Could I deign to suggest that if there is really any difference when
the filter plug is in place it is because it is reducing line noise
which had been getting through the (usually) poor PSU of the CD/DVD
player and upsetting it's decoding.

I think I am right in saying that it has been found that if the
decoding error rate is reduced on a CD player by whatever means - be
that new clean disc and/or a clean lens - as it is not struggling so
much to error-correct the decoded music the end result is a subjective
improvement?

One thing is sure. Most power supplies have some decent sized
electrolytics in them but few have any smaller value caps in parallel
to handle the higher frequencies. The late great John Lindsay-Hood
(and I seem to think Doug Self also) produced much on this topic
decades ago.


--
Woody

harrogate3 at ntlworld dot com