After another 5 or so hours of listening, the main thing that sticks out to me about this Amp/DAC is just now NON sibilant and smooth it is. I have three headphones with me right now that, with poor sources and badly mastered recordings can be merciless in revealing sibilance... the HD800, DT770 Pro 80s, and the HD25-1 II's. All these headphones, straight out of the D7 itself, is extremely smooth and liquid in the sibilance range and not harsh at all.
So I wondered if this surprising smoothness in the upper mids is mostly attributed to the DAC or the Amp section... so I put the DAC section through another test. I hooked up the D7 to the Gilmore Lite with the Kimber PBJ interconnects, as I believe Gilmore Lite is an extremely transparent Amp that simply amplifies whatever the DAC feeds it, and the PBJ interconnects (for those that believe in interconnect differences, anyway...) is also known as a pretty transparent sounding interconnect (music was outputted in WASAPI mode through foobar). And even after being amplified though the GL, I've noticed that all the headphones mentioned above still exhibited little to no amounts of sibilance in most decent quality recordings! Yes, even the ruthless HD800's. So I believe the DAC implementation here is overall quite forgiving with sibilance (of course, in recordings that do have excess amount of sibilance, you'll still hear it). Due to this, I think that there may be possibility of some people who will find this DAC/amp to give the illusion of being a little warm, or rolled off in the highs, but I don't think the highs are rolled off at all. I quite enjoyed these with the HD650's as well and the highs details are still plentiful, so I don't think it's a case of intentional highs roll off... I believe it's simply the case of it being smooth sounding in the sibilance region. Nonetheless, if you want a ruthlessly clinical and revealing DAC, these probably ain't it...
Another thing I've noticed about the amp/DAC section is its soundstage, which is exceptional and IMO noticeably more 3D-like than my previous uDAC.
Amp section is quite decent as well... I've mentioned already that it drives the DT770 Pro 80's without breaking a sweat, and it also does a fantastic job with both the HD25 and ESW10JPN. On high gain mode I find that it also does a surprisingly decent job with my HD650's... no match for my Hiface->DA100->WA6SE obviously, but still quite an enjoyable listen nonetheless. They sound too thin and lacking in body and tightness for amping both my HD800's and the LCD 2's, but obviously they're not the reason I got the D7 for anyway... I haven't tried the D7 -> WA6SE yet but I have a feeling both of those headphones will sound great out of that combo.
It'll be interesting to see if any of this changes more with burn-in (which I personally never really believed in strongly), but I actually really like the sound as it is now and hope that it won't change. :) It certainly blows away all the other standard USB implementation DACs that I've owned... so perhaps what I'm hearing here is due to the D7's asynchronous implementation of the USB input? Whatever it may be, this DAC really does sound very good to me thus far.
Edited by K_19 - 1/11/12 at 9:01pm