My Rev-A 12 inch powerbook has a weird "bug" that I can't figure out, and I'm hoping SOMEONE will have a suggestion. I often use my powerbook to listen to my iTunes Liberary though my stereo system (Phillips 5.1 tuner.) I have an RCA cable running out from the "CDR/Tape" input that terminates in an RCA to 1/8th-inch converter. When I plug this into the headphones jack on my powerbook I get a HIDEOUS audio hum. It is like fingernails on the chalk-board of my soul and quickly induces a blinding headache. (I must be extra sensitive to hum because it doesn't bother my wife.) This in and of itself isn't too weird lots of things could be causing the hum. But the weird part is if I plug my iPod or a diskman into the same cable there is no hum. And if I plug headphones or computer speakers into the powerbook there is no hum. Only when the powerbook is plugged into the stereo. Any thoughts? It is driving me slowly insane.