I got this noise too with the RE262.
Day 2 with the unit: it really reminds me of the NFB-27 but it is a bit grainy in the treble when the Audio-GD is perfectly smooth. This could be either the DAC itself or the fact the EF-6 is more transparent than the SA-31 I used to run the HE-5LE with, which would smooth out treble a bit.
Also, I find the sound a bit thin with the EF-6 + HE-6/5LE. Again, the SA-31 helped fleshing out the mids compared to the built-in amp in the NFB-27 (which I never really used for this reason. I found the SA-31 technically as competent and much more musical) so I suppose the Hifimen are to blame for that.
I totally agree with Tony's Ciunas review and the comparison with the DA8: vocals are better on the Ciunas, treble is smoother but the Yulong is more involving, more fun and has a better sound-stage/imaging.
Besides these 2 small issues, the DA8 is the most communicative (read dynamically involving) DAC I owned since I sold the Audio-gd. The imaging and details level is very good, especially on the sides where my other DACs tend to be fuzzy.
I'm going to order a new SA-31. I've been using the 5LE yesterday and every time I switch back to it, I immediately notice the drop in overall technicalities but, at the same time, I find it more natural than the HE-6 and much more focused (though smaller in scale).
I probably should wait for the A18 to arrive, though.