Tube Power Amp Reviews

I will never forget.

In 1988 I had my first experience with Western Electric 300B tubes. It took place on a quiet, streetlights-and-snow night at my friend Ryoichi's apartment on Riverside Drive, in Manhattan.

I had never heard of the late Japanese amplifier designer Ken Shindo, of Shindo Laboratory. But that evening, Ryo's audio system was all Shindo: a hammertone gray Shindo-restored, grease-bearing Garrard 301 turntable sitting on a Shindo plinth of glossy wood, with a Shindo-modified Ortofon tonearm and SPU cartridge, a Shindo moving-coil step-up transformer, and a Shindo preamplifier with a moving-magnet phono stage.

To audio designers in Japan and elsewhere, the single-ended, 300B-tubed amplifier is like a haiku: an art form defined by both its prescribed limitations and the potential such restraint offers for artistic expression. Here, the only hard-and-fast rule is a simple one: output devices are limited to one 300B directly heated triode tube per channel. From there, it's a blank slate: Do you want AC or DC on the output-tube heaters? Tube or solid-state rectification? Low or high gain? Fixed or cathode bias? New parts, vintage parts, or a mix of both? Triode or pentode tubes as drivers? Capacitors or transformers—or nothing at all—between the plates of the driver tubes and the grids of the output tubes?

There's no place for fashion in epidemiology, aeronautical engineering, or the mining and storage of uranium. Fortunately, domestic audio is less serious, its goals more scattered and ambiguous, than those and a thousand other pursuits.

And so, throughout the 20th century, any number of trends in domestic audio popped up their heads, some remembered as fads, others as legitimate approaches to playback. Among the latter are amplifiers whose output sections operate in single-ended mode, in which the entire signal waveform is amplified by a single device.

The great debate that has long separated audiophiles is tubes vs solid-state. Other topics, CD for example, may temporarily steal the spotlight, but year-in and year-out no other subject is the cause of as much controversy as whether tubed or solid-state circuitry produces the more accurate sound. As is typical with long-standing feuds, the split runs deep, and tempers often flare.

Doshi Audio first crossed my radar at the 2010 Rocky Mountain Audio Fest, where I wrote that the sound of the company's tubed monoblocks and preamp, connected to Wilson Audio Sasha loudspeakers via Transparent XL cables, "excelled in midrange strength as the system threw an exciting soundstage." After auditions of Doshi-Wilson pairings at many subsequent shows had convinced me that Doshi's products could truly sing, I contacted company owner and product designer Nishith "Nick" Doshi to inquire about reviewing one of his amps.

At a recent dealer event in Seattle, after being impressed by the musical rightness of an Audio Research Corp. LS28 preamplifier and VT80SE power amplifier driving a pair of Sonus Faber Guarneri loudspeakers, I spoke with ARC's Dave Gordon about reviewing one of the company's new amplifiers. Less than a month later, two ARC Reference 160M tubed monoblock amplifiers ($30,000/pair) were headed my way.

For this month's column, I did something I've occasionally set out to do but never quite managed: I lived with a new power amplifier for nearly two months, used it to enjoy a variety of records, made scads of listening notes, and wrote most of the subjective portion of my review—all without knowing what was inside it.