Hey, I was doing a live recording last week, and whenever the MBP was plugged in with the power adaptor, there was a huge buzz/hum coming through the house PA and in the recording. This didn't occur when on battery. The setup was the MBP, with an external M-Audio Firewire 1814 (bus powered), with two microphones plugged into it going through a snake (for those who don't know, it's basically multi cable). Those two were not connected to the house PA at all. There were two others, going through the same snake, that were plugged into the mixer, and coming through the house PA. When I unplugged the two microphones from the firewire interface, the buzz went away. Any ideas? Thanks.