Alright folks, I have now been testing the Yulong DA-8 against the DM Source (representing the Indistinguishables) long enough to form some opinions. First, let me say that this one is a bit more complicated than the others, in part because I'm now using the Benchmark DAC 2 as a switch, and have to assume that it is not discriminating between the two analog inputs. I don't believe it is, but I needed to state the changes in conditions for the record. I also can only test two DACs at a time, so this makes comparing more DACs than that more difficult.
In addition, the Yulong has multiple settings, with filters, polarity and jitter reduction all configurable. I started with the polarity set to negative, the filter set to sharp and jitter reduction on, since that's the way the DAC was set out of the box.
The Yulong was level-matched to the DM Source, and I played a couple dozen songs, many on the same playlist, but I brought in a couple of DSD recordings to see if I could hear a distinction.
As set up out of the box, with most file types, the Yulong sounds just like the DM Source -- it is among the Indistinguishables. However, it sounds significantly louder playing DSD files. I don't know if I can characterize this sound as better or not, because I don't trust the volume change. There is no way I can level-match the DSD because I don't have a DSD noise track. So all I can say is that the Yulong sounds VERY different vs. the DM Source playing DSD tracks. I would prefer to avoid characterizing the differences any more than that.
Next, playing with all of the settings just a few times, on a few songs, I heard no difference on any tracks with the polarity changed. According to my understanding of the Yulong manual (which is not well-translated) there is supposed to be some difference on older recordings, but I didn't hear any. I also heard absolutely no difference with the jitter reduction on or off. I heard no repeatable difference with the 50, 60 or 70Hz cutoff filter Yulong uses for DSD. Sometimes I thought I heard something, but then when I went back, I couldn't consistently find that difference. I definitely heard a difference with the filters set to fast or slow, which is the choice for all other types of files. More on that below, but suffice to say right now that there is an audible difference.
For the first time I also tested the headphone jacks on the two DACs. Both are respectably good HP amps, but the differences there are significant. Level-matched, particularly with the fast filter on, the Yulong is much leaner sounding, much more analytical, with much faster decay times than the DM Source, The Yulong sounds a bit more sizzly in the highs and sharper in the lows, or alternatively stated, there's more mid-range energy in the DM Source, up through and including upper mids. The difference is particularly pronounced in the upper mids, as pianos and vibraphones sound much leaner with the Yulong. Which HP amp you prefer when the Yulong's filter is set to fast depends on which sound signature you like better, or which other components/cans you will be matching them with.
However, switch Yulong's the fast filter to slow while using the headphone jack and the sustain grows audibly. Upper mids get louder and more prominent. Voices are louder, pianos and cymbals ring. The sound stage appears to shrink. I wanted to turn the volume down (but couldn't without messing up the level match). However, when I did a white noise level check just switching the filter on and off, guess what? The slow filter is actually almost 1 dB quieter than the fast filter. Totally counter to what I expected. I re-checked the results at least a dozen times to make sure I hadn't screwed up. I checked the sound levels again, this time playing through the Benchmark and the Odyssey amp. Still a difference, but this time about 0.5 dB, and again, the slow filter is quieter. And there is still a difference listening to music, but much more subtle. The sound with the slow filter is close to what I remember the Metrum being, or maybe the Ciunas. But with the #^&%ing switch broken I can't compare all of them at the same time. I will be putting the Metrum in the system in place of the DM Source next, just to hear the difference between the Yulong and the Metrum.
At this point I'm not passing any judgment on any of this. Just reporting what I heard, and measured. I can say that the Yulong offers some interesting features, including a headphone amp that has 2 distinct flavors, and a DAC with 2 audible, if less-distinct flavors. Otherwise it can be configured to sound as good as all of the other indistinguishables. It doesn't have analog inputs to work as a full-fledged pre-amp, but it does have a volume control (and a filter that changes volume too... whether you think that's a good thing or not). What I could not figure out reading the manual is whether it is a digital or analog volume control, but I am guessing it's digital, since they recommend setting it to "DAC Mode" for best sound. I didn't understand exactly what that meant based on the poorly written manual, but it appears to mean that it sounds best with the volume set to zero attenuation, and it doesn't go above that, so I'm assuming the volume control is digital.
Next, I intend to put the Metrum in the mix to see if the Yulong with the slow filter really does sound like the Metrum. Then I need to decide which of these DACs will stay here. The finalists, in no particular order, are the DM Source, the Yulong, the Metrum, the Emo Stealth and the Ciunas.