I'm using Traktor 3 LE (will upgrade to Pro) and can't cue tracks with my headphones. I hear a buzzing noise but no music. I set output 1&2 to the master and 3&4 to my my headphones but nothing. I know this is simple to set up and have seen this same question all over the internet but here we are... What do I need to do that I am not already doing?