Hi, just happening across this thread 6 months later, after having purchased a NAD C399 with BluOS module a few weeks ago.
I got this TERRIBLE clipping on an audiophile demo track (from an old magazine CD) with a very loud & dynamic sax in it.
I think I've pinned it down to the Replay Gain setting: if its on Album, Track, or 'Smart' then the clipping occurs; with Replay Gain completely OFF, it doesn't. Can anyone double-check this?
Regardless... so much for fixing the C658 if they've carried this bug forward to the C399!