A-B Tech REN Ethernet Isolator

by Marek Dyba / March 9, 2023

Already due to its name, A-B Tech REN Ethernet Isolator, Alexander Bladelius’ Ethernet cable stands out among competitors. It seems that rather than considering a transfer of the data its single function he decided that isolation between the network and audio system plays at least an equally important role.


October 2022, Warsaw, Audio Video Show. The second most important audio show in Europe and most likely the best consumer show in the industry in the world is back! People rush from all the corners of our country, Europe, and the whole world to find out what’s new in the business of consumer audio and video equipment. Funny enough, it seems that while many audiophiles used to complain about audio shows being boring and not necessarily worth going to prior to the „pandemic break”, after three years of having none of those they are all longing for the opportunity to meet other audio freaks, listen to dozens, if not hundreds, of various systems and discover new products and brands.

One of the latter, the new brands I mean, at least for me, is the A-B Tech from Sweden. Obviously, I knew Mike Bladelius and his products before. After all, he is one of the most prominent audio designers and has been for many years. A-B though stands for Alexander Bladelius and his own separate path in the audio industry. The story of daughters and sons following in their parent’s footsteps is nothing new also in our industry. Some of them continued the work of their parents, learning from them, sometimes better adapting said business to the ever-changing market expectations and conditions. Other, such as Alexander, stayed in the same business but used their knowledge and experience to develop their own products. And so, here it is, accompanying his father but proudly presenting his own first component, Alexander Bladelius. You can see it clearly when they stand one next to the other – father and son. While the amplifier by Bladelius seems to be the star of the setup they present there is another component hidden away from the spotlight but, as it turns out, quite important as well. It is called A-B Tech REN Ethernet Isolator.

Most companies classify this type of product simply as an Ethernet cable – that’s its core function. The A-B Tech, when you look at it, is no doubt also a LAN cable. There is an RJ-45 plug on one end, another one on the other, and a black cable in between. And, oh yes, there is also a „magic” metal box in the middle of the cable’s length. The latter feature is a bit odd, at least for an Ethernet cable as I saw various boxes on analog cables, interconnects, speakers cables, and even power cables. Still, I can’t remember any other Ethernet cable with this feature. It doesn’t mean there isn’t any, just that I can’t remember which suggests it is not a common solution with this type of cable. What is also odd is the name of the product, not the REN part, mind you, but rather the classification, as it reads „Ethernet Isolator”. Again, not that odd, as I (and many others) use an optical LAN isolator in my audio files playback system and have been for quite a while. A medical grade one, not an „audiophile” one, but it works and is yet another small cog in the bigger whole that ultimately improves the performance.

Still, the one I use is a box (a plastic one) with two LAN ports on two sides – one sticks an Ethernet cable from a router or wall socket (in my case) to one of them, and another leading to (usually) switch to the other. Its job is to isolate the system from noise coming from the network and it is pretty good at it. As you’ve probably noticed, the isolator itself does not employ an Ethernet cable – the user needs two of them. A-B Tech REN on the other hand is a cable and isolator, sort of two-in-one, or even three-in-one as it is intended to galvanically isolate not only signal but also ground. The latter might really be the key feature of this product, as many issues with LAN-connected audio devices arise from grounding issues. In theory, the reviewed product by Alexander Bladelius should help users to get rid of all, or at least a lot of, the noise that otherwise may enter an audio system from one’s home network and numerous devices connected to it. Does it actually influence the sound coming from speakers? We will see about that.

Design and features

Even though I had a chance to ask Alexander some questions he was rather reluctant to reveal the technical details of his first product. I can understand that – why would he make it easy for competitors? So actually what we know about this design is only what the website reveals. And it reads:

„The cable itself is a high-grade CAT 8 Ethernet cable that is specially designed for noise cancellation most commonly used for medical and military purposes […]. It features an aluminum PETP foil around each balanced twisted pair of copper wire. All four pairs are then housed with a special thermoplastic material, and finally wrapped in a custom noise-reducing sleeve normally used in the aerospace industry, that also provides a luxurious finish for the listeners’ eyes.”

And then:

„In the aluminum body milled out of two solid pieces of non-magnetic high-grade aluminum which is specially designed to keep out any interference, the isolator is molded in a vibration-dampening material. The connectors used are specially designed for high-end Ethernet cables and feature a die-cast robust zinc housing and high-quality latch-protectors.”

Now, let me add, that A-B Tech REN comes in a solid travel case with a thick layer of protective foam that ensures a safe shipment. It contains also a small bottle with some sort of fluid (with another reference to the aerospace industry) that allows users to take proper care of the aluminum box on the cable. It should be periodically applied to prevent oxidization. The leaflet one finds in the box explains all the above and adds one more piece of important information. Due to the „isolation” feature one may have to wait up to a minute after connecting cable on both sides before the actual connection is established. It isn’t the case in my system but as it turns out REN seems to have another inherent feature – we will get there in a moment. The plugs look really good, and the whole product is well-made, even if it probably won’t win many awards for the best-looking LAN cables (for me this title goes, hands down, to the David Laboga Audio cables with their wonderful leather sleeves, but that’s me).


I had a chance to spend some time with REN using it in my own reference system and another one by Silent Angel (Z1 + N8 PRO + Forester F2 + Expander E1). The former includes my custom passive server featuring JCAT NET and USB Cards XE (review HERE) powered separately using Ferrum Hypsos Signature (review HERE), while the server benefits from a linear power supply by Keces (P8 mono). The server is connected to Silent Angel Bonn N8 switch paired with Forester 1 linear power supply (at some point I shall replace it with an even better performer, the aforementioned Silent Angel N8 PRO) using David Laboga Digital Sound Wave Sapphire LAN cable (review HERE). Another DL Sapphire LAN cable connects the switch with the input of my reference LampizatOr Pacific DAC. Then via Soyaton Benchmark IC (review HERE) signal is sent to GrandiNote Shinai integrated driving GrandiNote MACH4 speakers (via another set of Benchmark cables). You will find other components used in my system listed below the review.

Those of you who read my review of the David Laboga Digital Sound Wave Sapphire LAN cable already know that after that experience I acquired two of these for my reference system. The fact that they were made in Poland was a factor, but only a minor one compared to the influence these had on the performance of my setup. It was undoubtedly positive, even if on a global scale (I mean of the whole system) not that big. Please remember that whenever you read one of my reviews – each component does its part in the setup, and some of them (electronics and speakers) have a much bigger influence than the rest. Still, even the small improvement added by some accessories or cables contribute to the final effect, to the performance I am, and I believe so are you, after. After all, we audiophiles and music lovers are constantly looking for ways to improve our musical experiences delivered by whatever audio system we use even if only by a little bit.

While I was happy with the DL Sapphire I never claimed it was the best LAN cable on the market (not even the top one from David Laboga Audio). So after talking to Alexander Bladelius at the AV Show in Warsaw last year, I got curious about his concept of an Ethernet Isolator rather than just a LAN cable or in other words an added feature of his product. It was hard to assess its influence on the performance of the system presented at the show – it was just one little cog in a much larger machine, and a „machine” I didn’t know that well. To get a better grip on what it has to offer I needed to check it out in my system that I know best. And finally, an opportunity arrived at my doorstep in a form of a small unassuming fight case and I gladly used it.

So how and if at all the tested Swedish product impacts the sound coming from my speakers? For starters, let’s be clear about one thing – A-B Tech REN is not the kind of a component that knocks people off their feet within seconds. And, as I like to remind beginner audiophiles, it’s a good thing! An overwhelming majority of audio products that do that, impress the hell out of you after the first several seconds of the first listening session in a long run turn out to be unbearable, fatiguing, or in other words, hard to enjoy. So if you decide to try the A-B Tech LAN isolator yourself do it only if you plan to give it more than 10 minutes of your time as it won’t be enough to fully appreciate what it does for the system.

In my case, it seems to have an inherent feature that it shares with a lot of tube amplifiers, Class A amps, tube DACs, phonostages, and so on. Namely, each time I start a new listening session having added REN to the setup it takes up to 20, maybe even 30 minutes before it makes a clearly recognizable difference. Obviously, my reference system includes tube DAC and solid-state but Class A amplifier, and both of them require some time before delivering optimal performance. Still, with other LAN cables at my disposal it takes less time to achieve optimal performance from the system as a whole, and it’s the A-B Tech REN that’s the only variable, hence the conclusion that it is the tested product that requires the most time to truly shine. To be clear, the sound is already very good after, say, 5-10 minutes, but it gets better and better the longer I let it play. Is it a matter of the „isolation” element of the design? Maybe. Anyway, give it time as it clearly pays off.

So what does REN has to offer? If I had to limit the assessment to a single sentence I would say that it offers unparalleled tranquility, closely followed by an incredibly orderly fashion of presenting the music. Yes, I know it requires further explanation. The tranquility here is understood as a complete lack of nervousness in the sound, even the one I usually don’t realize is there until is gone – that is a feature of some, most often power-related audio products. The noise in the background is gone hence there is no distortion and everything falls into place. All the elements of the music are presented without rushing things, without shortcuts, detours, timing issues, or any other sort of distractions in a pure, steady fashion. The presentation is no longer about the sound but it’s rather all about the music and all its building elements, even the tiniest ones, that are presented with amazing clarity and transparency.

To me, it feels like all other elements that may stand in a way between a recording and the listener (me) are just gone. Everything has its place in this calm, precise, orderly musical experience. And yet it is not one that is often referred to as cold or even clinical one, it is not focused on details, and it is definitely not dry. Quite on the contrary, the sound is beautifully rich, dense, and weighted while resolving and transparent simultaneously. It has a very natural flow, so while the amount of information is incredible, I have to intentionally look for them to realize this remarkable wealth. Otherwise, which is much more natural, by the way, I am engaged, even immersed in an intense, rich, riveting experience with all this information smoothly blending into a bigger whole.

On the one hand, it reminds me of all those live performances I love so much to go to, that are about the music perceived as a whole and about them being a unique, so incredibly enjoyable experience. On the other, it feels much more like music played from vinyl records than from audio files, as it is even more analog, so to speak, than with most other LAN cables I know. It is not the same, mind you, but there are some similarities that I, a huge fan of black records, truly enjoy and welcome! I can always focus on following a selected musician on the stage, but most of the time I simply enjoy the performance as a complete, exciting whole. While audio systems, even the best ones, can never convey the whole experience of a live performance, some of them get me closer to what I am looking for in all audio setups, a similar feeling to that I get when attending a concert. A-B Tech REN turns out to be one of these components that take my system a small step closer to my ultimate personal goal (even though I know it is unachievable).

The soundstage is more impressive (which is also more difficult to achieve!) in terms of depth than width. I mean the latter gives you no reason to complain – whenever there are sounds in the recording placed by a sound engineer outside the space between speakers that’s what you get. Like, say, on Pink Floyd albums (I listen to several of them) with a lot of out-of-phase sounds surrounding the listener that are delivered with the Swedish cable in an amazingly convincing way. It’s just that some audio components tend to add something extra on their own, which is impressive, maybe even welcomed, but is actually a deviation from the high-fidelity concept. REN gets you what’s there in the track and nothing more – take it or leave it.

It is the depth of the stage, and the precise layering clearly placing instruments closer or further away in the mix that impresses me most about this A-B Tech REN cable/isolator. The better the recording, the clearer the spacial placement and the more convincing the imaging. There are a few albums I like to use for such occasions such as „Carmen” with Leontyne Price and its incredible soundstage depth (chorus marching far, far behind the singers in the foreground) or „Monteverdi: Trace of Grace” by Michel Godard, and Arne Domnerus’ „Antiphone blues” both recorded in large spaces (an old Abbey and a church respectively). All of them, in terms of capturing spacial relations between phantom images, room ambiance, reverb, and so on is remarkable. While my DL Sapphire LAN cable delivers all of them in a very convincing, natural, airy way, REN does it so with even more precision, with better-pronounced contours and shapes.

The sound is also beautifully open, effortless, and natural even when a large orchestra or organs are involved. They sound powerful, and they impress with dynamics, both on the macro and micro levels, and with the scale of presentation. It seems as if A-B Tech REN is never shy to present grand-scale events with panache, and yet in a proper scale and perspective. The timbre of each instrument (also period ones) and vocals, their texture, characteristic features, and so on seem to be conveyed with proper fidelity hence beautifully natural. As a result, the presentation as a whole is truly immersive, it touches me on a deep level reminding me again of this unique feeling of witnessing something very special, a true ART, one that accompanies me during most live performances.

Still, for me, the most impressive feature of the A-B Tech REN is its ability to create the impression that I can hear more details, and that there is even more information in the sound with it than without it. It is not quite so as it’s rather about the clarity of presentation, about getting rid of all these aforementioned distractions which sometimes obscure relevant information from even the best, richest recording. It allows me to focus more effectively on the music in all its glory, with its abundance of details and subtleties, and emotions.

The resolution of the sound is impressive as well as the ability to differentiate sounds in every possible way. This is true for timbre and for dynamics thus resulting in a very realistic, engaging performance. I’ve only recently, for whatever reason, thanks to QOBUZ actually, discovered the Musica Nuda duo. She sings he plays double bass. With A-B Tech REN the wealth of information flowing from just these two sources of sounds keeps me on the edge of my chair as I try not to miss anything. Even when listening to the same tracks for the second or third time I keep discovering new details in them. It is amazing, by the way, how many of these are there in such a seemingly simple performance. Interestingly, there are not that many fingers sliding along the strings in the recording (live one titled „Verso Sud”), but every pluck is clearly defined and differentiated in terms of its speed and power. Also, the „wood’s” response is conveyed in a very convincing, deep, and accurate way. Add to that a lot of information regarding the whole acoustic environment combined with the ability to recreate the ambiance and mood and what I get is a feeling of participation in the event. That’s precisely what I am looking for in every tested component, as for me live performances are the ultimate reference.

I try out the A-B Tech REN not in one but in three ways. Firstly, I install it between the wall socket and the switch. It replaces two LAN cables and the aforementioned optical LAN isolator. To be honest, I can’t really point out any major differences between the two solutions. I can though, confirm once more that they both do the job of eliminating noise compared to an off-the-shelf CAT5 LAN cable. Anyway, the cheaper version offering the same results in this spot in my system are two high-quality non-audiophile LAN cables and a medical-grade optical LAN isolator.

The second way to utilize the Swedish product is to use it to connect an input of my JCAT XE NET card (in my audio server) with the switch. The differences again are not big but you have to remember that the tested product replaces another excellent competitor, the DL Sapphire LAN cable. Both deliver similar, „analog”, smooth, coherent, spatial performance although it seems that REN has a slight edge in terms of transparency and clarity of the sound. On the other hand, DL Sapphire may be a touch richer.

Finally, I replace another DL Sapphire with A-B Tech REN to connect an input of my LampizarOr Pacific with the switch, and… the results are similar to the ones just described. Both deliver outstanding performances with a tiny little advantage of the Swedish cable in terms of transparency and clarity, and the Polish one in terms of richness and maybe, just maybe, a touch deeper bass extension. My guess -these advantages of the tested product are the result of an even lower noise level due to the ‘isolator’ feature. Unfortunately, I don’t have two RENs at my disposal, as it would give me an opportunity to check if two of them combined increase the effect on the sound or if one does the very same job.


A-B Tech REN LAN isolator stands out among other audiophile LAN cables because of its more comprehensive functionality. Yes, it is a LAN cable and in this role does a great job compared to the other ones I have at my disposal. It is well-made, terminated with solid, high-quality plugs, and quite flexible which makes it easy to install in a system. It is the metal box in the middle of the cable’s run though, that makes a difference making it one of the most interesting products available on the market. With it, as the name suggests, isolating an audio setup from all the noise and distortion coming from the network is taken care of. What’s more, not only the signal but also the ground is galvanically isolated. It means that in many systems this one product can help you resolve more than one issue and contribute to the final sonic performance of your system when playing music from files, whether from local storage or from the Internet.

The overall sonic signature in my opinion is very analog. But it is not the warm, soft, rounded-on-the-edges, analog sound, but rather one that is incredibly coherent, smooth, and rich, yet resolving, spatial, and transparent. Obviously the final result, the performance of the whole system still depends on many other factors (components of the setup) but the A-B Tech REN can give it a push towards an immersive, highly musical, not-digital, quite live-like performance. So if that’s what you look for, you should give this first product Alexander Bladelius developed a try because it is one of the best you can find.

Technical specifications (according to the manufacturer):

  • CAT 8.1 Cable & Connectors
  • Complete galvanic isolation
  • RJ45 connectors
  • Different lengths are available

Prices (when reviewed):

  • A-B Tech REN: 1.100 EUR for 0.5, 1.0, 1.5 or 2.0 meters; 1,399 EUR for 2.5, 3.0, 3.5 or 4.0m
  • A-B Tech REN: PLN

ManufacturerA-B TECH

Polish DistributorAUDIO ATELIER

Associated equipment:

  • Digital source:  a custom passive server with WIN10, Roon, Fidelizer Pro 7.10, JCAT NET XE, and JCAT USB XE cards with FERRUM HYPSOS Signature power supply, KECES P8 (mono) linear power supply for the server, JCAT USB Isolator
  • D/A Converter: LampizatOr Pacific +Ideon Audio 3R Master Time (USB signal regenerator)
  • Analog front end: J.Sikora Standard MAX turntable, J.Sikora KV12 tonearm, AirTight PC-3, phono stages: Grandinote Celio MK IV, ESE Lab Nibiru V 5.
  • Power amplifiers: GrandiNote Shinai, Circle Labs M200
  • Preamplifier: Circle Labs P300
  • Loudspeakers: GrandiNote MACH4, Ubiq Audio Model ONE Duelund Edition.
  • Interconnects: Bastanis Imperial x2, Soyaton Benchmark, Hijiri Million, Hijiri HCI-20, TelluriumQ Ultra Black, KBL Sound Zodiac XLR, David Laboga Expression Emerald USB, David Laboga Digital Sound Wave Sapphire Ethernet
  • Speaker cables: Soyaton Benchmark
  • Power cables: LessLoss DFPC Signature, Gigawatt LC-3
  • Power: 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)
  • Network: Silent Angel Bonn N8 + Silent Angel Forester F1 + optical LAN isolator
  • Racks: Base VI, Rogoz Audio 3RP3/BBS
  • Anti-vibration accessories: ROGOZ-AUDIO SMO40 and CPPB16 platforms and ROGOZ AUDIO BW40MKII feet, Franc Accessories Ceramic Disc Slim Feet and Wood Block Platform, Graphite Audio CIS-35 and IC-35