Analog Corner #259: Audio Union Döhmann Helix 1 turntable and Schröder CB tonearm
Turntables, tonearms, and phono cartridges are tuned systems. That each of them can be adjusted to maximize the sound quality—especially the quality called tunefulness, which is difficult to quantify—drives vinyl deniers crazy. Today, one of them e-mailed me: “You are the stupidest motherfucker I have ever encountered. Go shove a tone-arm up your ass.” He followed that with this: “You are demented, deluded, and deaf. Records suck, and always have.”
Just ignore them. I do. (Well, I try.)
The ability to fine-tune a vinyl playback system is part of what makes it possible to combine an archaic technology with modern thinking and materials to create musical magic, and take listeners to new heights of ecstatic musical pleasure. It’s why so many young people are tuning in to vinyl, and helps explain why just today, as I write this, it was announced in the UK that, for the first time, revenues from sales of vinyl exceeded those from downloads.
You can buy a turntable that’s been pre-tuned by the designer—that is, the user can’t adjust its combinations of mass, materials, suspensions, etc.—or you can buy one that offers a few things you can adjust to your own taste. Either approach can be valid.
You can also buy a turntable whose designer has decided that high mass and heroic amounts of damping will solve any problems in the system’s electromechanical design, and has applied these with an iron fist but without careful, critical listening. You might as well buy a CD player.
I bring this up because both Audio Union’s Döhmann Helix 1 turntable (footnote 1) and the Schröder Captive Bearing tonearm (footnote 2) include instructions outlining how one can tune them—in one case through the use of heavy brass weights, and in the other by various degrees of screw tightening. These options are spelled out in well-written manuals, not because the designs are unfinished or the designers uncertain, but because the player’s international design team, headed by Mark Döhmann, consists of both scientists and careful, experienced listeners who understand the tuned nature of the system.
Audio Union
The last time we heard from Mark Döhmann, he was the chief designer at Continuum Audio Labs—it says so right on his business card. There, he headed a design team that created the no-longer-in-production Caliburn, Cobra, and Castellon turntable, tonearm, and stand. That was more than a decade ago.
I listened, I reviewed, I bought . . . and 11 trouble-free years later I’m still glad I did, though I’ve since replaced the Cobra with the Swedish Analog Technologies (SAT) arm (and am glad I did that, too). And I replaced the Castellon’s original magnetic-repulsion isolation system with one from MinusK.
Döhmann is now a member of the Audio Union team, based in Sofia, Bulgaria. Rumen Artarski, who holds a degree in electrical engineering from the University of Denmark and who also manufactures the Thrax line of electronics and loudspeakers, is Audio Union’s executive director of engineering and marketing. The other Audio Union team members from around the world include names familiar and unfamiliar: world-renowned tonearm designer Frank Schröder; Dave and Tom Kleinbeck, of EnKlein cables (Dave is a telecommunications engineer, Tom a patent-holding mechanical and aeronautical engineer); Bo Christensen, of Bow Technologies (and previously of Primare); and Dr. David Platus, inventor of MinusK’s vibration isolation technology. There are also two more Bulgarians: Stanislav Stoyanov, an aeronautical engineer who, among other things, oversees Artarski’s state-of-the-art CNC machining facility; and Dr. Plamen Ivanov Valtchev, an expert in the use of advanced software visualization, FEA modeling, and acoustics. You can read more about the team at www.audio-union.com/Helix.php; if you do, you’ll think they got together to design a great-sounding guided missile, but no—it’s “just” a turntable project.
Döhmann Helix 1 turntable
Mark Döhmann’s goals for the Helix 1 were the same as for his older designs: Isolate the groove-stylus interface from the outside world and from within. Drain away noise and various forms of energy produced by the turntable’s bearing, the motor, and the stylus/vinyl interface. And, of course, spin the platter at the correct and unvarying speed. (For details about how he accomplished this in the Continuum Caliburn, see my review in the January 2006 issue.)
The goals this time were the same, but with a desire to bring it in at far lower cost. By the time the Caliburn came to market, its retail price had soared past $150,000, and it couldn’t easily be dismantled for moving.
The Döhmann Helix 1 ($40,000) looks unlike any other turntable on the market. Its design concept and execution are equally unique, beginning with the integrated MinusK Negative Stiffness isolation platform (footnote 3). Simply put, MinusK is a totally passive leaf-spring design that isolates down to 0.5Hz vertically and 1.5Hz horizontally. Nothing from outside gets in. It wasn’t invented for audio applications, but it sure works well under whatever you want to isolate.
Interesting as that is, it’s probably the least intriguing aspect of the Helix 1’s design. More fascinating are other design features, each with its initials: Micro Signal Architecture (MSA), Mechanical Crossover Technology (MCT), Tonearm Damping System (TDS), and Resonance Tuned Suspension (RTS). You can read way more about these on Audio Union’s website than I have space for here. The language is flowery, but I found it free of another pair of initials: BS.
Basically, the Helix 1’s interior consists of various plates that can be thought of as leaves on a tree—or, as described on the website, “the bearing is the center of the ‘universe’ where ‘planets’ (motors and arms) sit on an orbital plane (the chassis/plinth). Vibrate the plane (chassis/plinth) by internal or external means and you get vibration patterns and nodes, which become visible to the naked eye using Chladni plate analysis.
“By placing the bearing and motor and arms into ‘optimal zones’ where vibration was well damped or controlled we provided the best possible place on the chassis for the sub-system to sit with the lowest possible vibration. Helix 1 chassis research created several eureka moments!” Want to know what “Chladni plate analysis” is? Go to the link.
In fact, if you want to see a Helix 1 partially assembled by Rumen Artarski at his factory, see my 25-minute video. More particulars include a plinth of 4″-thick, CNC-machined aluminum and structural alloys that, fully assembled, weighs 100 lbs. Not visible in the video are the aforementioned series of interlocking plates “fitted closely” to the MinusK platform, to which are attached the motor, the platter bearing, and two suspended, isolated platforms for mounting tonearms.
A “mechanical crossover,” produced by the various materials and their thicknesses and placements, creates, the manual claims, continuous, “smooth vibrational pathways that drive higher order vibrations generated through motor noise away from the bearing and platter via a complex coupling to the chassis.”
The 30lb platter is a triple sandwich of layers of an “engineered thermoplastic” and a nonferrous alloy that’s balanced and shaped for the lead-in groove and label areas of LPs. This is topped with a thin, permanently installed damping mat. The spindle is of brass.
The platter bearing is similar to the brilliant design used in the Spiral Groove turntables designed by Allen Perkins, who worked with Döhmann on the Helix 1 prototypes. The Helix 1’s bearing—clearly shown in the video, and well worth a look—is manufactured in Europe to precision tolerances. The spindle and housing are of maraging steel—an alloy of iron possessing superior strength and toughness. The spindle rides on a single ceramic ball and thrust pad.
A high-torque, low-noise, zero-cogging motor capable of 100W of power drives the platter via two dissimilar O-rings. The belts are purposely machined to have different durometers (degrees of hardness), so that each belt “beats” differently, with the motor-control system doing the final smoothing. Döhmann says that a “springy” belt is good because it addresses motor-bearing noise and motor cogging—but because of inevitable bearing friction, the belt slows (we’re talking on a microscopic level of course) and needs retensioning, which produces a “beat.” With the addition of a second, less compliant belt—which, when added to the system, won’t stretch at the same time or at the same rate—the two belts will then “average out,” smoothing the beat—and the motor controller can be programmed to further aid the improved belt performance. Döhmann figures that makers of turntables driven by two or more identical belts will eventually pick up on this.
The Helix 1’s custom, software-based motor-control system is housed in a handsome case the size of a preamplifier. This digital, closed-loop servo has greater than 16-bit resolution. The motor-control software was designed by Tom Kleinbeck, Rumen Artarski, and Stanislav Stoyanov. This international collaboration was necessary, Döhmann says, partly because of the different electrical needs of various nations, but also because they found ways to “voice” the motor with flexible programming. With each iteration of the software, each of the three independently listened, then shared his opinions with the other two. From the Audio Union website: “Absolute positioning reading occurs over 120,000 discrete positions of the rotor per revolution. The motor spins several hundred times to achieve one revolution of the platter thus increasing the system resolution by an order of magnitude over a direct drive topology.”
The Helix 1’s two speeds, 33 1/3 and 45rpm (78rpm is available on request), are set at the factory and, according to Audio Union, should not need adjusting. If they ever do, a smartphone/tablet app will do it—or the controller can be connected to the Internet, to allow AU’s service techs to remotely diagnose and adjust, as well as download firmware and/or software updates. There’s a screw-on record clamp.
Footnote 1: Audio Union, 251 Okolovrasten pat, Delta Center, 1766 Sofia, Bulgaria. Tel: (359) 2-988-9555. US distributor: Audio Union International, 2405 NE Cross Creek Lane, Lee’s Summit, MO 64086. Tel: (816) 875-6519. Web: www.audio-union.com
Footnote 2: Schröder Tonarme, Stuttgarter Platz 3, 10627 Berlin, Germany. Tel: (49) 030-611-51-81. Web: www.schroeder-tonarme.de/
Footnote 3: For more about the Negative Stiffness system, see my September 2012 interview with MinusK’s David Platus.
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