DAC general question

I agree with  jjss49.  I would only add that the quality of components can also make a difference.

As a side bar, you can purchase an inexpensive DAC that will "measure" extremely well on scientific equipment, but will not sound as nice as expected in a quality system.  This can cause a real reaction from the objective only crowd but it is true, thus the preference of many for the R2R Dacs. .00000000x distortion will not equate to a great sound depending on the rest of your components.  If it was only about a chip and measurements, we would all be buying the 800 dollar Chinese DACS that have a SINAD of 118+.   I agree with @mastering92

Ladder dacs are very popular now, so companies are making them.  Nothing wrong with that, but remember some of the best sounding dacs ever made used "off the shelf" chips.  The older top-line Esoterics used AKM, as did APL.  I believe Audio Note dacs use chips and the reviewers can't stop raving. Personally, I would buy what sounds good to you and forget about the design, unless it bugs you to the point where you can't enjoy it. 

Buy your DAC from someone who:
1. Only makes DACs
2. Offers a trial period

I like R2R style with a tube. AD1865 chip.

You are correct. There is a lot more to a DAC than the chip. The design of the input circuit, the power supply & the analog stage have so much more to do with the sound of the final product. In fact, I would say the chip is not the most important part at all.

Watch this video, Paul does a better job of explaining what I am trying to say.
https://www.youtube.com/watch?v=McoA82-fi9s

It’s all important, but from what I’ve heard from other hi-fi enthusiasts much more knowledgeable than I (and judging with my own ears, which may not be as keen as others’) it is the quality of the power supply and the type and quality of the output stage that make the most noticeable difference in a DAC’s sonic character, given that the clocking and conversion are above a certain standard of performance. Again, I’m sure others will disagree, but that’s been my experience.

input stage
clocking
d/a conversion (chip, fpga, or r2r ladder)
power supply (linear, switch mode, separate/combined for various stages needing power)
output stage (ic, tube, transformer, ss discrete...)
isolation (physical and electrical)

it all matters in determining what a dac sounds like

ibmjunkman

As I understand it the actual DA function is done by a single chip ... Am I wrong?

Yes. It's quite common for DACs use multiple chips, such as in balanced configurations. And as @verdantaudio noted, some use FPGA chips, which are essentially custom chips.

I agree! Circuit design is the key factor. In fact this can be done inexpensively. Witness the Khadas KTB DAC for $99! Yes it requires a case - but sonically competitive with four-figure DACs! For those not into DIY Khadas has the Tone Pro DAC for $199 - with even more features!

So...yes and no.  There are only a few chip makers.  Some do use resistor ladders and FPGA chips which in essence are customizable chips.  But you are right.  In the end, the design, implementation along with part quality is what really matters.