I'm very grateful to Ed who installed XDMS on my Extreme and helped fix a few bugs or issues that arose after the installation. Here are my quick impressions.
UI/UX
While the app is still in Alpha, the app installed on my iPad is well snappier and more responsive than TAS. TAS has more frustrating glitches or nits than XDMS currently has - the most annoying one being TAS's tendency to throw one back to the main menu after browsing 3-4 levels deep into a folder structure/Qobuz. XDMS also looks amazing on my iPad - it has a clean, modern and classy look. In terms of usability, it fits well with how I navigate music - the ability to browse folders already elevates the usability of XDMS beyond Roon. If it has an easy way to read longer file names (e.g. a scrolling function) that would be even better.
SQ
Going from TAS to XDMS is akin to going to 4k video from HD 1080p - the jump from 360p to HD was a much greater jump, but with 4k you are seeing a lot more information nonetheless. The jump in terms of resolution and musical information (and for equal measure, the lowering of the noise floor) is significant with XDMS - this is coming from an already very detailed digital system (PGGB upsampled files fed into a Chord DAVE). The increase in resolution is most evident in orchestral tracks, XDMS reveals musically relevant details that are masked on TAS. One of my favourite tracks is Liszt's Hungarian Rhapsody on Stowkoski's Rhapsody (HDTT, upsampled). With XDMS, among the massed strings, I could easily hear the detailed texture and resonance of the cellos and double basses which were not previously evident. On Anermet's The Royal Ballet (HDTT, upsampled), one is taken one step further to a live performance. Previously with TAS there was a lack of sense of depth of the venue and instruments. This is much improved with XDMS. Overall the noise floor is lowered, transient response is noticeably cleaner and consequently there is more "pop" to each instrument. This is the closest to a live performance that I got from the recording. Although it is a Kenneth Wilkinson classic, when played through TAS, one is occasionally reminded that this is is a 60 year-old recording - not so when the album is played through XDMS.
Another good example of XDMS's ability to retrieve musically relevant detail is the first track in the Cantate Domino album from the label Proprius (upsampled from 24/88.2). For perhaps the first time I could clearly hear what each singer was singing, whether in harmony or unison, etc. It was impressive. On the other hand, the improvement in resolution was less evident in cleaner, modern classical recordings such as Anne Akiko Meyer's Air: The Bach Album, perhaps because the recording has a lower noise floor. I have yet to try any well recorded modern orchestral recordings; this is on my to-do list, subject to the issue I address in the following section.
I suspect that those who listen to less complicated tunes, e.g. solo instruments or voices, girl with a guitar, may feel that the uplift in sound quality is less evident. Nevertheless, I felt that the solo piano on Nojima Plays Liszt had a noticeable uplift in realism and I-am-there-ness, with the improved clarity of transients and lowering of noise floor. Previously on TAS I was rather annoyed by the typical Reference Recordings veil which was also apparent on this recording, this is now diminished to a more than listenable state. I also played some pop music and feel there is a tad more detail and body in voices than before, but previously with TAS/Roon on the Extreme one already had detail in spades (one could easily hear the smacking of lips, the opening of mouths etc). On complex pop tracks there is a marked improvement in instrumental and vocal separation. My wife is a fan of a Hong Kong 12-member boy band (which shall not be named in this sacred place!) and on upsampled tracks one can follow each singer more clearly, as well as the instrumentation.
Roy (Romaz) mentioned that TAS was a tad dry and Roon sounded bloated and smeared. I completely agree. XDMS is somewhere between the two in terms of body and richness, but in my view closer to the TAS end of the spectrum (i.e. "clean" as opposed to "full"). For those who crave ultimate lushness XDMS is probably not the right direction, but then one has the option of Roon if that were what one desires. However, I do think that XDMS sounds more "organic" and less "digital" than TAS, particularly in the way it resolves transients and decay. Instruments and voices sound more tangible with XDMS (if one can exchange that word with "body") but without the bloat. This is very much welcome no matter which end of the spectrum of tonality one prefers.
Overall, the improvements to the sound quality are immediately apparent. My wife, who is not an audiophile, noticed the uplift in sound quality even sitting in the dining room adjacent to my listening room.
Classical music woes
As someone almost exclusively listens to PGGB upsampled classical music, the number one feature I would like to see on XDMS (no - not gapless play) is the ability to play lengthy 705 kHz / 768 kHz upsampled files without issue. Currently, longer upsampled tracks (~8 minutes or more) can be played on XDMS but playback may abruptly stop mid-way. Some files longer than 10 minutes cannot be played at all. Ed mentioned that the RAM size of 4092 MB on the RAM Disk may not be sufficient to play longer PGGB upsampled tracks and suggested that I try increasing the RAM to 8192 MB.
Update: As suggested by Ed, I increased the RAM Disk (Z drive) size to 8192 MB. With a reboot I managed to play some upsampled files I could not play before at all. I will need to test with longer tracks. Some 16.5 minute PGGB upsampled tracks (the largest possible size of 4.21 GB per track) remain completely unplayable at all while others would come to an abrupt halt just short of 6 minutes of playback.
