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Editor's Note: Apart from the CAT, Promitheus, Shindo, and Placette, all the Class A preamplifiers offer balanced inputs and outputs. And unless noted, the preamplifiers listed do not have phono stages.

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Audio Research Reference 5SE: $13,000
The Ref 5 SE is a tubed, remote-controlled line preamp with six sets of balanced and unbalanced inputs, three sets of balanced and unbalanced outputs, and a unity-gain Processor input. It uses 6550C and 6H30P tubes for power-supply regulation, and four 6H30P dual-triodes in the analog stage. Improvements over…

Editor's Note: Because of the disparity between typical tube and solid-state "sounds," we have split Class A for separate power amplifiers into two subclasses. Nevertheless, even within each subclass, Class A amplifiers differ sufficiently in character that each will shine in an appropriate system. Careful auditioning with your own loudspeakers is therefore essential. Except where stated, output powers are not the specified powers but rather those we measured into an 8 ohm resistive load. All amplifiers are stereo models, except where designated.

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Ayre Acoustics AX-5 Twenty: $12,950
In 2013, AD described the original Ayre AX-5—a $9950 integrated amplifier built around a recently rediscovered configuration of bipolar transistors known as the "diamond" circuit—as "one of the three best, most musical, most human-sounding solid-state amps I've ever heard." Then, in 2015, Ayre debuted a new version, the AX-5 Twenty—a nod to the company's 20th anniversary—promising even better sound. The AX-5 Twenty is built into the same foursquare aluminum case as the AX-5, and is controlled by the…

Editor's Note: Class A "Loudspeakers" are sufficiently idiosyncratic and differ enough from one another that prospective customers should read Stereophile's original reviews in their entirety for descriptions of the sounds. I have therefore just listed every system or combination that at least one of Stereophile's reviewers feels, as a result of his or her experience, approaches the current state of the art in loudspeaker design. (Note that, to be eligible for inclusion in Class A, the system must be full-range—ie, feature bass extension to 20Hz. It must also be…

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B&W DB1: $4500
The DB1 is a powered subwoofer in a handsome sealed enclosure measuring 19.3" H by 18.1" W by 16.2" D and weighing 97 lbs. Its solid construction includes: two mechanically opposed 12" woofers separated by a partially open internal partition, 1"-thick walls of MDF with ¾"-thick bracing panels to minimize vibrations, digital signal-processing circuits to run its menu-based control system, home automation capability, and a 1000W switching amplifier equalized to produce linear output. Also included are a calibration microphone…

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Audeze LCD-X: $1699
These large, luxurious, circumaural headphones have planar-magnetic drive-units with a thin-film diaphragm energized by arrays of powerful neodymium magnets on both sides. They employ Audeze-patented Fazor elements, said to guide and manage the flow of sound in the headphone. The circular drivers are housed in polished, black-anodized…

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47 Laboratory Model 4730 Midnight Blue: $1500 $$$
From Japan's reliably unconventional 47 Laboratory comes the Model 4730 Midnight Blue stereo FM tuner, surely the only tuner in current production that allows the user to dial in stations with an actual dial. Its modest size (4.8" W by 3.75" H by 8" D) and attractive dark-blue casework set it apart, as does its use of an old-style rotary variable capacitor—made in a small batch to designer Junji Kimura's order—instead of a crappy digital receiver circuit. According to AD, "Decent-quality broadcasts sounded better…

APC AV S15BLK: $730 w/battery backup ★
The S15BLK is a comprehensive power source, conditioner, and controller that features extensible external power and isolated EMI/RFI filtration for each of its outlet banks. Voltage regulation is accomplished electronically and without the hysteresis or rebound problems of slower, motor-driven compensation. Protected even the heaviest of KR's loads while also eliminating gray colorations and intermittent chassis vibration. "The S15 made the bridged eVo6 into an even better power amplifier—a super amp." (Vol.28 No.9 WWW)…

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BSG qøl Signal Completion Stage: $2395
The qøl Signal Completion Stage is a remote-controlled, solid-state signal processor with four pairs each of RCA and XLR analog inputs and two pairs each of RCA and XLR outputs. With the qøl activated, JA invariably noted a larger overall sound, with a greater impression of the ambience surrounding performers, increased image depth, and better layering within that depth. From JA's measurements, it appeared the qøl process is basically a variant of the well-known Blumlein Shuffler technique. "You must audition the…

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Sound Devices Model 722 portable audio recorder: $2775 ★
JM raved: "The coolest, most desirable piece of audio hardware I have encountered in a dog's age." The Model 722 is designed as a rugged, high-performance, foolproof, battery-powered portable stereo recorder for electronic newsgathering and video- and film-sound recording. However, with its line-level XLR analog inputs, onboard A/D converters, 40GB hard drive, and headphone amp, the 722 can also serve as a personal stereo. Offers 24-bit recording at up to a 192kHz sample rate. "The apotheosis of…