NAD 515 CD Player use with DAC

Has anyone tried using an NAD 515 multi-disk CD player with a DAC.
If so which DAC did you use?
Is is worth it?
I tried an MSB Link DAC III with my NAD 515. After a week's worth of burn-in, there was no discernable difference in the audio quality, except that the DAC added a low-level electronic hum. I sold the DAC and haven't looked back. IMO, the stock DAC in the 515 is probably as good as any sub-$1K DAC on the market.
i used to use an ase z-man tubed buffer stage w/my nad 515 (and the panasonic portable slp1a before that). this was the *only* way i could tolerate the digital nasties, when it was run thru an electrocompaniet ec-1a preamp, & then, a linn kairn preamp. but, since i've gone to a tubed preamp (1st rogue 99, then cary slp98, finally settled on a melos music director), i've found the nad 515 sounds fine run straight-in. in fact, it gives up *nothing* to the $1800 alchemist cd-player, & it gives up nothing meaningful to the $3k resolution audio cd-50.

to be honest, i was hoping these spendy cd-players *wood* be a big improvement (or even a small improvement!), as i really find digital sound doesn't compare favorably w/winyl. however, that was not the case, at least in my system. w/a tubed preamp, tho, at least cd is enjoyable for me, now...

ymmv, doug s.

Like Doug, my 515 was a bit sharp thru my NAD integrated, so I tried it thru a Creek passive pre to my Moscode 300 hybrid tube amp - much much better. Now I'm saving my pennies for the Marsh P2000t pre and A400 amp, but I doubt I'll part with the NAD just yet (though long term I'm considering the CAL 10 or 20).