Classe Amp buzzing/humming...any ideas??

I had a similar problem with my previous Classe CA-150 and Krell KAV-250a amps. I knew the toroidal transformer was humming, but could not figure out why. After much fussing, I finally found that the 125A service panel for my house was defective. It had some loose connections, and parts of it were literally beginning to burn up because so many circuits had been added. I replaced it with a new 200A unit, and have had no problems since, along with a much lower noise floor as well. If you have the ability to do it yourself, it should cost about $300. If you pay a professional, expect about $1700 to $3000. I decided that was just too much money, so I did it myself, but don't try it unless you are absolutely certain you know what you are doing...it can be too dangerous. Good luck.

After the recommendation of Classe, I opened the unit and checked the bolt holding the toroidal trans. and it took about 1 1/2 turns. The problem seems to be reduced. Oh, Glen...there were no birds inside, but thanks for your help! Has anybody ever trie the AH! A/C offset killer?

You may have a DC off-set somewhere. I get the same with my CA-200 when a floor standing halogen light is on "half-power". If I turn it off or to full power, the buzzing goes away.