Well, I spent 3 days listening to the D-1 (on a variety of filters and 2d harmonic settings, but obviously not all 2500 possible combinations; and only with upsampling turned off) in both of my systems and the results were a bit startling to me.
The TL;DR version is that in the Rowland 625 S2/Corus/Power Storage run system with a Aurender N20 and DALI Epicon 6 speakers, the D-1 showed more detail (quite a bit more) and a quieter noise floor than with the LTA Aero (in this case with rare GEC 12 volt B36 NOS tubes, that sound as good or better to me in general than TungSol black glass round plates), but on pretty much all types of music the net resulting sound was less pleasing to us. It was less “sweet” with less of the lit from within quality that I’ve come to count on from this system. This was particularly evident with classical guitar (e.g., Julian Breem playing Bach), string quartets, and cello piano duets (e.g. the amazing 1968 recording of Schubert’s Arpeggione Sonata (D. 821) by Rostropovich and Benjamin Britten accompanying his cellist friend on the piano), but also with Joni Mitchel, Betty Carter, Ella, and even Who’s Next. There was also what i perceived as the tiniest bit of harshness in the upper midrange and treble from the D-1 compared to the liquid sound of the Aero’s tubes.
Interestingly (to me at least), when i put the D-1 in the dining room system (JA Perspective 2 Graphene, Innuos Stream1 plus the standalone Phoenix USB reclocker and CODA CSiB V2 integrated amp), the result compared to the Aero (in that case with 12 volt TungSol black glass round plate tubes) was much closer. Again, more detail, but only slightly it seemed. Also less obvious hard edged sound. In fact, although i didn’t try a blind A/B test, my suspicion is that i would not have been able to reliably tell the difference blind. I am not sure what to attribute this difference to, other than a synergy of R2R tube NOS DAC and the Rowling electronics in the living room system (or perhaps room acoustics, but both rooms are untreated and fairly reflective due to lots of floor to ceiling windows (more of that in the living room, however). It is the case that when both systems have Aero DACs in them, the dining room one does sound more “neutral” or “clean” and less “sweet”. Definitely does not create what i am calling, for lack of better vocabulary or technical knowledge, the lit from within glow that is quite noticeable in the living room system. Presumably this is due to the CODA’s famed neutrality.
So, while this was only a relatively brief try-out, I did listen for many hours each day, both in focused listening mode and while doing other things in those rooms, and obviously a highly idiosyncratic take, I would definitely support @audphile1 ’s advice to test out this DAC before committing to buy it. I suspect many ( @yyzsantabarbara obviously) will love it, perhaps especially if your room is better acoustically treated than mine, but for me I am sticking with R2R NOS for now.
(I should note that i could not bring myself to bypass the CORUS & PSU and connect the D-1 directly to my 625 S2 amp; so perhaps the D-1 would have sounded better had i done that, but I know that i would not buy a DAC that doesn’t play well with that preamp and its power supply.)