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Acoustic Revive CS-3K AC Power Filter

08-02-2023 | By Wojciech Pacuła | Issue 128


Acoustic Revive is a Japanese company founded in 1997 and run by Mr. Ken Ishiguro. It specializes in audio cables, anti-vibration products, but also offers innovative products, the ideas of which are most often supported by the University of Tokyo. We are testing one of the products used to filter the AC supply voltage, CS-3K. It's its world premier.

I don't know if you know also noticed it, but recently the "revolution" related to the high-frequency noise reduction in audio systems has significantly accelerated. It seems that with the increasing awareness of the impact of power supply on the sound comes the growing knowledge in this field.

The Acoustic Revive, whose filter we are reviewing this time, has known this for years. It offers three different RFI filters: the RPC-1K with a large housing and plugged into a socket with a short cable and RAS-14 Triple-C filter plugged into the power cable, test HERE, and CS-3K; all three are new versions of filters offered by this manufacturer for a long time.

The CS-3K is the smallest of them. Its shape resembles the mass conditioning plugs of this company, bearing the company name Reality Enhancer Plugs, test HERE. Although similar solutions can also be found in portfolios of such brands as Nordost (QRT Qv2), Chord Company (PowerARAY), and also in the Q1 model from the Portuguese company Qualia Physic (test HERE), Acoustic Revive was the first, all others followed in its footsteps.


CS-3K is a product whose main task is to minimize AC power line noise. We connect it to an empty socket of the power strip to which the power cables are connected. However, press materials say that it can be plugged into any socket in the house and will perform a similar function, but to a lesser extent. Like all other AR products, this one is based on scientific research conducted at the University of Tokyo, Mr. Ishiguro works closely with.

A few simple words…

Ken Ishiguro, Owner, designer

The job of the CS-3K is to reduce HF noise and vibrations. It benefits from technology developed for for infrared computer mouse. It is the same as the function of RPC-1KM. It was built using highest quality materials with outstanding properties for vibration damping, conductivity and noise-removal: A2017 aviation grade aluminum alloy, brass, natural smoky quartz, natural silk, Kiyoh-stone & tourmaline powder. For internet connections we used PC-TripleC/EX conductor,

The second filter, RUT-1K (you will find its mini-test below - ed.) removes noise from USB bus, both power and signal circuit. Other brands products remove bus-power noise only, but RUT-1K can remove noise also from signal circuit. It has not only noise removal function but also damping by using natural smoky quartz and anti-static effect because we used Kiyoh-stone and tourmaline powder.

Almost all products for empty receptacle and USB port just change sound, but few offer a true effect. Even if it has noise removal effect, it decreases energy or give some character to the sound. CS-3K and RUT-1K do not have side effects. In addition, these products will improve energy. There are too many audio accessories that change sound but never improve it. A lot of people must think that all audio accessories are so. Acoustic Revive offer accessories that improve sound but without any side effects.

The CS-3K filter has the form of an AC plug, but no cables are led out of it. By the way, this is the second power plug in the history of Acoustic Revive, after the CFRP-1F, and the first of its class, and who knows, maybe it will be available with their cables in the future. And it would be nice, because it looks very good. The body is made of one of the varieties of aviation aluminum, duraluminum 2017, and the part with contacts is made of pure Teflon. Phosphor brass contacts are heavily gold-plated and cryogenically treated.

The primary purpose of the CS-3K is high-frequency interference suppression (RFI). A special coil is used for this purpose, connecting the two main contacts - positive and "earth". In addition, on each of the contacts, including the protective run, there are small discs made of smoky quartz, used by this company in various products, including Absolute power cables (more HERE). By the way, let's add that a similar disc, but without a hole, was glued to the body of the plug from the inside.

The name company uses for the CS-3K filter is "receptacle stabilizer." This is because its secondary function, after suppressing RF interference, is vibration damping. This is an effect recognized by audio companies quite recently, and—as it turns out—important. The wire inside an electromagnetic field vibrates—this field is produced by alternating current flowing through the wire. Such vibrations generate parasitic currents in it. They are not theoretically high in amplitude, but their frequency affects the high end of the audio signal, degenerating spatial information and fine detail.

You can see the presentation of the "stabilizer," prepared by the owner of the company in the video on YouTube HERE.


For the coil to work in the best conditions and not to vibrate itself, Mr. Ishiguro used several of his flagship solutions. We have already talked about quartz, so let’s add a cotton-like material that minimizes the static electricity of the materials, and paint all the elements inside with a paint containing a mineral called Kiyoh-stone, which is indicated by the letter 'K' in the name.

For the first time this solution was included in Acoustic Revive products in 2021. We have already written about it in the test of the RWL-III ABSOLUTE acoustic panels and it was already known that more 'K' products were being prepared, for example a matte for a record player, AC voltage filter, artificial mass, and cable stands.

As Mr. Elia Hontai-san from Muson, the representative of Acoustic Revive outside of Japan, wrote to me at the time, Kiyoh-stone is a rare earth element whose main component is aluminum silicate. It is available in only one place in the Land of the Rising Sun, in Gunma Prefecture. As he says, it is no coincidence, because the headquarters of the Acoustic Revive company is located in the same prefecture.

The property of this material that Mr. Ishiguro-san wanted to benefit from is that when it vibrates, it easily produces high-intensity negative ions, with a maximum in far-infrared rays. Kiyoh-stone generates up to 40 times more ions than tourmaline. This material was used in the form of paint that was used to paint the inside of the filter. Elia Hontai adds that it is one of the more expensive materials of this type available on the market, and in limited quantities. 



The AC Acoustic Revive CS-3K power supply filter was tested in the High Fidelity reference system and was compared to the RPC-1K filter, as well as to the power strip without any filter. It was plugged into the Acoustic Revive RPT-4EU Absolute power strip, and the latter, via a 2.5-meter Acrolink Mexcel 7N-PC9500 cable, to a dedicated Furutech NFC wall receptacle, supplied by a separate power line with its own fuse.

The problem I faced was the type of plug used on the unit I received for testing—it was a great looking type B plug, used mainly in Japan and the US (also China and parts of Central America). For now, there are no plans for the filter to be equipped with a Schuko plug. Therefore, I had to use the Type B Schuko adapter. It worsens the conditions the filter operates in, but I got the "blessing" of the head of Acoustic Revive, Mr. Ken Ishiguro.

It was an A/B and A/B comparison with A and B known.

Recordings used for the test | a selection

King Crimson, In The Court Of The Crimson King (An Observation By King Crimson), Island Records/Discipline Global Mobile/WOWOW Entertainment IEZP-128, 50th Anniversary Box Set, 3 x K2HD UHQCD + Blu-ray (1969/2019).

Mayo Nakano Piano Trio, Miwaku, Briphonic BRPN-7007GL, Extreme Hard Glass CD-R (2017); more HERE.

Art Pepper, Art Pepper meets The Rhythm Section, Contemporary Records/Craft Recordings CR00392, SACD/CD (1957/2022).

Enya, Enya, BBC Entertainment BBC CD 605, CD (1987); more HERE.

The Acoustic Revive FILTER, which we are dealing with this time, belongs to the "supporting" products. Not basic ones, not even auxiliary, but those that lay the foundation on which classic audio components build their sound. Its operation does shape the timbre, soundstage, dynamics, or any of the features discussed during the tests of audio devices, cables, etc. And yet... And yet when I say that the CS-3K has some properties, I deeply believe it. And that's because its influence is repetitive and I had a similar perception of how the sound changed when I played music from SACDs, CDs or LPs.

And it changed, shall we say, quite subtly. In the sense that by plugging the Japanese filter into the power socket and sitting in front of the loudspeakers or putting headphones over the ears, no one will exclaim "Eureka!," it does not work so. Its influence is perceived over longer period o time. That is, we begin to understand them over time; sorry for the "we," but I simply identify with you. And only then can one say that the difference between "before" and "after," although it seems subtle at first, is in fact clear.

I heard it right in the first minute of playing the title track from the King Crimson's In The Court Of The Crimson King (An Observation By King Crimson), in the remixed version released in 2019 on the K2HD UHQCD. The change was that I got "more sound in sound." For a while, when I compared playbacks A to B, where A was a system without the filter in the path, it seemed to me that after plugging it in, the sound got a bit closer to me and became clearer. After a few more tests, this time B/A, I had to verify this opinion. The filter does not change the spatial relations between the instruments, nor does it correct their distance from the listening position. If I read what I heard correctly, the point is that the filter allows the sounds to sound stronger, as if they were bigger, as if they were clearer, and thus more audible.

The difference in question, as it seems to me, is primarily in resolution. This is only a few percent "increase," and yet in this type of system, I use to listen to music with, it turns out to be valuable. The more so that—as I said—the basic characteristics of the sound do not change. With the filter, Michael Giles's drums, especially well treated in this version, had a clearer tempo, were more "present." While I initially thought they were closer to me, they actually were presented further away and had a better described space (spatial effect) around them. And because it was fuller, better defined, it seemed bigger.

I could say the same about Greg Lake's vocals. Distorted, overdriven, heard as if through a megaphone, with the filter plugged into the power strip it was clearer, fuller, and at the same time better pronounced. Usually, the clearer something is, the more aggressive it is, because clarity is often a function of treble opening. Here it was the opposite, because the sound seemed smoother, warmer. This is a common effect that I hear with increasing resolution, so I attribute all the changes I'm talking about to it.

It was no different with an album whose resolution is astonishing, namely Miwaku by Mayo Nakano Piano Trio. Recorded and mastered in DSD256, released in 2017 by the Japanese label Briphonic, it was burned on an Extreme Hard Glass CD-R disc (more about this technique HERE). Its sound "with" and "without" changed even more than the sound of the King Crimson's album. With the filter, everything "grew," filled in and became clearer.

After some time, I realized that the changes I experienced with it were exactly the same as with the Crimson album, only that because there was more information in the input, the filter helped to describe and define it even better. Just like on last year's remastered in an analog, tube system by Bernie Grundman, Art Pepper's album entitled Art Pepper meets The Rhythm Section. And it wasn't that it was "worse" without the filter, because it was still very good, but that it was "better" with it.

This distinction seems to me crucial in this case. When talking about products like the Acoustic Revive CS-3K, you cannot attribute them something they don't do. And they do not improve the sound of the system—they only allow better presentation of the strengths of the products that are in it. By themselves, they do not change anything in it, but only "bring out" what is good in it. If the system "does not perform well," either because it is poorly put together, or simply some of its parts are not the best, the CS-3K will not help. Yes, it will be better, there will be less RF noise in the system, and the supply voltage will be less distorted (because that's what this filter does). And yet, without something basic in the sound that makes us sit fascinated in front of the loudspeakers, it will not give us anything.


This little "gadget," or whatever we call it, does something very similar to the ground filters that I use in my SACD player. It allows the devices to sound fuller, denser and in a more resolving way. Although the timbre does not change, it still seems that everything is warmer with it. Listening to "Boadicea" from Enja's debut album, I immersed myself deeply in this, in fact, very simple melody.

Simple, but so inspiring that you can hear another song based on this theme Creepin' prepared by three producers: The Weeknd, 21 Savage and Metro Boomin (an interesting analysis of the influence of "Boadicei" for R&B and hip hop music can be found HERE) on the radio. And even with this simple theme, the Acoustic Revive CS-3K filter turned out a very good fit to my system complementing it. Maybe it does not interfere with its sound as deeply as another filter from this manufacturer, the RPC-1K, but it is also much cheaper and takes up less space.

So if you have a high-class system or just a properly-built one—you must listen to this "plug," you really must do it. I'm sure it will become a permanent addition to most systems.


Acoustic Revive RUT-1K

RUT-1K is a product designed to eliminate high-frequency noise. It has the form of a plug plugged into an unused type A USB port. In a small housing there are materials used in other products of this manufacturer, RCA and XLR plugs (more HERE). So we should expect that in the RUT-1K we will find dark rock crystal and a mixture of silk, quartz and other minerals. Since this is the version with the letter "K" at the end, it means that the inside has been painted with a solution containing Kiyoh-stone, a rare earth element whose main ingredient is aluminum silicate.

Plugging the RUT-1K into the USB port of the Mytek Brooklyn Bridge file player brings subtle changes. It's not like everything is suddenly better and we buy this "plug" right away. After some time, however, it becomes clear that even such subtle changes are valuable and in the case of files can be even crucial. It improves the resolution of the smallest signals. This gives more natural space and deeper vocals. Without the RUT-1K, the sound slightly "collapses" towards the center, and the vocals sound more HiFi, i.e. less natural, not so soft.

The timbre almost does not change, but it seems to us that with the "plug" it is smoother, and our attention is focused more on the midrange. As I say, these changes are not quantitatively large, but qualitatively they are valuable. You can live without RUT-1K and nothing bad will happen to your files. However, if we plug it into the USB socket and leave it there for some time, just listening to music, removing it will leave a slight "sediment" of dissatisfaction.

Acoustic Revive CS-3K AC Power Filter

Price (when reviewed): 480 EUR



Contact: YOSHI HONTAI | MuSon Project, Inc.


Provided for test by: MUSON PROJECT [email protected]


translation Marek Dyba

images High Fidelity | Acoustic Revive

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