S1 Evo

Reviewer: Joël Chevassus
Sources: Esoteric K-03 and N-05XD, Cybershaft 21A, Mac Mini M1, HiFi Rose RS201E, Lumin X1 & P1, XACT S1 & XACT S1 EVO [on review], CH-Precision C1.2 [on loan], Mola Mola Tambaqui
Power and integrated amplifiers: Coincident Speakers Technology 845 Turbo monos, Esoteric S5, SPEC RPA-W3EX, Kinki Studio M7, Red Dragon S500
Loudspeakers: Vivid G1 Spirit, Leedh E2 Glass, Recital Audio Illumine HEFA, Aretai Contra 100S
Cables: Phantom USB & Ethernet [on review], Luna Red series speaker cables s & interconnects, Vertere HB USB, Esprit G8 USB
Room: 7 x 7.5 m with high beam ceiling, acoustical treatment by Tecsart, Acustica Applicata & Hofa Akustik
Review component retail: €16'000 XACT S1 EVO, €12'000 XACT S1, €3'000 XACT Phantom LAN Cable, €3'000 XACT Phantom USB Cable

After a particularly memorable experience with the XACT S1, I finally had opportunity to explore its next level in the EVO version. I even went further, using a standard S1 as router in combination with an S1 EVO as dedicated player, the most advanced configuration XACT currently offer. Externally EVO looks almost identical to the standard model except for its more substantial Immotus CL ceramic‑aluminium feet. Made from aerospace‑grade aluminium with ceramic ball bearing, these provide greater resistance to vibration, always an enemy of sensitive electronics. The most significant changes are found inside. EVO runs a newly developed high‑precision OCXO clock and redesigned internal power‑supply cable known as the Phantom Music Drive. This uses the same advanced materials and precision construction as XACT's new Phantom USB and LAN cables included in this review. The Music Drive is engineered to minimize interference so preserve signal purity for files streamed from the integrated SSD. The main OCXO clock was entirely developed in‑house. The standard S1 uses a compact Emerald oven‑controlled crystal oscillator offering ±5ppb stability. EVO's oscillator on its own dedicated circuit board achieves the same stability while delivering markedly improved phase‑noise performance below -135dBc/Hz at 100Hz offset. The clock module powers from linear supplies derived from XACT's Optimo series with two power rails, one for the oscillator, one for its output buffer. For all features shared with the standard S1, refer to my earlier review. Both XACT players are unlike others on the market. Designed entirely from scratch with pure audio performance in mind, they avoid the compromises inherited from computer‑based architectures. The standard XACT S1 as the foundation for EVO reportedly required no less than six years of R&D. It's the most ambitious project designer Marcin Ostapowicz has ever undertaken. Three years devoted to developing just the motherboard, another three on refining the product to meet his standards. Creating a custom motherboard specifically for audio was essential. Most manufacturers rely on mass‑produced boards for cost and convenience but Marcin sought to eliminate not only noise from the power supply but also noise produced by the motherboard's own internal regulators.

As a result, the XACT uses linear regulators exclusively and the entire power supply is fully linear, an apparently unprecedented approach in the world of digital consumer audio. Both models run a customized Linux OS with real‑time kernel offering millisecond‑level latency. Since launch the system received several updates. Reflashing the SD card using Balena Etcher allows users to benefit from ongoing improvements. The most recent update released December 2025 pushed sonic realism even further. Like the standard S1, EVO offers a single USB digital output as the only interface that supports formats up to DSD512 [I²S does as well – Ed.]. The six GB Ethernet ports receive the same gold‑plated EMI‑shielded treatment along with 12‑core transformers for improved isolation. As noted in my S1 review, Ethernet ports for routing won't operate when this device is in player mode. Switching between player and router roles requires reinstalling the operating system by reflashing the SD card. This explains why XACT often show two S1 connected together, one serving as router, the other as streamer. This strict separation of functions exists because each role requires a different operating system; combining both on a single card would compromise quality. In player mode, the S1 connects to the network via the first Ethernet port; all others remain disabled. The Phantom cables in USB and LAN config were designed specifically to complement the XACT S1. The USB cable uses high‑purity copper conductors and custom aluminium connectors. Standard length is 1.2m extendable to 3m. A woven black nylon sleeve provides protection. Each cable is handcrafted and requires more than seven hours of labour. As usual with high‑end cabling, technical details remain scarce. According to XACT, the design focuses on precise mechanical and impedance matching along with a specific twist geometry aimed at eliminating interference and preserving signal integrity. The LAN cable follows the same design principles but includes robust shielding and the exceptional Telegärtner MFP8 IE Gold connectors as used on the International Space Station. It is significantly stiffer than the USB version which can make connections with very light components challenging.

The essential question of course is whether EVO delivers a meaningful improvement over the standard S1 to justify the price difference. To make it direct and simple: yes. The enhancements may seem subtle on paper but in practice have a significant unmistakable impact. Having both units on hand for several weeks allowed for direct comparisons. EVO improves every aspect of replay. It is more dynamic, offers a wider more holographic stereo image and retrieves more detail. The S1 platform is so transparent that even small design improvements magnify. Despite the resolution increase, EVO sounds no harsher. Quite the opposite: it offers slightly more sweetness, rivalling the finest vinyl or tape playback. Yet transient precision is razor‑sharp, something very few analogue systems can match. On Paul Dukas's The Sorcerer's Apprentice, each attack rendered with breathtaking impulse clarity while maintaining full harmonic richness and natural decay. This 1956 recording of the New York Philharmonic under Dimitri Mitropoulos revealed both its age via microphone hiss and astonishing musical energy. The Silk Road album on Indésens gained extraordinary presence. The timbres of viola and Chinese guqin were so lifelike that I felt the musicians in the room. Articulation and rhythmic definition were simply superb. On Improvisations for Nay and Percussion, timbral accuracy was astonishing. Traditional Chinese music often dismissed as aggressive or limited in expressive dimension takes on new beauty and tonal richness through EVO. I never heard another digital transport reproduce this music so convincingly.

Switching to more modern Western repertoire such as Varese's Amériques performed by the Cincinnati Symphony Orchestra, the XACT S1 EVO seemed to strip away digital fog, offering something remarkably close to live performance. Even the most powerful timpani strokes never overwhelmed the system. Everything felt natural. EVO invites endless listening. It combines the tonal beauty of great vinyl with the explosive dynamics and microscopic detail of digital. For demanding audiophiles, it is nothing short of a revelation. Marcin's operating system refinements push transparency to extraordinary levels. Updating the SD card via Balena Etcher was straightforward and each update brings meaningful improvements in sonic performance. Is a high‑end system required to appreciate EVO? Not necessarily. Even over modest speakers such as the compact OGY wideband monitors from Closer Acoustics, EVO's contribution was unmistakable. This will delight source-first advocates since whatever goes missing at the source can never be recovered downstream. The XACT S1 EVO pushes the boundaries of what digital playback can reveal. On the Béla Quartet's Trois frères de l'orage, Erwin Schulhoff's first quartet took on new life. Attack precision was exceptional. Low‑frequency articulation improved clarity in passages that previously felt muddled. The soundstage breathed more freely, reminiscent of what the finest tube amplifiers achieve. Switching from the Mola Mola DAC to the Esoteric N‑05XD brought further refinement. EVO was so transparent that the DAC became the limiting factor. The same was true for Thomas Adès's Exterminating Angel Symphony. The Minnesota Orchestra's explosive energy retained incredible resolution and naturalness similar to a live performance where even the most complex tutti never sound strained. It was astonishing to find speakers and amplification become secondary because the quality of the source dominated the entire system. Yet an audiophile's instinct is always after more. That is where the dual‑S1 configuration comes into play: one EVO as player, one S1 as router. The setup is incredibly easy, the results are stunning. Soundstage expands until room boundaries disappear. Dynamics and resolution increase noticeably. The benefits of this dual configuration become immediately clear.