OK, time to write about how it sounds! This is a very competent, amazingly feature-packed little thing, and the designer deserves applause. In his posts he calls it the "S2", and I will follow suit. After some experimenting, I have the S2 working well in all resolutions and modes. I have left the Audio Quality on "Best", which sets Distortion Compensation to disabled and the filter to Optimal Transient. Filters are disabled in MQA mode (thanks
@Pete-FIN ), and as you know a firmware update for the "popping" sound is promised.
The sound is very neutral to me, though some may find it bright if they are used to warmer systems. Comparing only the DAC to my Modi 2U, with both outputting via their preamps to my Genelec M030 active desktop monitors, I find the two products so close in sound that I wonder if I am falling prey to expecation bias when I hear any difference at all, but I do find the Modi 2U to be just a bit smoother.
This impression is stronger when comparing the headphone output to my Modi 2U + Magni 2U combo. The S2 is still very very close in sound, but I feel the Magni 2U offers slightly more detail, in a fuller, smoother, more pleasant experience overall. More expectation bias? Less likely at this stage. But the differences are not large.
The MQA, DSD, and ultra hi-res features of the S2 may more than make up for any such perception, and certainly are a lot of fun to explore. Switching on Distortion Compensation or changing filters could improve the SQ, so please post if you play with those. This feature-rich little box offers a multitude of possible distractions. I miss having a separate DAC and amp though, which allows me to for example insert a Loki Mini between them rather than only in front of the external speakers but not the headphones.
The headphone amp is more than strong enough to drive my DT-770 250 Ω headphones. I also tested it with my 70 Ω MDR-Z7 cans. But the Magni is much more powerful as I'm sure you know, and I look forward to seeing reviews here of the S2 paired with 600 ohm models and more.
This is first and foremost an MQA test box for me, and for that it is an excellent low cost swap-in-and-out choice. It certainly is not a high-end product, but — as with the Magni and Modi in their category — I think the S2 sets a new benchmark of price and performance for sub-$1,000 MQA and DSD DACs.