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This review first appeared in October 2023 on By request of the manufacturer and permission of the author, it is hereby syndicated to reach a broader audience. All images contained in this piece are the property of HifiKnights or the manufacturer- Ed.

Reviewer: Marek Dyba
Analog sources:
 J.Sikora Basic MAX turntable, J.Sikora KV12 tonearm , AirTight PC-3, phonostages: Grandinote Celio mk IV, ESE Lab Nibiru V 2.5
Digital sources: passive custom PC with Win10, Roon, Fidelizer Pro 7.3, JCat USB Femto card with iFi power supply, Hdplex linear power supply for PC, JCAT USB Isolator, LampizatOr Golden Atlantic +Ideon Audio 3R Master Time (USB signal regenerator), LampizatOr Pacific
USB: iFi audio 0, micro iUSB3.0 and 3x Mercury cables
Preamplifiers: Audia Flight FLS1
GrandiNote Shinai
Speakers: Ubiq Audio Model One Duelund Edition, GrandiNote Mach4
Interconnects: Hijiri Million, KBL Sound Red Corona, Metrum Lab Edge, TelluriumQ Silver Diamond USB, Stavessence USB Eunoia and Apricity, Ethernet Eloquence
Speaker cables: LessLoss Anchorwave, Metrum Lab Edge, KBl Sound Red Corona
Power components: GigaWatt PF-2 MK2 and GigaWatt PC-3 SE Evo+; a custom power line with GigaWatt LC-Y in-wall cable; GigaWatt G-044 Schuko and Furutech FT-SWS-D (R)
Rack: Base VI, Rogoz Audio 3RP3/BBS
Sundry accessories: Rogoz Audio SMO40 and CPPB16 platforms and BW40MKII feet, Franc Accessories Ceramic Disc Slim Feet and Wood Block platform
Retail price of reviewed components in EU: €12'000

Not so long ago, playing back audio files meant a generic computer. Today we may choose from going on hundreds of specialized transports and servers developed with audio purpose in mind. The sector has a few leading brands and the top models command dozens even hundreds of thousands of euros. Aspiring to be one of the best is the XACT S1 digital transport and music server. While I was still too young so with very limited access to novelties to observe first-hand the previous shift when the Compact Disc replaced vinyl, I did have a chance to closely watch the next transition when CD gave way to streaming. True, the CD remains with us as does vinyl and SACD. Yet there's no argument that a virtual explosion of purpose-designed solutions and a plethora of streaming services have cloud-based file playback the leading music carrier of 2023.  Still, many audiophiles like yours truly still love their physical media which explains not only the revival of the black discs but the small comeback of reel-to-reel even cassette tape.

Just so file playback popularity has had many manufacturers focus on developing the best possible D/A converters, music servers, network transports, streamers, USB and Ethernet cables and other ancillaries to improve the playback quality of local or cloud files. One such provider is from Wroclaw, Poland. They spearhead three brands, two of which already made names for themselves, JPLAY and JCAT. The former developed the eponymous software music player which has been to market for more than 10 years. The latter came a few years later and offers several components for file-based audio systems. I used JPLAY in the past and really liked its sonics though its basic interface was a bit of a deterrent. Some years ago before music servers became widely available, Marcin Ostapowicz as the man behind both brands advised me on how to build my first music server which featured a specialized JCAT USB card which significantly improved the performance.

If memory serves, this was the first JCAT product. USB and Ethernet cables followed as did linear power supplies, more advanced versions of the USB and LAN cards plus other accessories. In 2021 I reviewed the then latest versions of both cards together with the INITIO 3 linear power supply. Afterwards I acquired both cards for my server and added a USB + LAN ground conditioner. The improvement was significant and I happy; until Marcin contacted me again a while back. Did I want to review his latest master-clock upgrade for his USB and LAN XE cards plus his digital network transport and music server called XACT S1? The latter launched his third brand XACT. How could I have said no? The XACT S1 premiered at last year's Warsaw show. It's currently the only product in the XACT portfolio and a kind of crown jewel which marries the best JCAT hardware and JPLAY software IP in one chassis. If you have at least rudimentary experience with computer-based playback, you probably realize that specialized routing software and hardware play equally important roles and only together offer ultimate performance. Marcin Ostapowicz had already mastered both aspects. Even knowing that Roon became very popular with demanding users, he kept developing his JPLAY player until it was competitive. So the XACT S1 bundles proprietary hardware and software designed and developed by the same team.

Let's start with some history. How or why did you become interested in computer audio then turned it into a business?
Marcin Ostapowicz: I first became interested in high school. I had my first USB DAC based on a Texas Instruments DIY kit and experimented with the foobar2000 software player and various plugins. I knew back then that digital transports didn't sound alike so decided to pursue this field, first as hobbyist and a few years later professionally when I founded JPLAY.

I remember the first and a few following versions of JPLAY. It was interface-less software focused on sound quality not convenience. What changed your approach when today's version reminds me more of Roon than the earlier JPLAY?
Sound quality was always my top priority and with JPLAY for Windows I tried to correct the sound. With the new JPLAY iOS app, it was time to add ease of use.

When exactly did the JCAT brand launch and am I right about the USB card being its first product?
JCAT as the hardware division of JPLAY launched in 2013 so two years after JPLAY. The USB Card was one of the first products, yes. Now we have its 3rd iteration, the USB Card XE.

How did making components intended to improve the quality of in most cases DIY or custom servers/transports turn into a complete solution?
I always wanted to offer a complete music server. I could have done it years ago using available parts but wanted to make it my own way without any compromise. The S1 synthesizes all my research and experience of developing innovative audiophile hardware for JCAT and software for JPLAY. Every product I developed over the years made an important contribution to the eventual creation of the XACT S1 music server.