Hey all, please bear with me on this: I run sound in a small bar/venue, and everything was ghetto-rigged when I took over here. The other day I was in the ceiling running new power cables for the front of house, lights, and an RCA pair from our Yamaha MG20c's REC out to the house stereo so DJs and bands can be heard on the outdoor speakers. Due to a weird spacial setup and lack of power outlets, I decided to run the FOH speakers (Active JBL Eons) and the lights (2 par cans) to a single extension cord in the ceiling that drops down to a rocker panel and power conditioner in the rack. Everything is fine when I power up the speakers and lights (now all terminating at one extension cord), but as soon as I switched the house stereo to the AUX input coming from the board, I get a nasty 60 cycle hum from the house stereo, but not the FOH. I unplugged just the lights- no hum. Plugged in the lights, but didn't turn them on- hum. Ran the RCA out to the stereo with the FOH and lights unplugged, no hum. Did the same with them plugged in, but off, got the hum again. The RCA is about 75' and does not run across the power cables anywhere. Am I creating a weird feedback loop or something? Any ideas about what could be causing this and how to fix it? I'd prefer to have as few cables as possible coming from the ceiling, as we really have no way to hide them (historic building, can't do anything to the walls or floor). I'm fine for now without running to the outside speakers, but it is something I've wanted to do for a while now, so any help would be greatly appreciated!