I had some noise in my 4 surround speakers (60 Hz hum mainly). I tried to bust it thinking it was a ground loop, but was unsuccessful. Anyway, the solution I came up with was to increase the level calibration of the 990 to +10 in those channels, and then back down the amplifier trim levels appropriately (Adcom GFA-2535) to increase signal to noise. It worked, even with my ear up to the speakers I cannot hear unacceptable noise, let alone from the listening position.
I noticed this today I tried to turn my system up loud, and it only went to +1. And this was on bypass mode so the surrounds weren't even active. Besides striking a compromise by turning back down the level calibration, any ideas?