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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
ariaaudio
9 posts
 
If the hum eminates from the chassis and not from the speakers then it's quite likely that the amp has a noisy transformer. You'll want to check with the manufacturer to see about getting an amp with a quiet transformer. There's nothing you can do (cheaters, screwdrivers, etc.) that will help quiet a noisy transformer.

If the transformer is not undersized, then tranny noise is usually the result of incomplete vacuum impregnation (sucking epoxy varnish or the like into the transformer under a vacuum to glue all the wires and magnetic bits together into one solid mass) and simply replacing the tranny with another one will take care of the problem. If the transformer is underdesigned -- too small for the job, running at too high a flux density -- then it's gonna be noisy no matter how thoroughly it's been impregnated.

Contact the manufacturer -- they should be able to sort this out pretty quickly.
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.
jewel_hasan's avatar
jewel_hasan
98 posts
 
A bad, leaky or not screwed in tightly capacitors can also generate hum from an amp (alone) through speakers. In my instance, the hum was a constant one. After replacing the capacitor the hum went away...

Good luck!
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