Hi, my MBP is making a buzzing noise audible through my speakers, connected via a mini-jack to phono from the headphone jack. I originally thought the noise was a ground loop but i've tried plugging both my amp and laptop into the same wall-socket and it still buzzes, even when the laptop is running off battery. The phono cable is fine and produces no noise when connected to my iPod. The headphone jack also produces no noise through my headphones. What could be causing this buzz? I think it's processor whine as it changes depending on whether windows are maximized or if i'm scrolling a page etc. Not sure if it's relevant but comp is an MBP SR, connected via mini-jack to phono to a Marshall AS50r acoustic amp. Any ideas on how to alleviate are greatly appreciated, it's pretty annoying!