I am betting blow drive transistor
but is it really worth it? The likelihood of it being something simple/inexpensive to fix is small, and the cost of an excellent replacement is quite modest, so I think you should just bite the bullet, so to speak.
If one of the transistors dies then you only get "pushing" or pulling". Without the current draw from its complement, the surviving transistor is starved for current and its gain is greatly reduced. More importantly, either the positive or negative lobes of the waves are practically cut off, making for a severely distorted waveform with lots of nasty overtones.
I'm having issues with my mid-90s Sony solid state amp.In particular the right channel is of lower volume (~-12dB in my measurements) and the sound is distorted in a way that there is noise added when I feed a signal to the amp. On silent parts, there is no additional noise. I ruled out the signal source and the speakers as the cause, it has to be the amp. I looked inside to see if I can find burned components, but I haven't had luck yet. I can't see the whole circuit board without disassembly (which I haven't done yet) though.I uploaded a file here, with the following setup:sound card output -> amp line level input; amp speaker out -> sound card line level input & speakersCould anyone give me hints where I should look for the defect? Is this typical for some specific defect?Thanks a lot!edit:link now pointing to upload thread
I downloaded your files and don't get the same FFT spectral analysis showing a rise in the noise floor when tones are present.In my spectral analyses, the noise floor stays about the same whether or not the tone is being added. I can obtain spectral plots like yours by including the areas where the tone turns on or turns off.
Thank you for your opinions. Seems I (sort of) solved the problem today. I wiggled the Input/Source selection PCB with it's electric source selection component and the noise was gone. The channels are 0,9 dB apart now. So it seems to be either mechanical (something inside source selection mechanism) or solder joint related. As soon as I have a free weekend, I'll pull said PCB out and resolder suspicious joints (if I can find any) and/or clean contacts.