Will grounding plugs improve the sound of my NAD ?

I did not notice any sonic improvement but,they sure do a good job of keeping the dust out.

nope. Its a simple as that. Now, if you have components (primo dollars) that can pick up signals from Planet AP (audiophilicus preposteri)...then you would here a difference.

Concur with R about the Planet AP and all it entails,YMMV,Bob

Planet AP (audiophilicus preposteri)

LOL, good one!

While in typical circumstances I fully agree with the preceding responses, there are some specific situations in which shorting plugs can be beneficial or even necessary:

1)If a preamp or integrated amp includes a phono stage that is not being used, shorting plugs on that input may (depending on the design) prevent transient clicks that would otherwise occur if the source selector switch is rotated through the phono position.

I have an older Mark Levinson preamp which has two phono inputs and two independent phono stages. For just that reason, it specifically advises using shorting plugs if one of those stages is not used, and in fact provided the plugs with the preamp.

2)Depending on the specific design, it is conceivable that noise or rfi/emi picked up at an unused phono input could, following amplification by the phono stage, cross-couple internally into the signal path that is being used.

3)I suppose it's conceivable that in a poor design noise or rfi/emi picked up at an unused line-level input could couple through the source selection circuit or switch and affect the signal from the selected source to some minor degree.

Regards,
-- Al