries clearly sound better.

I use the 100 amp hour Power Sonic.

corndog71

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Re: I built out some TDA7297 amps
« Reply #12 on: 8 Apr 2014, 01:44 am »
Looks good. Did you notice any change in how it sounds?

I wanted to use them right off the bat so I have nothing to compare them to.  I will say this amp sounds a lot better than my last one which uses ordinary radio shack binding posts but it's probably more because it uses a killer driver circuit and bigger tubes.

I think it looks cool but then I'm a bit biased.

« Last Edit: 8 Apr 2014, 12:04 pm by corndog71 »