I'm outputting fiber out the back. More specifically:
I'm powering a pair of Paradigm Studio 40v3s off a Sony DS845(?) via a digitial fiber port to the Sony PS3. A particularly outstanding example of the problem was an Elton John song which sounded like there was a piece of paper vibrating on his mike.
I unplugged the fiber cable from the PS3, plugged it into a Toshiba HD-DVD player I baugg about 2 days before HD-DVD lost the format war and the problem is gone. The sound quality difference varies from "subtle" to "my GF who likes her computer speakers for music can tell from a room away" depending on the source material.
I've not noticed it in movies: but it's possible its there and just less noticed (again, because of source material).
I'e noticed that the fiber doesn't like to "lock in" on the PS3". I wonder if it could be a connectivity problem. I'm not sure how the digitial signiture sounds as it degrades here (used to the stated-packet computer world)