So I'm using my UMC404HD with ableton live. I have 2 mics going into inputs 1 and 2 and I have a guitar and a bass plugged into inputs 3 and 4, respectively. I also have a keyboard plugged into the midi import. When my band gets together to jam and record, it sounds absolutely fantastic except for a huge scratching feedback that occurs around once every 3 minutes. I don't know if this is an issue with either the mics or the instruments but the feedback is never audible on the midi track. If anyone has any ideas on how to fix this please let me know. Other than the occasional feedback, my 404HD is working like a charm and sounds fantastic.