Just bought a Harman/Kardon 330B receiver. I've noticed that sometimes when I press the power button there is an audible boing noise that seems to be coming from the left side of the unit, that can also be felt. Does anyone knows what this could be?


If it is an older amp (and that one seems to be), my guess is it's probably rapid charging of the large capacitors in the power supply causing a brief current surge in the power transformer. Most likely it has always done it and not usually a problem...

  • And this is why many amps have a standby mode during power on to allow this, before then switching to fully on. – Rory Alsop Oct 14 '16 at 22:43

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