I want to have a small portable system to play out so I bought a Traktor Kontrol X1 mk3 and a Komplete mk2 audio interface so I can listen to tracks I'm cueing up through the headphones. I followed the Youtube setup tutorial but I can only hear the channel that's playing through the headphones and not the channel I selected on the X1 to monitor on the headphones. Is there something simple I'm doing wrong?