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Buzz coming from power amp - not through speakers

Hi, first post here. I just picked up a Harmon Kardon PA5800 off ebay. It sounds great, no issues there. However, the amp itself makes an intermittent hum/buzzing noise (ie, the sound comes out of the amp unit, not through the speakers). It fades in, peaks, then fades back out with a period of about 5-7 seconds. Sometimes it's not noticeable at all, but occasionally it's loud enough to hear even with a moderate volume level through the speakers.

Anyone have ideas? DC noise on the AC line? Basic service needed, ie new filter caps? (I'm a tube guitar amp guy, not even sure this type of amp has filter caps).
logan7

Showing 1 response by gakman

gakman
60 posts
 
Hi, I don't know if you solved your issue but a while back I went through some similar problems with my Classe CT-2300 and to a lessor extent an Acurus A200 used for surround channels.
Some phone time with Classe tech support and through some experimenting, it was decided that my Plasma television was introducing DC into the AC line.
I have since plugged the television into a different circuit altogether, and my complete audio system is on two circuits on the same power leg.
My amplifiers are quiet and my system sounds great.
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