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Preamp noisefloor

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Michaelaudio:
Hello guys, im Michael and new to the Forum here, starting right into it with an annoying Problem.  So I designed a 2.1 Amp Board with 3 TPA3116. I soldered the parts on the pcb and everything works as expected BUT: there is a VERRY loud noise coming out of the amps. So if I turn the pots down (they are right are the input channels) the noise is gone so it hast to be Come from the preamp but I absolutley have no idea how to solve that, I hope u guys can help me! 

magic:
So many parts :scared:

Could you give a specific example of one noisy signal path? Which input the signal comes in, which ICs it passes through, which output the noise comes out?

I see at least two pots, which of them is involved?
What if you turn the pot all the way up, does the noise disappear?

Is it white noise or hum or some other crap?

Michaelaudio:
Basically the noise (white noise) appears on all inputs of the amp ic's. I can see the noise with my scope but dont know how to solve this. Tomorrow i can show a pic of my scope on the amp inputs when the pots are turned down (no noise on the outputs) vs when they r pulled up (noise increases as I turn the pots up, depending on how much i pull them up). Made a pic of the board, as u can see i had to make some improvements (schematic is Updates to the actually improvements) but I dont think thats the Problem

Marco:
That D1/D23/D24 DC biasing network is silly.

magic:

--- Quote from: Michaelaudio on July 26, 2020, 06:49:27 pm ---Basically the noise (white noise) appears on all inputs of the amp ic's. I can see the noise with my scope but dont know how to solve this.

--- End quote ---
That's easy mode - just track it down. Turn RV2 to zero to eliminate the possibility of amp IC current noise playing tricks on you. You will probably find that there is noise on the output of IC2D. See if there is noise on IC2A. See if it depends on RV1. Keep backtracking through that jungle until you see something interesting.

Could it be those zener virtual grounds? No idea...

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