I am sure Wolf did a good job, and
his measurements in isolation were not a cause for great concern. What is puzzling is WHY they were so different from SMSL's own measurements. Explanations could be (A) that SMSL "polished" their own measurements one way or the other, (B) that SMSL measures using different settings from those of Wolf and Amir, or (C) that there is significant variation in production units, which might point to QA issues. I think (C) is the most likely, which is cause for some concern: Since I don't have an AP Analyzer, I don't know whether I am getting a good unit (like the one SMSL measured) or potentially one that's worse than Wolf's unit.
Wolf's M200 measurements were also worse across the board than his
earlier measurements of SMSL M300 MkII (a lower priced DAC using the same AK4497 chip) with SINAD 3dB lower, and Linearity and Multitone somewhat cleaner on the M300 MkII. Of course one can hope that that's a sign that his M200 unit was a bit off. SMSL obviously do know how to make DACs that measure well -- and care about it's impact on sales.
I would love to see new measurements from Amir; not because I don't trust Wolf's measurements, but because it would be a different unit. He'd be the umpire, as someone posted in the M200 thread on ASR.
But as I first posted here, I am resigned to that situation, and trust that M200 units are generally transparent. And I think it is the DAC for me!
My questions here are about the output stage, again M200 as a digital preamp. While I absolutely pay attention to measurements, I also believe that you have to LISTEN (as Amir himself stated
here, in the context of speakers). I do not believe that all DACs that measure well sound the same. And certainly not all preamps and amps. It is particularly the analog parts of DACs (output stage, power supply etc) that most separate them.
Thanks again for the great response here!