"Jon Myatt" wrote in message
.. .
I have what appears to be a ground loop, and it's driving me *mad*.

My S90 keyboard is plugged into my ST Audio DSP24 C-Port sound card (well,
rack).

The balanced outputs of the DSP24 then go to the power amp.

When the S90 is connected I hear a constant whirring in the background,
which gets worse if I move the mouse. Disconnecting the S90 makes it go
away.

I've tried about five different pairs of jack-jack leads - all the same.
Other devices plugged into the DSP24 are fine. The S90 plugged into the
power amp directly is fine.

Any suggestions? I'm tempted to ditch the DSP24 and buy a Motu or
M-Audio...


If none of the other suggestions work, just use a ground lift and forget
about it. They cost a dollar or so. It's just an adapter that goes from
3-prong to 2 prong...thus removing the ground. I don't reccomend doing this
to everyone for all situations...but it sounds like this would work for you
just fine.