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Amp Hum

I've got a B&K AV5000 Series II amp with a hum. It gradually builds up over about a 5 second period on startup. I've disconnected everything (preamp, speaker cables) and still the hum persists. I tried a different power cord (Shunyata Sidewinder), made sure everything else was off, tried a cheater plug, different wall socket... still have the hum. I tried the Monidal Magic thing for the cable, still the hum torments me. Is it time to take it in or am I missing something? Thanks-
scrapiron

Showing 2 responses by sean

sean
6,231 posts
 
Is the factory cord actually grounded i.e. a three pin connector ? If it isn't, you might have the polarity reversed on the plug or the outlet. This can introduce a hum into the amp which is then fed through the speakers. Sean
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sean
6,231 posts
 
This could be a lot simpler than i thought. I've run into this on other amps, including B&K. Pull the lid and check to see if the toroidal transformer is tightened down. I have seen where these were not snugged down properly at the factory and have vibrated loose in transit or over time. I would suggest unplugging the unit from the wall first though while leaving the amp on. Let it sit for a few minutes and then make sure that it is snug using the proper tools. Sean
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