WestminsterLab Rei power amplifiers review

Right before the 2019 year's end, another product, that I've highly anticipated has landed at Mono and Stereo. The WestminsterLab Rei Class A solid-state power amplifiers were highly promising with all of the insights I've been getting. 

Among many unique features, Rei employs a WestminsterLab's proprietary iBias and CCS systems which translates to a much faster warm-up time compared to the typical Class A amplifiers. The iBias technology constantly varies the bias depending on the current and also the loading of the amplifier. This results in the best of what Class A has to offer without the usual drawbacks. 

As you can discover in this installment WestminsterLab amplifiers are most highly unique and I'm more than happy for accepting the Angus Leung proportion to give them a try.


The development of the Rei amplifier was kindled by the ambition of reimagining the possibility with Class A amplification technology, to produce a pure and clean transmission of both signal and power while reproducing the essence of the original music as coherent as possible.


From the initial designing of the circuit, WestminsterLab performed endless computer simulations along with countless real-live performance assessments and auditions. They are highly aware of how over-dependence on one approach may blind many possibilities for improvements.

For instance, focusing solely on the low distortion of the circuit may sacrifice listening experience. And in this particular example, apparatus and computer simulation can give you a measurement of distortion but they don't provide the listening experience. Hence, it is necessary to come up with multiple methodologies to cover the blind spots and the WestminsterLab team did just that and at the extreme level. 


The approach in designing the schematic of the Rei amplifier is very different from what’s available on the market. Rather than adopting an ultra-high bandwidth generic signal amplifying schematic and optimizing it for audio use, WestminsterLab'S approach was to design a circuit specifically for audio band frequency and audio use from the ground up.

This approach allows WestminsterLab to completely rethink which component or section of the circuit is really needed for signals within the audio-band. Reducing components count is the key to the WestminsterLab philosophy. No matter how good a component is, it is still not perfect, and by distilling their circuit and keeping it as simple as possible, the result is as you can read on profound.


By reducing the numbers of components and simplifying the schematic WestminsterLab has gained another advantage in the flexibility in designing the layout of the PCB. This flexibility enables them to design the layout in such a way, that utterly minimizes the interference between signals and power supplies. 

If possible, signals often run perpendicularly to each other, even if not, they would run as further away from each other as possible to reduce unwanted interferences.


The most common solution of building circuitry is the implementation of a printed circuit board (PCB). As WestminsterLab investigated this standard solution of the industry, they've discovered that it is impossible to maintain the purity that is required during transmission with the typical PCB solution. The amount of copper, the manufacturing process and also the materials and density of the board all have influences in how PCB performs.

With help from some suppliers who specialize in the aerospace industry, WestminsterLab team has managed to manufacture an ultra-thick, low capacitance, high-density board that they firmly believe to out-perform the majority if not all the PCB board technology used in the audio industry. This main component is one of the reasons why Rei excels in speed, agility, and power.


WestminsterLab paid tremendous attention to the magnetizing effect and eddy current, even when they were hand-selecting and evaluating the screws, nuts, and o-rings. When a signal or current passes through a conductor, the electric field will generate a magnetic field within the metal and this potential energy is reintroduced to the signal. In their tests, these interferences generated a blur and unclear effect on the sound. To minimize the effect, 

WestminsterLab decided to go for high strength non-magnetic 316L stainless steel screws, nuts, and o-rings throughout the entire construction.


Another problem connected with metal is that it actually absorbs radio interferences from the environment and these interferences are then converted to electrical noise and magnetic disturbance which further affect the whole system, giving a blur and noisy background.

Therefore, WestminsterLab adopted extensive use of carbon fiber as shielding materials for both amplifiers and cables, instead of the usual copper or aluminum braids and foils, which does not generate any magnetic fields and unwanted eddy current, and amazingly in return, it rejects interferences without absorption in nature. 

It also provides very high stability over environment changes and extreme rigidity which gives low resonance and vibrations.


The bias setting is one of the key elements in settling the character and performance of an amplifier. Since transistors perform differently at a different temperature, if a constant bias model is used in an amplifier, it may either take quite a while to warm up and reach its optimal working temperature, or it will warm up quickly but exceed the optimal working temperature in no time. Not exactly the outcome that is wanted.

WestminsterLab first used the iBIAS technology in the class AB UNUM amplifier. This technology enables the amplifier to adjust and optimize the Bias in realtime depending on loading and the status of the amplifier. This flexibility in the modulation of the BIAS reduces the warm-up time significantly and stabilizes the BIAS in the optimal point depending on the loading of the output and also the operational temperature of the transistors, ensuring the system is running at its optimal settings in all conditions.


WestminsterLab understands that the best solution for a speaker system is a single amplifier driving only one speaker unit, in which impedance change and power handling will be much better. They've considered how some pre-amplifiers with only one output cannot connect two or more power amplifiers, or they were not designed to drive more power amplifiers as input WestminsterLab team has come up with a special by-pass for connection to the next power amplifier. With this design, users can use several power amplifiers even the preamplifier has only one output.


Toroidal transformers are widely used in the audio industry. They are efficient and very easy to source. For transformers, WestminsterLab has raised two considerations. When they've designed the Rei amplifier, they hoped to make it smaller and more compact in size so users can easily place two or more amplifiers on the rack or stack them. They also wanted to make a statement with Rei size and its neither typical Class A amplifier neither is big and bulky on contrary to usual norm. 

Even not considering power quality, neither EI type, R type nor normal toroidal type transformers can be fitted inside such a small case, with footprint and space limitation. The second consideration is power quality. The O type transformer used in WestminsterLab's amplifier provides even higher efficiency than usual toroidal and a cleaner, purer, faster power due to its different iron core design. O type transformer is simply smaller and better for this application. 


As mentioned above, WestminsterLab put much consideration into the stability and rigidity of the whole amplifier. This is because, under a stable environment, signals and power can go through a more stable and undisturbed flow. For that, the chassis must be very stable and rigid with very low resonance and vibration.

Every single panel of the Rei's exterior casing is designed to have a different resonance frequency and that is as furthest away from the audio band as possible, so the case will have a very high damping and low magnitude of vibration during the listening session. Reducing the chances of these micro-vibrations also reduces the polluting of the purity of the music.


The thermal performance of the heatsink is one of the crucial factors in designing a solid Class A amplifier. The Rei is a pure class A monster that generates more than 120 watts of heat from the power transistors and the main heatsink of the unit has to dissipate that effectively and efficiently.

Most manufacturers expose their heatsink out in the environment to increase efficiency. However, having the heatsink exposed to the listening environment means the sound pressure generated by the speaker within the listening area also transmits the vibrations to the heatsinks. These vibrations can cause unwanted micro-distortions similar to the “microphone effect” found in tube amplifiers.

To reduce this phenomenon, WestminsterLab studied different approaches in heatsink design and what kind of profile or materials would be the best in this particular case. With hundreds of hours of finite simulation, prototyping, and critical listening test, they've come up with a heatsink with an asymmetric fin design, which has its resonance frequency furthest away from the critical audio frequency and is highly effective in thermal dissipation.


During the months of evaluations, WestminsterLab Rei power amplifiers served without a hint of problematic behavior. They are simple to use, most straightforward with no brainer connectivity on the backside. Rei accepts only balanced input and along with double XLR input/output, there are only speakers binding posts and an IEC connector. 

To keep the Rei minimalistic aesthetics and keep up with the internal structural purity approach, the main switch is hidden below the on the right side and it requires a simple, single-finger move to turn them on. 

Rei amplifiers don't require the usual long warm-up time as it's common merit with Class A amplifiers. 

The only time I've pushed the WestminsterLab mono amplifiers into overload protection was by driving them insanely loud into the Soundspace System Aidoni flagship speakers. This was at the levels that most people would screamingly and scared leave my reference listening room. 

From day one of the evaluation WestminsterLab amps have provided an insightful look into the music by forging an unexpected symbiosis of laboratories like precision and life-like vibrancy that never extended into the saturated realms. 

Music was served for what it is and what it can offer. Rei amplifiers were not designed to flatter the high-end audio system. They were conceptualized from the very beginning to deliver music with full potency and in the absence of oversimplifying or making it harmonically denser than it is. As you can read further, this is among the Rei amps' most prominent features and what sets them apart by miles from the usual offerings...


As with any review, there is not enough space to put down all of the music and transcribe all of the listening notes. Here is some of the music that was used in the evaluation with the references to particular sonic qualities. With Rei, the list was long and there were more than plentiful listening remarks to work with. It was an uplifting musical adventure with a lingering effect...

Rarely an amp captures the inner should of Joshua Redman's "Blues for Pat" (composed by late Charlie Haden) from the album Wish as Rei WestminsterLab can. 

Rei has a unique ability to reveal the very nucleus of the "Blues for Pat". While many power amplifiers can take it up to a certain degree, it's Rei's potent core that makes all the difference by it's insightful and captivating transcription.

With WestminsterLab amplifiers the live feel was instantaneous. This should be, but it's not exactly the leitmotif of power amplifiers with an even heftier price tag. I simply loved how well Rei could distinctly lurk into the live happening, separating the instruments with feather-like ease and without losing the grip. Managing the speed of attacks and rhythm consistency in no slouch for any amplifier regardless of the price and WestminsterLab excel in this regard. There is a certain believability factor intimately connected with this particular live track. Just listen to the handclaps from the audience and notice the difference if the system is on par. With Rei amps in action, the audience's energy is at the tip of the hands. At least it should feel like this at this upper plane. WestminsterLab amplifiers are exemplary in preserving the live feel as well ready to keep the music the listener attentive.

Rei's splendid potential to revive the very momentum of the music was further confirmed with Pat Metheny Group "The First Circle (live)" from The Essential Collection: Last Train Home. This live track adds an additional layer of complexity. Pat Metheny's music is always the epitome of multilayering and with this particular track Rei divulged with  convoluted sonic scenery. 

Lyle Mayes who made an essential part of the magic duo has sadly recently passed. With Metheny they could compose unforgettable sonic escapes, always complemented with unfolding stories. I'm not the dissecting kind of listener, but sometimes it's worthy to break down the chord progressions and dig deeper into the music's writing and how everything was forged to fully appreciate the level of compositional skills. Such a quest revealed the unmatched syncopation and lyricism of Metheny and Mayes. All that and more before even touching the masterful musicianship... Anyhow. The Rei amps again reveal something extraordinary, that is far from the usual affairs. Let me unfold the story of Rei with another splendid album and even more magic. Moving a bit away from the sheer complexity and entering into the domain of lock and load calls for another marvellous feat. I like and love the splendid collaboration of two guitar wizards (Pat Metheny, John Scofield) on the album I Can See Your House From Here. Each track holds its forte, but "Everybody's Party" seemed to bring the very best from WestminsterLab monoblocks. 

With "Everybody's Party" it's all about the narrative and the capability of delivering music's pace uncluttered and not imbedded by too many distractions. It calls for a sort of sonic cut & paste. The Rei amplifiers' easiness of keeping the pace surprised me. On top of locking instantly with the groove, the Rei amps portrayed the ongoing pulsating without the hyperbole. This quality is too often overlooked when it come to power amplifier evaluations. It's easy to instantly impress with the power or some other particular attributes. Yet... When it comes to laying down the aural presentation in the way it was meant to things I all become consulted far too quickly. WestminsterLab Rei amps gave a fulfilling presentation that kept me literary glued to the Metheny/Scofield wizardly guitar playing from the beginning to the end without letting my logic to kick in. The rhythm pulsation and tone of
I Can See Your House From Here is recorded really well and it's a pure of letting it expand on the well balanced high-end audio system. With guitar-based albums, there can be too much push forward focus. As a great example I Can See Your House From Here is handling the bass, guitars and drums equally distributed. The album creates a harmonious whole that (when all is right) escapes the speakers and creates an immersive 3D portrayal enriched with ongoing and highly immersive palpitate. Despite their small size, the Rei amps threw an expanse one would expect from fare mightier boxes and follow the rhythm with rarely seen evocativeness. 

The more music I've listened to the more pleasant qualities were revealed to me. With each new track and album WestminsterLab power amplifiers have proven naturally pertinent and not acting with a far fetched. "Everybody's Party" can sound like it comes from remote time or place with the system that is not optimized, but Rei amps conveyed the music with naturally deduced quality.

Many consider Keith Jarrett, Gary Peacock, Jack DeJohnette, Keith Jarrett Trio the greatest living piano-based trio. Playing together for over thirty years has made them act, react and adapt to the symbiotic changes in a very unique way. There are no superfluous traits in their act. It's all about a harmonic music langue outspoken so vividly and harmonically rich that one needs a hard defense system to avoid its impact. WestminsterLab Rei revealed something that not many amps can do regardless of the price. The very dialogue between Keith Jarrett, Gary Peacock, Jack DeJohnette! This interchange is equally well spread across the complete Somewhere, yet it again somehow culminate with "Somewhere/Everywhere". I should point out what such a peculiar distinction really relate to in order to prevent any confusion. It's not that Rei amps cannot decipher the magic of every track. On opposite. With Rei amplifiers, something very peculiar and unusual occurred. With certain songs WestminsterLab amps allowed far more intimate aural exposé. 

Despite "Somewhere/Everywhere" being almost 20 minutes long the Rei amps managed to pull me into the tale without skipping a second of fully immersive sonic escapade. The Rei amps' juxtaposition of a pure Class A nub vs ultra-fast dynamic core has proven to be of a remarkable equipoise. With Rei these two qualities, coexist in an intriguing sonic pact that needs to be heard to fully comprehend.  

WestminsterLab Rei amplifiers can resonate with music and preserve the very nature of human voices (choir), the timbre, tone, and the color with at exceptional level to say at least. Their ability to blend so many virtues in such an optimized package is refreshingly provoking. 

Classical music represents an epitome when it comes to the conveying of the dense multitude of connected music events. Across the variety of reference tracks, Rei amplifiers kept the music' narrative spot on. Even with the physically bigger sized amplifiers, it's not easy to capture and re-transmit dynamically challenging content, yet WestminsterLab have proven to be of constitutional authority. 

What might look like a ton of irregularities must be formed as a harmonic whole. Such believable reproduction must present the music event as both an entity of its own and as a sum-up of a wide variety of singular traits. We’re not talking only about the rendering of various instruments, but the objective formation of tones, decays, delays, anchor points, tone overlays, etc. All of them need to unify without losing their leading edge and inherited identity. 

This is also one of the most challenging tasks for power amplifier regardless of the operating class., price and size. Retaining the imprint and DNA as well the multitude of underlying micro activities is no simple task.

Sheer amplifier power specs mean little in the real world scenario if it collapses and smitten the original message. WestminsterLab Rei amps unexpected aptness to act like a higher-grade oculus rather than chaotic kaleidoscope was something I've repeatedly written down in my listening notes. Somehow Rei amps managed to keep the order in the massiveness of colossal impact without drifting away from the intended course. 

When the going gets tough the power amp can easily swing its dynamic power like a gigantic pendulum and lose the control at one point... Even a massive pendulum stops for a moment when it reaches it's (left or right) peak. At this threshold, the sense of power shifts the momentum and a mass pull it down as it has reached its peak limit. 

This phenomenon can be without difficulty recognized by a careful listener.

On the contrary to such occurrence, the Rei's propriety iBIAS circuit seems to be acting lighting fast when it comes to the monumental dynamic needs like gargantuan dynamic shifts, crescendos, etc. WestminsterLab power amplifiers' handling of the musical force was controlled, but of brutal impact when needed. 

The music delivery should mimic the inspiration. When it’s striking, it's there and should be nabbed immediately. Similarly, the music impetus can not wait to be formed, delayed or to be constituted with the decayed time lapse. 

I was a bit skeptical at how well WestminsterLab's Rei amps will handle the classical music, but any of my presumed constructs were quickly dispensed with a few songs. 

WestminsterLab's Rei amplifiers are exemplary proof of how we shouldn't judge the book by the cover. While generally, the sizing logic does resonate with the form factor, as a counteragent Rei has shown beyond the doubt to be a genuine David among the Goliaths! 


It's a fact that WestminsterLab Rei operates in a pure Class (but, then again so do many amps). It's also a straight fact how it doesn't sound like any Class A amp I've tried so far. Quite an entrance into the sum-up...

Yes, I was surely pleasantly surprised by WestminsterLab's monoblocks performance. But... I wasn't surprised by them performing so out of the box. Over my correspondence with Angus Leung, I've could learn all about the painstaking efforts and countless hours that Leung and his team have spent in creating and refining their amps. And during Leung's visit at my reference studio in September 2019 I've really had a great opportunity to know him and how his mind-set operate as well to find more about technical profundities of the Rei amps. Leung is not only a broadminded highly educated individual, but a genuine good minded high-end audio entrepreneur.

It's evident with everything that connects with the Rei mono amplifiers how they were designed from the ground up with one clear goal... To explore the very best that is possible within Class A without compromises and in the best possible way by exploring the uncharted realms. 

If you made it so far throughout the review you've probably already deciphered how WestminsterLab amplifiers are light years away from being a happy accident. These superb amps were voiced, tuned and optimized inside out to a level that it's hard to match. 

The WestminsterLab Rei amplifiers are an exemplary act of a well-tuned team in their mid-thirties that under the baton of high-end audio visionary Leung strive to make a difference on the market. Unlike the usual deja-vu efforts of making the difference for the sake of the difference, WestminsterLab thoroughness modus operandi endure to manifest something meaningful.  

It cost an arm and a leg for small boutique manufacture to achieve something so substantially objective as what WestminsterLab has done with Rei and the amps are successfully continuing the legacy they've set with their high-end audio line of cables. It's not exactly the rule to make it right twice. Especially in high-end audio where too often manufacturers wants to milk the cow even if there is no milk (or cow) to start with...

Watch out for this brand as they are speaking out with more than just a purposeful voice...

As we need affordable, feature-packed high-end audio devices, our beloved industry also necessitate push forward-thinking components like WestminsterLab Rei amplifiers. There are enough of chewing the chewed products out there riding the same old trail, holding on to the wave of past glory or exploring the unimaginable marketing budgets (that do come with a hidden price tag). I'm rarely smitten by a newcomer in such a way that I was with the WestminsterLab Rei Class A amplifiers. Their capability of delivering music so profoundly unaltered is more than worthy of pointing out. For what they are representing technically and music-wise I'm wholeheartedly giving out a very rare 2020 Mono and Stereo Editors Choice Award.  

And the unfolding continues. The WestminsterLab is already working on its own all-new super high-end audio preamplifier that is designated to be on par with the Rei performance and qualities. From what it has been revealed to me so far the prototype is already operating within expected scope! Do count me most interested in what Leung and his team will end up with! Stay tuned...•

Matej Isak 


- 30.000 USD for a pair (without VAT)


  • 100 watts @ 8Ω
  • 200 watts @ 4Ω
  • 400 watts @ 2Ω

Power ( Bridged )
  • 400 watts @ 8Ω
  • 800  watts @ 4Ω

Frequency Response
  • 5 Hz to 40 kHz, ±0.1 dB
  • 2Hz to 52 kHz, -1 dB

  • (100 watts @ 8Ω)
  • less than 0.1% at 1 kHz

Signal-to-Noise Ratio
  • 104 dB, A-weighted​

  • 1 balanced XLR input

  • 1 balanced XLR output​

Input Impedance
  • 200 kΩ​

Output Impedance
  • 0.018Ω

  • W232 x H112 x D320 mm

  • 16KG


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