Sony DVP-NS999ES - Manual (Page 27)

ES Series DVD-Video/CD/SA-CD Players; Version 3.0 Page 27
Sony's choice of a grounded AC input assures a more stable electrical
and mechanical connection.
Gold-plated output jacks (all models)
To maximize electrical conductivity and minimize the effects of oxidation
over time, the audio, composite video, S-Video and component video output
jacks are plated with gold. Noise at the contact points is held to a bare minimum.
You might not notice that the output jacks are plated with gold. But they
protect the audio and video signal quality from oxidation which can
degrade the output signal over time. And that can make a noticeable
difference.
R-Core power transformer (all models)
The video and control circuits can introduce imperfections to the power
supply voltage, which can trigger audio distortions. To protect the audio circuitry,
these DVD players use a separate power supply, just for audio. In addition,
power supply regulation on the audio circuit board itself helps establish stable
operation for the audio D/A converters.
Transformer cores and windings can vibrate and degrade the sound,
radiating 60 Hz hum into nearby audio circuits. That's why Sony chose an R-
Core design. The R stands for round. Not only is the core round, it has a
cylindrical cross section, enabling the transformer windings to be wrapped