I use a Dell Inspiron 5100 on the job and at home. I use a MidiSport USB cable for midi, but when I want to use mp3's I plug a heavy duty 1/8" stereo plug into the headphone jack with either two RCA jacks or a stereo 1/4" jack on the other end to go to the PA. Any wiring setup I use causes a hum. I can't seem to find the right combination of sheilded/polarized or whatever. I have good, Hosa and Conquest cables, but still have plenty of hum. Any help.