Tube Power Amp Reviews

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Art Dudley  |  Jan 24, 2019  |  39 comments
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?
Art Dudley  |  Dec 20, 2018  |  5 comments
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.

Jason Victor Serinus  |  Oct 23, 2018  |  16 comments
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.
Herb Reichert  |  Oct 16, 2018  |  18 comments
When I began writing for Stereophile, I dreaded doing comparisons. They were stressful and tedious—and what if I got them wrong? But I quickly learned: Not only do readers enjoy comparisons, they need them. How else might they imagine the relative merits of the component under consideration? Once I realized this, I began acquiring a range of reference amplifiers.

But conspicuously missing from my audio menagerie has been a fast, neutral, 100Wpc tube amp to put more pop, fire, and maybe a little glow, into the Harbeth M30.2s.

Jason Victor Serinus  |  Sep 20, 2018  |  9 comments
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.
Art Dudley  |  Aug 28, 2018  |  15 comments
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.
Ken Micallef  |  Jun 21, 2018  |  111 comments
Back at the beginning of 2017, Greg Roberts, of Volti Audio, devised a clever way to bring his Rival floorstanders up to my penthouse pad, for what resulted in a rave review of those horn-loaded wunderspeakers.

I live on the top floor of a seven-story, elevatorless building on a busy street in Greenwich Village. A vertical challenge? No problem! Roberts is resourceful in many things, from speaker design to his former profession, the building of custom homes. Affixing a pair of unguent-saturated straps to the screws on each side of a Rival, we lifted and transported the 106-lb speaker high in the gritty Manhattan sky as if it were child's play.

Michael Fremer  |  Mar 22, 2018  |  18 comments
Designers of hybrid amplifiers can use solid-state devices in an amp's input stage and tubes in its driver and output stages, as Music Reference's Roger Modjeski did in his RM-200 Mk.II—or they can use tubes in the input and transistors in the output, as Ypsilon Electronics' Demetris Baklavas prefers.

The advantage of solid-state at the input stage can be lower noise. In the RM-200 Mk.II's fully balanced design, carefully matched input devices result in high common-mode rejection and low-noise operation close to the levels achieved with the best input transformers. The RM-200 Mk.II's signal/noise ratio measured a healthy 95.4dB.

Jason Victor Serinus  |  Feb 01, 2018  |  16 comments
"How natural the sound," wrote Jonathan Scull in March 1994, in his Follow-Up on the original Jadis JA 200 monoblock amplifier, which then cost $18,990/pair. "How easy it was to follow the musical line and fall into the music. How deep, controlled, tight, and satisfying the bass. How magnifique the midrange—the traditional strength of the Jadis presentation. How full and satisfying the lower midrange. How open, airy, how right the highs—not at all hard, but very extended and natural. How involving their presentation. How full, how harmonically correct, how wonderfully compelling. How magical."
Jason Victor Serinus  |  Nov 02, 2017  |  15 comments
Prelude
The setting of the Prelude to our opera, The Margules Saga, is the California Audio Show, in August 2012. There, on first hearing Margules Audio's tube electronics, I wrote in my notebook, "great inner vitality, warm but with a welcome and appropriate bite." An encounter the following January inspired me to write, of a system that included an earlier version of the company's U280 amplifier, "The sound? Beautiful and warm. I've heard these electronics at two shows, and each time, I've left the room feeling good."
Herb Reichert  |  Sep 26, 2017  |  13 comments
I have always been fascinated by audio power amplifiers. I even tried building about a hundred of them. My best friend in high school, Bill Brier, taught me the basics of soldering, wire management, and reading schematics. He loaned me his Dynaco Stereo 70, and gave me a hot-running, 20W, class-A transistor amp that he'd built on his mother's kitchen table. Bill took me to concerts, and taught me about classical and jazz music. He had perfect pitch, tuned pianos for money, played every instrument in the orchestra, and had memorized the complete keyboard works of J.S. Bach before he turned 16. And this stuff was all on the side—mainly, we built drag race cars together.
Herb Reichert  |  Nov 02, 2016  |  6 comments
Let us pretend . . . you have a pair of loudspeakers that have proven themselves to sound articulate and musically responsive in your room, without excess boom, bloom, or frail leanness. They mate with your décor and impress your friends. But maybe you're bored, and feel certain that your speakers would sound better with a better amplifier than the one you have now. Maybe you feel an urge to spend money? Perhaps a new amp will make your records sound the way you imagine they should sound?

I have had these thoughts many times.

John Atkinson  |  Apr 22, 2016  |  7 comments
Driving the Model Sevens at the 2014 CES were Vandersteen's then-new M7-HPA monoblocks, which provide a high-pass–filtered output (above 100Hz) to the upper-frequency drive-units of the Model Seven. At the time, I made a note to myself that I would like one day to try these amplifiers with the Sevens in my own room. That opportunity came later rather than sooner, after Vandersteen had updated the Model Seven to Mk.II status.
Art Dudley  |  Apr 03, 2015  |  1 comments
I was weak and easily led.

In 1978, after enduring four or five years of wretched music made by men with long hair and beards and tendencies toward eonic guitar solos, I suddenly discovered that the only music worth hearing was made by clean-shaven men of limited musical proficiency. I embraced the Clash, the Pistols, the New York Dolls, the Ramones, and the Buzzcocks. I cut my hair and gave away some of my old records. I even threw out my copy of Jethro Tull's A Passion Play—which, now that I think about it, wasn't that bad an idea.

Then I woke up and remembered: I'd left the baby in the bathwater.

Art Dudley  |  Nov 12, 2014  |  13 comments
It's no secret, especially to those who've been following Stereophile for more than a short time: In the first half of 2007, I took the plunge and bought a Shindo preamplifier and monoblock amplifiers—handmade products characterized by low output power, generous numbers of vintage parts, steel casework finished in a signature shade of green, and richly textured, impactful sound with lots of sheer musical drive. And while we tend not to alert the major newspapers whenever someone on staff buys new electronics, the change was notable for two reasons: The compatibility of Shindo's amplifiers is limited to loudspeakers of higher-than-average sensitivity and impedance; and, throughout the seven years that followed my switch to Shindo (footnote 1) both my system and my point of view regarding domestic audio in general have evolved in the direction of the artisanal and the vintage.

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