Pardon the re-awakening of this thread...but I've owned the HLLY DMK-IV since early Jan '10, and thought I'd chime in.
HLLY is still selling these on EBAY at various prices, close to 300 US. I got mine by losing an EBAY auction, but then was contacted with a second chance offer of what my last bid was. The seller was politely asking for a few words on one of the audio forums...ok...8 months later I'm ready to comment.
First off, Skylab did an awesome review! I have many same impressions, some slightly different.
My unit arrived in perfect shape, no loose jacks or anything like that. It does have one annoying quirk: I often have to mute then un-mute the unit in order to get sound out when I first turn it on. I love the remote control that comes with this amp, so this mute/un-mute operation is pretty painless.
Burn in is an absolute must! I don't think I used it more than a minute or so as a head amp before I put my "burn-in" CD on autoplay and stuck it away in a closet. A 100 hours later, I could get thru a few songs (I tend towards classical guitar-LAGQ, etc), but it was still a bit grainy. At about 200 hours...now then...this is sounding alright. Bass was fairly tight, not exaggerated, mid-range maybe a little bit forward but nice sounding, and the highs...are ok. Not great, not bad, can't call the highs smooth but they're not harsh either. Slightly zippy? Just a bit overly detailed? Overall, I do like the sound, but this unit as a head amp could probably be improved quite a bit. For the money, though, I think it sounds way better than I paid for it. (I think I paid $228 plus overseas shipping). Ok sound as a head amp, just not great.
The DAC, however, is awesome! OMG, this is worth the price and then some. I haven't used the coax input, just the toslink and USB. I see that HLLY is going to upgrade the USB, and I guess that is ok, but from my perspective, even the USB as applied in this unit is pretty good. Most of my music is imported into iTunes as Apple lossless off of my CD's, so I'm not quite sure how a USB chip that can go above 48k is going to help me much anyway. Imaging is precise, I don't hear any smearing, actually, I don't hear the DAC much at all, I guess the word I want for the DAC sound is clear. I compared it to my Fireface 800 and I think I like the HLLY a bit better as a DAC, and I like my Fireface as a DAC plenty. But this might be an apples/oranges comparison, as I connect to the Fireface through firewire.
Both the head amp and DAC on the DMK-IV were noise free to my ears. That is quite an accomplishment at this price.
Overall, this unit is quite the value even at the 300US that HLLY is asking for it now. I'm interested in the new unit promised by them, the SMK-III, as it appears they are going to significantly upgrade the head amp portion, which is really what I wanted when I purchased the DMK-IV, a stellar head amp (which it's not). Moving to the highly regarded PCM1704 chip is also enticing, as long as they get the rest of the circuit right.
Why did I wait so long to comment on this unit? After all, I've had it since the first week of January. Because they didn't hit it out of the park with the head amp, and I just couldn't get exited about writing about a stand up double. Only after recently using it as a DAC did I feel I could say enough good about it to post here. I know, we need to hear about the so-so too, but I just couldn't get into it. Finally using it as a DAC got me exited enough to comment.
To all, please forgive my first post being more of a review than a comment, and a long winded one at that.