Last night myself and a senior sound technician were running sound for a play rehearsal in a church gym. (NO the acoustics DO NOT suck). We're running two combined snakes, 24 channels, 4 returns, probably 250 feet of snake. We're getting inherited noise from the cable length I assume, because we have a lot of noise when channels are gained too high, we're having to drive the instrument and mic outputs hot so we aren't gaining to hot at the board. Problem--two of our three wireless mics are running very very strong hum and noise. Worse than any channel, and the cable runs are actually the shortest on these two channels. We've tried ground lift/ground switch (yeah..everything's on the same ac circuit). My suspicion is the receivers are located near the first electric (fact), and whenever those lights go up, the hum gets much worse (fact), I just have yet to determine if that's whats causing the whole hum problem. My other problem is I'm getting local radio through miscellaneous wired microphone channels (ie, not through the wireless microphones). I cannot get rid of it, no matter what I do.