For anyone that has kept up with my thoughts on the Classe Audio DAC-1, you may remember me mentioning how I noticed a big difference putting a 15dB attenuator on my SPDIF cable using my JKSPDIF MK3. The attenuator is included with the unit with the thought that it helps reduce signal reflections, I believe it was. Hearing that difference made me very curious as to how other converters might impact the Classe DAC-1's sound.

I didn't want this to be a costly experiment, and I stumbled on the Gustard U12 unit while browsing eBay one day. On paper it looked like it might be decent. XMOS chip, and I was curious to try a converter that wasn't based on the M2Tech HiFace stuff like the JK. Supposedly utilizes an independent, linear power supply. I don't know enough to confirm if that's 100% true or not. 32/384 and DSD support. AES/XLR, coax, HDMI I2S, and optical output. You can get them for around $170 shipped, which I felt that was relatively cheap enough for the sake of experimentation and held little risk.

Now that I got it in, it seems well built and works without a hitch even from USB3.0 (though, I am using some modified drivers I found from a Head-Fi thread - not sure if that makes a difference with 3.0 compatibility).

I have no idea where the JK converter stands when compared to other devices. I've heard it's good, though how it's technicalities and other characteristics compare to other stuff, like the OR5, I can't say. All I can comment on is how it compares to the U12. I also tried using the U12 with AES/XLR (Mogami-based cable) and with coax (BJC-based cable), and if there were any audible differences, they were negligible relative to the differences between the two converters.

Sound Impressions/Comparison: It took me a while to initially pick out differences, as you'd expect them to be small in the grand scheme of things, but I found a small drum sample in a track that made differences fairly apparent. The JK unit sounded a bit more focused and a bit cleaner at the expense of sounding edgier than the U12. Snare drums in particular sounded almost too crispy and brittle from the JK, yet they did have a bit more pop to them. Everything on the JK just sounds a bit crisper, but almost in a way that can be too much at times. Depends on the track.

The U12 seemed to give every instrument and vocalist, or whatever fart noises you're listening to, a slightly bigger sense of internal body and presence, though it could make things a bit more crowded sounding. The JK may have been a bit airier and more expansive sounding, but that was harder to tell. I noticed vocals on the JK sounded a bit more two-dimensional and physically flat when compared to the U12. The U12 generally seemed a bit more intimate sounding.

The JK might have handled delicate details a bit better, or, rather, presented delicate details in a delicate manner, such as light tapping or brushing of cymbals. The U12 made things sound less delicate despite being more laid-back, not pushing things forward, and still generally keeping the same sense of detail or ability to pick things out. It's hard to explain. There were several moments where I felt details popped or came through better on the JK, sometimes too much so, but switching back to the U12 made me realize they were still there. It was all just generally less forward and more relaxed on the U12. Slightly less focused but not in a way that seemed to smear, cloud, or lose details compared to the JK.

I'm not actually sure which unit would be more technically accurate in most regards. The JK certainly has the edge on focus and excitement, though at times it sounded too edgy, sharp, or exciting. Like I said, it depended on the track. And, hey, maybe that's how the music should truly be. I'm hesitant to say the U12 has less technical capabilities, but it does seem more laid-back and comfortable with itself w ithout necessarily losing much or anything in the process. Just more of a different presentation with me leaning towards saying the JK is a bit more analytical and edgier and the U12 is a bit more musical and rounded without necessarily sacrificing detail.

I'd have to hear more converters to start ranking things or giving anything "good" or "bad" labels, so take this as it is...just a comparison of these two converters with the Classe Audio DAC-1. For my tastes and preferences, I think I like how the U12 pairs better with the Classe. But I might also be crazy and be hearing things wrong (U12 might be garbage), so don't take this all too seriously.

Even if the Gustard U12 turns out not to be super amazing compared to some of the best converters, it might be a good entry-level deal at under $200.

Couple links with details and pics. Just search for it if these stop working:
http://www.shenzhenaudio.com/gustard-u12-32bit-384khz-xmos-usb-digital-audio-interface-2014-new.html
http://www.aliexpress.com/store/product/U10-XMOS-USB-digital-0-1PPM-crystal-independent-linear-power-supply-384K/514210_1859929284.html