I took a few hours tonight to do some listening comparisons. The scope of my "tests" and comparisons were bit limited, admittedly, and I do hope to go back with different setups and gear. I might even do a bit more later tonight/this morning. Keeping that in mind, I went for something fairly simple but consistent.

Desktop -> Auzen coax out -> DAC -> Leckerton UHA-6S Mk.II headphone amp -> modded Tascam TH-02
JRiver Media Center, 24/96, upsampling enabled

I know it would have been better to get out the HE-500, but my pair, even with HM5 pads, seems to share many of the same characteristics after mods as Marv's pair show in his measurements. It's a bit on the warmer, bassier side, but it's surprisingly capable of rendering details except where it dips around 4-5KHz. I don't mind the dip there because it really helps me with listening fatigue, but you do lose a noticeable amount of information there. I can't say how closely it matches the response after that point, though. At the very least, it seems to have been enough to make DAC differences mildly apparent. I'll get the HE-500 out sometime when it won't disturb people as much.

For now, I only tried the NOS1704, the Metrum Quad, and the Leckerton's built-in DAC. I plan on trying the SB1240, but I'd have needed to drag out the laptop for that. I think this is my first time I've sat down and really compared DACs, so take this all with a grain of salt.

The first thing I'd like to say is that the NOS1704 is noticeably noisier than the Metrum Quad. You could turn the gain and volume up all the way on the Leckerton with the Metrum as the DAC input, and it would barely pick up noise. Not so with the NOS1704. However, I could not hear the NOS1704's noise until the volume was set well above normal listening levels. I doubt this really had much or any of an impact when listening.

I believe the NOS1704 does indeed have a more syrupy (not necessarily less clear), darker sound than the Metrum. The NOS1704 sounded a more intimate, more densely packed, and less expansive than the Metrum. Instruments and vocalists generally had more of a tangible presence to them than on the Metrum. The NOS1704 seemed better at conveying dynamics and the emotion behind the music.

On the other hand, the Metrum seemed to do a better job putting space between everything. It had a lighter, more expansive, airier sound than the NOS1704. It was often easier to clearly identify and differentiate between instruments, especially fast-paced bass drum kicks during heavy, complex, dense music. Generally, it was the best at allowing me to pull out individual instruments and details.

That wasn't always the case, though. Because it had a lighter, more expansive sound than the NOS1704, some background details were actually more likely to get lost in the mix and a bit hazy despite most other things still being easier to pick out. I think the denser, more up-front nature of the NOS1704 helped bring out some of these smaller details. And while the Metrum provided more space between everything in the sound, I often found the stronger, more immediate presence brought by the NOS1704 to give a slightly more life-like presentation.

At one point in my notes, I mentioned that the Metrum sounded the most sterile of the bunch, but not fatiguing. That's just speaking relatively among these three unites alone, of course. I often noted that I thought the NOS1704 sounded the most natural with cymbals. Overall I gave the nod for clarity to the Metrum. Most times it was too close to really tell between the NOS1704 and Metrum.

When using the DAC in the Leckerton, I thought it sounded good, but it was missing something. Often times it placed itself in the middle of the two DACs sound-wise, but it had this sort of mushy quality to the sound that was hard to describe. Whenever complexity picked up in the musi c, even in softer genres, it had a tendency to present the least coherent sound of the three DACs. It did not share the separation of space and clarity from the Metrum or the sense of presence and dynamics from the NOS1704. It was as though it tried to capture the good elements of both DACs but instead mostly pulled more of their unique bad traits and mixed them together. I thought it had the least natural presentation of cymbals of the three, but otherwise noticed no oddities among all of them. At one point while listening to orchestral music, I switched to the Metrum from the Leckerton and was more easily able to hear individual instruments that were tightly packed together.

Again, I did think it sounded good and enjoyed listening to it. And, also again, take this all with a grain of salt, especially if anything I say sounds confusing or contradictory (likely falling into the realm of placebo).

I'll try to test out the SB1240 and try some other software/hardware setups. I'd love to add the Beef Roast with Uber AnalGland Upgrade in the mix for comparison purposes, given all the good things I've heard about it lately.

I would really like to try the OR5, but I'm not willing to spend that much money on it...yet. I would also be very curious to do jitter measurements with it. Clearly the JKSPDIF wasn't doing the NOS1704 any favors with how I had it setup, at least.

I also can't speak for how similar the M7 and NOS1704 are in terms of design and whether the coax implementation on the NOS1704 is better, the same, or worse.

With the NOS1704, I definitely think so. It seems to work better with the Metrum, but I'm in the process of posting additional measurements for that which show it performing no better probably worse than the Auzen out. I'll have to try the JK with my desktop to verify.

Those jitter measurements don't look "right" - as with what is typically seen.


Which jitter file are you using again? The 16-bit?