Not sure how you expect us to help here..where do you hear this sound? is it in the headphone output as well as the main outs on back... does it happen only when the Audio box is connected to the computer? what position do you have the gains for the inputs set to? what happens when you turn the gains all the way down? what position is the 'source' knob in... input, or playback or centered? and what happens when you go fully clockwise, or counter clockwise? You see there is a LOT of possibilities here. Be as specific as possible what exactly has happened here... is this a new issue? is this a new device? did it ever work properly? maybe you can see why I'm confused.