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a new amp hum problem...checked the archives

Recently, I purchased a new amp. It hums. Not just the speakers, the amp itself. The only thing I haven't done is open the amp and tighten the screws. Here's what I have already checked out -

Disconnected everything from wall except amp, then disconected everything from amp except speakers. So the only players are the wall, the amp, and the speakers. Tried a cheater plug - no help. The amp still hums and the speakers still hiss. I've plugged the amp into different outlets on different circuits - still hums.

I have noticed that the hum and hiss seem to cycle a bit - it appears to get louder and softer, but I may just be crazy. I love the sound of the amp, but can't live eith the hum. If it's an electric problem, why doesn't it affect anything else? Didn't affect my receiver (which is now a preamp). I have a HSU Research amp for my subwoofer that used to hum, but (I know, I know...) a cheater plug solved that problem. I don't know what to do.

I am very frustrated and need your help.

Thanks,

Dan
dklap

Showing 1 response by bob_bundus

bob_bundus
1,834 posts
 
I've read of a transformer mechanical hum issue due to external influences - namely lamp dimmer interferences - anywhere in the house. One other situation involved an electrically noisy vent fan that somehow excited the transformer laminations into a loud hum.
It may be possible to clamp down on the noisy transformer by adding some long bolts with large washers, effecting a "squeeze". Check to see if there are any available bolt holes? A long hose clamp wrapped tightly around might also work. Also check the mounting hardware for tightness & possibly add some rubber or sorbothane washers or footers. If in warranty then insist on a replacement xfmr. If this is a Belles amp then this is not an unusual scenario.
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