MIxtrack Pro 3 has a hissing noise when connected to my computer

My Mixtrack is just 2 weeks old, works perfectly but there's a hissing noise coming from the output whenever I connect to my Laptop or PC. I use Serato but i've not even got Serato open on the PC. Just as soon as I plug the mixtrack in via USB the hissing starts.Need some help please as it's hissing me off :-)
2 people have
this problem