JCAT XACT S1, the Worlds First 100% linear powered digital music server REVIEW


This is a review written by Terry Ellis April 2024.

For my video review please see my YouTube channel link here

History and Passion

I think the JCAT XACT S1 music server is a very cool product that ticks nearly every box for what I would want from a product like this or how I would want to build it myself. But at the same time its clearly not designed for every audiophile, its designed for audiophiles who value specific things above others and its for audiophiles who are looking for the absolute best, again for those specific things.  I appreciate that sounds vague but bear with me.

I think its important to start with the history of getting to this point because hopefully you will appreciate it more or at least see it better through my eyes. I have been a computer audiophile enthusiast for well over a decade, I was into it before I even realised. My first exposure to accessing a music library on an iPad was a revelatory experience and its something we take for granted today but not way back when. My first real experience of listening to music like this was using a Meridian Sooloos setup, using an MC200 as the source and I later found out it was a computer in a fancy Meridian case.  Not that there is anything wrong with that, lots of audiophiles listen to music on computers every day, not just music servers, but phones and tablets are all computers of course too.

Once I realised the Meridian was a computer I became obsessed with building my own, because that meant it could be and do exactly what I wanted. The big motivator for me was Dirac Live and using it as a room correction solution for my HiFi system. At the time running software on a computer was the only way to get Dirac Live that was affordable to me but beyond that the sound quality I was getting from a standard built computer was not great so I started to explore ways to improve things. Over the last 10 years I have tried all sorts and I learnt that sound improvements generally come from three key areas, hardware, power and software believe it or not. I continued my passion up until very recently with my last main build being back 2019 but that computer was continually improved with all the latest and greatest parts, with the most significant of them being a huge linear power supply from JCAT, the Optimo S ATX, the worlds first ATX 100% linear power supply for a computer.  Its a monster, its larger and heavier than most power amplifiers and demonstrates the challenge of providing clean, stable linear power for a power hungry by its very nature computer. I made a video about this power supply you can see here

My very high end music server thanks to all the quality components power and software optimisations was very ahead of its time and it cost a lot of money to build, with even more cost to my time to optimise the software and OS. It was great solution for me for years but also a problematic one which means at times more time fixing than listening.  I think the overall HiFi music server and digital source market has massively caught up and in some cases exceeded what I had done in ways but even the very best of the “computer” based music servers available in 2024 generally have something important in common with my build. They all use “generic” for want of a phrase computer motherboards in them, I was using an Asus server motherboard with an Intel XEON CPU so standard computer parts. With everything else in the server intended to make it sound better doing so by bypassing as much of the motherboard as possible for the cleanest signal and power with software optimisations helping too. This is how the majority of the best computer music servers are still built today to the best of my understanding and you can get great results.  That is where the new JCAT XACT S1 differs because it’s the world first to have a custom motherboard that has no DC-DC switching components that are said to generate noise, so its 100% linear powered and free of those noise generators.

Understanding it XACTly

From the front, from the sides and the rear the XACT S1 has a very understated appearance and while it feels well built, its not built like a tank or doesn’t exude a hugely luxurious feeling for its premium price tag. But I do like the rounded edges of the case work and its colour contrast and for some reason I really like the orange illuminated  main and only button, for powering on and off of course.  Being orange is certainly different and I think it looks pretty cool. When I look at the S1 compared to my old music server case which was also from JCAT its a clear step forward in its visual design from a computer case to something better and more special.

On the rear there is not much to see either, there are two USB outputs for connecting to a DAC, one with and one without 5V, some DAC owners will be thrilled by this option, you of course know who you are. There is a third USB for connecting a hard drive or to upload music to the internal 4TB SSD storage. Stranger to many will be the 5 Lan and the single Wan port on a music server, that is strange. Its because you can use the XACT S1 as a dedicated network switch instead of a server which would require two of them for real extreme audiophiles and systems but I didn’t test that feature. Also strange to some will be the SD card that has a custom very optimised linux based operating system fully made by JCAT in house and its software that put JCAT or JPLAY really on the map many years, so this is a huge part of the S1’s appeal.  The SD card doesn’t like anything special and its the least modern thing here but its used for its extremely low power consumption and therefore low noise generation and I know all too well that whats on the little SD card is years of work and expertise. If you been an extreme DIY music server builder like I have, this SD card approach is one of those attentions to details you know you would want in a product you built yourself so I am happy to see it and value this a lot.

However I think to fully appreciate the S1 you need to remove the lid to look inside and there are several things that really grab your eye. The overall power supply is custom made for the S1 by JCAT and its using a very quality transformer with Nichicon Muse capacitors and a lot of them, as much capacitance as some power amplifiers. There are a number of specific attentions to details that DIYers will love such as the quality of all the cabling, the non standard choice of the specific 4TB SSD for music storage and the really high quality +/- 5 parts per billion OCXO clock and more.  So its very high grade parts everywhere.

But most exciting of course is the custom motherboard or mainboard because it’s the worlds first 100% linear powered for a music server, so even though other high end music servers have linear power supplies, some use several the computer motherboards in them still use switching components that are said to generate noise. Using linear supplies to power a motherboard is a better situation than using a switching ATX supply but its still not perfect because the motherboard itself is still a limiting factor, its not designed for high end audio after all. The XACT S1 takes this design aspect the furthest of any music server on the market at the time of writing the review by being fully 100% linear powered with no DC switching at all.  JCAT call this ZeNA, Zero Noise Architecture and I think it’s a great name and its a super cool technology development. I have to think JCAT are setting a new benchmark here that others will follow so I am sure we will see more of this in the future and that is exciting for all audiophiles as the technology trickles down in affordability.

I do wonder how many audiophiles still doubt the importance of power quality in purely digital products. I have made loads of videos on the topic in the past, even demonstrating sound differences in them with one of my favourites was upgrading an Oppo 4k blu ray player from its SMPS to a linear supply.  The Oppo was used just as a CD transport feeding into a Chord Qutest DAC, the sonic difference was remarkable.  The video is here and if you check the comments many people inquired as to where they could buy the power supply such is the sonic difference, even audible in a YouTube video using a poor quality on camera microphone.  Experiences like this are powerful motivators.

What sound?

Assessing the sound quality of a digital source is extremely difficult because it depends on the DAC you use and how good that is. I have used 4 / 5 different DAC setups with the S1, all of them worked simple plug and play with no problems and it was a great relief not having to worry about installing Windows drivers or endlessly testing settings for them. I have had some very high end HiFi gear here just recently to around £100,000 and the S1 is easily good enough as a source for a system at that level. I just reviewed the epic good German Physiks Borderland Mk IV speakers which cost about £30k with the new Gryphon Diablo 333 integrated amplifier £25k and a £17k Ideon Audio DAC. With this setup I felt I was really hearing how good the S1 can be because as a source its super clean and smooth there is no digital edge to the music at all. Everything sounded right to me, the music’s timing, tone and timbre, its three dimensional sound stage, the vocal quality, clarity and detail with clear treble information again completely edge or splashiness free.  I think the sound I have been hearing has always been “limited” by the speakers or the DAC or the amplifier or mostly the size of my listening room but never the source for once. I think digital sources, especially when streaming from the cloud are never fully transparent as we always know or are aware that we are listening to digital music.  So it might only be a small amount but I think some “digital-ness” is always present but with the S1 its definitely reduced or less obvious and maybe I could say its a more analogue sounding digital source than others I have had in my room.

Now I am getting into vinyl playback I am even without actively doing so comparing how  how vinyl sounds compared digital or compared to the JCAT S1 with a DAC in this instance. At the moment I can’t get vinyl to sound close to the overall quality level of this digital setup but its still early days for me and I have a lot still to learn spinning the black discs.  But If I categorised an analogue sound as one that is free of the “digital-ness” I mentioned before, where the sound is smooth, warm and very musical, not mechanical, Maybe its crazy talk to say it, but the S1 with the right DAC gives me more of those qualities than vinyl right now so in my instance I think its fair to say the XACT S1 sounds more analogue than analogue which is very high praise for a music server streaming from the cloud.  At the moment I really can’t find a fault with the sound of the JCAT XACT S1 server but I don’t have its main “best of the best” competitors here to listen to side by side,  maybe they would show me some shortcomings or maybe not I don’t know.

Nothing is perfect, yet

So what is the catch here or what are the negatives you might ask, for me there are two big ones. Firstly is the price which is 12000 euros, so it’s a huge amount of money for a digital music server. But its important we consider the price of the S1’s main rivals, the Innuos Next Gen Statement server costs around £19k, the Antipodes Oladra costs around £30k, but does do some USB reclocking if thats important to you.  Then lastly the Taiko Extreme server also costs around £30k so all of them cost significantly more than the JCAT and none of them offer a computer motherboard free design, so none of them are 100% linear powered.  So the JCAT is offering a newer technology approach for a lot less money.

The second big negative is the fact the XACT S1 is very minimalist stripped down product by design, the less is more, or less is less noise approach. As such there is no WiFi, no dsp or bass management and none of the bells, whistles and thrills that many other products offer these days at very affordable prices. Like I said this is a server for audiophiles who value specific things and that is very much me because this is very much a music server I would build for myself but its better than one I could build for myself.  I would have to use a generic computer motherboard and build around it like I had done before, and with every build you learn something new but I know I couldn’t build a better server than the S1 and I couldn’t optimise it better either. Even so I cant say the JCAT XACT S1 is perfect because its not, but it will be the best digital music server source available right now for some audiophiles.


There is a second product I am reviewing here also and its much more affordable at £43.99 / $49.99 a year.  That works out to less than £4/$4 a month and I use it for many hours every week so its offering great value to me. I am referring to JPLAY the music library control app. I have been using the JPLAY app for over a year now as I was using it all through its beta testing and its come a long way since then. I can say that from all the music library apps I have ever used in my life and there has been lot’s, JPLAY is by far my favourite for several key reasons.

The first reason is simple, it seamlessly combines my Tidal music library with my own CD ripped music library into one and I can navigate it all together or I can navigate them separately if I want to.  Its always lightning fast, especially considering its using UPNP for control and that means you can use the JPLAY app with nearly every music streamer and server available and I do. I compare it to every manufacturers own app and I always end up going back to using JPLAY because its so nice to use.  The UI is slick and its easy to build and develop a playlist over time that stays in the app forever without needing to save it. I can keep going back and listening to a selection of the same music which is really useful for gear assessment. Especially as I have such bad memory for songs and album titles, I remember new music better from the album art and you can’t search for that, so if I discover new music during a session I don’t have to worry about saving it as it will not be gone from the list when I go back later.  Silly piece of mind maybe but it matters to me.

Another thing I love about the JPLAY app is the visual aspect of it, the album art size and layout ratio to the text I think is almost perfect. Also almost perfect I think is the Tidal integration in terms of searching. You can quickly search all music, or just Tidal to find specific albums, songs or artists without needing to change the page of the app to a specific search orientated one. This makes searching a pleasure not a chore as it can so easily be. The Tidal integration is so well done that you can get to it from the home page or you can go much deeper into Tidal more like you would on the dedicated Tidal app.  Its the seamless quick integration that I find so fantastic because it doesn’t feel like your using two different systems, like it does in a lot music control apps where you are in and out of them separately.  Its all just one excellent app experience.

I also feel the layout and navigation of the app is almost perfect, maybe its because I am so familiar with it now but I find in the main its less cumbersome to use than others. I can get to the music I want to listen to really easily and fast but the experience of getting there is still nice. This is definitely aided by just how fast the app is, its so fast everything feels almost instant, you hardly ever see any buffering of album art which drives me mad about any app in 2024.

The app menu system is a little confusing at first and maybe could be polished a little better but you get used to it.  There are not a lot of menu options to choose from so its nice and simple to setup and customise what your clicks do but the important options are there such as selecting gapless playback or selecting how you want your music added to your play list.

Then lastly what I really like is how the app experience is equally good on my iPhone as it is my big iPad pro because the experience is of course better on a bigger screen but most of the time I just use my phone as I always have it on me.  I can still enjoy the same great experience when doing so and also I can have a different playlist on the my phone compared to my iPad that’s there at all the time so it helps me in this job but also gives me some variety that helps with my sanity.

Jcat xact s1 music server website 7

App negatives
Now there are some big negatives with the JPLAY app that will be obvious to you if you are a Roon power user for example. JPLAY by design doesn’t do nearly as much for you as Roon in terms of offering equalisation and other bells and whistles features some audiophiles might rely on and use all the time.  JPLAY is more about selecting and listening to music simply, while also easily finding and discovering new music.  Its an app thats designed for sound quality over features and that is aided by not needing a dedicated computer just to run it, such as you need with Roon. Roon offers you more features overall but I think JPLAY matches it for the music library management experience and costs less.

The second and likely negative with PLAY is its an app for IOS only and that of course wont be great for everyone and worse still for some is the streaming service integration is limited to Tidal and Qobuz only.

Its interesting, I have seen a number of music server manufacturers recently advertise their products as JPLAY certified so this app is making real waves across the market and its very easy to see why once you have used it. Its offering a great experience with your money being used to continually better that experience and stay up to date with the many changes and developments Apple and the streaming services make.  That is essential to a long time happy user experience product and its not free to do this so paying for it makes sense.

However for owners of XACT S1 music server it is free, you get a lifetime of free access to the JPLAY app which is cool and I think right given the price because of course the two products are designed to work perfectly together, but they are not exclusive.  You could use any UPNP control app with the S1 and JPLAY with any UPNP controllable server or streamer.

Final Thoughts

This pairing is the best digital source solution I have had in my listening room to date and its much better than anything I have built myself. I have to applaud JCAT for creating not one but two really great products that are pushing the audiophile experience forward. JCAT have for a decade now been at the computer audio cutting edge for both hardware and software.  Given it’s a small company with one main man Marcin Ostapowicz as the mastermind is even more impressive.  For someone like me who has been along for the whole ride I take my hat off once again.

pecial Performer Award Website No Background

An Essential Audition Award is granted in recognition of a products high performance but with a certain uniqueness that makes auditioning even more essential.

For the full specification of the JCAT XACT S1 music server please see their website linked here