Ground loop issues? Slight hum? Ok, what are the ground loop issues, how does one correct them and since it is not an issue with Amp, what causes the hum in the amp? Connections? Wiring? speakers?

BTW: When researching the other forums (especially Rotel)I have found that when making comparisons between the two Pre-/Proc.s are generally between their 1068 and Outlaws somewhat dated 770 (or is it 750), however, I have yet to see anything posted on Rotel forum comparing the 990 vs. the 1068.

THINGS THAT MAKE YOU GO.....HMMMMMMM!