Thanks for your input. It is a well respected high power SS class A amplifier. If all will forgive me, I would prefer not mentioning the manufacturer, as I believe it is power related.
No change with a Furman IT-20i reference power conditioner...still low level buzz with or without input which gets slightly louder with volume increase. It is not on a dedicated circuit, but only a single light on the same breaker number. I just thought the Furman with it's large transformer would "isolate" from most AC impurities.
Biggest problem with the Furman is it buzzes pretty loud itself (with its transformer) but not through the speakers.
Again, not too big a deal as I am delighted with the sonics of the amp, but was hoping for near silence :)
Perhaps a dedicated circuit may be the only reliable way.
Thanks
Brian