Tube or R-2R DAC for Tube System

generalizations are not true and it really comes down to implementation.

Bingo. When they are true its someone using a brute forcet echnology to overcome design limitations.  "I cant make it warm and natural so I'll throw in some tubes".  Pass, with apologies to Nelson LOL.

Whys is tubes and R2R a choice? Why not both if you happen to think they are to your liking?
Orthogonal decisions.  Like "V8 or red car?"
Anyway i personally think that choosing by technology type is not particularly valid. I can make FETs, BJTs and Tubes sound pretty much alike.  Choose the product that you find musically enjoyable.

there seems to be some confusion with terminology.  Multibit = R2R.  They can be discrete resistors soldered onto a PCB or thin or thick film hybrids on a IC; but they are both ladders, and both take in PCM and spit out PAM.

Bitstream is a different animal, based on pulse density modulation.


Arguments can be made for and against chips based R2R but the real reason for the proliferation of discrete DAC is that R2Rs vanished from the market place long ago.  AD has re-introduced one that is used by several, including Schiit, but it is not designed for audio and glitches.

Whether you place a tube I/V and filter after it or the same deal with transistors is an independent question.  tubes of course help get glowing reviews (ducks for cover after bad pun).

Learning now!  Entirely passive seems like a tough proposition since the output will have a variable impedance and a high one at that.  For a home/hobby project where you can control the next stage maybe its feasible - but in commercial proactive that sounds, to me, like suicide.

Transformers are a natural for the task, but are typically big and expensive ( and most that are not , are not very good) . I have not experimented with any custom ones.  I plan to use discrete circuitry, combining FETs and BJTs where each as an advantage - and keeping it pretty simple. (what was it that Einstein said? "as simple as possible, but no simpler" :-)

The output characteristics of bitstream DACs vary quite a bit too- some only give a voltage output - meaning an onboard opamp i presume. The real world gets messy.   But again, still learning. All my DACish work so far has been on the other end of the chain - input, isolation, clocking etc. 

@charles1dadsI
I must be missing your point,since i addressed why one of those options is commonplace and sub optimal, and the other has serious issues.  Could you clarify what you are pointing out, or want to know?
G