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TechDAS Air Force One: $105,000 plus tonearm ★
"A visually stunning technological tour de force," the 174-lb Air Force One has a three-laFyer chassis of damped aluminum, a forge-processed stainless-steel platter, and a massive AC synchronous motor controlled by an outboard dual-50W amplifier. The platter uses an air bearing; LPs are held to the platter with vacuum suction. The review sample was equipped with a Graham Engineering Phantom II Supreme tonearm. Though it didn't sound as smooth as the Continuum Caliburn or the Onedof One Degree of Freedom, the Air…

Editor's Note: SACD and DVD-A player ratings are based on how they sound with their respective hi-rez media, not CD.

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Antipodes DX Reference: $6950–$15,530
What could tempt the frugal JA into forsaking his computer-based file-playing system for a high-quality dedicated music server? The latter must offer sound quality with which the former does not compete—and that's precisely what he found in the Kiwi-built Antipodes DX Reference. The DX Reference, which runs on the Linux operating system, runs…

Editor's Note: The sound of any particular CD transport/digital processor combination will be dependent on the datalink used-see "Bits is Bits?" by Christopher Dunn and Malcolm Omar Hawksford, Stereophile, March 1996, Vol. 19 No.3 (WWW). Unless mentioned, processors are limited to 32/44.1/48kHz sample rates. To be included in Class A+, a digital processor must be capable of handling DSD or 24/96 LPCM data.

We strongly recommend those interested in using a computer as a true high-end digital audio source visit our sister website www.AudioStream.com, which is…

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Merging Technologies NADAC Multichannel-8: $11,500
Among pro-audio companies that have set their sights on the domestic market, the Swiss manufacturer Merging Technologies is noted for its experience with high-resolution networked-audio interfaces. Their NADAC Multichannel-8 (its first name stands for Network Attached Digital to Analogue Converter) is intended for use with network-based file players, and is compatible with the audio-specific Ravenna protocol. Via Ethernet, the Multichannel-8…

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Audio Research REF6: $14,000
Replacing Audio Research's Reference 5 SE of 2011, the Reference 6 is a product in which everything—parts, circuitry, the whole megillah—has been revised, the upgrades including a heftier mains transformer, an improved volume-control circuit, and new custom-made capacitors. The audio circuits include three 6H30 dual-triode tubes per channel,…

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.

A (Solid-State…

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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 The King: $3995
Created by legendary electronics designer Bascom H. King—geddit?—the hybrid tube/MOSFET The King headphone amplifier is built into a large (12.8" wide by 4.3" high by 11.8" deep) case supported by four substantial, shock-absorbing feet. It operates in class-A, and its two parallel, front-mounted, ¼" outputs can be calibrated by the user for…