My Belles 150 is buzzing when I turn it on..

Sounds like you make have some transformer hum, a very common problem without a single/simple solution, and which poses no real problem for you if you can't hear it from the listening position. Could be the transformer has become loose, could be caused by the the incoming current, etc. You could lift the lid (after a long turn off so the amp is tatally discharged) and check the connections of the transformers to the amp frame and or your could mass load the transformers/amp lids to reduce the resonance. You could also borrow a power conditioner to see if that would help. Hope that helps........

I owned a Belles 150a Hot Rod for a couple years and it hummed anytime my power supply was polluted by line noise from appliances, etc. This amp seems inordinately excited by such noise! Try to see if you can trace any correlation to lights, motors, etc. turning on. I talked to Dave Belles, the designer, about this issue. He more or less just shrugged it off with the observation that toroids are prone to buzzing & humming in certain circumstances.

more than likely transformer noise. quite common with that model.

mike

I have an OCM 500, the older sister to the Belles 150. It used to buzz a bit when I had it plugged into a different outlet. I also noticed the buzz would change as certain other things in the room would power on or off (e.g. a vacuum cleaner).

I eventually plugged the amp into the amp outlet on the same Monster AVS 2000 as all of my other components (which are plugged into an HTPS 7000) and the buzzing went away. I know what is said about not plugging amps into power conditioning which is why I originally had it straight to wall on a separate plug, but the buzzing was too annoying for me. I don't know if it was specifically the AVS 2000 that made the buzzing stop or (effectively) putting it on the same wall plug as everything else. In either case, I'm happy with it now.