Why is amp toroid humming?


My 6 week old Belles 150A Hot Rod amp has started to emit a humming noise. The volume is such that it can be heard from 4-5 feet away in a dead quiet room. David Belles, the amp's designer, is being helpful and suggests that line voltage over 124v. could excite the toroid, as could line interference from rheostats, etc. However, the amp ran silent for the first six weeks and nothing has changed in the electrical system to my knowledge. Time of day/night makes no difference in presence or volume of hum. Disconnecting speaker cables or inputs makes no difference. Nor does changing power supply to a different house circuit. Anyone had experience with a problem like this?
photon46
I would say that the manufacturer should take it back for repair. I had an amp that hummed. It drove me crazy. It is not worth the time or trouble. Tell them you want it repaired.
I have high voltage and also had an amp hum. You can check the voltage with a radio shack voltmeter. You might also check to see if it's a ground hum coming from your Cable TV (if that's hooked to your system in any way). If those aren't the problems, it's probably the amp.
I would keep on to the manufacturer until you get the "hum" problem resloved. I am sure David will work with you on this. In our own experience (and assuming your supply line voltage and frequency are within limits of THE UNIT) we have found that very often a simple "dressing" of the transformer and wiring can solve this type of problem in most cases. This involves unbolting the transformer and mounting rubber bushing(s) and metal plate cap, turning the transformer thru 90deg and then re-assembly. The transformer wiring can be braided if possible or "dressed". If you are qualified and capable of working on the unit then you can undertake the work yourself, but as the unit is only six weeks old you should fully discuss this with David regarding warranty, etc. Don't attempt opening the unit unless you are qualified! Hope this is of help to you...?? Richard, www.vantageaudio.com
I don't know why they hum, but I've had 4 amps that drove me various states of crazy. I sold two, one is low level enough that I can live with it, but the fourth, a Sonic Frontiers tube amp, can be heard at 15-20 ft. in a quiet room. So, after talking to the SF Tech. Rep.-- he said the amp should not hum, and to send it in. Good Luck. Craig.