Output knob on the front only adjusts the level going to the headphone jack and rear output jacks. You have to adjust the digital levels in the I/O menu or on the grid itself. Check the input and output level meters on the STATUS page of the UTILITY menu to make sure your levels are not too high or too low. As for the USB monitoring level, you have to adjust the output level from your DAW. There is no on-board adjustment of the return USB feed. Also, make sure you leave a bit of extra headroom when you setup your presets, since the extra audio input from the USB return feed can cause output clipping if it is too hot.