[Bob Simon]

I got a new plasma TV and just upgraded cable service to digital with
HDTV. After hooking everything up, I hear a low-level hum from the
stereo. I presume this is a ground loop. Here are what I believe to
be the relevant connections:

Set Top Box
audio to receiver (2 channel only) via RCA cables
video to TV via component video cables
DVD Player
audio to receiver via RCA cables
video to TV via HDMI cable

I can eliminate the hum by doing any one of the following actions:
unplug the audio cables from the DVD player
unplug the three component video cables from the DVD player
unplug the audio cables from the STB
disconnect the coax cable feed from the STB.

When I unplug the HDMI cable from the STB, the hum gets much louder.
Why?

Based on my experiments, I believe I can break the ground loop by
replacing my DVD player and receiver with models that can be connected
by fiber. (I want a Dolby decoder anyway.)
WIll this work?

I also scheduled a service call with Cox and requested a ground
isolator. I'll see what actually happens on Sat.
Bob