Tube Power Amp Reviews

Closing his review of the AirTight ATM-1S amplifier in the November 2014 Stereophile, Art Dudley wrote, "The AirTight ATM-1S is right up there with the best I've heard: the artisanal, the small, the artistically sensitive, the colorful and characterful, the smart. The AirTight is as serious an EL34 amplifier as I've heard, offering texture, color, poise, musical drive, and rightness, all in good proportion to one another. It also looks nice and represents at least decent if not outrageously good value for the money."

Art's ATM-1S was a step in a long succession of tube amplifiers produced by AirTight since its 1986 founding. First came the original ATM-1; AirTight has also produced the ATM-2 (which used KT88 tubes), the ATM-4 (6L6GCs), the 1S that Art reviewed (EL34s; the S stood for "special"), the ATM-2 Plus, and now the ATM-1 2024 Edition ($14,975).

Tubes, tubes, tubes—how we love to bask in their glow, roll them, and take their second-harmonic distortion into our hearts as if it were a child or a pet. Some may put out so much heat that we have no choice but to open a window, turn on the air conditioning, or listen in the garb of Adam and Eve before that fatal first bite. As they and you age, you can never be sure who's at their best. Tubes, at least, can be replaced, albeit at significant expense...

I haven't reviewed much tube gear, but when I have—Bruce Moore and VTL (in my pre-Stereophile days), Audio Research, and in our September 2022 issue, the towering Octave Jubilee Mono SE tubed pentode push-pull monoblocks—I've been enamored of their sound. I waxed ecstatic about the "captivating beauty" and "heavenly" highs of the Jubilee Mono SEs. I can still recall how gorgeous they sounded; every listen was special.

Hence, my enthusiastic "yes" to a solicitation from John Quick, VP of Sales & Marketing for Dynaudio North America, Octave's North American distributor, to review the smaller MRE 220 SE mono push-pull tube amplifier.

Like many other industries, audio has its power couples: behind-the-scenes movers-and-shakers who shape the trajectory of the industry and who also happen to be, well, together. Angela Cardas and Josh Meredith of Cardas Audio come to mind, as do Dave and Carol Clark of Positive Feedback, Eli and Ofra Gershman of Gershman Acoustics, Luke Manley and Bea Lam of VTL, Carl and Marilyn Marchisotto of Nola Speakers, Edwin and Gabi van der Kley-Rynveld of Siltech and Crystal Cable. George and Carolyn Counnas of Zesto Audio are a hi-fi power couple I'm especially fond of; I'm always happy to see them at shows, catch up with them on the phone, or exchange emails with them. Their sweet demeanor and good vibrations always lift my spirits.

George designs Zesto's preamplifiers, power amplifiers, phono stages, and step-up transformers, while Carolyn, a talented fine-art painter, gives Zesto's products their unique organic curves...

"Do you swear to tell the truth, the whole truth, and nothing but the truth, so help your filaments?" asked the audiophile judge of the tube.

"Since I am the truth," respondeth the tube, "I have nothing to say that is not already declared by my sound."

"But I must have the truth, and without bias!" proclaimeth the audiophile.

"What good is a tube without bias?" answereth the tube.

VAC's Statement 452 iQ Musicbloc amplifier ($75,000 for a single amp; $150,000/pair mono, as reviewed) is tall, young, and lovely, but unlike the girl from Ipanema, it isn't tan. Nor, at 280lb in its flight case, is it likely to "go walkin'." Getting the pair moved into my listening room required considerable effort—fortunately not mine.

I had never been alone with a Russian-manufactured 6C33C tube. At least not at night, in the dark. The first night Balanced Audio Technology's VK-56SE tubed amplifier was in my system, I sat on the floor studying the unusual shape and dark orange glow of its four 6C33C-B output tubes. I noticed their brightly lit, cathedral-like innards. My Russian neighbor told me they were used as regulator tubes in MiG jets during the Cold War. I could believe it—their exposed cathodes were the exact color of the Soviet flag. From more than a foot away, I could feel the heat from their high-amperage filaments.

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?