Dave,
 You may need to isolate your TV from your preamp on your stereo wth an
isolation transformer.This is a common problem between different audio
sources or when running from differnt AC sources.
As far as how to wire the cable, assuming that you only have two leads,
one hot and one ground, the shield should be connected to the not-hot
lead on the source side, not tied all the way through.
Bonnie *:>
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