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There are tens, if not hundreds, of isolation devices in audio. Their stated aim is to isolate your precious audio equipment from the local environment and in particular the sound/vibrations from the loudspeakers.

The range of these isolation devices is wide. There are nice looking wooden platforms and racks, such as those from Hifi Racks that my 211-valve amplifier resides on, as well as racks that are modelled on North Sea Oil rigs. Hideous. The prices range from a reasonable few hundred £s for a nice wooden rack to 5 figures for blingy oil rigs.

These racks can be accompanied by all sorts of platforms and isolation/coupling feet. They can be made from solid wood, metals, and complex material mixtures that have structures that are so secret they must be guarded and patented no matter what.

For fun, you could always go to the company’s web pages and try to understand how they work. At this point, you start to appreciate that some of these companies do not have a good appreciation for engineering or physics. Does the device couple or isolate? Is there any engineering behind the product’s development or was it found by more empirical means? By empirical I am being generous, for some companies, it must have been potluck.

More recently there has been a parallel growth in the number of companies trying to isolate audio equipment from Radio Frequency Interference (RFI) and Electro-Magnetic (EMI) Interference. This is a serious business, and many companies have worked for years to produce electronically quiet environments. RFI problems have increased because of the wholesale introduction of mobile phones and many computer peripherals that use RF connections in place of good old copper wire. Even my doorbell has an RF link to the bell in the living room.

Given we are now in a sea of RFI and EMI, are they causing problems with our audio systems?

As this is audio and there is a ‘new’ problem (RFI and EMI) to resolve, many new products have appeared that are claimed to help reduce RFI and EMI.

It is a sea of confusion.

I have found a couple of products that helped and then gave. Starting with a nice DBase rack, the company make something that is not too ugly and as they have worked in the professional field, they know what they are doing. I also bought three Stillpoints to isolate my new Vitus RI101 Mk2 amplifier. Vitus regard Stillpoints as essential and at one point offered them for sale with their amplifiers. Job done.

I was recently drawn to another company that offered to deal with vibration isolation and RFI and EMI, all with one device. The company was Quiescent. They claim their couplers significantly reduce vibrations coming from external sources and they also reduce the vibrations coming from inside your equipment that disturb the other components, mainly noise from the mains transformers. Not only that, their couplers significantly reduce RFI and EMI from outside the equipment and from inside the equipment. I am not sure there is anyone else that claims to deal with both the mechanical and the electrical interference, apart from possibly Entreq. Quiescent is a fairly new company having evolved from Vertex and has been working on reducing RFI/EMI for many decades. They have worked with the MoD in the past so should have expertise in this area.

I did ask them how they reduce the RFI and EMI and got the answer that their couplers are multi-phase filters that significantly reduce the effects of RFI and EMI. Yes, a little obvious. However, I understand their stance as they have patents pending on the details of how they work. They do not want others to ‘borrow’ their work. It happens.

To add credibility to their products, Vertex, asked Acuity (also an MoD contractor) to carry out measurements on the effectiveness of their devices. This work was done with Nordost who was part funder. Acuity had developed a different way to measure the couplers' effectiveness by measuring the impacts of Vertex and Nordost’s equipment in the time domain rather than the more common frequency domain. They tried to correlate these measurements with listening tests. This work was mainly led by Gareth Humphries-Jones of Acuity, independent of both audio companies. Initial results were encouraging and a paper was issued highlighting their early results. Unfortunately, Gareth Humphries-Jones has since passed and this work has stopped. A pity as the tests could have had wider use. A summary of the results has been issued: https://rightnote.co.uk/wp-content/uploads/2015/09/ka-paper.pdf

Given the background of the company, their attempts to measure the impacts of their products and trying to relate them to listening tests I was encouraged to try out some of their products. A quick discussion with their effervescent leader Nigel Payne resulted in a selection of couplers being sent to George Towers. I also managed to get a set of their previous generation couplers, the 74mm coupler, from an audio friend. Quiescent sent me their new generation 40mm and 60mm couplers and as a bonus a new ethernet cable they had just finished developing. They also make 50mm couplers.


The couplers are made of 3D-printed black plastic with an interesting set of grooves cut in them, presumably to reduce vibration paths. If you turn the coupler over there is what looks like a resin fill that hides the inner workings of the coupler. The couplers contain labyrinth paths to absorb the vibrations and RFI/EMI. Slightly off-centre from the top of the cut-off pyramid is a very sharp steel spike. This spike makes electrical contact with your audio’s case, through the anodising. If you have very light equipment it may be necessary to provide a GENTLE push to help the spike make electrical contact. It does not damage the case. The couplers can’t work fully with wooden cases, so my 211 amplifiers could not be used. The couplers are sold in threes to avoid any issues from non-flat component bases.

A problem with using the 74 mm couplers is the extra height they add to your audio, especially in a rack. I had to use the 74mm couplers on my power amplifiers as they are used outside the rack on a wooden platform on the floor. The new 40mm couplers are squatter and lower and I did not have any issues with them in the rack. The 60mm couplers are brutes in that they have a larger footprint and can give practical problems. I tried using them on my power amplifiers without problems with my ARC Ref 110 and the Vitus but the Bryson 3B3 I had in for review was too small and getting the couplers in place was not possible with the amplifier’s feet in place. I did not want to take the Bryston apart so I could not use the couplers with the Bryston. I also had the same problem with using the 60mm couplers with my dCS Bridge streamer but the 40mm couplers worked without any issues

The ethernet cable replaced my ENO silver ethernet cable.

So how did they work?

I tried the 74mm coupler with the Vitus RI 101 Mk2 integrated amplifier. It was fed by an Audionote 4.1x DAC and a dCS streamer with a Melco front end. I use Cut Loose silver ribbon cables and Puritan mains cables. I started with the ‘bare’ Vitus on the floor platform. The sound was very good although the bass did sound heavy. I then added my Stillpoints to the amplifier and that took away the heavy bass and lightened the overall sound making it much clearer in the bass. The overall pace of the music was much faster. A good result although I thought the frequency response may have been altered with the top-end sparkle reduced, but probably not by much. Adding the Quiescent couplers was straightforward but needed care as I would not want to get my fingers caught between the coupler spike and a 45kG amplifier. I put on a fast-paced track from Led Zeppelin IV: Rock and Roll and off we went. This was much better. The soundstage was bigger and far more 3D. Using the Stillpoints there was a reduction in the realistic metallic sound of the cymbals but not with the Quiescent couplers. They kept the overall frequency balance the same but added some real pace to the track. On to Black Dog from the same album and that big powerful sound remained with all the drive you expect from Zep in their prime. For some contrast, Stairway to Heaven from the same album. This quieter-paced track starts with a haunting sound with a simple flute accompanying Jimmy Plant’s melodic guitar. This tune builds up in intensity until the chiming guitars release the tension from Jimmy Page. And then in comes Bonham with some great drum fills and a great guitar solo from Jimmy Page. All accompanied by some soulful singing from Robert Plant. Audiophile? hell no. But what great rock. And to think that when it was first played to a live audience at a concert in Belfast’s Ulster Hall they politely applauded afterwards. Bassist John Paul Jones said, “They were all bored to tears waiting to hear something they knew.” Some people.

OK, something quieter, Dark Angel by Blue Rodeo with a beautifully recorded voice. The couplers gave the track a huge soundstage and the detail in that voice was superbly captured. It was easy to hear the words all the way through the song and the piano was well captured. Digital glare, edginess? Significantly reduced.

Something more classical? I. Gnomus by Jean Guillou from Pictures at an Exhibition playing the magnificent Kleuker-Steinmeyer Organ in the Tonhalle Zurich, Switzerland.

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It sounded magnificent and I had no choice but let the rest of the album play through. The huge soundstage captured the sheer size and power of this great organ and the superb playing. It was much easier to imagine the scale of this organ with the Quiescent couplers in place. And the bass pedals use long, low bass pipes that literally can shake and rattle loose items in a room, like the plates my other half loves to collect.

This was a great start.

I noticed that the digital edge had reduced but I have to admit that there was still some there and it was not easy to ignore. Could it be that I needed to add more couplers to the system?

I was advised by Nigel Payne to try using the couplers at the front end as that is where I would get the most benefit, especially with digital audio. I placed the 40mm couplers under the Audionote CD4 Transport and another set under the AN DAC4.1. I got the same benefits as before but the noise levels were much lower and the digital edge was gone. Having heard these problems reduced I noticed that I had become more sensitised to their effects and I was only truly happy once all the components in my system had been Quiescent coupled. I agreed with Quiescent, there was a big change with couplers under the digital front end. Gains with my PS Audio phono amplifier were there, but the digital front end was where the most gains were heard.

I also tried the couplers under my ARC Ref 5 and Ref 110 with the same effect but the power amplifier gained the most. The impact with the Ref 5 was not as noticeable with the 40mm couplers. I could not use the 60mm couplers with the Ref 5 preamplifier as it is in the rack but the Ref 110 power amplifier improved considerably from their use. The noise levels were reduced and the 3D stage was made much larger without altering the frequency balance of the valves. Playing I Gnomus took me to the Tonhalle in Zurich Switzerland. It was easier to imagine that great instrument being expertly played. I was there.

I have to admit I was surprised by what was happening as all that I did was put three (passive?) feet under each piece of audio on an already decent isolation rack. The sound improved and I was imagining I was there, in the Tonhalle in Zurich.

On to the Quiescent ethernet cable. Having reviewed the Network Acoustics ENO choke, I also bought their silver cable as a package. I did not expect any real changes as ethernet digital signals are robust. But that was not the case. I did a straight swap and the sound became far smoother and more natural. The voices became more human and the emotion in the voices was much easier to hear, even with badly recorded music. I left the cable in circuit for a few days playing a wide range of music from rock and pop, jazz (not too much), folk, classical and big powerful orchestral and prog rock. I played the latter as I was concerned that the smoothness may have been at the expense of the drama and impact. But playing Roger Waters's Us+Them, One of These Days (Live in Amsterdam) the start of the track where he plays some powerful bass that after the intro, goes at a great pace with all the drama I associate with this track. Another great result.

Cost? Researching and making these items is not cheap. The 40mm couplers cost £695 for three feet. The impact on audio is high and people would be prepared to pay 4 figures to get these gains from a good amplifier. These gains are difficult to get any other way. Fortunately, Quiescent is establishing a number of good dealers who will be happy to lend these items so you can try them before you buy. If they work great, if not return them, nothing is lost but some time/postage.

And a quick tip, some of the dealers have first-generation couplers. They are not as good as the new couplers but they are very effective and the current prices are much lower. I got my 74mm first-generation couplers at a great price and they work really well under my Vitus amplifier.

Quiescent Products: https://quiescent.co.uk