Quest & Rei

This review appeared in the October 2025 PDF issue of Audiophile Magazine. We publish its English translation in a syndication arrangement with the publisher and by special request of the manufacturer. – Ed.

Reviewer: Joël Chevassus
Sources: Esoteric K-03 and N-05XD, Cybershaft 21A, Mac Mini M1, HiFi Rose RS201E, Weiss Helios [on loan]
Power & integrated amplifiers: Coïncident Speaker Technology Turbo 845 monos, Esoteric S-5, SPEC RPA-W3EX, Kinki Studio M7, Red Dragon S500
Loudspeakers: Vivid G1 Spirit, Leedh E2 Glass, Recital Audio Illumine Hefa
Cables: Luna Red series for speakers and interconnects. Vertere HB USB and Esprit G8 USB.
Room: 7 x 7.5 m with high beam ceiling, acoustically treated by Tecsart
Review component retail: €25'490 Quest, €36'390/pr Rei

Direct from Hong Kong, today's brand is still somewhat underground despite having traded for a good ten years already. Founder Angus Leung is the designer of all their products, a diehard audiophile whom I've dealt with since he began collaborating with Lumin on first fine-tuning their cables, power supplies then amplifiers together with Li On, the other pair of Lumin's golden ears. But this collab did not preclude the development of his own activity under WestminsterLab. And if at Lumin one favours the rationalization of costs and a certain industrial logic, WestminsterLab play the artisanal micro-brand card, selecting their components very carefully without really bothering about costs to mainly pursue excellence in design and manufacturing no matter what. After all, beyond a certain level, price stops being of primary importance.

The name WestminsterLab reflects a time when Angus together with two university friends in London decided to create a high-end hifi company in parallel to studying. The chosen name thus refers to the famous English Westminster City and central London borough which in addition to its cathedral hosts one of the UK's most advanced high-tech centres. Their brand's maiden project was the Unum power amplifier at the time quite at odds with the codes of high-end hifi. It escaped the logic of always bigger forever more expensive. It also offered unique finish options like premium rose gold or platinum plus innovative detailing of gold-plated copper dissipators coated in shiny black diamond-like carbon in lieu of classic heatsinks. Involving physical vapor deposition, this surface treatment improved thermal performance and added to Unum's unicorn or UFO status upon launch. Whilst it gained a reputation, it didn't necessarily reflect in the most dynamic response of a market not yet entirely ready for its mix of luxury and hi-tech.

Today's Rei amplifier rationalizes the Unum project as a more accessible implementation whilst preserving its essence and uncompromising performance to become an even more accomplished product that should be more in phase with market expectations. "Our objective was to bring Unum's advanced technology and sound to a wider audience. With unfailing dedication we approached this project by designing and carefully developing each aspect to achieve excellence and the same exceptional performance, musicality and immersive experience as its predecessor." The Rei mono operates in pure class A and integrates WestminsterLab's proprietary iBias and CCS system. It develops 100wpc into 8Ω and keeps doubling into 4 and 2 ohms, remaining stable into 1Ω. iBias also shortens the warm-up time of classic class A circuits and dynamically adjusts the polarization current with the real-time load behaviour. It claims the coveted benefits of class A without its disadvantages of heat generation and energy consumption to become a more modern green proposition. The matching of output transistors is a fairly classic approach but WestminsterLab practice extreme selectivity beyond just 1% tolerance down to several operating points on the curve, then stress-test these paired transistors under extreme loads for several hours to guarantee reliability and optimum performance. It's how the amp can make 400wpc/2Ω. Unlike the monocoque chassis of Unum, Rei uses aerospace-grade 6063 CNC-machined aluminium halves which help isolate the power supply from the signal-path circuitry. The left cheek is the heat sink whilst the top and bottom panels are carbon fibre to manage vibrations and shift resonance modes far beyond the audible bandwidth and that of our loudspeakers. They also anchor to the power-supply sub enclosure to isolate the signal-path circuit. Like certain Japanese manufacturers who pay special attention to the quality of printed circuit boards, WestminsterLab exploit ultra-thick ultra-pure copper traces which, according to its designer, approach the performance of classic point-to-point wiring.

Let's move to the companion Quest preamplifier where control of the ground plane has a significant impact on micro-signal performance. This led to 'Hybrid Grounding' which can be switched on the fly. The gain circuit is fully balanced dual mono for minimized interference and crosstalk. As a modular concept, there's an add-on RCA module. For attenuation, Angus opted for a shunt network of 64 stepped resistors each across four channels run off their own power supplies and regulators. To minimize distortion further, the control logic interfacing the beautiful dot-matrix display and remote control was tweaked to avoid noise artifacts. With this combination of shunt-type attenuation, dedicated power regulation and simple control logic, WestminsterLab believe that they have solved a large part of the sound-degradation mechanisms typical in competing devices. But there's still a soft-start protocol and certain sub sections of the circuit compartmentalize to minimize cross talk whilst the extended carbon-fibre option below adds extra shielding layers for the most demanding buyers. On the rear are two expansion slots to support emerging tech and features. As mentioned, an unbalanced-to-balanced converter module is already available. Vinyl fans have their own two options. One is a three-stage RIAA module with special capacitive summation for minimal distortion and coloration and all adjustments made via classic dip switches. There's also an optical phono module which runs a dedicated power supply for its LED cell and a bypassable -6dB/20Hz rumble filter all certified by DS Audio. Because this user interface is purely by remote to avoid all of the usual control knobs, the Quest ships with two IR wands to have a backup in case of momentary malfunction.

Although it seems extremely banal, it's still good to highlight the perfect complementarity of the Rei and Quest. As we like to say across the Atlantic, the result is greater than the sum of its parts. Undoubtedly proper impedance adaptation was superior to mixing separates between brands. I encourage anyone interested in these products to audition them as a set to mirror my own impressions generated as a set. In the end I'll attempt to indicate how they might be considered separately. The general impression that the threesome generated in me was one of unprecedented transparency and great softness. It's a very liquid holographic sound reminiscent of the best tubed efforts. However, it is necessary to here envision a still more organic dense reading with increased energy as we'd expect it from beefy class A solid-stage amps. The WestminsterLab set won't be as materialized as the Dan d'Agostino separates but it is a very great compliment for such relative newcomers to be compared to the great d'Agostino representing the best of transistor amplification. This Quest/Rei set presents great neutrality as a clear absence of colourations which contrasts the expectations often associated with a pure class A aesthetic. That routinely is a quite flattering, warm and very elegant affair which embellishes at the risk of appearing a bit homogenized in the long run. The WestminsterLab ensemble thwarted these pitfalls and almost called upon the neutrality of certain class D amplifiers beyond their flat sterile instances to here perform very alive and dynamic.