Great small headphone preamp, but the major flaw is that it is mono. It takes mono (TS) input on 6,4 jack (that would be your pedal board) and stereo (TRS) on 3,5 jack ,but at the output everything is mono. This is not mentioned in the specs or anywhere. Changing balance on the input slightly changes only the level of summed signal. What a pity. It could be nice to play mono guitar to stereo backing track, no?