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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 4 responses by logan7

logan7 OP
4 posts
 
What do you mean by tack? Considering that the noise has a very distinct pulse to it, I'd expect there's a more fundamental underlying cause, and that just dampening the vibration would be going after it directly.
logan7 OP
4 posts
 
Yep, it's toroidal. I'll open it up and see what I can do. It was bugging the heck out of me last night, very clearly audible from across the room.
logan7 OP
4 posts
 
I picked it up on ebay for $135, so I don't have much invested in it. I wouldn't be able to hear it over music, but it was audible while watching TV due to the pauses and breaks in the audio. I'll probably just live with it for a while and upgrade to something a bit nicer a few months down the line.
logan7 OP
4 posts
 
Yep, I that's what I was doing. RCA outs from the directv box to a Marantz AV7005 and into the H/K, with the TV speakers set to zero. I would be running everything HDMI through the Marantz but I don't have cables long enough yet. I'm going to be rearranging the whole room over the next couple weeks, so it's possible that a new outlet and/or different location in the room could clear it up.
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