SIX HOURS BURN-INIt has two modes, selectable via the internal jumpers - either 44.1 or 96khz....I had a typo above, where I said 48 or 96, which I edited (but then again, the literature is kinda misleading). I'll try it in both modes, and post more on the differences later.
As for impressions at six hours of burn in - this thing seems to be the real deal. The differences are subtle (less than say, a different DAC would be), yet when you listen "into" the music, it's really easy to pick out what it's done to the sound. First off, there's much more low level detail and dynamics. Things have sharpened up considerably all around - it's almost like looking out of the same window every day, and one day you looked out and realized the window has been cleaned. There's a sharpening of transients and imaging...instrumentation seems more focused, soundstage is wider and deeper. Aside from the focus of instruments, spaces between them seems more defined, giving an airier feel to music, especially live recordings.
Most strikingly, vocals seem to have taken on a much more realistic or natural presence. There's a real "heft" to them now, male and female. It's not a coloration of the sound, just a more accurate and vivid presentation to them. The "presence" factor goes beyond just the vox though...everything feels more immediate and realistic. It's not quite like the difference between say, a Grado vs. Senn presentation (up front vs. laid back)...the phones still feel the same, and the volume level is the same, but there's just more "there" there. Bass isn't hitting harder, it's just more solid. Highs are clean and shimmering.
I finally feel like my DAC is living up to it's potential...it's the GIGO rule in effect - "Garbage In, Garbage Out", not that it was garbage before. I just mean that the OMZ is being fed a REALLY accurate and strong signal (the output is about 5V, fed into the DAC), and it's able to really shine now. It doesn't fundamentally sound "different"...it's still extremely natural and spacious, detailed and clean without digital harshness, just like it always was, it's just kicked up a notch, to borrow a phrase.
EDIT: Note that at this point, these differences are subtle...I'm not trying to say that every change is DRAMATIC(!), but they are readily apparent if you are listening for them. That's not to say it's "expectation in action", and I'm hearing what I want to hear. I really AM looking for a reason to think that the benefits and performance are outstripped by the cost, but if there's this much of an improvement so far, I can't wait to hear it when I get home today (that'll be about 24 hours constant burn-in).
I'll let it burn in fully, and post more later, with impressions of both settings, and also take it out of the chain and compare as well. Right now though, it's a worthy $279 expense. I think I'm almost there...just a headphone cable away from nirvana. That is, until I build a balanced system...
EDIT: Note...the cans I used are the HD650's this time around. I'm not a believer in the notion of the "Senn veil", I think they just have a "house sound"...but...I don't know how...it seems to have lifted somewhat. The highs seem less rolled off and muted. It's probably due to the signal boosting again. They sound so rich and awesome right now...*sigh*