UPnP and Qobuz
The S1’s software adheres to the UPnP standard, which means that the Femto server can also stream to other endpoints on the network to create a multi-room system. Likewise, the XACT S1 player can be streamed to from other UPnP libraries on the network. Here, the JPLAY app comes in extremely handy as it always allows the user to combine or filter between the various local and online libraries.
I have tried both external streaming variants, but in all cases, the sound was always the most coherent and expressive when using the S1 as an integrated server and player. Upon checking with Marcin, he confirmed that when music files are played from the built-in server, the playback is direct (inside the unit), and the network connection is used only for controlling playback. In other words, the music stream is not sent to the switch and router and back but remains inside the unit.
This certainly goes some way to explaining why the server sounds so special. But it can’t be the whole story because the S1 also sounds absolutely superb, streaming from Qobuz. I did many comparisons using my own CD rips as well as Qobuz downloads, and found that, sometimes, the local files sounded better. But other times, the streaming files actually sounded better! This was especially the case with more modern music where I presume the shorter and more direct export path has an advantage versus the more extensive production required for CD mastering and stamping. Even so, when there were differences, they were small enough to ignore, and without an AB comparison, I would not be able to identify a streaming source from a local source.
Roon
Roon can work well in the right system, but in the context of my system, it has a rounded and rhythmically- and dynamically restrained quality to it, whether running on the Antipodes Oladra or the Grimm MU1, that I do not hear with UPnP in general and the XACT S1 in particular. The XACT S1 is easily as smooth and fluid as Roon on my best server, but it is more organic, as well as more rhythmic, expressive, and communicative. It’s worth noting that a running Roon Core on the network has an audible “rounding” impact on the sound, even when not used for playback. Therefore, the full extent of the XACT S1’s performance is most pronounced when the Roon Core is stopped, the server is shut down, or the server is disconnected from the network.
Conclusion
With a custom 100% linear power supply with 100% linear regulation, a fully custom motherboard, a custom Operating System written from scratch and optimized for the hardware, and proprietary Femtoserver software running, all under control from the superb JPLAY for iOS app, the XACT S1 is a truly unique proposition.
The server is so utterly even-handed, neutral, and well-balanced, yet so utterly free from artifice or traditional “digital” artifacts, that to summarize it as sounding one way or another is selling it short. Whereas most music servers excel in certain areas, the XACT S1 performs at the highest level across the board. Precisely thanks to its natural neutrality, I can see it fit right in with any system. Unless one is looking to add hysteresis-like roundness or euphoric coloration deliberately, the XACT S1 is the closest thing to analog-done-right in a digital music server.
When the same team designs every segment of the digital front end, you get a normally unattainable opportunity for synergy. This shows very clearly when using the XACT S1 server in combination with the XACT Phantom LAN and USB cables, which yields a performance that, even more so than the server by itself, exemplifies what is often aspired to as an “analog”-like reproduction. The distinguishing factor with the XACT S1 is that it remains uniquely nimble and foot-tappingly rhythmic, highly transparent, and highly resolving, in addition to being deliciously liquid and smooth.
The XACT S1 sounds simply superb, and I cannot recommend it more highly. The only provision is that it works with UPnP to achieve the best possible sound quality. But if you are willing to live without Roon, the JPLAY app makes the transition as painless as possible.
External Links
Manufacturer: XACT
Some of us at the JPLAY forum have tested the JPLAY iOS app, via an RJ-45 cable, from the Audio Network router to a Lightning to Ethernet adapter, connecting the latter to the iPad or iPhone, with impressive results. If you still have the XACT S1, you might want to look into it. Carlos
You mentioned that the JPLAY for iOS app runs on iPads and iPhones, and although it is not officially endorsed for MacOS it runs perfectly fine on the original M1 MacBook Air as well.
Marcin told me that a Mx MacBook with JPLAY for iOS running on it can output directly via USB to DAC.
So it might be possible that this software gives the Macbook a nice uplift in SQ.
Did you try this?
Thanks
Hi Matt, Although it might indeed work and sound decent enough, I’d be hesitant to expect anything beyond that, given that the Macbook has no special power supply, audio interface, or USB hardware. Earlier experiments with several Windows PCs and my previous Intel Macbook Pro did not yield anything spectacular. That said, I have never used my current M1 MacBook with any of my DACs, so I don’t really know:-)
Thank you for your review, Christiaan. I appreciate that you’ve taken the time to evaluate the performance of both the player and server apps, especially noting the shift in hierarchy favoring UPnP/mpd. We previously discussed Squeeze + Squeeze, but unfortunately, it is not compatible with JPLAY. Additionally, your comparison with Taiko (though I understand you won’t review it), Oladra, and CDs helps put sound quality into perspective.
In a high-performing setup, we’re always eager to understand when and how the system performs at its best. You suggest that S1 may benefit from a complementary S1 running bespoke firmware to achieve optimal sound quality. Given the meticulous attention to detail—from the specially-selected industrial-grade 4TB SSD with the XACT Link drive cable to the highly durable OS SD card designed for military conditions—it seems clear that playing local files represents the pinnacle of sound quality in a single S1 unit, followed (closely) by streaming from Tidal or Qobuz.
Is that correct, or am I mistaken? If you did compare with differnent file types that also would be very interesting to know.
All the best,
Paul
Hi Paul, I’ve not heard the dual S1 setup. That part is added for information only.
The SQ delta between local and streaming depends on a few variables, an important one of which is the recording date. Recent files often sound better streaming than when ripped from a CD. For older albums, it can go both ways, especially when comparing originals with remasters. But under equal circumstances, more often than not, local is better.
When comparing purchased and downloaded Qobuz files, I tried WAV and FLAC but can’t be sure which is the master format. It could very well be FLACs, from which the WAVs are derived. In any case, in these particular circumstances, local WAV sounds best, followed by local FLAC, and then streaming. However, the differences are quite small, especially between local FLAC and streaming FLAC. Ultimately, I find I am very comfortable listening to either source or format, regardless of the small differences.
From all my switch reviews, I know they affect both streaming and local music playback. In other words, the music stream need not actually travel through the switch for the latter to have an effect on the sound.
Thank you for your response. I was already aware of your preference for WAV files and local storage, but I’m curious if this also applies specifically to the S1, given that Marcin emphasized the integration of the local SSD.
It seems we’re constantly at a crossroads between playing from local storage and streaming, with difference in sound quality often diminishing. However, in certain setups—and particularly with certain files like WAV—a noticeable difference can still be heard in 2024. Apologies if I misunderstood your point.
Hi Paul, to clarify, there is still an audible difference between local WAV and streaming FLAC, and this is audible with the Grimm, Antipodes, and XACT S1. The difference is smaller between local FLAC and streaming FLAC. And, sometimes, streaming can be better than a ripped CD. My stance is that the difference is not always large enough to warrant worrying about too much. Marcin is also a huge fan of DSD, and playing DSF files through XACT S1 was an important part of the fine-tuning process. For DSD playback, you obviously need local storage, which helps explain the emphasis.
That makes more sense to me now. I really appreciate it.
Thank you!
In addition to considering how a switch affects local file playback, we should also factor in (any) network noise from the modem all the way to the streamer and dac, and any connected devices, power supplies included.
In sensitive systems, even minor network noise can become noticeable. This might explain why disconnecting the Ethernet cable sometimes improves audio quality, although it’s not a practical solution if you prefer to use well-designed music apps and software.
Regarding file formats, besidesc using the WAV format, achieving optimal sound quality is often best with files that match the original sample rate and bit depth of the recording, provided you can determine those specifications.
Fantastic review, as always Christiaan. You are an asset to the audiophile community, keep up the great work 🙂
Thanks, Watts!
I own a Taiko, Should I sell It for the XCAT?
Given that I also work for Taiko Audio, I need to avoid a conflict of interest. So, I’m afraid I cannot comment on the Taiko Extreme.
Allow me to give it a try. Based on the review, it seems that the XACT S1 is a strong contender but if price isn’t a concern, it might not quite reach the level of the top-tier servers like the Antipodes Oladra or Taiko Audio Extreme.
That said, it’s an important question to consider. Also, do you currently own a Taiko + a network card + an Extreme Switch + an Extreme Router?
If you lean towards local files, Marcin (and likely Emile as well) have put considerable effort into optimizing local playback. What types of files do you typically play?
Ultimately, they each have distinct sound qualities, so your decision will come down to what suits your listening preferences best. Happy listening!
I own the USB card, a sotm switch with clk inside and a super clock sotm. I used sotm linear power supply for both and 2 Sotm Ethernet with filters cat7 and one stack audio Ethernet filter. My Dac is apl sr mk2, have kondo g700/melius Accu A80, TAD cr1tx
I assume you’re primarily focused on streaming, which makes sense given the attention you’ve paid to your network. Even upgrading the router’s power supply could make a difference.
Perhaps Christian could help you by identifying the distinct sound characteristics of the Taiko, Oladra, and XACT S1 without preference. If anyone can articulate the sometimes subtle audible differences between them, it’s him!
Thanks Paul, I have a Sotm power supply too on my internet box.
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All I can say is that the two severs sound very different. One is not better than the other, but they do have different perspectives, making it a personal matter. Also, the two employ different music playback suites (UPnP/JPLAY and Roon). What I would recommend is to audition the XACT S1 next to the Extreme to form your own opinion.
Thanks Peter, I leave close to Lille, I think you too? If one day possible to make an audition. Edward is installing last version of XDMS at same time I make my email. I will saw what it will able to do
If you’re open to all possibilities and recognize the potential of networks and switches in high-end audio—especially after hearing it yourself—why not consider selling the Taiko for two XACT S1 units with a few recommended JCAT cables? It seems that “the XACT S1 can be paired with a second S1 to achieve the best sound quality. Of course first we keep waiting for further audible insights from Christiaan 😉
If I recall correctly, Marcin mentioned that he connects directly to the router (or box) and either disconnects his iPad or uses a wired connection. Given that, with a S1 combo you might also consider selling the SoTM switch with the internal clock, along with the Super Clock SoTM, SoTM linear power supply for both, two SoTM Ethernet cables with filters (Cat7), and one Stack Audio Ethernet filter.