I just tried to throw together a tempory system. It's a pc as source (and pre amp) to a quad 303 to kef drivers in homemade cabinets. When I touch the amp input cable to the case of the pc there's a high pitch humming from the speakers (and when I plug it into the socket on the pc this continues and there is no music coming through). But when I connect another source to the amp (straight to an ipod) the sound is fine. And when I connect earphones to the pc all is fine. So what could the problem be. Could it be an earth is needed, in which case how do i go about it? I've also just tried putting it through another integrated amp. There is no noise with this, just sweet sound. But when I run the pre out from this amp into the quad the noise comes back and I get no other sound. What's going on? Thanks for any help
The answer is to not use the Quad. Yes, the problem is likely to be a grounding problem. But, how you solve the problem is to not use the Quad which has unusual grounding techniques. You should contact Quad customer service for anything specific they might suggest. There are isolation transformers which might resolve the problem; but unless I were told by a qualified technician to try this route, I wouldn't simply insert transformers into the line. I believe the best source for these transformers is Janzen Transformers. Give them a call if you don't get an answer from Quad.