computer noise coming through usb mixer?

katrinarawlings Asked: computer noise coming through usb mixer?

hi, i am having a problem with my home studio set up and want to see if anybody can help me out. i have a 4 channel usb mixer (alesis multimix4) hooked up to my computer which i have a pair of powered studio monitors (krk rokit rp5) rigged into. the problem im having is, i seem to be getting what sounds like computer noise coming through the usb lead which as a result is coming through my speakers. i have tried a few different usb cables just incase the lead was faulty, but no change. i also have an (m audio fast track USB audio interface)which i am trying to use as an external sound card for my computer but i have exactly the same problem using this too. the mixer, speakers and the fast track are all brand new kit, so cant see it being any of those. maybe there is somthing wrong with the comp? if any one could help me out with this frustrating problem, i would be very grateful. cheers