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
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
hammer_223
2 posts
 
Problem solved! I contacted David Belles, he understood my problem right away, and immediately sent me a pair of "RC snubbers" (his term) that easily installed over the amp binding posts. Slipped them on in 1 minute, turned on the power, hum was gone! I did not discuss the problem in detail with David, but I suspect the RFI from the toroidal transformer was the culprit. I would guess that these filters were not installed "stock" in order to maintain purity of design, since probably not all systems, and particularly speaker cables, would be as susceptible to the interference as my particular setup was.
jelliott78's avatar
jelliott78
39 posts
 
interesting, my hotrod 150A just blew up this past monday out of now where. i was making dinner my music selection had ended and out of nowwhere a large hum and popping sound on the right channel. so much power went to the right channel that it caused my warning LED to come on in my 2ce sig II. i quickly turned the amp off waited turned it back on same thing. unhooked righ channel turned amp on left channel was fine. powered down then hooked right channel speaker to left amp channel and bam, no power at all the amp would not even power up. as we speak it is on its way to david belles himself under warrenty to fix the oddity. . hmmmm
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