Hi to all.
I am not an expert, but I noticed something similar in my system (still SS) after clean all the connection (RCA and Power) the sound was gone, then came back again, after increasing the volume to notice where the bad connection can be moving all the RCA and power cords the noise was present louder, and suddenly my wife told me, as soon I turned the lights on the sound came out your speakers. Voila! the dimmer is putting noise in the line or RF, not sure yet, turning of the light my speakers turn dead quiet again. now is not just when is one is only in one position of the dimming range. Min or max its fine.
my 2 cents
Cheers from Fla.
Andre.