Michael Fremer

Nuvistors—miniature, small-signal, vacuum tubes made of metal and ceramic—were introduced by RCA in 1959, at the dawn of the transistor revolution. RCA used them throughout the 1960s in its New Vista line of television sets, mostly in the tuner section. But by the early 1970s, solid-state devices had all but replaced tubes, nuvistors included (with a few notable exceptions). Ampex based the electronics of its well-regarded, late-'60s MR-70 open-reel tape deck on nuvistors, which were also used in microphone preamplifiers—in both cases for their very low noise and reputation for reliability and long life. For a time, Conrad-Johnson used them as well. While nuvistors may seem exotic today, they're hardly rare. On eBay you can find for sale hundreds if not thousands of used and new-old stock (NOS) nuvistors, as well as nuvistor sockets, without which the tubes are less easy to implement. (But they can be, and often are, hard-wired into a circuit.)

Class-A amplifiers have a well-deserved reputation for being power guzzlers that run hot enough to burn fingers. They're inherently inefficient because their output devices conduct full current at all times, and much of that current is dissipated as heat—requiring, in the case of class-A solid-state amplifiers, massive heatsinks. This is why class-A amps tend to produce relatively low power, and tend to be heavy and expensive to buy and run. And these days, energy inefficiency is out of fashion.

Pear Audio Analogue's Peter Mezek can keep you up all night spinning fascinating turntable tales. Had my mind not been numbed by Sunday evening, October 12, the last day of the 2014 Rocky Mountain Audio Fest, I might have insisted that he do just that.

Over dinner that evening he regaled Pear Audio's North American importer, Michael Vamos of Audio Skies, and me with turntable stories dating back to the late 1970s and the Linn Sondek LP12, which, until the early '80s, he distributed in Czechoslovakia. In the mid-'80s, Mezek was involved in the development and distribution of the Rational Audio turntable, designed for Mezek by Jirí Janda (pronounced Yeerzhee Yahnda), who died in 2000. For those of you old enough to remember, Janda, a founder of NAD, designed that company's 5120 turntable; among other features, it had a flat, flexible, plug-in tonearm that you could easily swap out, much as you can with VPI's current models.

Stereophile normally doesn't review audio systems. We review individual components. We've made an exception for the Bel Canto Black system because it deserves to be evaluated as such. It consists of three dense, almost identically sized cases of black-anodized aluminum. One, the ASC1 Asynchronous Stream Controller, is what in a conventional system would be called a "preamplifier." The other two, a pair of MPS1 Mono PowerStreams, would in a conventional system be called "monoblock power amplifiers."

Clearaudio began making moving-coil cartridges in the 1970s, and only later got into the moving-magnet business. Moving-magnet cartridge designers must now be mindful that most of today's tonearms are of medium to high mass and that therefore, to be compatible, their MMs must be of low to medium compliance and of higher mass than those of the 1960s and '70s.

Founded in 1984, Boulder Amplifiers is a conservative audio company that goes quietly about its business, choosing not to call attention to itself with marketing flash or acronym-laden features. Change comes slowly to such companies, which is why the just-retired 2010 preamplifier enjoyed a 17-year run.

Can a power-supply upgrade produce audible sonic benefits? If you've upgraded the power supply of a phono preamplifier, you probably don't need to be convinced that it does, and those usually cost only a small percentage of the price of the model they power. But to add Simaudio's Moon Evolution 820S power supply ($8000) to the Moon Evolution 650D DAC–CD transport ($9000), which I reviewed in the November 2011 issue, almost doubles the latter's cost—though the 820S can be used to simultaneously power two Moon Evolution components, like the 750D DAC ($14,000), 740P preamplifier ($9500), and 610LP ($7500) and 810LP phono preamplifier ($13,000).