Hi.

Just a few shot in the blind, but....
Have you tried to move the main volume slider up and down several times?
I've heard about a similiar issue, and that at the end the volume slider
had to be replaced.

Also check if the noice are there when no cables connected to/from any
of your other equipment, just to be sure it's not a cable poblem or it's
any of the connectors damaged by cables being stretced or something.

Good Luck and Happy Plaiyng
GJ