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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.
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Showing 2 responses by bigtee

bigtee
803 posts
 
If anyone in your vicinity has a light dimmer or similiar device around(off of the same feed in your building) or in your apartment, this could be the culprit.
I looked for a week trying to find why my Belles amp had a humming transformer. Part of the time it was dead silent, then it would hum. I finally traced it to a Leviton dimmer in one room of the house. I replaced that switch and it hasn't hummed since.
The switch does not need to be on the same feed from your breaker. My amp was upstairs on a dedicated 30 amp service. The switch was downstairs on a 15 amp line.
bigtee
803 posts
 
Belles mounts his transformers very well and they are isolated. Unless the transformer is physically defective, I doubt that is where the problem is. It's something coming in on the line. Otherwise, it would hum all the time.
Good question about whether they all would do this. Most amps I've used in the past had an E-core.
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