When I first set up the UX2 I had sound when the guitar was plugged in, although I was getting popping/crackling noises every 10-15 seconds .To try and determine why I was getting those noises,I eliminated the possibilities of faulty cords,USB connection etc,and when I plugged the guitar in again I had no sound whatsoever.I went on youtube and played a music video to see if the UX2 box was working properly and the level meters and external speakers were working fine.I shut everything off,rebooted the computor and still no sound from the guitar input jack.