flyingtele

No it doesn't, and that's the problem. I am not sure if the audio signal is not modulating the power supply buck converter to track the output waveform, or if there is a fault in the audio output stage that is preventing the signal from passing through correctly, and the power supply rail voltage isn't changing simply because there is not enough gain. I did scope the audio signal from the preamp board to the main board and there is plenty of signal there. Do you know where the power supply modulation gets its signal from? Is there a control line from the preamp, or does it just 'listen' to the main amp output?

Hello ngem33r, and firstly let me say thank you for such a helpful and informative thread. I work as an electronics repair tech and have also repaired many different BASH amplifiers, however this one has me stumped and I'm hoping you may be able to help. It is one of the Klipsch Synergy Sub 12 amps, that seems to feature on this thread the most. Problem with it is very low level audio only when gain control is at max. I have confirmed the power supply is working, measuring the two resistors by the ribbon connector I'm getting approx 3.43 volts from each rail to ground, or ~6.5 volts between them. Is this within spec? I have replaced Q5, tested the zener and its holding 13v drop, and I have replaced all capacitors. I removed the BASH board and tested all components individually and they all check out OK. Could this fault still be in the BASH drive circuit or is it more likely to be a fault in the output stage? Any thoughts or recommendations would be greatly appreciated.