[Chris Hornbeck]

On Thu, 15 Mar 2007 16:54:49 -0800, (hank alrich)
wrote:

I'm helping folks who have a sports bar get some of their audio action
working better. Following info from RAP in other ground problem threads
I've determined that the ground is good and that the AC to the closet
with the CD changer, Onkyo receiver and a stack of DishNet video
receivers is good, too.

2. There is a ridiculous amount of hum coming via the audio feeds from
the DishNet video recievers, fed to the Onkyo receivers audio inputs.
Yet there is no comparably appreciable voltage showing between those
chassis; measuring again RCA's-to-RCA's I see single-digit millivolts.

Do the sat receivers have *video* lines run out to the various TV's,
or is the picture run over, for example, channel 3?

In either case, a good first troubleshooting step might be to
disconnect all of the video feeds. If the hum goes away, you
know you have ground loop issues. If it doesn't, you may still
have ground loop issues, but it won't be *those* ground loops.

I tend to think that the CD changer issue might be a blind
alley, but does disconnecting it from the system remove the
hum from the sat receivers?

FWIW, sat dishes and their downfeed are potentially the worst
case ground loop issue; Code (almost universally ignored, but
there are Boy Scouts) requires Earthing before entering the
building; DC power must pass up the downfeed; no "ground
lift" is (practically) possible. Just an aside; sorry.

All good fortune, and much thanks, as always,

Chris Hornbeck