Let's say it doesn't take the DAC's output voltage into consideration and I would like to volume match further, should I just add 2 Volts on Setup1 and it would volume match with Setup2 then?
(@SpeleoFool).
A little background:
I recently purchased a Holo May and have integrated it into my loudspeaker setup alongside my existing reference DAC, an Ayre QB-9 DSD. Both DACs are sources for my preamp, and I can toggle between them with the press of a remote control button. Furthermore, I have both of these DAC endpoints tied together in Roon so that I can do direct A-B comparisons by simply toggling between DACs. Well,
almost.
As I quickly discovered during casual listening, the May sounded more full, particularly in the mids, with significantly tighter bass. I checked the output level of both DACs in their respective manuals and found that the May outputs a stronger signal.
Holo May Specs:
Ayre QB-9 Specs:
Without correcting for the discrepancy, audio from the May is ~3.25dB louder than audio from the Ayre, explaining the subjective differences I heard. My loudspeaker chain uses a fancy preamp (McIntosh C2600), which allows me to trim input levels in 0.5dB increments. After cutting the May input by 3dB the differences between the two DACs evaporated; switching between the two DACs on my C2600 in real time sounds fundamentally same-y. I did not do enough critical listening to determine whether I still hear repeatable differences, but suffice to say that any such differences are small in magnitude and no longer bluntly obvious like they were before level-matching.
Incidentally, I have a second chain that routes the two DACs through a passive switch to any of several headphone amps. One of these chains uses a Goldpoint level control (47-step attenuator) into "Zone B" of my McIntosh 8207 multichannel amp, then out to an XLR adapter for Susvara. While this chain is a little more prone to error (since I have to guess at level matching), I do hear clear differences in staging between the May and Ayre DACs using Susvara. The May presents a larger, more 3D stage, while the Ayre stage is smaller, flatter, more coherent and more intimate. I also tested Susvara on my desk setup of ADI-2 -> A90 and found that chain to similarly present a "more intimate" stage like the Ayre.
These differences were repeatable across multiple recordings. At this point, though, I don't have any theories to explain them. Could it be some "R2R flavor"? Some unique aspect of May? Something to do with filters on the D-S DACs or NOS on the May? I dunno. But it's interesting that I do hear repeatable differences on headphones and not-so-much on loudspeakers. Data points worth further exploration.