Conrad-Johnson Premier Eleven power amplifier Page 2

Tu-be or not tu-be
Intriguing? You bet! The Premier Eleven is chock-full of intrigue, and also of high-quality parts. Designed to be the entry-level amplifier of Conrad-Johnson's flagship Premier line, it's rated at 70Wpc. It uses two 6550 output tubes per channel in a push-pull configuration, two 5751s control the voltage amp, and a pair of 6CG7s are the phase inverter/output drivers. The amp's output stage is described as being ultralinear, and boasting unusually wide-bandwidth output transformers rated in excess of 100kHz. Additionally, I find it to be one of the most gorgeous jewels in all of audio, with its golden chassis putting the glowing tubes right up front and out in the open. (It comes with a cage to enclose the tubes, but I couldn't imagine using it.)

Three transformers, ranked behind the output tubes, give it an architectural look—like a gleaming city on the cover of a 1930s sci-fi magazine. The speaker connections, made via a pair of five-way binding posts (not the barrier strips C-J used in the past), are very well-made and readily accept even gargantuan spade-lugs. I found them a pain in the butt, as they don't have a standard ½" nut—just two opposing flat sides on an otherwise cylindrical post. But I'm told that, after auditioning many, many sets, C-J gave these the nod on the basis of sound quality alone. I must, of necessity, change cables frequently, but if you like to just connect and forget about 'em, these will do just fine. (Hint: Use a 7/16" crescent wrench for that last little turn, but be vewy, vewy careful. By the time the posts have been tapped for bananas and cut for threads, there's not much metal left; the ham-handed among you—well, okay, I—can snap them like twigs.) The amp can be configured at the factory to drive 2, 4, or 8 ohm loads, and is typically set-up coming off the 4 ohm taps. If your requirements are different, talk to your dealer and specify what you want.

C-J's choosing to use the 6550 tube has generated controversy in the audio community, some going so far as to claim that it's not a proper tube for use in audio circuits. I felt keen disappointment when I heard that the Premier Eleven was designed around these pentodes. Most of my listening experiences with 6550 configurations have left me feeling unfulfilled: the amps that used them seemed hard, with a glare—or something close to it—on top; overtones seemed stacked on top of the note—not organic to the fundamental. Oh my, I thought arrogantly, why would they use a tube so obviously flawed?

Hey, what do I know? I've never designed a circuit. I've butchered a few kits—my soldering is a sick joke—and I've looked inside almost every audio component I've met; but my ability to read a circuit diagram is slightly worse than my music sight-reading. So where did I come off second-guessing a design that I hadn't even heard? Sheer hubris—because the instant I heard the circuit, I was forced to concede that my previous encounters with the tube had not defined its possibilities.

Define resolution (resolve definition?)
I called Lew Johnson and asked him why C-J had settled on the 6550 as opposed to other thermionic favorites. His answer was pithy: resolution. Well, of course, that made sense. Just as we design systems from the front-end down—with the philosophy that nothing can put back what has been removed—it seems obvious that the last thing you want just before sending signal to the speakers is to lose information you've sent down the chain.

The design's extremely high resolution is emphasized by its almost uncanny, untube-like silence. Those of you who avoid tubed designs because tube roar is anathema to you might want to seriously listen to the Premier Eleven. As a longtime tube-lover, I'm familiar with the argument that steady-state tube roar is much less noticeable once the music starts. I find it easy to ignore, but I also listen to scratchy old 78s of dead musicians. For many people, the chief appeal of the modern age of audio—eg, solid-state and digital—is the absence of noises that you need to ignore. This, then, is a tube design for the audio modernist. I paired the Eleven with the Wilson WATTs/Puppies (93dB/W/m)—speakers so sensitive (and accurate) that they'll throw any extraneous signal into high relief. I heard nothing. Nada. Nichts. Niente. (Well, not technically true; I heard a tube starting to get hissy in my preamp's phono section—a tube that still sounds fine with less efficient speakers. But you get the idea—we're talking profoundly silent.)

Control? Sure! With the WATT/Puppy combo it was easy to shake the house. Of course I did. (That's a very efficient transducer—even 20Wpc triodes shake the house with those babies.) But the bass—even the very low bass—was relaxed and natural. Pairing the Premier Eleven with the much larger and less efficient Energy Veritas v2.8 (86.5dB/2.83V/m) was a different story. Driving four 8" woofers down to 30Hz put an audible strain on the C-J. The overall sound was coherent, and the midrange and high frequencies sounded natural and assured; but the amp just ran out of steam at high volumes and extreme low frequencies. The power supply, when tapped out, caused the sound to "waver"—much like looking at a faraway object on a hot day. This may be unfair, as Energy suggests using at least an 80W amp, but torture tests reveal a lot. I should also mention that the Veritas exhausted a pair of 160Wpc tubed monoblocks as well, so the Eleven did not acquit itself badly here.