Tube Preamp Reviews

As part of my employer's never-ending attempts to transform me from an engineer into a manager, I am constantly being sent to seminars and courses, some of which are eminently practical—like "Managers and the Law," which taught us how to avoid getting ourselves and our company sued. Others are more esoteric, like a recent seminar on "paradigm shifts." A paradigm shift, we were told, is a fundamental change in the way we look at things, arising from a change in a belief so inherent that it's unconscious.

For example, imagine a long plane flight, late at night. A mother and two small children occupy the seats near you, and throughout the flight, the children are screaming—but the mother seems oblivious. After about two hours, you're getting pretty annoyed, so you complain to the flight attendants, who, inexplicably, also seem oblivious. They reply that the family is returning from the funeral of the children's beloved grandmother, the woman's mother. Instantly, annoyance becomes sympathy and empathy, and all you want to do—once you crawl out of the hole you wish you could sink into—is to help in any way you can. Bingo! A paradigm shift.

I enjoyed the class, though I never quite understood what paradigm shifts had to do with being a better manager. I did realize, however, that the concept perfectly described my experience with the Conrad-Johnson Premier 17LS line stage. See, I had developed a pretty firm impression of C-J products over my 20-plus years in audio. What's more, I'd developed this impression without having owned, or even used, a C-J product since 1985!

High-end audio began for me in the late 1970s. At that time, the big three were Audio Research, Mark Levinson, and Conrad-Johnson. Each had its strengths and weaknesses, each its own personality. C-J's was big, vivid, and colorful, if perhaps a bit lacking in subtlety and detail—lush and wonderful, but far from neutral. My experiences with C-J products—owning an MV75 amplifier and spending a lot of time listening to a system built around a Premier One power amp and Two preamp—reinforced this impression. My MV75 also spent about half its time being repaired or in transit, which added another dimension to my paradigm: C-J products are over-designed and under-built.

Although I'd read numerous reviews of C-J products in the intervening years and followed the evolution of their designs, my underlying beliefs never changed. When I read a review that talked about clarity or detail, I intellectually processed the information while never quite internalizing it. At my core remained a fundamental belief that all C-J products were not so very different from my MV75 or the original Premiers. It was only deep into this review, as I kept struggling unsuccessfully to fit the Premier 17LS into my preconceived notions, that the light went on and I realized that those notions even existed. Bingo! A paradigm shift.

So what makes a Premier 17LS tick?

The Premier 17LS is C-J's "most affordable implementation of the engineering advances pioneered in our flagship Anniversary Reference Triode preamplifier." Wes Phillips described the ART's design features and philosophy in his review in the May 1998 Stereophile, and Lew Johnson added his perspective in an accompanying interview.

The 17LS's amplification circuit, like the ART's, is simplicity itself: a single triode stage with no global or local negative feedback whatsoever. And rather than add a cathode follower to lower the unit's output impedance, C-J chose instead to simply parallel several triodes, lowering both the output impedance and the noise floor. The ART uses ten 6922 tubes, each channel's paralleled ten triodes resulting in an output impedance of ~500 ohms. The 17LS has four 6922s, resulting in an output impedance of ~850 ohms—a little on the high side for some applications, but more about that later.

What really makes the 17LS tick—literally—is that all switching and control functions are microprocessor-controlled and implemented by relays. Volume up? Click click click. Change input? Click click click. Wes commented that he found the noise strangely comforting, and I'll admit, so did I. I tell myself it's because I'm a mechanical engineer; I don't know what Wes's excuse was. The relay scheme was chosen to completely remove the switching circuitry from the signal path, and the relays are driven by their own separate power supply, from the transformer on.

The relay approach is typical of the attention to detail that C-J has lavished on the 17LS. Every cubic millimeter of the unit is lusciously finished, from the thick, textured faceplate to the heavy, gold-plated RCA jacks. Even the remote is milled from a solid chunk of aluminum, and finished in C-J's traditional champagne gold anodizing. Inside, things are equally impressive, with beautifully laid-out boards jampacked with laser-trimmed Vishay bulk-metal resistors and other premium bits. Signal paths are kept as short as possible, and the boards are elastomer-mounted to prevent air- and ground-borne vibrations from reaching the tubes.

The Premier's Sovtek tubes themselves are carefully burned-in and matched, and supplied with damping rings to reduce microphonics. In a wonderful touch, C-J designed the unit so that the tubes can be accessed via a small, easily removable panel on the unit's top.