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Open source layout for a TDA7293 composite amp
Open source layout for a TDA7293 composite amp
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Old 27th September 2021, 06:52 PM   #51
MalleMike is offline MalleMike  Spain
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Join Date: Dec 2018
Location: Mallorca
If you , or any other , want to read loads of opinions about different op-amps read this thread :

Shui Yuan Audio TPA3255 Modification Thread
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Old 27th September 2021, 07:25 PM   #52
joensd is offline joensd  Germany
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Join Date: Dec 2001
Location: Fürstenwalde, Germany
Quote:
Did you hear from the guy?
Yes, I heard from KalTecs; not sure if this is a company or not.
They said it is best to have the Open Loop Gain and Phase VS Frequency function of the TDA7293 and that LM4562 and OPA1656 are great opamps.
(I mentioned that I tried both in our prototype)
So not much information given which is OK.

Quote:
I'm very curious how to find the best possible Op Amp.
You obviously need an opamp that is good enough to perform error correction.
As each opamp probably needs an individual compensation that´s quite a task but doable.
Take your favourite opamp and compensate measuring THD each time you progress.
Most opamps we talk about here are quite capable BTW but an old 741 probably won´t do.

Quote:
It is a great project (TDA7293- done right?) but in quite early stage I think.
I do have a working prototype (working as in stable til full output voltage with 8Ohm load and capacitances in parallel to the load up to 1µF).
That doesn´t mean much though as I haven´t measured THD as I stated before. In its current state the controlling opamp might be so slow that the error correction is only barely working.
See graphs from the project linked in post #42.
One of the chosen controlling opamps hardly improves the THD in comparison with a single/non-composite TDA7293 which means that either the opamp is not capable enough to do error correction or it isn´t properly compensated.

So yes, early but maybe not so early.
And again, this is not a circuit to wildly swap opamps in.
You will have to perform another stability evaluation with each swap (and following changes in compensation) and measure THD.

Quote:
I read the thread but still not clear what is the best op amp to use and not much info about the performance.
I think the above should answer that too and I already stated that I can´t perform THD measurements at the moment.
And yes, as Mike said, this is a hobby and time for it limited.

If you can measure THD and want to join the testing club I could share the gerbers for the prototype. I need to ask FauxFrench first though as this is his circuit.

Last edited by joensd; 27th September 2021 at 07:49 PM.
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Old 27th September 2021, 07:54 PM   #53
WLA is offline WLA  United States
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Join Date: Mar 2021
Thank you so much for the detailed answer!
Highly appreciate it!
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