Tube Power Amp Reviews

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.

Writing a regular column can be a funny thing; the repetition it requires brings up questions that grow increasingly urgent. Chief among them: What are we doing here, and what is this for? For all the handwringing about story-telling and prose style, what we're up to in the equipment-review section of this magazine is writing about metal boxes filled with wire, capacitors, circuit boards, and other bits of hardware. Life is difficult and goes by in a flash, love and satisfaction are fleeting at best—so why should we care? Well, because some of these boxes manage to connect us to beauty and meaning in a way that can enhance and gradually change our lives. (And yes, both have to be in the mix: Beauty without meaning is anodyne and lacks whupass.)

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.

Lee de Forest filed for a US patent on his "Audion"—the first triode—on October 25, 1906, but never could explain why it worked (footnote 1). It was up to Armstrong and Langmuir, in their pioneering work, to place the hard-vacuum triode on firm scientific ground. When the US entered World War I in April 1917, the Army had to rely on French tubes. Six months later, Western Electric was mass-producing the VT-1 receiving tube and the VT-2 transmitting tube. However, it was only in the decade following World War I, as designers became conversant with the triode amplifier, that many of the crucial elements of tube amplification were nailed down. Technical issues such as coupling two gain stages and selection of optimal coupling impedance were already resolved by the mid-1920s. The triode ruled supreme until the tetrode came along in 1926, followed in 1929 by the pentode from Philips's research laboratories in Holland.

At the last few audio shows, whenever I heard a pair of the big Cary CAD-1610-SEs, I fair licked my chops. The two-tiered monoblock looked positively stunning in black and polished aluminum, exotic tubes bristling from the top "floor" of its two-story edifice. The Cary always induced pelvic tilt in me—you know, when your lizard brain takes over and tube lust is in the air.

For anyone who's been around the audiophile block a few times, Conrad-Johnson Design is a brand that needs no introduction. My first acquaintance with Conrad-Johnson was before I began writing for Stereophile (more than two decades ago—time sure flies fast when you're having fun!). I was in the market for a new preamp, having become convinced that my Dayton Wright SPS Mk.II was the weak link in my system, and had narrowed my choices to two similarly priced products: a solid-state model made by PS Audio (I'm not sure of the model number), and the tubed Conrad-Johnson PV-2ar. They were carried by different dealers, who allowed me to take their preamps home over the same weekend for a direct comparison. I was impressed by both preamps, and was sure that either would represent an improvement over the Dayton Wright, but in the end decided to go for the PV-2ar. I later traded it in on a dealer's demo unit of another Conrad-Johnson preamp, the PV-5. And, as it turned out, one of my first reviews for Stereophile was of Conrad-Johnson's PV-11 preamp.