Positive Feedback Logo

WestminsterLab Quest Preamplifier and REI Amplifier

03-22-2021 | By Wojciech Pacuła | Issue 115

WestminsterLab is a company founded in London (hence the name), currently headquartered in Hong Kong, run by Angus Leung. Its offer includes connection cables and amplifiers, belonging to the top high-end level. For this review we received the Quest preamplifier and REI monoblocks; the preamplifier has its premier in HF.

There are brands in audio whose products we associate unambiguously with high-end, and thus—with high prices. Let me mention such brands as: Dan D'Agostino, SOULUTION, FM Acoustics, Spectral, GRYPHON, Kondo, to know what we are talking about, focusing only on amplifiers specialists. Although these are, by the standards of the audio-visual market, small companies, in the world of perfectionist audio are the so-called "Big fish."

Apart from them, however, there are many less known, tiny, often one-man companies that develop real works of applied art. In Poland, the Ancient Audio would be such a manufacturer, again involved mostly with the devices used to amplify the audio signal, and out there in the world, another example could be the, based in Hong Kong, WestminsterLab.

The company was founded in 2007, and its founder and designer is Mr. Angus Leung. Its most famous products are audio cables. It was one of the first companies in the world to offer self-made high-end USB cables in 2007! Mr. Leung made himself known to a wider group of audiophiles thanks to the fact that he prepared cables for the Lumïn company, connecting their file players with external power supplies. The cooperation had to be satisfactory for both parties, as the head of WestminsterLab was also the chief engineer during the development of the manufacturer's first amplifier (the Amp).

Cables, however, are not the only area of interest of Mr. Angus, his company also offers amplifiers. The first product was a power amplifier called Unum, hand-made, with point-to-point assembly (and it was a solid-state amplifier!). Later it was joined in the lineup by REI monoblocks, and two weeks ago the Quset line preamplifier was launched.

A few simple words…

Angus Leung, Owner, designer

Mr. Angus Leung

I started this hobby of listening to the music when I was 13 years old. I started playing around with DIY kits, speakers set, amps sets etc. I still remember my first pair of earphones and my first pair of Speaker, the Clone ProAc 1SC. I started working as a past time during there summer holiday as a HiFi repair technician, and that's the time where I started to learn about the design and schematics of a lot of HiFi legends.

I started WestminsterLab when I was still studying in the UK with a few of my friends and partner. Our first product is a USB cable and we focused on cable, it was more or less a hobby at that time as I am still studying in the UK, interesting I was trained as an architect. It was until 2012, the time which I graduated and I have decided to bring WestminsterLab back to Hong Kong, since then it become more than just a serious hobby.

Mr. Angus' workshop - Hongkong

Our ultimate mission is to bring all the music lovers to what music truly is and guide them through the path to find their unique kind of music.

The definition of what music or music reproduction is, is different for everyone, who has their own personal views and experience to music. The paths towards music may not be the same for everyone. We solely become a guidance along the path to music, distilling every single detail, easing the bumps and clearing the obstacles for everyone, with the goal for them to find their unique kind and definition of music and the acknowledgement of the relationship between music and themselves. As a pioneer along the road to music, everyone can follow our footsteps and continue to explore on their own, tasting what music is all about in its purest form.

There is no definite conclusion to music. We serve to provide the best elements, parts, components and schematics and allocate them to the best possible locations in our products. Every now and then, we review our thinking process to see if our thoughts and cognitions are on track. Our path is an exploration, an endeavor, an ever-going process. The more we know, the further we want to go and the further we can go. 


The so-called "White paper," a technical document describing the new WestminsterLab preamplifier, it reads:

The ultimate aim of the Quest is to create the perfect preamplifier to accompany the Rei and the cables lineup. With the Quest, it completes the loom between your source and pair of speakers. Setting out to push the boundary, it redefines how a preamplifier can contribute to the system and the ability to extract every bit of potential from both the recorded music and the music reproduction system.

The Quest is the latest device of this company, but Mr. Angus says that not everything that had been developed for Unum and REI amplifiers could be used in it, even though all these devices share a balanced dual mono design—it was supposed to be an even more ambitious project. The tested preamplifier uses an advance power supply with ten separate voltage regulators and two toroidal transformers. Since the "heart" of each preamp is an attenuator, WestmisterLab has built its own based on relay-switched resistors, allowing user to adjust the volume in 64 steps.

It is extremely minimalistic, both in terms of design and functionality. Before we turn it on, it seems to be just another, small power amplifier, because there are no manipulators or indicators on the front panel. The device comes to life only after turning the power on with the standby button on the remote control. Then, a fragment of the logotype lights up, as well as a large "dot" LED display hidden under the raster. Both illuminations are white.

Feature-wise, the device is minimalistic as well, because it does only what a line preamplifier should do—you won't find an in-built digital-to-analog converter, streaming module, Bluetooth connectivity, or even a phono preamplifier or headphone amplifier in it. On the back of the device you can see two, blinded slots, described in the manual as "Option Bays," so it is possible that this will change in the future with optional modules (I would prefer a phono stage first). Today there is a card with optional RCA inputs available. Let me remind you that similar expansion slots are offered by Accuphase, MBS, Octave, Gryphon and others.

The Quest is a balanced preamplifier. It is an absolutely—I repeat myself, but I would like to emphasize it - minimalist design, therefore the signal path uses as few elements as possible and it is very short. In the basic configuration, i.e. without the optional RCA inputs, we only get three XLR inputs and two XLR outputs. The latter can be used to connect four power amplifiers in bi-amping mode or—this is my idea—to connect a subwoofer or even two of them. Many large loudspeakers feature an active woofer section, and in such cases they can be connected in this way.

The chassis of the device is made of aluminum plates and carbon fiber panels, same as used in racing motorboats. Carbon fiber is an optional upgrade set called Extended Carbon Pack, but—this is my opinion—there is no point in thinking about purchasing Quest and Rei without it. Both materials have been selected to minimize distortions caused by magnetic fields and vibrations. Aluminum 6063 is used in aviation, and the carbon fiber braid, as we read in the company materials, was chosen for its "better shielding properties than copper and aluminum," because it does not generate a magnetic field and does not create eddy currents in it, distorting the useful signal.

This is an important clue, because a lot of space is devoted to the description of the mechanical structure of the device. As we read, the idea was not only to make the chassis an integral whole and to make it vibrate as little as possible, but also to distribute vibrations that cannot be instantly suppressed, because then they are easier to control. Therefore, each panel of the preamplifier and power amplifiers chassis has a different resonance frequency.

Not only the top and bottom panels are made of carbon fiber, as are some elements inside the device, the top panel, end caps on the back panel and mounting plates with a LED and a power socket. The latter is a high-class one with gold-plated contacts from Furutech, as is the fuse integrated into it. Gold-plated XLR sockets are products of Neutrik.

The preamplifier stands on three feet in the shape of hemispheres, gold anodized. One might suppose—as I did initially—that they are made of aluminum, but they aren't. Mr. Angus says the feet in both Rei and Quest are solid brass with a special coating that slows down its oxidation. And brass is the "holy grail" for audiophiles who are fans of vintage turntables and drivers.

The preamplifier, apart from a ground switch (we can choose one of two grounding ways), does not feature any manipulators. The only way to operate it is via the remote control. I've seen this type of remote control, small, made of aluminum, used for various products. They feature buttons for volume control and input selection, a "mute" button and a standby button. I think that this device of this class deserves a nicer, better looking remote—maybe with elements made of carbon fiber.


REI is a monaural amplifier that is surprisingly small, at least for a device with an output of 100 W @ 8 Ω, 200 W @ 4 Ω and as much as 400 W @ 2 Ω! Besides the fact that when the load impedance is halved, the power doubles, which indicates excellent current efficiency, this could suggest a class D amplifier - which REI is not. It is a proprietary design working in "sliding" Class A.

Circuits of this type have been known for years, and their greatest "promoter" in the 1990s was the American Krell. This is a manufacturer who started its career with powerful KSA50 monoblocks working in Class A. His next step was a circuit in which the amplifier worked in Class A, but the bias current of the transistors was not always set at maximum—it changed with the input signal. The higher it was, the greater was the bias current. It required a special circuit to coordinate these changes, but in this way the advantages of class A were obtained without the transistors overheating, which was the point.

Let me add that the latest version of this solution, Krell presented at CES 2014, and it was called iBias and, as it happens, WestminsterLab uses exactly the same name in its technical materials.


For the first time, WestminsterLab applied the iBIAS in the AB class amplifier Unum. It allows the amplifier to adjust and optimize the BIAS in real time depending on the load and input signal level. This flexibility in modulation significantly shortens the heating time of the elements and stabilizes the bias current at the optimal point depending on the output load (of the amplifier - editor), it also stabilizes the temperature of the transistors, allowing the system to operate with optimal settings under all conditions.

source: ENGINEERING THE REI. WestminsterLab Rei Mono Amplifier Technical Design White Paper, WestminsterLab 2019

Knowing that, it is no longer surprising that the Rei monoblocks are small in size. The reduction of their dimensions, as we read in the company materials, is further supported by perfect pairing of the output transistors. The basic circuit, with a single transistor pair working in a push-pull mode, is obviously possible to design, even for high output, but it generates problems of a different type. For this reason, several transistors connected in parallel ("parallel push-pull") are most often used.

But this solution also has an "Achilles heel"—each transistor has slightly different characteristics. In order for them to work with the lowest possible distortions, they must be selected and paired, which is a time-consuming and costly solution. The WestminsterLab company, however, went a step further and not only does it pair the transistors with a tolerance of 1%, it also does it based on several point on the current curve, not just one.

Similarly to the Quest preamplifier, the Rei monoblocks are a balanced design, feature a short signal path and a chassis made of aluminum and carbon fiber. The reduction of magnetic fields was pushed even further, using bolts and washers made of non-magnetic 316L steel throughout the device. Let me remind you that in the Unum model Mr. Angus used nylon screws (!).

There is no display module on the front panel, but as in the preamplifier, the white backlit logo element was used. It will glow red during start-up and when the device detects a DC signal at the input or is overheated. The protection circuit will then cut off the output of the device. A medium-sized heat sink was used on one side of the unit, and the stereo pair is just two of the exactly same amplifiers. Their asymmetrical design (with a heat sink on one side) also has a practical purpose—Mr. Angus says that he studied various variants and, based on listening sessions, chose the asymmetrical one.

Rei is a "beauty", everything in it looks great, everything is well-thought-through and small. Every detail has been taken care of, including ultra-thick printed circuit boards, proper arrangement of elements on the board and mechanical reinforcements. There are also beautiful WBT speaker sockets and a gold-plated Furutech AC power inlet with a suitable fuse. A "plug" is screwed under the sockets. This is a place for optional trigger sockets—the amplifier can be turned on remotely from the preamplifier, you only need to connect the devices with additional cables.


The listening session of the Quest preamplifier—in the Extended Carbon Pack version—and the REI power amplifier took place in the High Fidelity reference system. In this case, however, I used cables from the same manufacturer, hence using the WestminsterLab system, which was compared to the reference system, with the Ayon Audio STRATOS III preamplifier and the SOULUTION 710 power amplifier as well as Siltech Triple Crown cables.

The tested system included:

  • Ayon Audio CD-35 HF Edition SACD Player
  • WestminsterLab XLR Standard
  • Power cable AC: Standard for the WestminsterLab Quest
  • WestminsterLab XLR ULTRA
  • Power cable AC: Standard Carbon Fiber for the WestminsterLab REI (x2)
  • WestminsterLab ULTRA
  • Harbeth M40.1

The preamplifier was placed on the top shelf of the Finite Elemente Master Reference Pagode Edition rack, and the amplifiers next to each other on the middle shelf.

Recordings used for the test a selection

  • AKESHI INOMATA, The Dialogue, Audio Lab. Record/Octavia Records OVXA-00008, SACD/CD (1977/2001)
  •  BURT BACHARACH & DANIEL TASHIAN, Blue Umbrella, Big Yellow Dog/Sony Music Labels (Japan) SICX 30088, BSCD2 (2020)
  •  CHET BAKER Peace, Enja Records/Warld Records TKCW32153, "Jazz Masterpiece," SHM-CD (1988/2007)
  •  DIANA KRALL, This Dream Of You, Verve Records UCCV-1181, SHM-CD (2020)
  •  MARIO SUZUKI, Masterpiece II: Touching Folklore Music, Master Music XRCD24-NT021, XRCD24 (2018)
  •  MAYO NAKANO PIANO TRIO, MIWAKU, Briphonic BRPN-7007GL, Extreme Hard Glass CD-R (2017)
  •  PRIYA DARSHINI, Periphery, Chesky Records JD446, Master CD-R (2020)
  •  SANTANA, Santana, Columbia/Sony Records Int'l ‎SICP-10134, SACD/CD (1968/2020)

It happens to me once in awhile not too often though, quite rarely actually, but it does. It is about getting into the sound of a given product or system in an incredibly smooth way, as if I were immersing myself in a silk bedding. The sound produced by the WestminsterLab system is so free of mechanical artifacts, so stress-free, that it could be prescribed instead of antidepressants.

I played Diana Krall from her latest album The Dream Of You and immediately heard a big, warm vocal in the foreground and rich, warm strings behind her. Same happened with Priya Darshini's recordings from the Periphery Master CD-R disc, burned for me by Jeff Lanier from Chesky Records. This recording, in turn, is incredibly spacious, with the foreground set quite far away, and yet even in this case I felt like being surrounded by something warm and pleasant.

It is difficult to gather one's thoughts after something like this and to analyze this presentation without any emotions involved. I am not one of those who kneel before each new product and the more expensive it is, the deeper the kneel is. I appreciate what is good, I express enthusiasm, if something is exceptionally good—all that, however, within certain limits, with a distance. This time, maybe not quite on my knees, but I listened to the following albums focused and with great interest. Because apart from the warmth—which is amazing—smoothness—it's the same—there is also outstanding dynamics. And this is rare when it comes to "warm" sounding products.

It's only that with the Quest preamplifier and the Rei power amps, the dynamics in question was not something imposed, something from the outside, which "energized" the presentation. I heard it in such a way as if the presentation energized the communication, as if the dynamics flowed from the center of the sound instead of being superimposed on it. It didn't matter whether I was listening to the heavily "produced" Krall's album, or the ultra-natural recording by Chesky Records, or finally Santana's debut album with the material remixed and released on the SACD 7-inch disc.

The combination of these three elements—let me repeat: warmth, smoothness and dynamics—comes in the tested system from incredible sound resolution. Listening to it, we have the impression that we are sitting in front of a top 300B SET amplifier, but without any limitations in the scale of the sound—including its scaling with volume level increase—or without problems with driving loudspeakers. I think that if someone loves tubes, SET designs in particular, and would like to pick up their loudspeakers freely, or just doesn't want a tube amplifier for some reason, the WestminsterLab offers something incredibly similar, without pretending to be a tube system.

Because, by the way, the last thing I could think of is that Mr. Angus's system is faking something. It is quite the opposite. Listening to the numerous recordings, I realized that it was doing just the opposite, as if it was trying to influence the sound as little as possible. This is an illusion, I am aware of it, because every element in the signal's path changes it, but it was an exceptionally convincing illusion.

This time the designer managed to achieve something that I heard with Kondo Ongaku, with Ancient Audio Silver Mono, what I can hear with my system and what I have experienced with maybe two others, namely that these components found a way to present music in their own way, but so that it seems there is just music, and nothing else. There is also perfect space presentation here, fantastic dynamics and flawless timbre, from the very top to the low, very low bass. One does not perceive any of these elements of the sound separately, but as a whole—and this is where the feeling of absolute effortlessness of sound comes from.

I mentioned the band extremes for a reason. They are a bit soft and smooth. But this is largely only an apparent softness, because when on the Mayo Nakano Piano Trio's Miwaku, played from the Extreme Hard Glass CD-R, the kick drum hits, it has a physical slam, it is fast, sounding almost like in a live performance. On the other hand, the drum cymbals sound quite warm and dense, but when necessary, as on the Dialogue, an album prepared by Mr. Okihiko Sugano, they hit hard and have weight that other amplifiers could only envy the WestminsterLab. Both the low bass and high treble are presented in a way that allows the instruments to be recreated in their fullness, density, depth and their physicality.

This is a top amplifier, I have no doubts about it. However, it differs from the High Fidelity's reference system, which shows that the same recording can be conveyed in different ways, keeping the content unchanged. The WestminsterLab system is warmer and more focused on the midrange. The reference system sounds even lower, has a denser lower midrange, but as a result it sounds a bit more "distinct," as if its sound was "made." This is not the case, but the naturalness and sound of the tested system, as if casually, make us feel that way.

The spacial aspect of recordings is also presented a bit differently. The tested amplifier moves the foreground a bit further away and does not boost vocals as my system does. So it delivers a bit more distanced presentation. It is still quite close, but a little less intense. So it will appeal more to those who listen to classical music, or who just like to see everything behind the line connecting the speakers. What is shown behind it will be accentuated a bit more by WestminsterLab. The back of the stage is placed as far away as in the reference system, which is a unique achievement, although our attention is focused more on what is closer to us.


What is a characteristic feature of the tested system, which is even better than in the reference system, and what I heard once with the already mentioned Kondo Ongaku amplifier, is the effortlessness in music presentation. It seems that it flows unobstructed, that nothing stands in the way between music and listener, and that the amplifier is a kind of portal to another dimension where music exists. This is why you are equally committed to listening to both the powerful, explosive performance of Carlos Santana and the beautiful, melodic sound of the Blue Umbrella EP by the Burt Bacharach & Daniel Tashian duo, for which they have just been nominated for the 2021 Grammy Awards in the "Best Traditional Pop Vocal Album" category.

The reviewed system allows for long listening sessions in absolute comfort. Unlike other "warm" amplifiers, Quest and Rei do not soften the presentation, although their sound seems soft. It's a paradox, but in all this "silkiness" we get a lot of information that shows differences in the recording and production of albums, as well as in the way they are released. Nevertheless, we only pay attention to it when we want to, that is, when we turn our focus to it. If we don't, the "mechanics" of music recreation are communicated, but not in the foreground, or even in the background.


WestmisnterLab products are beautifully designed. Their chassis, made on CNC machines, are precisely fitted, which is emphasized by precisely cut panels of carbon fiber - cast in resin and pressed. We have already talked about their appearance, so now it's time for what's inside.


The preamplifier was tested in the Extended Carbon Pack version, i.e. with many elements made of the aforementioned carbon fiber. It is also used inside the device, shielding the audio circuits from the bottom and top. The power supply takes up half of the interior and you can see many capacitors suppressing mains ripple, as well as a battery of Wima polypropylene capacitors operating in voltage regulating circuits. There are also two toroidal transformers—it looks like the attenuator uses a separate one. There are, as has been already mentioned,  ten independent power supplies.

The signal path is fabulously short. From the inputs switched in the relays signal goes to the heart of the system, that is the resistance attenuator, made with the use of precise resistors switched with relays—as the manufacturer says—"ultra-low noise" ones. This circuit allows you to adjust the volume in 64 steps. It is mounted on a separate PCB, so it can be replaced with a better one in the future—if, of course, one is ever prepared.

From the attenuator signal goes to a single integrated circuit, and then to a five-pin "driver" circuit mounted on a heat sink. The latter is used in studio products. The markings were removed from both elements, making it impossible to identify them. I asked Mr. Angus about it, and he replied that it was not about a secret—these elements were coated with graphite paint, which helps to reduce interference from environment. Parallel outputs are switched in another set of Omron relays.


The mechanical structure of the REI monoblocks is based on a system consisting of an inside, horizontally placed aluminum plate and a heat sink. A transformer is bolted to the plate, and the capacitors protruding above it are soldered to the board underneath. In this way the power supply is shielded, but most of all, it is also mechanically decoupled. As we read in the company materials, micro-vibrations generated by the power transformer adversely affect the sound.

The output stages were bolted to the heat sink. Each of them employs six pairs of push-pull transistors, working in Class A. Typically, this type of design uses field-effect transistors of the MOSFET type. In Rei we find BJT by ON Semiconductor. BJTs are "Low VCE (sat) Bipolar Transistors." Their use in a class A amplifier is quite rare because they are very difficult to control at high temperatures, unlike MOSFETs. In the input of the output stage you can see a complex driver system with its own small heat sinks. The entire chassis is made of 6063 "aircraft grade" aluminum.

These are one-of-a-kind products, and they look really great.

Technical specifications (according to the manufacturer)

  • Frequency range: 5 Hz-100 kHz (±0,1 dB)
  • Distortion (1 kHz): 0.0001%
  • S/N: 120 dB (unweighted)
  • Chanel separation: <120 dB
  • Gain: 6.5 dB
  • Input impedance: 51 kΩ
  • Output impedance: 0,018 Ω
  • Input voltage: 6 V rms
  • Dimensions (W x H x D): 470 x 110 x 392 mm
  • Weight: 13.2 kg


  • Output: 100 W/8 Ω 200 W/4 Ω 400 W/2 Ω
  • Frequency range: 5 Hz-40kHz (±0.1 dB), 2 Hz-52kHz (-1 dB)
  • Distortion: (100 W/8 Ω, 1kHz): <0.1%
  • S/N: 104 dB (A-weighted)
  • Input impedance: 200 kΩ
  • Output impedance: 0.018 Ω
  • Dimensions (W x H x D): 232 x 112 x 320 mm
  • Weight: 16 kg

Price (when reviewed): Quest– 26 200 EUR, REI – 31 900 EUR/pair

WestminsterLab Ltd.



Provided for test by: AUDIO ATELIER



Images: WestminsterLab Wojciech Pacuła

Visit High Fidelity