When feeding a DAC Hi-Res files, DSD128, 256, 512, PCM 32/768, etc are NOS DACs prefered?

Can you give an example of a modern dac that always oversamples??

Grimm MU1 (and I think MU2) would be examples.  you can turn it off, 2x, or 4x.

Jerry

Not sure what you are asking, but look at the the Bricasti M21. It has a true 1 bit DSD for DSD content.

"Can you give an example of a modern dac that always oversamples??"

Well...I may be wrong, but I thought something like the Meitner MA3 upsamples everything to DSD 1024?? 

“Why oversample files that are already Hi-Res?”

Some folks get a kick out of it…nothing else sound as natural as original resolution. Instead of over sampling, focus on getting the best version out there, regardless of its resolution. I have 16bit/44.1kHz files that sounds absolutely sublime. 

I like whatever DAC I'm using to playback files at their native resolution.  It's OK if it can upsample, as long as it can be defeated 

Most DACs turn off oversampling when playing DSD files.  They even use different filters.  And unless your DAC oversamples with a factor of the original file (44.1k oversampling to 176.4k and 48k oversampling to 192k, etc.), straight oversampling to one frequency may not be beneficial to the sound quality.

I’m using a Denafrips DAC and all of their DAC’s are either OS or NOS and it’s up to your ears which you like best. I’ll give you a hint, some files sound better NOS and some files sound better OS.

@jim94025 tubes are not necessary if dac is very good , an example of a modern dac that always oversamples : some top possibility is APL hi fi dac or Playback design dac.

I have good expirience with APL DSD AR dac - also PCM files sounds amazing.