How much does a DAC do the more expensive it is?

“So what do those much more expensive DACS do for sound?”

Distort the sound less. Have way better output stages than the lower cost units. Generally speaking of course. 

For the one millionth time price has nothing to do with anything. It's the parts.  Nichicon audio note v-caps ac filter choked, etc.

@thyname wrote, "The specs on the op-amps are fabulous and digital engineers are inherently seduced by the beauty of the math story. There are minor differences in the sound quality between various op-amps, but it's kind of like the difference between a Duncan-Heinz cake mix and a Betty Crocker cake mix."

What then of DACs that don't even have op-amps like say a Denafrips Ares II 12th Anniversary edition?  Is that "better" than using op-amps in some way? What are the tradeoffs? It is a "softer" sound, perhaps not as dynamic?

You said most DACs are sigma-delta.  Maybe so. There's some at every price point.  But are the qualities most of the YouTube reviewers mention about R2R DACs (their "natural tonality and deep and wide soundstage" which have been repeated ad nausem) artifacts of that architecture or "real"?  Did the recording engineer and mastering engineer hear the playback that way, assuming they are using high quality sigma-delta DACs and not R2R ones?

Power supplies obviously play a huge role in how "black" the background can be, but I want to note that linear power supplies might not always be king. Analog Devices and others are working hard on developing switch mode power supplies that should compete well with linear power supplies. They are targeting the medical device field currently, but you can be sure these will eventually find their way into audio gear (or we can hope). 

Just as "some" audiophiles are ready to adopt Class-D amps, no doubt, some will eventually adopt well designed switch mode power supplies and call it a day.

Thanks.  

I have an Oppo 105 and 103. Never particularly liked either as CD player or transport.

Completely agree.

In fact I don't believe any Blu-ray player should ever be used to play CDs.

So what do those much more expensive DACS do for sound?

I like the analogy that a DAC is like a cart. DACs shape the sound. They can smooth out edgy highs, preserve the all important mid-range and tighten up bass. but...EVERYTHING matters.

2 months ago I thought my $600 Bluesound Node (current model) was pretty darn good, and I was also a digital cable naysayer. 

Out of necessity, I upgraded and tweaked my digital front end (details in my virtual system). I still have the Node but I will replace it at some point now that I know what I know:)

You get what you pay for but if you are patient and do your research, a killer digital front end can be had for under $5K. But if money is no object...go nuts.