Tube Power Amp Reviews

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.

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.

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.

It's going to happen very soon.—Leonard Cohen, "The Great Event"

With a parts list that includes 18 new-old-stock Black Cat capacitors, 16 vintage-style Cosmos potentiometers, two Tango chokes, one Tango power transformer, and some of the loveliest steel casework I've seen on a contemporary product, no one could accuse Noriyuki Miyajima of skimping on the build quality of his company's only power amplifier, the Miyajima Laboratory Model 2010 ($9995, footnote 1). Then again, because the 2010 is an output-transformerless (OTL) tube amplifier, Miyajima-san spent considerably less on iron than would otherwise be the case. Think of the money he saved!

Big tube amplifiers were once scary monsters reserved for those who didn't mind heavy maintenance, careful tweaking, and the occasional explosion. Blown tubes required replacing, preferably with pricey matched pairs, then biasing with a voltmeter. Optimal sonic performance required regular bias monitoring and adjusting, and because of current surges on startup, you had to choose between leaving the heat-producing monoliths on, or turning them on and off for each listening session, thus shortening the life of the tubes.

The road to hell is paved with good inventions: clever ideas that appear, in hindsight, motivated more by a desire to sell clever ideas than to make musically superior products.

The DiaLogue tube amplifiers from PrimaLuna have, at their heart, a clever idea of their own: an output circuit that is user-switchable between triode operation, in which the screen grid of a tetrode or pentode power tube is defeated by means of connection to the tube's anode; and Ultralinear operation, in which the screen grid of a tetrode or pentode carries a portion of the AC music signal, supplied by a tap on the output-transformer primary, in a feedback-like effort to reduce distortion and increase power. Fans of the former often report a sweeter, more tubey sound, while fans of the latter report a tighter, more detailed, more timbrally neutral sound. Audio enthusiasts are given to reporting any number of things.

Domestic audio is based on two simple processes: transforming movement into electricity and electricity back into movement. Easy peasy.

Audio engineers have been doing those things for ages. Have they improved their craft to the same extent as the people who, over the same period of time, earned their livings making, say, automobiles and pharmaceuticals? I don't know. But if it were possible to spend an entire day driving a new car from 50 years ago, treating diabetes and erectile dysfunction with the treatments that were available 50 years ago, and listening to 50-year-old records on 50-year-old playback gear, the answer might seem more clear.