this is a followup from the other thread I started,
I have a 7.2 system driven by a tsr-608
with RCA's I feed a QSC usa 400, and a precedent series 400 for power to sub and couch effects respectively
the system is silent if I simply switch off power to the qsc
in standby (ie everything on, but no source media playing) there is a hum from the sub, that comes and goes, varies in intensity, occsionally with a wah wah effect as it comes in
I am running the qsc bridged, off channel 1. and while playing with it today, (heence the post) discovered that the hum is changed by moving the gain pots
minimal hum is achieved with the channel 2 pot turned all the way up, and the channel 1 pot in the middle position, with hum increasing turning it either up, or down, from there.
I must say, I am starting to think this has nothing to do with ground, but rather trouble inside the qsc