all sound coming out of headphones

i’ve recently got a new DDJ 400 and straight out of the box, with all the settings at default, ive only been able to hear both channels and not been able to single out just one? i know a couple of other people that got this controller however they’ve always just heard one channel, the only difference being that they’re on windows and i’m using mac. only one channel has the que on and the knob is set all the way to que, yet i still heat both tracks just as loud as eachother, thanks.