Have had macbook pro for 6 months and love it . Djing for 17 yrs and going digital . Run numarks cue version of virtual dj and use djio external sound card so I can use 2 channels on the clubs mixer (rane mp24) . When I configure it it comes out muffled and distorted on the channel that uses usb port. I've tried 3 other sound cards and the same is happening . The usb port works with ipod and camera. Any advice would be GREAT .