I've tried the knob straightup (halfway) to full playback. If I have it all the way to "input" I can't hear it out of the headphones. I've also set the settings to my Audiobox USB. I can record fine, playback fine, hear the playback through the headphones, just nothing out of the main output jacks, no matter where the main volume or the mix knob is set. The symptom is the same with live monitoring also. Just can't get anything to come out of the Main 1/4" outputs.