I figure I'll try an external power supply soon, since I already have a good one that I'm currently not using for anything. But I understand from Sir Nigel that his external supply didn't eliminate the PC noise anyway, so it may not make a difference. In any event, experimenting is part of the fun of this great hobby. Also, I see from some of the info on the PCS website that the center pin is indeed positive; guess I should have searched for the info before posting!
![:roll:](./../images/smilies/icon_rolleyes.gif)
At least when it comes to the PC (fan?) noise, you can't hear it when the music's playing. It's only present during a silent carrier, and even then, you only hear it when you crank up the radio almost full blast. So it's not THAT bad, mostly just an annoyance. Maybe the ultimate solution is running the PCMAX as a stand alone unit, away from the noisy PC.