I have this odd grounding problem I can't make sense of. The setup is a bit elaborate. I have a home recording studio. Keyboards, mixer, rack-o-effects, etc. All works great. I also have a network of 5 Windows machines. All works well. Every sound source in the room connects to a 32ch mixing console, including all of the computers audio outputs. All this works and sounds fine. I upgraded one of the machines to include an ATI All in Wonder TV/Capture card. Agaiin, it works fine at first. As soon as I plug the cable TV into the video card, a hum comes through the mixer. I can't isolate where the problem is. Some notes: - I'm in Canada - I've checked every electrical socket in the room. All sockets and power bars are showing proper wiring and grounds. - The hum occurs even if all audio sources on the mixer are muted and the mains turned down. - The hum is worse if I un-mute the machine with the TV card in it. - The cable comes out of the wall from the pole outside the house right beside this machine. If this machine is the only thing plugged directly into this cable, I still have the hum. My first guess is that there's an imbalance between the ground the cable TV has and the ground the house's electrical system has. So I figure I'll balance it by connecting the cable and the house grounds together at the source. It does reduce the hum considerably but it's still there. If I disconnect the cable TV from the computer and the formentioned ground bridge, the hum disappears. Here's where it gets weird. If I mute the computer and turn the mains on the mixing board up to half, the hum almost completely disappears. If I turn it all the way uip or down the hum increases. Any ideas? I'm somewhat stumped. Sorry if this is in the wrong place, it's an odd topic. Thanks!