I have a Numark Mixtrack (not pro - I didn't buy it so don't hate on me for being so foolish ) I cannot cue because I don't have an external soundcard, or one built into the Mixtrack. I have read it is possible to play sound in mono and cue it through headphones whilst still keeping normal output through speakers. My set up is Mixtrack plugged into PC/Laptop via USB. Speakers Plugged into computer through standard 3.5mm jack. I have headphones that I can plug into the computer or the speakers, but there is no output directly from the mixtrack. I have a very poor understanding of soundcards so If you could explain in absolute simple terms I'd much appreciate it. The program that came standard with the mixtrack is Traktor.