Len Warner wrote:

> Try the following tests:
> * switch off computer by its power button - if still hum, must be
>   wiring!
> * check that computer and stereo are properly grounded to mains
> * if either is on a two-prong reversible plug try the other way round
> * power both units from the same mains outlet using distribution strip
> * check the earthing on your mains outlet (careful!)
> * check the shield continuity on your audio cables (again ;-)
> * waggle the audio cables - if the stereo crackles
>   you have an intermittent cable fault.

Len,

I tried all you suggested, except checking the earthing, I'm not sure
how to do that.  It does seem to be in the building wiring.  (I wonder
what changed, it worked before.)  Anyways, the hum comes through with
the computer turned off.  If I unplug the computer, the hum is still
there, being transmitted over the parallel port cable from the printer.
(This shocked me, I'm figuring it's a pretty large problem.)  The
computer is plugged into an UPS, everything uses grounded plugs.

I'm lost on the grounding issue, anyone have any ideas on how I can fix
the ground or at least get the circuit my computer's on grounded
properly?  Also, is this dangerous to my equipment?  It seems to be
throughout the building, as I tried running a grounded extension cord
from outlets in other rooms (on different circuits I assume) and the hum
never went away.

Kevin