MAC Noise

Not normal - seek a tech. Arthur made a good contact suggestion.

I would send it back to McIntosh they are very reasonable and that would assure you that is leaves them as it did when it was new.

What type of speaker do you use. If they are high efficient, this may be the nature of the beast. I have the same 'problem'. I turn the amp 1/2 way down when I'm listening at low levels and crank it when I'm rocking. The high volume levels mask the hiss that I expeience and I have no problem. I sounds as though you have the same.