Non-Oversampling (NOS) vs,

Depends, converting redbook the 2R2 Multibit Holo Spring dac, sounds far better on NOS than it does with OS, and you find that goes for most R2R Multibit dacs that can do it.
I'm not into Delta Sigma dacs "trying" to redbook so I won't comment on those.

Cheers George

OP>
I am just trying to better understand a NOS DAC vs one that upsamples.

I’m wondering myself how great a part this plays in the final result?

I mean after all, does this really matter somehow?

I believe regardless a dAC be an OS or NOS DAC, there is more to this than the philosophy or approach being lent to the solution.

like the OP alludeed to, as such, EVERYTHING in the dAC build and implementation has to be considered as a ‘WHOLE’, despite the OS or NOS digital side of the affair.

as I understand OS DACs some sonic aberations are attenuated or ameliorated outright via up sampling the rate. the other approach handles things differently, of course.

then to, some dACs deal with sonic issues on the analog side.

doesn't that all by itself sort of make the design argument nonessential?

for eX… lets say you got to hear similarly priced but not exactly, two dACs. one of each design, and in your own rig.

in the end, things were close. very very close. its come down to a coin toss.

the thing then is cost. Right?

one must stay focused on the overall, or end result and not merely at which way they went to achieve it.

it do make for some interesting debates though, from time to time.

if the dAC has the short list of options I desire, I can afford to buy it, and its a decided boost to the sQ in the system, I could care less if they got blind squirrels juggling knives while jogging on a treadmill inside the thing.

well, so long as I don’t have to feed or clean up after them, and they maintain their hygiene.

Upsampling allows mathematical filtering which is more accurate than anything in the analog domain. It also tends to randomize differential non-linearity from physical devices.

Anything built in the real world will suffer from differential non-linearity. This occurs in both time (jitter) or in amplitude. (True whatever your DAC topology)

It is simple physics. Build anything with discrete levels (steps) in time or amplitude then you will have inherent physical limitations in accuracy between adjacent levels (steps). The errors are always there whatever you physically build. So building something with many more than necessary steps (levels) means the errors are far more likely to be smaller, benign, inaudible and random.

It is always better to have a higher bit resolution and higher sample rate than actually needed. This means differential errors are more likely to occur outside the audible range (below the noise floor or at higher than audible frequencies).

Think about it.

What is better?

Errors that are close to or within the audible range (16bit 44.1KHz) or errors that are way outside the audible band and can be filtered out (upsampled or high-resolution)

For these reasons most folks find that mathematical upsampling in Roon or other software can help improve the sound from many DACs. This is because it changes the nature of the physical analog errors that absolutely every DAC suffers from.

Latest DAC Chip design tries to leverage this issue by having a hybrid solution - a mathematical random software selects the actual circuits combined to create the amplitude on every cycle - ensuring that no two adjacent samples ever use the same circuit and thus inherent physical differential non-linearity errors are random.

Random errors are several orders of magnitude better than any noise that correlates to a musical signal.

The most accurate DACs like Benchmark DAC 3 are using this hybrid approach. They are equivalent to a 6 bit R-2R DAC running at a very high sample rate. This approach minimizes BOTH the impact of errors in time (jitter) and signal level (amplitude or bits). This approach measures an order of magnitude better than the very best most expensive R-2R NOS design or the very best 1 bit Delta Sigma or DSD.

If you don’t like the sound of accuracy and prefer a bit of distortion then you are part of a large camp. I like tubes too!!!

The above is just a discussion of pure performance accuracy and does not account for tastes.

dacs are the biggest snake oil in hifi

I only have one NOS DAC, a MHDT Labs Orchid.  I'm listening to Pink Floyd Wish You Were Here with it as I type this and it sounds glorious.  Out of the many DACs I have, it's the one I chose for the system I listen to with headphones most office.  It's the least "digital" sounding DAC I have, but very detailed and easy to listen to.  I don't really care about the technical aspects of it, I just love the way this one sounds.