Hey, Recently my MacBook Pro has started to crackle with music... firstly i thought it was just the quality of which my music had been recorded, or the plug that is in the head phone jack to my amp was faulty... but after playing my iPod thru the Amp... It seems that the MacBook Pro was crackling?? To be sure, I just played music thru the MacBook Pro Speakers... Still Crackling... Can any one help??? please!! 