Drive, He Said Part 4

In previous installments of Vintage Whine, we’ve looked at belt-drive turntables, idler-drive turntables, and direct drive tables. This column deals with the unclassifiable, the weird, the mixed-genre, the “what the hell is THAT?” of the turntable world.

When you get right down to it, the amount of time that’s been spent over the last century on figuring out how to spin a record at a constant rate, is really quite ludicrous. Really: the damned thing has to spin. What’s difficult about that?

As it turns out, the whole affair is a lot more complicated than it would seem after a cursory examination. As I’ve pondered in this issue’s Audio Cynic, record playback is a medium that seems almost prehistoric in its lack of sophistication, but in reality, is capable of undreamed-of precision. If you don’t believe that, look at J.I. Agnew‘s column in this issue; machine tools were capable of almost-molecular levels of precision a long time ago. If all the record had to do was spin, that’d be one thing—but the tricky parts come from trying to trace that wiggly groove and turn it into a usable, meaningful signal.

So: think about it. If you started with a clean sheet of paper and wanted to design a record playback system from scratch, how would you do it?

You’d want to isolate that groove-tracing signal from mechanical noise as much as possible, and ensure that the process wasn’t affected by that train running past your house, your footsteps on the wooden floor of your 1920’s Queen Anne cottage, or the sound coming out of your speakers. You’d want to make sure that the stylus tracing the groove didn’t somehow trigger noise or resonances in the playback system, that the vibrations of the vinyl disc didn’t bounce back off the platter, that the disc didn’t slip, that the stylus didn’t drag enough to overheat and distort the vinyl—-

See? It quickly gets really, really complicated.

As is true of almost any human endeavor, and especially in audio, different designers latch on to one aspect of design or performance as the one true way, the crucial element—and those choices determine the course and focus of a design. And some get pretty wacky.

Take, for example, support of the record itself. Most would say that in order for playback to be clean and undistorted, the disc needs to be glommed on down to the platter as closely as possible. Some do that by means of a weight or clamp; some do that by suction. Each disparate method has its advocates and fans.

But wait! Some really bright people think of that issue almost as an irrelevance. How about Ed Meitner? Probably one of the most highly-respected audio engineers of…EVER, Meitner once designed a line of stereo gear for the brand Museatex, made for less-than-gazillionaires. At the center of the Meitner system was a turntable— and not just another Thorens 160 clone. The Meitner AT-2 turntable looked like a turntable designed by Henry Moore, a gathering of organic, geometric masses that somehow managed to play a record.

How well it did that, is subject to debate. Keep in mind only 40 or so were made, so most tales on audio forums can be written off as apocryphal. I can’t imagine that an old Van Dyke Parks RCA Dynaflex release would do well on this thing, but who knows?

The Museatex website says, “Even today we cannot be certain that we have unlocked all the treasures stored in the record groove. The AT-2 Record Playing System features ‘platterless playback’. The platter is replaced by a metal flywheel with knife-edge machinings to support the record beneath the label area. The playing surface of the record couples to air on top and bottom.

“Turntable designers have made enhancements to platters and mats through the years. As far as they have evolved, however, platters and mats are left with one fundamental problem. The point at which the record contacts the mat or platter is an energy interface that vibrations, traveling at high velocities, must traverse. These vibrations will not be completely absorbed by the interfacing surface, and a significant portion of the energy will be “mirrored” back into the record. Because most of the energy is generated by the cartridge stylus, this is the area to receive most of the reflected energy. The result is a form of distortion read by the stylus and incorporated into the music signal.

“Overlooked by most, the twelve inch diameter of the typical record makes it an increasingly ideal half-wave coupler of acoustic energy from the lower mid-range up, and improving as the frequency rises. The record naturally dissipates vibrations, particularly at the levels and frequencies that they occur, to air. Thus air becomes the absorbent “platter”, the only substance that does not give energy back to the record. The reproduction of music is open, dynamic, remarkably natural.”

One of the brightest folks I know in the world of record-playback, a world that alternately attracts the cerebral and the ham-fisted, is Frank Schröder. Frank is more the former than the latter, being a former watchmaker; he’s also a walking encyclopedia of audio history.

I mention that because I have zero tolerance for the misguided hubris of designers who trumpet an idea as new, when I can cite five or six predecessors who did the same thing. If Frank utilizes elements of a vintage design, he will cite that design, tell you what the flaws of that design are, and how he has fixed those flaws.

Luckily, Frank has a terrific sense of humor, and frequently mocks his own nerdiness—otherwise, such behavior would be hard to take.

Frank has also designed turntables which have platters that are smaller than usual. Back in the day, lower-end models from BSR, Dual, Garrard, and others, had platters that were 10″ or so in diameter. Frank makes what he calls a “compact turntable” with a platter even smaller than that—I’d guess 8 1/2″ in diameter. He showed one such turntable recently at RMAF, and of course, sound quality was superb.

When I asked Frank why he built the tiny table, he said it was to demonstrate that a “properly designed” turntable didn’t have to be mammoth to sound good. He also mentioned that the table largely appealed to men, and that women in general seemed to be put off by the small size. I would’ve expected just the opposite.

Other tables w/ skeletal or minimal platters? There are a number; most striking are Be Yamamura’s peculiar table and arm, and the famous Transcriptors Hydraulic Reference (A Clockwork Orange, anyone?): 

Every now and then, some turntable designer revisits the thought, “if low friction is good, then how about floating the platter on magnets? Or air?” Plenty of folks have tried one or the other, but neither idea has ever been featured in a table that was a huge commercial success.

I should qualify that proclamation with, “to the best of my recollection”. One of the challenges of writing about vintage audio is that I’m doing it with a vintage brain…..

Let’s start our look at kinda-floaty turntables with those that have used magnets to either relieve the main bearing of some or all loading, or to couple a driven sub-platter to the platter, causing it to rotate. Speaking of that vintage brain—somewhere in the back of it is the notion that this was tried long ago by a company that I can’t recall, but that info is not forthcoming. Oh, well.

The first table I can recall that used magnetic drive was only a decade ago, pushing the definition of “vintage”. The Disc Master (or Disk Master) turntable was designed by Tim de Paravicini for his company EAR (Esoteric Audio Research). Tim is one of the most amazing engineering minds I’ve encountered in any field, and he’s equally-knowledgeable in all aspects of audio design, automotive engines, aerodynamics, and probably a dozen other fields. He also does not suffer fools gladly, so if you ever choose to challenge him on a subject, you’d bloody well better be right.

I speak from experience.

Anyway: the Disc Master looked like nothing else. An assemblage of finely-machined skeletal metal parts, the table—-well, the US EAR website puts it as well as I can:

“Tim de Paravicini began contemplating a radical new design for a turntable several decades ago, but the advent of digital audio put the project on hold. Now, with interest in analog not only continuing, but growing, he has finalized his design, and introduced the Disc Master turntable. While many turntables have appeared on the market in recent years, few offer as many novel features as the Disc Master, but this is not novelty for its own sake. The Disc Master represents a new standard for LP playback.

“Most striking is the no-contact drive system. The need to transfer power to the platter of a turntable has always been problematic, as any system with the capacity to transfer power can, by the same means, transfer vibration. Flexible rubber belts have proved a satisfactory solution, but suffer problems of slippage—hence, uncertain speed—and they pull the platter sideways, which can result in stability problems. Tim de Paravicini has arrived at an ingenious solution that solves these problems. A low-noise motor, controlled by a carefully optimized servo loop, drives a subplatter via a geared belt that ensures absolute speed control. The subplatter drives the platter via an arrangement of opposing magnets. This method not only eliminates slippage, but allows enough compliance to filter out any remaining vibration from the motor and belt, while applying a fully symmetric driving force. [That “geared belt”? I asked Tim to explain, and he told me the Disc Master used “a fine-toothed very compliant belt as in a miniature version of a car cam belt. 3-D printers use similar thin belts. Then the motor-to-position relationship is fixed. No slippage as in conventional turntable belts.”]

“Bearings are another problem for a turntable designer, one that Tim de Paravicini has solved by the use of Swiss-made, precision angular contact bearings, which are as quiet as the more common point-contact types, but wear much more slowly, so that their performance after years of use will be as good as on initial purchase.

“The platter is made of an ultra-low-resonance composite of resin and inorganic filler, accurately machined and supported on an instrument-grade aluminum chassis. Adjustable, damped feet support the assembly. Three speeds—33, 45, and 78—are offered, with a continuous speed control for 78 to accommodate discs cut at non-standard speeds.