⌈ AB-Tech was founded by Alexander Bladelius, the son of Mike Bladelius, and began operations around March 2022, when it launched its first product, the REN Ethernet Isolator. The company specializes in products designed to improve file transfer and audio signal transmission - primarily those related to files. We are testing its latest product, a USB cable with an active filter. ⌋

I BEGAN MY REVIEW OF AB-TECH’s Still LAN filter by addressing the biggest problem facing modern audio systems: interference in the form of high-frequency noise, and by noting that Alexander Bladelius, the company’s founder and CEO, had clearly identified this issue and focused on eliminating it. The latter is my own observation, while the former is a consensus - this is how Mr. Koji Yamamoto begins his review of the LAN switch for “HiVi” magazine; more → HERE.

The importance of this issue in today’s ultra-high-resolution audio seems to be underscored by the efforts of both major companies (Nordost, Audioquest) and boutique manufacturers (Acoustic Revive, Thunder Melody) striving to address it. I’m referring here to both technical resolution - that is, the number of bits and the sampling rate, and actual resolution - that is, how the music sounds.

Alexander’s two latest products - the aforementioned LAN Still filter and the Klar USB cable we’re testing - fit seamlessly into this trend. Both also offer a proprietary approach to this issue and its proprietary solutions, which are the result of their own experiments; you can find the test of the Still filter → HERE.

▲ A few simple words…

ALEXANDER BLADELIUS
owner & designer

‖ Alexander Bladelius at the Warsaw Audio Video Show 2020 • photo courtesy of AB-Tech

FOLLOWING THE DEVELOPMENT of our Ethernet isolators, the USB interface emerged as the next critical weak point in digital audio chains. USB connections between computers, streamers, and DACs are particularly susceptible to high-frequency noise, ground loops, and power-line contamination that degrade signal integrity.

‖ Aluminum housing before assembly • photo courtesy of AB-Tech

Klar is a fully galvanic USB isolator and reclocker that provides complete isolation of data, power, and ground paths. It regenerates the USB signal with ultra-low jitter while blocking EMI, RFI, and common-mode noise. The circuit is housed in a precision-milled, non-magnetic aluminum chassis with extensive viscoelastic damping to eliminate mechanical resonances and microphonics.

‖ Cable assembly • photo courtesy of AB-Tech

The result is a cleaner, lower-noise digital link that lets the DAC perform at its full potential - with improved black backgrounds, sharper timing, and more natural timbre. ‖ AB

▓ Klar

THE KLAR USB CABLE is the latest product from this Swedish company. It was introduced last March and is not only a cable but also an isolator (filter). It is designed for high-speed USB 2.0 connections (480 Mbps). According to the manufacturer, in addition to its filtering function, Klar (which means “clear” in Swedish) regenerates the signal and - as stated - provides “complete galvanic isolation of the signal, power, and ground to eliminate all noise.”

Klar does not resemble a typical USB cable. In the middle of its length there is a large box containing an (active) filter circuit. Its aluminum housing is made of two pieces of “high-quality” non-magnetic aluminum, which is intended to further help minimize interference. The circuits inside are encased in a material that doesn’t fully solidify, which eliminates mechanical resonances and the microphonic effect - and it’s the same material found in the Still filter.

The cable itself uses large-gauge conductors made of tinned copper. As a reminder, tinned copper was the standard material in the early days of our industry, and Western Electric cables of this type are sought after by collectors and audiophiles, mainly in Japan. Today, this tradition is carried on by Belden in the U.S., Melodika in Poland, and Supra in Sweden. I think it’s safe to assume that it was this company that supplied the wires for AB-Tech.

The wires are routed separately for signal and power: one twisted pair is for the signal, and two separate wires are for power. Shielding consists of a layer of aluminum vapor-deposited onto Mylar tape and a tin-plated copper braid. The entire assembly is encased in a noise-reducing sleeve used - as stated in the company’s materials - in the aerospace industry. The cable is terminated with gold-plated USB-A and USB-B connectors. It is available in lengths of 1 m, 1.5 m, and 2 m.

According to Alexander, the cable is unidirectional (as indicated by the connectors) and operates with a load of up to 100 mA. The circuits inside the box are powered by the 5 V line connecting the USB transmitter and receiver. If the load exceeds this limit, the isolator will automatically shut down and restart once disconnected. We read:

The cable comes in a sturdy case, the same as the one for the Still LAN filter. Inside, you’ll find both the cable and a cleaning cloth, along with a small bottle of aluminum cleaner. The whole package looks handcrafted and solid, as if it came from a small workshop that pays close attention to detail. The only thing I would improve is the connector mounting. Instead of “sleeves” (heat-shrink tubing), I’d prefer to see custom aluminum sleeves here.

▓ SOUND

HOW WE LISTENED • The AB-Tech Klar filter was tested in the HIGH FIDELITY reference system. The files were played from a Lumin T3X player acting as a transport, and the signal was decoded by the DAC section of the Ayon Audio CD-35 HF Edition player. All file types were sent from the transport in their native format and converted to a DSD256 signal in the Ayon. The Acoustic Revive USB 1.0PL Triple-C USB cable served as the reference.

The setup configuration looked like that:

router » FunBox 3.0
↕
router » Mikrotik Hap ax3
LAN cabel » Acoustic Revive LAN-Quadrant Absolute
↕
File player (operated as a transport) » Lumin X3
USB cable » Acoustic Revive USB 1.0PL Triple-C vs AB-Tech Klar
↓
SACD Player » Ayon Audio CD-35 HF Edition

» RECORDINGS USED FOR THE TEST ⸜ a selection

• BELL & SEBASTIAN, It Only Takes One Lion, Matador Records/Tidal, SP, FLAC 16/44,1 ⸜ 2026.
• DAVID CHESKY, Graffiti Jazz, The Audiophile Society/Tidal, FLAC 16/44,1 ⸜ 2022.
• MICHEL PORTAL, Dockings, Label Bleu/Tidal, FLAC 16/44,1 ⸜ 1997.
• ANDY AKIHO, SANDBOX PERCUSSION, Seven Pilars, Aki Rhythm Press/Tidal, FLAC 24/96 ⸜ 2021.
• ANGELA BERANN, Groovy Womann, Astromedia/Tidal, FLAC 16/44,1 ⸜ 2015.

• MAHAN MIRARAB, Unspoken, ACT Music + Vision/Tidal, FLAC 24/96 ⸜ 2022.
• BERTRAND RENAUDIN, OLIVIER CAHOURS, Douö, CC Production/Tidal, FLAC 16/44,1 ⸜ 2001/2003.
• FABIANO DO NASCIMENTO, VITTOR SANTOS e ORQUESTRA, Villa, Far Out Recording/Tidal, FLAC 24/44,1 ⸜ 2026.
• THE HI-FI COLLECTIVE, Slow Reduction, The Audiophile Society/Tidal, FLAC 16/44,1 ⸜ 2022.

THE TESTED USB CABLE (cable + filter) offers nothing but benefits. And I’m not just saying this by comparing it to a generic USB cable from a supermarket, although I did make that comparison as well. After all, I compared it to an Acoustic Revive cable - perhaps not the most expensive, but truly excellent. And it was precisely in this comparison that the Klar really shone.

What immediately caught my attention was the emergence of greater soundstage depth. Both in terms of the soundstage as a whole and the distances between sound sources, both of these aspects improved significantly. I heard this not only in top-tier recordings designed with spatiality in mind - more on those in a moment - but also in a virtually monaural recording: the new single by BELL & SEBASTIAN, titled It Only Takes One Lion.

It begins with vocals in the center, accompanied by guitars spread across the channels - this is the only distinct aspect of the horizontal soundstage. I listened to this track with the Acoustic Revive cable and didn’t feel like anything was missing. There was innocence, joy, and a lack of pretentiousness in it. The Swedish cable added a touch of thoughtfulness. It was as if everything had been “polished to perfection.” With it, the separation between the vocals and the orchestra positioned in the background improved, and the soft bass that kicks in exactly at 1:00 was more distinct.

This combination of softness and spaciousness perfectly complemented what DAVID CHESKY composed for the Graffiti Jazz album. In ˻ 2 ˺ Graffiti Jazz Number 2 I didn’t actually hear a wider soundstage, since it was already enormous before. However, I had the impression that the sounds around me - this recording was produced, among other things, using a “virtual head” - were more independent of the sound source, i.e., the speakers. It was as if they “floated” better in space.

The bass sounded interesting. The double bass played by the composer is supported here by a pad that generates sub-harmonics for the bass. It sounds truly excellent. With the Klar cable, the low frequencies seemed less muddy than before. For a moment, I missed that, but ultimately that’s exactly why I use this track in my tests (playlist All that bass… → HERE). And I was just about to write that Acoustic Revive does it better, when I tried turning up the volume by 1 dB while listening to music with the Swedish cable.

It turned out that the sound seems slightly less compressed with it. What I had previously heard with the Klar in the Chesky recording - and which I interpreted as better separation and a sense of “spatial freedom” - was also audible as less emphasis on the attack of the sound and more on its body. Actually, it wasn’t the body itself, but rather the way it filled the space - as if the Klar revealed a deeper 3D quality to the sounds. That’s why the baritone saxophone of MICHEL PORTAL, a French clarinetist and saxophonist, in the ˻ 2 ˺Dolphy track from the Dockins album, sounded more beautiful with the reviewed USB cable.

Somehow, I can’t find another word to describe what I heard, but maybe it isn’t necessary after all. I thought exactly the same thing while listening to Belle & Sebastian earlier, because Stuart Murdoch’s vocals were less bright and “sat” more pleasantly in the mix with the Swedish USB cable. I’m deliberately not saying they were darker - that’s not the point. It seems as though the Klar warms up the sound, but that’s not actually the case. The attack of the fretless guitar in Unspoken, a track from the MAHAN MIRARABA’S album , was just as clear and selective as with the reference cable. The same was true for Lars Danielsson’s accompanying double bass.

It may seem, however, that the dynamics with the tested cable are more subdued than with the Acoustic Revive. The Japanese cable handles this feature superbly - something I also hear with cables that use Triple-C copper. A slight softness, on the other hand, is the “distinctive character” of tinned copper, which I hear every time I use Western Electric speaker cables or pull out a Belden interconnect.

Here, it’s better controlled than in other cables. It’s even channeled into something that makes the sound more intimate. Let’s listen to SANDBOX PERCUSSION from the Seven Pillars album, and we’ll hear both what’s far away and what’s close, at the very same moment. With the cable we’re discussing, the sound felt closer to me, more dense, and even more spacious. Similarly, that is incredibly soft and dazzlingly spacious; sounded the BERTRAND RENAUDIN and OLIVIER CAHOURS album, titled Douö.

Recorded in 2003 for CC Production and later reissued by Harmonia Mundi, it features only guitar and drums, reminiscent of the jazz duets from The Dialogue album by Japanese jazz drummer Takeshi Inomata. Despite such an unusual combination of instruments, it is interesting, surprising at times, and often simply beautiful. The instruments are immersed in a long, generated reverb, which creates distant sound reflections and produces a very wide soundstage for the drums, enhanced by the Klar cable with “bottom-end” airiness, making the sound richer.

▒ Summary

I CONCLUDED THE TEST with the ˻ 1 ˺Slow Reduction track, taken from THE HI-FI COLLECTIVE’s album, recorded - just like Chesky’s album - for The Audiophile Label. Everything I had written about was confirmed. The Swedish cable sounded (modified the signal) in a soft way, giving the recordings an intimacy that neither the reference cable nor, even less so, a generic cable offered.

The lowest bass - which extended truly very low - was rendered densely and dynamically. Its attack is rounded and slightly warmed - this is one of the distinctive characteristics of the tested cable. It is also exceptionally well-resolving bass. There’s more going on here than with the reference cable, but in the background, not in the attack. But perhaps that is precisely why this cable, above all else, brings the sound together into a coherent and dense whole.

This is true both for the slightly bright vocals in the Bell & Sebastian track and for the VITTOR SANTOS e ORQUESTRA heard accompanying the FABIANO DO NASCIMENTO trio in the ˻ 2 ˺ Spring Theme track from the Vita album. With this cable, all the other tracks I listened to during this test sounded deeper, more beautiful, and smoother. The cable itself has a “smooth” sound. And yet it’s detailed. A truly interesting, exceptionally satisfying product. ‖ WP

THIS TEST HAS BEEN DESIGNED ACCORDING TO THE GUIDELINES adopted by the Association of International Audiophile Publications, an international audio press association concerned with ethical and professional standards in our industry, of which HIGH FIDELITY is a founding member. More about the association and its constituent titles → HERE.

→ www.AIAP-online.org