Based in the Czech Republic, KR Enterprise is headed by an occasionally gruff Dr. Riccardo Kron and his American-born wife, Eunice, who operate the company out of a partially abandoned factory that was once part of the state-owned Tesla High Vacuum Technology facility in Prague. The Swiss-funded company is unique in that it manufactures both amplifiers and the tubes that power them. KR's tubes have found favor with other amplifier makers as wellespecially the 300BXS, electrically identical to a standard 300B but rated at 25W in class-A.
Victor Tiscareno and Byron Collett of AudioPrism are known in audiophile circles for their complete line of power-conditioning products. (See Barry Willis' omnibus review in the December 1998 Stereophile.) Their intimate knowledge of the ever-capricious electrical supply has resulted in a series of front-end components bearing the company's logo. The flagship Mana Reference monoblocks, under consideration here, represent AudioPrism's collected wisdom and engineering savvy taken to its logical extreme.
Many tube aficionados hold that amplifiers built with the venerable 300B tube hold the aces when it comes to sonic purity and beauty of harmonic line. Cary Audio Design's Dennis Had succeeded in producing what many believe is the definitive moderately sized single-ended triode (SET) amplifier: the CAD 300SE. This monoblock, powered by classic 300B Western Electric or derivative tubes, could provide 8–10Wpc, requiring the adoption of relatively moderate volume settings and/or sensitive, easy-to-drive loudspeakers. Cary also produced a lower-priced "integrated" stereo chassis, the CAD 300SEI.
Nagra's VPA amplification system consists of two slim, handsome monoblock amplifiers intended for vertical placement. They look good adjacent to the speakers. However, two 845 tubes put out a lot of heat, so the amplifier should be at least a foot away from your speakers...unless you're looking for a nice crackle finish.
Conrad-Johnson is one of audio's "marquee" companies, and charges accordingly. The Premier Twelve tube monoblock power amplifier, rated at 140W, sells for a rather steep $3495 each, meaning that unless you listen in mono, be prepared to lay out almost $7000 just for the amplification link in your audio chain. Apparently, many audiophiles feel the money is well spent: according to Conrad-Johnson, the Twelve has been a consistently strong seller during its approximately five-year production history.
They say you never forget your first time. For me, it was an Audio Research SP-6B that had been heavily modified by Analogique in NYC—which meant, among other things, that yellow capacitors shunted other yellow capacitors all the way up to the top plate. That first taste of the High End—prior to that, you might say my face had been pressed against the window—was definitely love at first listen. That SP-6B was warm yet detailed, and I ended up building a system around it that at least one friend described as a huge musical wet kiss.
In conversation with Cary founder Dennis Had at a recent audio convention breakfast, I learned that he had a long career in electronics, specializing in military/industrial high-power radio-frequency amplification and transmitters. However, his dream was always the re-creation of single-ended tube amplifiers, especially zero-feedback designs.
Although I retain a firm hold on the established audio world, and recognize and value all that it has achieved, I feel inexorably driven to make some space in my life for single-ended amplifiers—more especially, those that eschew negative feedback (footnote 1). A classic if costly example of the art is the Cary CAD-805C, which, to my ears, has earned the right to teach audiophiles what negative feedback really sounds like, and what damage it can do to the musical message when poorly handled. This shouldn't be taken as an out-of-hand dismissal of those many great pieces of electronics and amplification that use negative feedback—it is simply an acknowledgment, or even an assertion that negative feedback generates a sound of its own.
How much power do you really need? What does it do for you, anyway? Even before the single-ended renaissance, the prevailing wisdom was that you really didn't need that much power. When I had a pair of Met 7 speakers, even the "1 watt" indicator LED was hardly ever lit. Ditto for my time with a Threshold Stasis Two—all those cool power-indicator LEDs just sat there dark. Besides, everyone knows that power can be had only at tremendous cost, both monetary and in terms of other performance attributes.
Just who does Bruce Rozenblit think he is? And why is he saying those things about the late Julius Futterman? Rozenblit, relying heavily for guidance on his Electrical Engineering degree, has crafted an OTL (output-transformerless) amplifier that flies in the face of contemporary design dogma. To hear Bruce tell it, he's tamed the breed—this is how OTLs should have been done to start with, Futterman notwithstanding.
I'm always eager to fulfill my prime Stereophile directive: "To go where no audiophile has gone before," as JA often quips. As it happens, I've long suffered an itch to audition OTL (output-transformer–less) amplifiers, wondering how eliminating the output transformer might affect the sound. Enter the Graaf GM 200, with nothing but wire between its power tubes and the crossover.
Some audiophiles tend to get a mite sniffy around those of us who have expensive tastes and limited budgets. I've always been willing to spend the price of a new car on a set of speakers, but I never had the cash or credit. The sonic virtues of hefty, high-powered Krells and wondrous, single-ended tube designs always enchanted me, but when you're raising a family you make do. Through my experiences in a high-end audio establishment I learned the metaphysics of mixing and matching as befits my lowly caste, and I gradually developed sophisticated reference points, so that as the years swept by I managed to inch my way up the aural food chain.
Most reviewers look for a "hook" or angle of some kind when it comes time to write a review. After all, how many ways are there to get excited about audio equipment? Kathleen and I like to focus on the human side of the High End. So it was with some amusement that I watched the obstacles swirl around what I thought would be a fairly straightforward review of the Vacuum Tube Logic MB-1250 Wotan monoblock power amplifier. My thought was to return from single-ended to push-pull with a bang! I'll say...
It all began at the January 1996 WCES, where I found my shorts positively welded to the listening chair during a memorable musical blast at VTL. Luke Manley and his extreme audiophile wife Bea had a good thing going and they knew it. People were talking. "Did you hear those monster two-storey VTLs on the Alón Vs?"