Ok, I thought maybe the input cable to that amp was picking up noise, so I put a very high quality shielded cable on it. same problem,the amp comes on if the air conditioner turns or, or I flick the wall fan switch, and the amp goes on. So, I tried braiding the cables. same problem. Next I tried my iPod, and that works fine. Soon as I plug the cables back into the Mac I get the problem. So I guess the noise is coming straight through A/C connections. Is there anything (short of finding another outlet), I can do to filter this out?