Kuzma Stabi XL Turntable/ Air Line Arm, Walker Proscenium Black Diamond Record Player

Equipment report
Kuzma Stabi XL
Kuzma Stabi XL Turntable/ Air Line Arm, Walker Proscenium Black Diamond Record Player

As most of you alread y know , when analog records are mastered , the cutter head that inscribes the signal in the lacquer blank travels in a straight line from the outer edge toward the center of the spinning disc. It is generally accepted that, all other things being equal, the tonearm should follow the same line as the cutter head for the most accurate playback and lowest tangential error. Of course, all other things aren’t equal, but we will come to that in a moment.

Both the $40k Walker Proscenium Black Diamond and the $28.5k Kuzma Stabi XL turntable with Air Line tonearm are air-bearing, tangential (straightline- tracking) record players. Both tonearms ride on a very thin (10-micron) cushion of air, which acts as a frictionless bearing; both arms trace the same straight line across the LP that the cutter head did, theoretically playing back discs with zero tracking error. Why, then, do they sound so different?

Well, part of the difference is attributable to the different ways these two superb record players spin LPs.

The Kuzma Stabi XL is a suspensionless, modular, twin-belt-andmotor- driven turntable that depends on the carefully chosen materials it is made of for damping. Since it has no suspension and no means to adjust level, the Kuzma ’table and arm must sit on a sturdy stand or air-suspension table, like a Vibraplane, that can itself be precisely leveled.

The Stabi XL doesn’t have a traditional rectangular plinth. Instead, it has a 59-pound “base”—a beautifully machined cylindrical hunk of brass, with an inverted, oil-bathed, non-metallic, ruby-tipped bearing-shaft in its center. An aluminum subplatter is fitted snugly onto the bearingshaft, a 48-pound platter—made of a sandwich of aluminum and acrylic plates and topped with a proprietary rubber-and-textile mat—onto the subplatter. Drive is supplied to the platter by two cylindrical, brass-encased motors that fit into cutouts on either side of the turntable base. Twin belts run from both motors around the subplatter—a symmetrical setup that is said to maximize stability and minimize vibration. Motor speed is controlled by a quartz clock in the Stabi XL’s outboard power supply. The whole thing looks exceptionally cool—a genuine work of applied art.

The Walker Proscenium Black Diamond is an air-suspended, singlebelt- and-motor-driven, air-bearing turntable. It, too, depends on the mass and composition of its component parts to provide damping, although the Walker also sits on air-suspension feet that decouple it from whatever else it rests on. Unlike the Kuzma, the Walker can be leveled via adjustments to the pressure in its feet, and since it has its own built-in air-suspension system, you will not need to buy a Vibraplane—something to keep in mind when you consider the considerable difference in price between it and the Stabi XL.

The Walker does have a rectangular plinth—a 165-pound composite of crushed marble, epoxy resin, and lead, finished in a piano-black gel-coat. Unlike the Kuzma, the Walker does not use a conventional ball-andthrust- plate bearing. Instead, its platter, like its tonearm, rides on air. A ten-inch-diameter air-bearing subplatter (the largest yet made for a turntable) and its attendant plumbing are fitted into a large hole in the center of the plinth. A 75-pound, fully-sealed lead-platter is then placed (very carefully) onto this airbearing subplatter. Pressurized air routed from reservoirs in the Walker’s huge, filtered (for moisture, dust, and oil) air-supply box is sent through three low-pressure, hand-lapped jets in the air-bearing subplatter, lifting the massive lead platter and allowing it to rotate frictionlessly. Because of the size of the airbearing, it only takes 1.2psi to lift the platter.

Drive to the Walker ’table is supplied by a single, outboard, low-torque, instrumentgrade, ball-bearing AC motor, encased in a marble-epoxy-lead box of its own and mounted on Walker Valid Points (giant brass tiptoes). The motor sits in a brass cradle that allows you to tension the silk belt that runs from the pulley to the platter and is controlled by Walker’s Ultimate Motor Controller—an outboard device that filters AC in addition to stabilizing speed.

The turntables—with their diverse suspensions, bearings, drives, materials, and masses—are sufficiently different to account for some of the dissimilarities in the way the Kuzma and Walker sound. But, then, their tangential airbearing arms are also different.

The Kuzma Air Line is what might be called a “traveling air bearing,” in that its sleeve-like bearing glides (with the tonearm, which is attached to it) on a cushion of air along a fixed, polished, large-diameter spindle. The Walker is what might be called a “fixed air bearing,” in that the bearing does not move along a large-diameter spindle; rather, a smalldiameter spindle (to which the tonearm is attached) moves, on a minute cushion of air, through a long, pressurized hole in the bearing itself.

Perforce, the Kuzma Air Line’s traveling bearing is considerably shorter than Walker’s fixed bearing—just two inches across. Lined on the inside with a highly porous material and supplied with air from an outboard pump at extremely high pressures (65psi), the bearing, says its designer Franc Kuzma, is so stiff that it’s virtually immune to mistracking caused by the centripetal forces that “pull” the cartridge through the grooves of an LP and that tend, simultaneously, to twist it away from its ideal straight-line course.

Walker’s fixed air-bearing is housed in a large rectangular brass block—six inches long, two inches wide, and two inches tall—with a hole, just a bit larger in diameter than the spindle that travels through it, running through its center. Air from the same huge outboard box that supplies the air-bearing turntable and airsuspension feet is piped into the hole in the tonearm-bearing assembly at 50psi through eight hand-lapped jets in what Walker calls a “high pressure, medium-flow” arrangement. Once again, because of the bearing’s stiffness and the considerably greater length of spindle that is being “supported” by the air in the bearing, the effects of torsion are virtually eliminated.

Bearing size and type are not the only differences between the two tonearms. For one thing, there is the way they are attached—or not—to the turntables. As with the free-standing modular parts of the Kuzma Stabi XL ’table, the Air Line tonearm is itself free-standing, bolted at its far end to a thirty-one-pound brass pillar that can be moved up and down via a thumbscrew. Kuzma supplies a digital VTA gauge that reads the height of the pillar with great precision, allowing you to experiment with VTA and return precisely to the same spot on the gauge. You can also adjust VTA, precisely and repeatably, via a numbered knob on the tonearm assembly itself.

Because it is not physically attached to the ’table, the Air Line tonearm does not “see” any of the noises or resonances of the turntable/motor assembly, save as they are fed back through the stand on which both ’table and arm sit. Not being fixed to the table does, however, make arm setup a bit more complicated, as the entire freestanding arm/pillar must be carefully moved, rotated, and leveled vis-à-vis the platter to make sure that the tonearm travels at the right height in a straight line across an LP. (Kuzma supplies well-written instructions and an alignment tool that make this process a snap.)

The Walker tonearm is attached to the ’table—sort of. The massive air-bearing block is fixed on top of two sizeable carbon-fiber rods that come up through holes in the plinth. Although the rods are bolted on their bottom to the plinth’s base, you have to wonder how much vibration the tonearm might see, given its own material composition, the mass of the air bearing and plinth, and the facts that both tonearm/spindle and platter ride on air and that the motor is physically isolated from the ’table. Although not as cool or convenient as the Kuzma in this regard, the Walker arm also allows precise repeatability of VTA adjustments via two knurled knobs on the tonearm pillar, and because the Walker’s bearing assembly and arm are fixed in relation to the platter, arm/cartridge alignment is somewhat easier.

Another significant difference between the Kuzma and Walker is the material composition of their tonearms. The Kuzma uses a stiff, hollow, conical tube—beautifully machined from three solid blocks of aluminum and damped internally—that is welded to the traveling air bearing. Air is fed to a nipple on the bearing via flexible tubing that runs between it and a valve at the supported end of the tonearm assembly. (A nifty little gauge at the free end of the tonearm assembly tells you how much air pressure you’re running through the bearing.) Air is supplied to the bearing by a regulated, oil-lubricated, industrial-grade compressor that filters for dust and moisture. Because of the occasional loud “spitting” noises it makes during its duty cycle, the compressor is best stored in a separate room, with the air piped to the bearing via thin (4mm) PVC pipe.

The Walker Proscenium Black Diamond turntable is fitted with an entirely different arm/spindle assembly than the Walker Proscenium Gold (thus the new moniker). Gone are the small-diameter carbon-fiber arm-tube and carbon-fiber spindle of the Gold; in their place are a small-diameter armtube and spindle made of an entirely new, expensive, proprietary material—some sort of ceramic-composite that is said, by Walker, to be twenty-times stiffer than the carbonfiber arm/spindle and so hard it can only be cut with diamond bits. Whatever this mystery material is, the new arm and spindle have made a huge improvement in the sound of the Walker ’table (and the Proscenium Gold was scarcely low-fi to begin with).

There is one other difference between the Kuzma and the Walker that I might as well point out right now: The Kuzma Stabi XL turntable and Air Line tonearm comprise the most beautifully machined, professionally finished, and intelligently ergonomic straightline- tracking record player I’ve seen or played with. While the Walker is also beautiful and beautifully made, if high-tech sexiness and ease of adjustment are your first priorities, then this contest is over before it starts. The Kuzma wins.

Before I turn to the sound, let me tell you how I tested the ’tables. First, using the same discs, I compared the Kuzma and Walker to each other and to the sound of the real thing in a real space (as I hear it). I made no attempt to determine which ’table was more “faithful” to what was on the mastertapes. I’m not equipped to do that; plus, tapes sound different than vinyl. Second, I used identical cartridges (the Air Tight PC-1) in both arms, set at the same tracking force and as near as I could come to the same VTA. All other equipment—from phonostage to preamp to power amp to loudspeakers—remained the same for both ’tables, as did the loading of the cartridges. Third, both ’tables were seated on top of the same massive platform— Lloyd Walker’s 450- pound, rock-maple, shot-loaded, Valid- Point-tipped Prologue Reference equipment stand—which was carefully leveled, fore and aft. The only variable in setup—and it was unavoidable—were the tonearm interconnects. The Kuzma comes with singleended Cardas interconnects hard-wired to the tonearms leads; the Walker has RCA outputs at the back of its plinth, to which you attach interconnects of your choice (in this case, Tara Labs “Zeros”).

Since both record players showed the same sets of virtues on every record I played—no matter what kind of music or how large the ensemble—I am going to try something a bit different in this review. I am going to talk, primarily, about how well each turntable let me hear one representative piece of music, Alfred Schnittke’s Quasi una sonata [EMI]—a brilliant post-Modernist caprice for violin and piano that is extraordinarily dynamic, extraordinarily rich and nuanced in tone color, and extraordinarily well-recorded.

First a bit about the piece itself. In Schnittke’s words, Quasi una sonata “is a report on the impossibility of the sonata in the form of a sonata.” It begins with a tremendous crashing G minor chord played sforzando (suddenly, with great force) on the piano, followed after a long moment of silence by a rippingly dissonant chord played sforzando on the violin—tonality and atonality (the twin poles of twentiethcentury music) deliberately pitted against each other at the top of each instrument’s voice, like a shouting match between, say, Samuel Barber and Arnold Schoenberg.

As the piece goes on, these two kinds of music are stated and restated at different dynamic levels and with different articulations, like the “themes” and tonal centers of a traditional sonata. Yet despite constant attempts to set them in joint musical motion—including an adagio ironically based on the classic B-A-C-H motive and a fugue also ironically based on the classic BA- C-H motive—the two musics refuse to be reconciled. No matter how loudly or softly the instruments play or what manner they play in—and they are played in every form of staccato and legato known to man, making for a stunningly virtuosic sonic exercise—musical momentum keeps breaking down.

To make musical sense of Quasi una sonata, a record player has, first and foremost, to capture realistically the unusual timbres that are at the heart of this argument between the tonal and the atonal; while doing this, it also has to capture the bravura way the piece is played—for the extreme means it takes to produce these timbres is the other great point and pleasure of Schnittke’s composition.

If leading-edge dynamics were the whole of these tasks, the Kuzma Stabi XL/Air Line would win by a nose. It is phenomenally quick and clear and clean. Though it gets a leg up in these regards from being paired with the Air Tight PC-1, which is the “fastest” cartridge I’ve auditioned (marginally faster, even, than the super-speedy London Reference), even when paired with lesser cartridges the Kuzma reproduces violinist Gidon Kremer’s pizzicatos, collés (where the bow is thrown forcefully against the strings, making a hard, explosive “T”- like sound), and ricochéts (where the bow is bounced off the strings, making a kind of rat-a-tat-tat noise, like “ta-ta-ta-ta-tah”), with unprecedented realism. Indeed, anything transientrelated— such as the little ripping noises that the hairs of a violin bow makes just as they bite into a string, or the slight, soft shifting of a piano’s action when a key is jabbed or of a foot-pedal when it is depressed or released—is more clearly reproduced by the Kuzma than by anything else I’ve heard, digital or analog, including the Walker.

When it comes to the performancerelated details that describe how the instrument is being played—one of the twin heartbeats of Quasi una sonata— the Kuzma is superb. It gives you the full articulation of each note, no matter how loudly or softly or lengthily or briefly it is sounded, regardless of pitch or register. If, for instance, pianist Andrej Gavrillov pedals a G minor chord, you hear harmonics fill the air for as long as the pedal is depressed. (And the Kuzma will tell you exactly when he lifts up on the pedal.) If, on the other hand, he plays an arpeggio staccato in the top octave, you hear each sparkling sixteenth note distinctly, without any blur or slur. Resolution of this order cannot help but clarify style, tempo, and line.

(What is true of this smaller piece is just as true of larger ones. For example, on Peter Maxwell Davis’ parody mass Missa Super L’Homme Armé for chamber orchestra and speaker [L’Oiseau Lyre]—another postmodernist prank that, like the Schnittke piece, deconstructs a traditional form of tonal music [in this case, the mass] and derives much of its wit and expressiveness from its unusual timbres and outlandish dynamics—you hear the performance style, tempo, and inner voices somewhat more distinctly through the Kuzma than you do through the Walker. For instance, the Kuzma makes Alan Hacker’s flutter-tongued bass clarinet whirr like a card in the spokes of a bicycle wheel. Through the Walker that whirr is just a bit less crisp and clear. Ditto for the individual strokes of percussionist Gary Kettel’s drum rolls, which the Kuzma preserves intact and the Walker slurs just the slightest bit.)

When it comes to timbres—the other expressive pole of the Schnittke piece— the Kuzma sounds just plain gorgeous, without sounding just plain real. It persistently adds a slight voluptuous darkness to the timbres of the violin and piano. In the treble, the Stabi XL consistently sounds a bit quicker and slightly more extended than the Walker, but also brighter, less airy, and more forward. In the bass, it is just a bit “faster,” leaner, and tighter. (Because of its speed, definition, and reach in the bottom octaves—and because of the overall way it clarifies rhythms and tempi—the Kuzma is simply a killer on beatdriven music like rock.)

You’re probably thinking, at this point, that all of these “little bit fasters and clearers and better defineds” should add up to a clear victory for the Kuzma. And were we talking about the Kuzma versus the Walker Proscenium Gold—my analog reference for the past four or five years—I’d be tempted to agree. Certainly the call would be very close.

However, we’re not talking about the Kuzma and the Proscenium Gold; we’re talking about the Kuzma and the Proscenium Black Diamond. And to me, the call, though a bit of a split decision, isn’t finally all that close.

Here’s the difference between the Kuzma Stabi XL/Air Line and the Walker Proscenium Black Diamond on Quasi una sonata (and everything else): The Kuzma reproduces the violin and piano on the Schnittke piece like the best possible hi-fi—everything you could possibly want to know about how they are being played is there for the hearing. All the Walker does, by comparison, is make that violin and piano sound a bit less like superb reproductions and a bit more like real instruments playing in your room. That’s all.

Returning to Quasi una sonata, the very first thing you notice when you switch from one ’table to the other isn’t what’s gone missing with the Kuzma but what’s been added by the Walker. The change isn’t subtle—not something you need “golden ears” to hear. It’s as if some of the air from the Walker’s massive airsupply box has been piped directly into the soundstage. The space between the violin and the piano—and the sense of space around both instruments—grows much larger; the stage “walls” seem to move considerably farther back and farther apart; and the instruments themselves sound bigger, as if some of that same air has been pumped into them, blowing them up and filling them out more fully in three dimensions. As a result, you suddenly realize that this is a live recording, made in front of a real audience in a real space. You also realize that part of what makes Quasi una sonata work is the way that the violin and piano bisect that space—each owning (and holding) its own ground in this contest of musical wills.

Then there are the changes in the timbres and dynamics of the instruments. The Kuzma’s slight overall darkness vanishes, replaced by a neutrality that simply sounds “right.” No, the violin’s pizzicatos and collés aren’t quite as fast as they are on the Kuzma (though still plenty fast), but its fundamentals and overtones are considerably more realistic; no, the piano doesn’t have quite the articulation of the Kuzma in those top-octave runs, but it has more of the color, authority, and solidity of an actual grand piano from bottom to top. That hard-to-find but essential quality that I call “action”—the way instruments change their size, shape, and projection with changes in register and intensity, making them seem to “bloom” out towards you and recede back away from you as the pulse of the music rises and falls—is much more clearly in evidence. Indeed, through the Walker both instruments sound less like superb two-dimensional reproductions, and more like living, breathing, three-dimensional semblances of the real things.

What the Walker’s bloom, space, size, air, neutrality, solidity, dimensionality, and dynamic authority buy you, musically, in Quasi una sonata, is not just more lifelike timbres, but a keener sense of how each instrument’s timbre both separates it from and, on occasion, joins it to the other instrument. You hear that pedaled G-minor chord of the piano, for instance, and the answering atonal shriek of the violin, and because of the realism with which the timbres of each instrument are stated and sustained, you suddenly realize that a musical offer has been made and musically answered—that the piano and violin (and the musics each represent) aren’t just insisting on their own separate identities but are also attempting to share some of the same harmonic ground. You also realize—once again because of the truthfulness with which their tone colors are stated and sustained—that this will never quite come to pass, because all they don’t share is also more clearly audible.

Most of all, what you get with the Walker— and what sets it apart from any other source component I’ve auditioned—is a “fool-you” sense that you’re hearing actual instruments there in the room with you. Whether it is Kremer’s violin or Gavrillov’s piano, or the coterie of string, wind, and percussion instruments in the Maxwell Davies mass, or Joan Baez singing “Gospel Ship” in Carnegie Hall, or the London Symphony Orchestra summoning up the Roman legions in Repsighi’s Pines of Rome, the Walker Proscenium Black Diamond comes closer to sounding “real” more often than any other source I’ve heard in my system. (Just for the record, the Kuzma comes in second.)

If the differences between these two record players seem familiar to you, it is because they are familiar. If I weren’t talking about record players, you might think I was talking about great solid-state amplification and great tube amplification. Like great solid-state, the Kuzma is a bit higher in low-level resolution, more extended and incisive at the extremes, gorgeous but darkish in tone color, and outright superior on transients, pace, and big dynamic swings. If fidelity were simply a matter of extraordinary detail (particularly performance-related detail) presented with extraordinary beauty and clarity (and, in the case, of transients, extraordinary realism)—and I concede that for a number of you it might well be—the Kuzma would be the winner of this shootout. But if the “gestalt” of a live concert or recital—the lifelike presence of instruments, their colors, their dynamics, and the space they play in—is what fidelity means (and I believe that it is), then the Walker wins handily. Like the best contemporary tubes, it is fuller and more realistic in tone color; bigger, bloomier, airier, and more three-dimensional in imaging; wider, deeper, more layered in soundstaging; and a bit more authoritative dynamically. If the Kuzma gets the small parts closer to right, the Walker gets the wholes closer to right.

Understand that neither of these great record players is a “loser.” I switch back and forth between them fairly often and, if push came to shove, could live with either. For much less money, the Kuzma is a no-brainer recommendation—and would undoubtedly be the best tangential-tracking record player money could buy, were the Walker Proscenium Black Diamond not available. But, of course, the Walker is available. It’ll cost you more and, though gorgeous, won’t be quite as sexy to look at or play with, but if you have the dough, are married to LPs, and are into symphonic or folk or chamber or jazz you simply can’t find a better source component for any amount of money. Sonically, the Kuzma may come a bit closer to the best hi-fi, but the Walker comes closer to the absolute sound. TAS