XACT S1. The music server you've been waiting for

JCAT WILL LAUNCH ITS OWN HIGH-END MUSIC SERVER AT AVS 2022 - XACT S1 – FEATURING WORLD’S 1ST 100% LINEAR POWERED MOTHERBOARD.



Designed from scratch, XACT S1, is a purist’s dream for those in the know. Based on JCAT’s ZeNA (Zero-Noise-Architecture) motherboard, the S1 does not rely on switching DC-DC converters. Instead, super-low-noise linear regulators are used exclusively making XACT S1 the world’s first music server running on linear power alone.



The market lacked a genuine audiophile-grade motherboard. Most of the available streaming products are assembled using general-purpose PC motherboards. According to Marcin Ostapowicz, JPLAY & JCAT Founder, such motherboards with noisy switching converters all over the place should not be used in a high-end audio system.



XACT S1’s proprietary motherboard, apart from linear regulation, features extremely low-jitter OCXO clock with ±5 ppb frequency stability. The extensive power supply section based on JCAT’s renowned OPTIMO linear PSU delivers 140 000 uF of capacitance provided by Nichicon’s flagship Muse and Fine Gold capacitors series.



Software is custom made and finetuned personally by JPLAY’s Founder, Marcin Ostapowicz, who promises superb sound quality and ease of use via included brand new JPLAY iOS app which combines Qobuz, Tidal and local content in a single beautiful interface.



According to Wojciech Pacu?a, chief editor of High Fidelity, the sound of XACT S1 is 'insanely difficult to distinguish from an analog source'. Come and hear it yourself.


When: 28-30th October


Where: Warsaw, Poland. Radisson Blu Sobieski Hotel, Room 718

 

The combination of KS/WASAPI Exclusive and Hibernate Mode produces an audible improvement in transparency, micro-detail, and soundstage depth, along with a lower noise floor compared to traditional players. Essentially, JPLAY eliminates unnecessary audio-engine stages and superfluous system processes, delivering a more precisely timed signal to the DAC. Already by 2010, JPLAY offered one of the most effective solutions for transforming an ordinary PC into a high-level digital audio source.

In subsequent years, the development of JPLAY never stopped. The introduction of the Dual PC Setup separated playback control from audio processing, further enhancing performance. Updates to ASIO support, expanded compatibility with a broader range of DACs, and optimization of buffers were introduced to minimize latency and maximize sound transparency. In 2013, JCAT (JPLAY Computer Audio Transport) was founded as a hardware division designed to complete the optimization philosophy of JPLAY, debuting with a high-performance USB cable, soon followed by the USB Card and other dedicated accessories. JPLAY evolved to support network streaming via UPnP/AV, becoming a more flexible solution suitable for modern hi-fi systems. This transition gradually culminated with the release of JPLAY for iOS, turning it into a true UPnP control point.

Today, with the launch of the JPLAY for iOS app, users can control UPnP streamers and DACs directly from their iPhones and iPads, optimized for managing high-resolution streaming from local servers and online services, and featuring an improved interface for precise and easy playback control.

As a regular and long-time user of ROON, I can confirm how excellent JPLAY for iOS has become. There is now no perceptible difference in usability compared to ROON. Apart from usability, the key aspect is the introduction of a dedicated, optimized streaming engine that reduces unnecessary network traffic, maximizing signal clarity. The app connects to UPnP music servers (NAS, PCs with UPnP software) and sends the signal to a compatible renderer, eliminating the need for a dedicated computer to manage playback. JPLAY has transitioned from Windows software to a comprehensive high-end audio playback platform with hardware solutions (JCAT) and an advanced mobile app.

 

Discussing JPLAY essentially means introducing JCAT's flagship product, their top-of-the-line music server: the XACT S1 EVO. It embodies years of digital audio development. The server is equipped with a motherboard powered exclusively by proprietary linear stages, aiming to reduce noise generated by traditional switching modes. Internal signal paths are wired with shielded Phantom conductors to contain high-frequency interference, and timing is managed by a low-phase-noise Master OCXO Clock designed to minimize jitter at its source. Completing the design, IMMOTUS™ mechanical isolation and a fanless design ensure operational silence and thermal stability.

Let’s go into more detail namely, how it was conceived during the design phase. Its immediacy and extreme sense of transparency are clearly a direct consequence of the design choices. The genesis of the XACT S1 EVO stems from the observation that almost all music streamers rely on mini-PC motherboards designed for general computing. In these more commercial designs, the CPU is powered by a multi-phase switching VRM, typically 8+2 or 12+2, switching at several hundred kHz and generating RF spurious noise. This often leads to the characteristic "coil whine," a type of noise that remains on the motherboard’s ground plane and can contaminate audio lines. All other sections chipset, USB ports, M.2 slots, RAM, and audio codec do not have their own multi-phase VRMs but rather small point-of-load regulators, individual buck or LDO regulators, also switching, which add further high-frequency noise. Even when using an external linear power supply, these onboard converters continue switching, so the noise remains trapped in the PCB, couples with clocks and digital buses, and ultimately increases jitter and background noise, giving the sound a timbre perceived as more “digital.”

Moreover, fully filtering out these spurious signals is very complex. In practice, the only truly effective route seems to be eliminating switching regulators at the root—a design decision that adds complexity but promises tangible listening benefits. From this premise, the ZeNA motherboard was born, followed by the XACT S1 EVO: a platform that replaces every DC-DC converter with ultra-low-noise linear regulators powered by an equally linear PSU, avoiding all internal switching, reducing noise, and minimizing jitter at the source.

Let’s rethink this carefully: one must envision a truly “full-linear” solution, radically different from the current market offerings, which increasingly rely on standardized hardware and ubiquitous switching architectures. Unfortunately, even in the professional realm, motherboards use components intended for generic applications—certainly not for audio playback—further aggravating the problem. The only viable path appears to be redesigning dedicated hardware from the ground up, conceived from the outset with a single goal: pure audio playback.

The XACT S1 EVO is equipped with a new type of fully linear motherboard. The ZeNA (Zero-Noise-Architecture) was conceived from the ground up to ensure the highest purity of the audio signal. This is not a recycled PCB taken from a mini-PC or general-purpose server, but a custom-designed circuit created specifically for audio file playback at the highest possible level. Unlike conventional platforms that rely on switching converters, ZeNA uses exclusively linear regulators (Low-Dropout, LDO) to generate all internal power supply voltages. Linear regulators operate by dissipating excess voltage as heat, thereby avoiding the switching noise typically generated by DC-DC converters. This design choice guarantees an extremely clean voltage supply for powering the CPU, chipset, clock, network controller, and every other critical component.

 

To reduce power consumption and simplify passive cooling—since the chassis is completely fanless—a quad-core 1.6 GHz processor was chosen, known for its efficiency in networking applications and low thermal output. In a full-linear design, the heat generated by the dissipation of linear regulators must be kept under control; for this reason, a more conservative processor avoids exacerbating the system's overall thermal balance while also generating no additional electrical noise.

The power supply section, which is always integrated inside the XACT S1 EVO, is the OPTIMO™ X1—a linear power supply based on a high-quality toroidal transformer, supported by a bank of smoothing capacitors with a total capacity of 140,000 µF, made using flagship Nichicon Muse capacitors (Muse and Fine Gold series). This enormous capacitance buffer further reduces voltage fluctuations and ensures a stable, noise-free current delivery.

Mains voltage is brought to the required level via linear regulators, without going through DC-DC converters. This approach is unique in the world of music servers, as it completely eliminates electromagnetic interference (EMI) and switching spikes that could degrade the audio signal.

In a digital system, one of the most crucial components for overall performance is the system clock and how it is powered. For the synchronization of digital data, the XACT S1 EVO uses an OCXO (Oven Controlled Crystal Oscillator) clock of the Stratum 3E type, developed in-house, with a stability of ±5 ppb (parts per billion). This level of stability, even in the presence of external factors such as temperature variations, vibrations, and electromagnetic disturbances, ensures extremely low jitter on the USB Audio 2.0 stream. Moreover, the OCXO clock is not powered by a switching converter, it too is powered via linear regulators, preserving the system-wide “all-linear” design philosophy.

Inside the XACT S1 EVO music server, only proprietary JCAT wiring is used specifically the PHANTOM™ Music Drive Cables, the brand’s flagship product. Each cable, entirely handmade in over seven hours, uses ultra-high purity copper conductors combined with precise impedance matching and laid out in a proprietary shielded geometry that suppresses both common-mode currents and electromagnetic interference. Derived from the established USB and LAN versions of the same series, these conductors drastically reduce noise and preserve digital signal integrity, an essential prerequisite to allow the system to fully express its sonic potential.

The final element is the IMMOTUS™ CL decoupling feet, made of ceramic-aluminum and also developed and built in-house. Each footer features an aerospace-grade aluminum body and high-hardness ceramic spheres arranged in a single-bearing system. Three units are mounted under the chassis of the S1 EVO. The mechanical geometry is optimized to channel chassis-generated vibrations into the most critical frequency bands, preventing them from turning into unwanted resonances.

Returning to the key issue, switching regulators, we can state that their widespread use in mainstream digital electronics does not serve the goal of absolute sound reproduction. A different point of view, a new way of designing computing components is essential to reach a new level of performance that would otherwise be nearly unattainable.

 

Let’s finally get to the heart of the matter: how does the XACT S1 EVO sound?

In a word: neutral. So neutral, in fact, that it almost seems… invisible. It may sound like a paradox: we invest time, energy, and resources to introduce a new component, and once it's in the chain, it “disappears.” But that’s precisely the appeal, we’re passionate about paradoxes, always searching for that extreme element capable of intervening as little as possible, allowing the music to flow freely, without filters. This means there is more, at every level. Its true virtue lies in its absence: every nuance, every whisper that was once seemingly or genuinely hindered or restrained now resurfaces with greater credibility to our senses.

As we ran through our usual selection of favorites, we couldn’t skip the album An Evening of New York Songs and Stories by Suzanne Vega (Qobuz 44.1 kHz, 24-bit). Once again, we’re inside the iconic New York venue, the Café Carlyle, where our ever-vibrant singer sounds even closer and more believable, performing with a naturalness we had never heard before. That edge, that brazen assertiveness disappears, giving way to a more refined territory where micro-details shine more brightly and emerge more easily, fully capturing the atmosphere that was felt in the venue, on that evening, in that moment. There’s more ambient character, more layering, and everything becomes easier to reconstruct. Less aggressiveness, which doesn’t mean less energy, but everything is more polished.

Let’s move on to another classic in our listening rotation: The Raven (Qobuz 96 kHz, 24-bit), which we recall was remastered in 2007 from the 1994 original at MasterSound Studios in Queens, New York. Here, Pidgeon expresses herself with greater resolution and clarity, channeling that physicality more toward expressive energy, bringing to the forefront those details that used to play a supporting role, now painting a richer and more multifaceted harmonic picture, naturally and without apparent effort. Once again, we’re faced with a more intimate, more immediate performance, but less harsh; the sound has been ennobled, it’s wearing a dark tuxedo for a special gala occasion.

It’s time to recount a meeting that speaks the deep language of four strings: the one between Christian McBride and Edgar Meyer. From mutual curiosity emerges a dialogue in which the two double basses become a single, grand voice. The result is But Who’s Gonna Play The Melody?, released on March 22, 2024, and available on Qobuz in Hi-Res 96 kHz/24-bit. It’s not a double album, but a “double” in the literal sense: two instruments, two visions, two eclectic and unique personalities in contrast. On one side is McBride (nine Grammys and a pedigree that spans jazz, R&B, and classical); on the other, Meyer (seven Grammys, an American double bassist and composer who loves blending classical, bluegrass, and jazz). The album was recorded live-in-studio at Ingram Hall at Vanderbilt University: a single room, a few ambient microphones, no overdubs. The choice of a chamber-like auditorium allows the interplay to be captured without filters, with the natural acoustics becoming a third musician—something very important to us.

On the first track, “Green Slime,” Meyer’s pizzicato ostinato is countered by McBride’s bow: a dialogue that surprises with density and spatiality like nothing heard before. Then the roles are swapped with juggler-like agility, and the momentum becomes so intense that it pushes the playback system almost to its limits. The bow, intensely vibrated, draws psychedelic swirls between the speakers, so refined I find myself staring at the new XACT S1 EVO music server. It’s what opens up this dimension: more substance but never a sibilance out of place, more timbral contour simply because there’s more micro-information, more vibrato as if from a freshly unsealed 180-gram record.

The second track, Barnyard Disturbance, is literally a “barnyard commotion” chickens fleeing or something of the sort. In four and a half minutes, the two bassists recreate the semi-serious energy of a rural courtyard, blending funk, bluegrass, and tightly hypnotic lines. Here, timing becomes the focus: the XACT S1 EVO is fast, but more importantly, it paces the music impeccably. It might sound like an exaggeration, but it’s really not: try powering your electronics with an undersized supply, and then you’ll hear the difference. Heard through a neutral and detailed server like the XACT S1 EVO, every finger tap or bow scrape stands out sharply, giving the illusion of being surrounded by that joyful, controlled... disturbance.

Bebop, of Course is McBride’s first composition and the third track on the album. The piece, McBride explains, “was built on the alternate blues changes of Confirmation: I just thought I’d do what I do best.” It’s a piece that alternates bow and pizzicato from the very first bar. All that plucking injects a constant vibrational energy into a sequence that seems endless, requiring speed so that the low notes don’t overwhelm and saturate the listening space. That’s not my case, not because of the room, which is acoustically treated, but especially because of the pairing of the XACT S1 EVO and the TOTALDAC Sublime, a pairing truly over the top. They set the rules, rules of precision, speed, and substance, without being thrown off by feedback waves.

 

Microdynamics emerge in micro-transients: light bow strokes, harmonics (those ultra-brief attacks that produce delicate high frequencies), and slaps, achieved by pulling the strings and letting them snap against the fingerboard for a sharp, percussive hit rich in high-frequency transients, bring most streamers to their knees, flattening everything. Here, the opposite is true: we’re almost in paradise, with a density and harmonic richness I’ve never heard before, everything is crisp, full, and expansive.

With the XACT S1 EVO, depth of field, seen as the difference between McBride (right channel) and Meyer (left), is crystal clear, yet the natural reverb of Ingram Hall remains intact, creating a stereo image that’s surprisingly airy and believable. And so, in just under three minutes, the duo manages to fuse the urgency of bebop with the breath of a chamber hall. The XACT S1 EVO music server, stripping away yet another layer of digital interpretation, places the listener squarely at the center of that dialogue and it’s here that you feel it all: perfectly articulated, chiseled, sculpted between the speakers in a privileged space no one can disturb.

The company’s entire know-how converges into an ambitious challenge: to create a reference-grade Music Server capable of handling digital streams with the utmost purity and temporal integrity, right up to the DAC input.

JCAT’s XACT S1 EVO stands out as both a radical and deeply thought-out proposal in the high-end music server landscape. The decision to eliminate all switching components both in the ZeNA motherboard and in the OPTIMO™ X1 power supply is not a marketing gimmick, but the conceptual and technical cornerstone of the entire project. Every detail, from the proprietary low-jitter OCXO clock to the Nichicon Muse capacitors and PHANTOM™ internal wiring, contributes to a result that can be perceived not only with the ears, but also in the sheer absence of noise.

The resulting sound is pure, stable, coherent free from that digital sheen that often taints even high-end solutions. What you get here is an absence, a cleanliness, a clarity that doesn’t attack the listener but restores music to its natural space and breathing room. And it’s not just about the hardware: the XACT OS™ operating system and JPLAY™ player are integral parts of this vision, designed so that every hardware element works in perfect harmony with the software, without bottlenecks or compromises.

In the world of digital audio playback where numerical “perfection” often conceals audible flaws the XACT S1 EVO proves that a linear approach, when implemented with extreme consistency and paired with software designed to match the hardware perfectly, can still make a difference. And not a subtle one. This is one of those rare creations where form follows function, and the result is not only technical but emotional, vibrant, and analog-like.

 

...that's a very fine review. Thanks for posting @gionaz
Cheers...

 

...that's a very fine review. Thanks for posting @gionaz
Cheers...

@MarkusBarkus Thank you for the encouraging feedback! I’m really happy the review proved useful.
It was my pleasure to put it together, and I’m here if you’d like any extra details or clarification.
Cheers,

 

@Marcin_gps is it possible to upgrade the S1 with the better Clock?
From pictures I saw that the S1 ‘s motherboard can accept the pcb connector for the clock cable.