heh heh, that stings a bit.
Have you tried another kettle lead or two?
Also, I bought one of these used. It has a horrible noise going on all the time too, like the sub harmonic effect is on all the time.
This comes through the headphones as well as all the outputs. When hooked up to a power amp and speaker, it's quite pronounced.
If it's new, maybe you can return it for another.