Reply to Vestax Typhoon w/ Traktor LE - No sound from headphones?

Morning all, this is my first post, my first post of many hopefully.

I can't seem to get any sound out of my headphones.

I have my controller plugged into a desktop pc and speakers plugged into the desktop pc also. Sound is coming out of the speakers fine and the fader, pitch, effects e.t.c are all working also.

What shall I try to get the headphones working?

I have probably missed something obvious being that this is my first controller, so apologies in advance if this turns out to be the case.

Thank you for your time.

Slice.