2. amps-preamps
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Belles amp hum ... rf problem?

Hi all. I have a noticeable hum problem which I have isolated as coming from my power amp, Belles 150a hotrod. The amp hums when I have it plugged into the wall with nothing else attached. The hum is not always present. I'll go a couple days without it and then it will re-appear ... comes and goes. I called David Belles and he told me the issue was likely a quality of electricity problem which was exciting the torroid transformer. (I live in a large apartment building in Manhattan.) He recommends a RF filter. Can anyone recommend a RF filter brand? Would something like a Blue Circle Noise Hound or PS audio ultimate outlet/power conditioner serve this function? If it is a electrical problem I don't think it's coming from within my apartment. I've unplugged everything that I can and the hum persists. Help it's driving me crazy. I may be imagining this but when it does hum the system doesn't sound as good. High frequencies are really grating. Thanks in advance for any suggestions.
tooter

Showing 5 responses by tooter

tooter OP
85 posts
 
Hammer 223, as unappealing as it may seem, I would recommend checking/replacing your dimmer switches in your house. I had 3 dimmer switches in my house and after exhausting all other options I finally took these out and replaced them with regular on/off switches and my hum disappeared!

On another note, did you compare the 21A preamp to the 20A preamp before settling on the 21A? I'm interested in trying a tube preamp for my 150A hotrod but am tight on funds and am wondering how much of difference there is between the two.

Tooter
tooter OP
85 posts
 
Hi Ryno. Thanks for the suggestions. Checking the transformer to see if it was mounted properly was the first thing I tried. Everything is nice and tight there. I also tried a cheater plug on the PC to lift the ground but that didn't do it either.

Do you think it's possible that an improperly grounded outlet would cause a hum? My Manhattan apartment building is pretty old (pre-war) and I have a feeling the wiring may not be ideal. I don't know much about the electrical end of things as you can tell ...
tooter OP
85 posts
 
Thanks for the responses guys. Actually I have 3 lights in my apartment that have dimmers but I always make a point of turning them off when I am listening to my system. Is it possible they are putting garbage into the line even when they're off? I think I will try replacing the dimmers with regular on/off switches.

If it turns out not to be something in my apartment causing the problem but say my neighbor. Would something like a power regenerator fix this? I've always been told not to use any sort of conditioning on my amp but I don't think I can live with this hum. If it's quiet, I can hear the hum across the room, 20 feet or so.
tooter OP
85 posts
 
One more question ... Are all torroid transformers equally susceptible to this electrical hum? Does it have to do with the size of the torroid or is it more related to how the amp is built/designed? I guess what I'm trying to get at is, in the future if I decide to change amps am I going to have the same problem? Thanks.
tooter OP
85 posts
 
Thanks for the tip Rhyno. I definitely would not have thought to try that. Hopefully I can get this figured out quickly!

Tooter
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