Use a 1/4" TRS for line level inputs to this unit!
The XLR input is for the mic preamp...phantom is turned on and off in settings...you will brickwall most line sources if ran on XLR's...note there is a little red light on left side of the LED level meter that lights when you brickwall the Mic Pre.
There are mic and line level adjustments...the two small posts adjust mic pre and the large dial within a dial adjusts the line level gain...