On Thu, 15 Jun 2006 07:53:13 -0700, "Richard Crowley"
wrote:

From reading the above I think the problem is a ground earth loop.
What we usually do is open the unit and remove the earth linking the
mains earth to the audio earth. This should clean the noise up.

You are only bandaging the symptom, not discovering and
remedying the cause. It is a potentially leathal "solution". It
would not be acceptable to me.

Surely a ground loop IS the classic cause of hum? There may indeed be
better ways of curing it.