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Acoustic Research A-04 Amplifier Speaker Thump.

When the amp is powered up or down, a loud thump comes through the speakers. Is there any mod that I can do to stop this ?
Cheers, Kev.



Acoustic Research A-04 Amplifier Speaker Thump.

That is an indication of DC getting to the speakers; not a good sign. If that amp has a protection circuit it is NOT working.
You need to service that amplifier before using it again.
PS: I just looked at the service manual and it appears there is NO protection circuit in that amp (YIKES!!!). You will need to adjust the bias at the very least; this should be done with load resistors (not speakers). If bias can't be set correctly you have a component failure in the amp.

Acoustic Research A-04 Amplifier Speaker Thump.

Thanks for your help. I will look into that. Cheers.