Power Amplifier Reviews, Preamplifier Reviews

WestminsterLab Quest preamp and Rei mono power amps

Christiaan Punter 6 May 2025 No Comments

Sidenotes: Mechanics

The Quest preamplifier is dead-quiet; even with your ear on the top panel, it is entirely silent. However, both Rei amplifiers produce a mechanical hum that can be heard within a range of about three meters in a quiet room. In my listening position, I could still faintly hear it, but only when there were no other sounds in the room. The hum was inaudible as soon as music played, even at a whisper-quiet level. As Angus Leung explains, this is by design:

“The O-core transformers we use in the Rei should be quite resistant to humming (mechanical vibration). But if they get saturated, the only way to dissipate that energy is through mechanical vibration. Another solution to avoid this is to pot the whole transformer, which in our case is a space issue (we end up with a much smaller transformer), but more importantly, we prefer the acoustics of a non-potted transformer”.

It has been suggested that my household mains power may contain DC components. I cannot test this, but I should add that the P20 can reduce small amounts of DC. In any case, even if we accept that my mains power could be the culprit, it is likely that this will also be the case for many other households.

To be clear, it is not unique for an amplifier to emit a bit of hum. Countless products do this, and the ones that don’t usually either use switched power supplies (e.g., Soulution) or have transformers that are potted (e.g., Accuphase) or mounted in or on rubber (e.g., CH Precision). However, I should note that the hum remains present whether the Rei power amplifiers are connected directly to the untreated mains power or are powered by the PS Audio P20 PowerPlant. Incidentally, the P20 contains a huge toroidal transformer itself, which does not hum.

The Rei’s enclosures produce a couple of fast-transient “clanks” as the amplifiers warm up or cool down. As Angus Leung explains, this is also by design:

“The heatsink of the Rei is a key structure to the unit chassis; panels are mounted to the heatsink as a structural element, all panels are part of the unit’s structure, and the tolerances of these panels are very tight. Unlike most amplifiers (especially class A amplifiers), where a steel chassis is used, heatsinks are mounted to the chassis, with cladding on the outside for the appearance. The conventional design has more margin of expansion available for components to expand and contract. We rarely observe the noise, but it happens more often when the ambient temperature is cold”.

That does make a lot of sense. I can add that I also observed this effect with Jeff Rowland model 6 power amplifiers, where the entire enclosure was simultaneously the convection heatsink. It is nothing to worry about, even if it can be startling when first observed.

Conclusion

Since I reviewed the CH Precision components and made them a central part of my system, I have seen several preamplifiers and power amplifiers come and go. A few performed surprisingly well considering their price, and some offered interesting features with notable strengths, but always at the expense of other qualities. So far, only one amplifier has performed at the same overall level, the Soulution 711, and only one that exceeded it in a few key aspects: the Halcro Eclipse. Both are significantly more expensive. Now, we can add WestminsterLab to this very short list.

The Rei power amplifiers are magnificent. Utterly neutral and highly revealing, yet fluid and delicate, they combine everything one could expect from an ideal power amplifier while being massively expressive and dynamic.

While the Quest preamp deviates from the Rei monos with its lusher, smoother, and more relaxed nature, it is a superbly liquid and natural-sounding preamp with resolution and musicality in equal measure. As a combo, the Quest works harmoniously with the Rei’s toward the company’s goal of providing the essence of the music, or, as the company so very rightfully puts it: “Experience music as it is”, without tipping over to a lean, dry, or anemic experience.

WestminsterLab Rei mono power amplifiers