Since the spatial aspects of all live recordings are what I turn to, I played albums recorded in sundry venues such as Tokyo's Blue Note, Warsaw's Jassmine, Green Mill and others to learn how well the Polish server differentiates. The S1 did not disappoint. I only know some of these venues from personal experience yet was ready to bet that how the server presented them was as realistic as it gets. Each differed in size, depth, distance, reverb trails and more. While it's the performance we pay the most attention to at a concert, the same band will sound quite different depending on venue and the XACT proved fully capable of conveying such differences. Listening to Whitesnake's "Starkers in Tokyo", Steven Tyler's "We're All Somebody From Somewhere" or Patricia Barber's "Monday Night Live At The Green Mill", I couldn't help but think that not only was every one of these uniquely phenomenal vocals exquisite live-like and expressive but also more palpably here/now. It was particularly clear on David Coverdale's vocals and accompanying guitar. The S1 delivered not only the timbre and texture of voice and guitar plus the ambiance surrounding them but then also all the fingering noises on the strings and the singer's breathing. Key for me was that it did not push these aspects forward but rather clearly presented them behind the soloist so they became building blocks of credibility.

There are three more features which make the S1 a quite unique proposition. Since the OS loads onto SD card, it's hot swappable. An alternate OS creates a dedicated audiophile switch. Whilst the price makes this rather excessive, it's how Marcin runs his personal system where he explores new ideas. One S1 is his transport/server, another S1 his network switch. For the time being he considers this cascaded duo his ultimate solution. I did try it with the single XACT at my disposal. It did an excellent job and might be the best audiophile switch I've tried except perhaps for the combined efforts of Silent Angel's Bonn NX and Genesis GX clock. I'd have to run both side by side to be sure. The latest JPLAY player is completely different from what some may remember from 10 years ago. Back then it had to improve and work around the intended Windows OS. One had to use commands to load/play music. It was a minimalist solution focused on best possible sonic performance. It wasn't very convenient and deterred some. The S1's JPLAY license loads a very different iOS interface which for this Android user is its only flaw. I pointed out the same to Lumin many times until they finally wrote an Android app. Marcin gave me no clear answer about whether we can expect an Android JPLAY any time soon if ever. If you find the S1 as good as I did to want it, an iPad or iPhone are essential. While it was impossible for me to compare Roon and JPLAY each on its own very different server, for ease, convenience, smoothness and reliability of operation both offered an excellent user experience. While Roon offers more features, presets and meta data, the question is whether we actually need/use them. JPLAY's Qobuz and Tidal integration worked as trouble-free as local files off its built-in SSD.

Vitally the S1 OS and JPLAY are being constantly refined. Some changes target sound, others features. A few days before I wrapped, Marcin released a new OS version for still better sonics. He asked whether I wanted a new card or download the code and flash it onto the existing card. I chose the latter and went through the clearly documented process. It proved simple, relatively quick and worked perfectly. It operated as reliably as before without the smallest hiccup. As for any sonic advance, a comparison wasn't easy. I realized after the fact that having two cards for both OS versions would have made it a lot easier to map differences. Even though my assessment isn't based on a direct comparison, I still thought that there was something to Marcin's claim of still better sound. The change wasn't dramatic but felt denser and more coherent. At the same time, clarity and transparency seemed higher which suggested lowering the already very low noise for an even deeper insight into every recording. So yes it got better; not by much but at this level, even tiny improvements are most appreciated. Knowing Marcin, he'll keep tweaking both hardware and software. So while for now the XACT S1 is his statement product, it will still refine over time.

I reviewed a lot of gear over the years, some reasonably priced, some extremely expensive. Yet it happens less than you might think that I am this objectively impressed and subjectively delighted to wish that I could add a component to my system. Unfortunately in most cases things are beyond my reach and the XACT S1 is such a one. I'd replace my server with it in a heartbeat if I could afford to. How much purer of a signal the XACT S1 delivers to a D/A converter was obvious after pairing it with three top-tier examples from LampizatOr, Playback Design and Weiss. Each showed inherent sonic character then performed at its best. The sonic results differed in tuning but ultimately the performance was as remarkable, immersive and addictive regardless. Music streamed from Qobuz even Tidal was close enough to SSD streams to almost make no difference. Yes the built-in drive still ensured top quality but cloud streaming came so close that I stopped paying attention. The latest JPLAY s player turned out to be very different, far more advanced and convenient to use than its previous versions. There are many similarities with Roon so users of the latter will find the former as easy and pleasant. The XACT S1 seems to be one of the best music servers and transports to market and while it is expensive, it still costs less than its most worthy competitors. That deserves our award.

Publisher's comment: After asking to get Marek's review syndicated, Marcin offered me a separate review sample. Knowing that I don't do WiFi, he suggested a wired hookup option for an iPad. I demurred. With a 27" iMac with Audirvana Studio and an external 4TB SSD drive as my server/streamer, why would I step down to a far smaller display? Couldn't I simply connect to the S1 through Audirvana's UPnP protocol? Now it was Marcin's turn to demur. He insisted that I use his iOs app. So no dice. Which isn't the point. The point is that his response reiterates how to his mind, a lot of performance really lives in his own software. Why go into a review that'd only exploit 50%? It's a good reminder for those who underestimate the influence of signal-routing/processing code on the final sound. Shiny hardware is sexier but player software just as essential. Srajan Ebaen