Cartridge, Arm and Turntable vs. the Groove: Who's Winning? (Vol.1, No.4: July/August /Sept 1977)

Part I: In which we emend and update our original article on tracking geometry, find a mind-blowing sonic gap between optimized alignment and currently accepted practice, and as a result send all equipment reviewers back to square one. Also: a common-sense critique of 10 tone arms and turntables.

In our first issue (January/February 1977, pp. 31-35), we published an article under the title of "Have Tone Arm Designers Forgotten Their High-School Geometry?" Our message (namely that correct geometry in a pivoted tone arm costs no more than incorrect geometry, yet there's no arm on the market that's 100% correct) put quite a few noses out of joint, for which the blame must be placed on the unfeeling laws of nature. If it's any consolation to those who were upset by our facts, we now consider that article to have been somewhat superficial. Not in the sense that the argument it presented was in any way in correct; far from it. We still stand behind every statement made in it, as far as the physics and mathematics of the subject are concerned. But it's quite obvious to us today, after approximately nine additional months of investigation and listening, that we didn't go nearly far enough. We grievously underemphasized the sonic consequences of the mathematical sloppiness we were complaining about and gave no inkling of the chain reaction of invalid conclusions that can result from complacency about the cartridge/arm/turntable vs. groove relationship.

The man we must credit for steering us in the right direction and dispelling our initial doubts about the audibility of ridiculously small deviations from optimum tracking angle (both lateral and vertical) is Mitchell Cotter, the encyclopedically learned technologist of Verion Audio. Mitch has been spreading the word with apostolic zeal; he has undoubtedly aligned more record players just as a favor to the innocent and distributed more Xeroxed instruction sheets on how to do it than there are letters on this page. The Boston Audio Society is still reeling from his panzer assault on the subject (massively documented as usual) at their March 1977 meeting. Our own experiences since our first issue and recent conversations with other proselytes (who are still few and far between) bear out the Cotter doctrine without qualification.

The unsettling but inexorable facts.

It would probably be more logical to start with certain unarguable givens and then lead you step by step to our somewhat disturbing but nonnegotiable conclusions. But we feel that the latter are too important to be shared only with those who are willing to track with us through our exposition. Since we don't want to lose anybody at this juncture, not even tone arm designers with a short attention span, we've decided to spell out our message first and explain later. Thus:

1. Lateral tracking error, if large enough to be at all measurable with simple tools (straightedge, triangle, protractor, ruled paper, piece of thread, or whatever), is readily audible through a speaker/amplifier system of reason ably high resolution. Even the difference be tween the successive zero-error and maximum error points of an optimally aligned pivoted arm is audible, let alone the difference between an optimally and a non-optimally aligned arm.

2. Optimum lateral tracking alignment of commercially available pivoted arms can only be achieved by ignoring the manufacturer's instructions and twisting the cartridge in the headshell to obtain the correct combination of overhang and offset angle. All other approaches, including the one suggested in our first article, are unnecessary compromises.

3. Vertical tracking error (i.e., a difference between the original vertical cutting angle and the effective vertical playback angle) is similarly audible within the limits of the finest adjustments that can be made by hand (such as barely raising or lowering the vertical pivot of the arm, shimming up the record by means of a thin cardboard disc or another thin record, etc.). Without sophisticated test equipment, correct vertical tracking angle can only be determined by trial and error coupled with careful listening. Visual guidelines, such as the apparent forward tilt of the stylus, the angle between the stylus bar and the record, or the parallel position of the arm tube with respect to the record, are almost entirely useless.

4. Unfortunately, the correct vertical tracking angle is different for all records cut at different times, in different places, by different people, on different lathes, with different cutter heads. No adequately stringent industry-wide standard is in force, even today. This is very bad news, since it means that truly optimized playback requires constant adjustment by hand (and ear) from record to record, unless a uniformly cut series of records is being played.

S. What makes all the above agonizing worthwhile, or at least meaningful, is that optimum alignment of the cartridge and arm for both lateral and vertical tracking error improves the average sound quality of a record collection to an astonishing degree. Records previously thought to be hopelessly bad often end up sounding quite decent, and the better records begin to approximate what high fidelity is supposed to be all about: a creditable imitation of live music. In other words, phonograph records are a more accurate medium than jaded audiophiles suspect.

6. By the same token, listening tests and equipment reviews based on phonograph records are of highly questionable validity unless the lateral and vertical tracking alignments are religiously optimized and maintained.

Since that's hardly ever the case, most evaluations of cartridges, tone arms, turntables and even other components in either the commercial or the underground audio publications can be expected to be quite erratic. Alignment according to the manufacturer's instructions will randomly favor or handicap A over B; after proper alignment the order of preference is often reversed. We now believe that this is one of the principal causes of disagreement among otherwise unbiased and keen-eared equipment reviewers as well as rank-and-file audiophiles.

This is admittedly pretty heavy stuff, and we don't expect it to penetrate some of the pointier heads in high places for some time to come. The consequences aren't exactly negligible, when you stop to think about them: all pivoted tone arms should be redesigned and their mounting instructions revised {and even then a correctly executed radial-tracking arm will be audibly better-but try to find one!); furthermore, all tone arms, whether pivoted or radial-tracking, should have a mechanism whereby the vertical tracking angle can be conveniently changed during play; or better yet, the recording industry should immediately adopt an ironclad vertical tracking angle standard and enforce it internationally.

Are you beginning to see the dimensions of the problem? All we can accomplish here is to make a few small waves and hope that some body out there gets splashed a little bit. Any kind of serious dialogue on the subject within the audio community would require the participation of some of the largest commercial interests, and Nick the Greek isn't putting heavy odds on that probability.

Meanwhile, we'll try to illuminate our main points with some simple explanations and also provide specific instructions for optimizing your cartridge/arm/turntable set up. Remember, though, that this is only Part I of what we plan to be a continuing exploration of the subject, so that a number of questions may not be resolved to your satisfaction until next time.

The stylus/groove interface.

The key to understanding the requirements of distortion-free record reproduction is a clear and uncomplicated mental image of the stylus riding in the groove. All the facts and all the nonsense you've ever heard about cartridges, tone arms and turntables relate, more or less directly, to that single interface. If you think about just that and nothing else- if you don't get bogged down in peripheral considerations such as, say, bearing friction -everything falls into place and the subject is no longer open to techno-freak obfuscation.

Visualize the cutter stylus, plowing a stereo groove into a lacquer master. Its lateral motion is from side to side, exactly in line with the radius of the disc at the point of cut ting. It's obvious, therefore, that the lateral motion of the playback stylus in the groove must be along that same radius. If it isn't-if one wall is contacted ahead of where the cutter stylus was at a given instant and the other wall is contacted behind of where the cutter stylus was at that same instant-there will be a falsification of the information that was cut into the groove. This is commonly called lateral tracking error and the most serious consequence traditionally attributed to it is second harmonic distortion. We, too, accepted that at the time we wrote our original article. But it just isn't so. The most important distortion that results is time distortion. The playback stylus is ahead of real-time reproduction on one wall and behind on the other wall. And the ear is considerably more sensitive to that kind of time smear than to harmonic distortion.

Now think about the vertical motion of the cutter stylus. For practical reasons that don't really concern us here, this motion isn't perpendicular to the plane of the disc but at an angle to it, the line of motion leaning in the direction of the groove already cut. Now any up-and-down motion at angle also has a back-and-forth component. On the down stroke, the cutter stylus is adding a tiny amount to the linear speed with which the groove is cut; on the up stroke it subtracts a tiny amount. Aha, you say, time distortion is being cut permanently into the groove.

Exactly. But what if the playback stylus is set to move up and down at exactly the same angle as the cutter stylus? Then its own velocity modulation will be synchronized exactly with that of the original cut, and the signal will be reproduced in real time. Again, we must repeat that the ear is enormously sensitive to the time domain (see also our loudspeaker survey in this issue) and that you don't easily get away with any kind of fudging there.

So there's your picture: the playback stylus is riding in the groove, mimicking the motion of the cutter stylus exactly and in all dimensions. That means (1) it must be firmly seated without any loss of contact whatsoever; (2) its points of contact with the left and right wall must both be on the same radius of the disc; and (3) its vertical motion must be at exactly the same angle from the perpendicular as was the cutter's. You can ensure (1) by set ting the vertical tracking force as high as possible, as long as the stylus cantilever doesn't collapse. (Contrary to untutored opinion, this will not shorten the life of the record as long as the stylus tip is in good shape and the cartridge design isn't the kind that permits ultra sonic hammer blows by the stylus on the groove wall.) As for (2), that's what lateral tracking alignment is all about, and in a moment we'll give you the most practical and effective alignment instructions available anywhere. When it comes to (3), you're pretty much on your own, but it isn't a completely hopeless situation, as we shall see.

First, however, we must point out how useful this mental image of the correct three dimensional stylus/groove interface can be in explaining and understanding design requirements for cartridges, arms and turntables.

For example, why is a biradial stylus, such as the Shibata, superior to a conical stylus? Obviously because the Shibata's longer and narrower areas of contact with the groove mimic much more closely the geometry of the cutter stylus and permit a finer resolution of the time-related details inherent in the cut.

But then why does the conical stylus have so many partisans who claim it sounds better than the Shibata? Because it does sound better when the lateral and vertical alignments haven't been properly attended to. The Shibata resolves the consequent deviations from time coherency much more precisely and audibly, whereas the conical stylus glosses over them to some extent.

A properly aligned Shibata, on the other hand, eats a properly aligned conical for breakfast when it comes to resolution of detail.

Or take antiskating compensation. Why is it so important? Because the skating force deflects the stylus and creates tracking error (i.e., alters the stylus/groove geometry). The usual explanation that it creates unequal stylus pressure on the two groove walls and therefore unequal indentation is only part of the story.

And, for the same reasons, too much antiskating bias is just as bad; it's simply a reversal of skating force in the opposite direction. Now think about tone arms. Why should the arm be absolutely rigid? Because any kind of flexing or axial "pumping" will shift the stylus with respect to the groove. And why should the arm be nonresonant? Because if it can store and release energy in the frequency range relevant to the groove, at least part of the energy will end up driving the stylus in a way that's completely unrelated to the stylus/groove geometry. What about turntable rumble or acoustic feedback? Same thing-the stylus will be dislocated with respect to the groove with some kind of low-frequency periodicity. On the other hand, why is pivot bearing friction a less important consideration? Because as long as it isn't large enough, relative to the vertical tracking force and the stylus compliance, to apply a bias to the stylus and thus alter the stylus/groove geometry, it can't possibly have an effect on the reproduced signal. And so forth and so on: the geometrical (or call it topological) explanation covers everything.

Can we really hear all this? Our recent experiments with fanatically careful alignment to optimize both lateral and vertical tracking geometry have produced astonishing results. Going from routinely conscientious mounting of the tone arm and cartridge, by following the manufacturer's instructions unquestioningly, to optimum alignment, in accordance with the procedures out lined below, made in every case a greater difference in audible quality than changing to an other good cartridge, preamp or power amp! The sound just opens up and assumes a totally new character-and the listener's mind reels.

In fact, we now recommend that you perform these alignments before you change any component in your system, otherwise you'll never know exactly what kind of sound you're giving up-and switching to. Where this leaves the typical listening tests performed in audio stores, manufacturers' sound rooms, and equipment reviewers' homes we'll leave to your imagination. All we can say is that, whenever someone now tells us that he found component A to be superior to component B after extended listening to reference records, the first thing we ask is, "How did you align your tone arm and cartridge?" If the answer is a blank stare or "Huh?" or "Just like it says in the instructions!", we say thank you and change the subject. (And then we thank our lucky stars that our initial insight into the importance of all this came before our preamp survey was too far under way.) When you begin to think about the dimensions of the micro-world in which the stylus and the groove operate, none of the above is the least bit illogical. The linear speed of the groove, at 33 1/3 RPM, varies between 51 cm/sec and 21 cm/sec from the maximum to the minimum radius of the modern 12-inch LP. Let's take a nice frequency like 4 kHz, where the sensitivity of the human ear is at its peak. One full cycle of 4 kHz therefore occupies anywhere between 0.13 and 0.05 mm.

(Note that The Audio Critic is going metric; this is as good a place to start as any.) Let's take 0.1 mm as a convenient average value.

That's 100 microns. Now let's assume that a 5% time modulation of the signal at this frequency (in other words, a time smear of +12.5 uS) can blur the focus of a stereo signal to some extent. (This is not an unreasonable figure to assume.) You're then dealing with a 5-micron linear portion of the groove. That's only 50,000 angstroms; you're approaching optical dimensions! When you consider that the stylus overhang specified in the mounting instructions of the Grace G-707 is 15 mm in stead of the correct 17.5 mm and that the unmodified offset angle of the arm is off by more than 1° from optimum (and that this happens to be one of the geometrically best optimized arms on the market!) you begin to realize that we aren't just whistling Dixie here.

There can exist a serious non-synchronism between the recorded and the reproduced signals.

How to optimize lateral tracking geometry.

We're publishing a completely new table of lateral tracking alignments here, simpler and more useful than the Universal Design Graph in our first issue. Not that the latter was in any way incorrect; in numerical data it differs from our new table by less than the least possible measurement error. The main difference is that the maximum and minimum radii of the recorded area assumed in our table are the official IEC values, standard on all Neumann and similar mastering lathes. The graph, which predates the stereo era by several years, was based on very slightly different limiting radii; furthermore, it didn't contemplate the possibility of twisting the cartridge in the headshell, so that it also provides correctly matched overhang values for other than optimum offset angles, an audible compromise that turns out to be quite unnecessary.

Editor's Note: We've been informed by Mr. Warren B. Syer, the publisher of High Fidelity, that our Universal Design Graph was a reproduction of page 23 of the August 1957 issue of the now defunct Audiocraft magazine, with copyright still owned by High Fidelity. Need less to say, we committed this infringement unwittingly; a photo-print of the graph had been in our files for all these years, with only hand written notes to relate it to the original Sea grave equations. Our apologies to High Fidelity; our acknowledgment to Dr. John D. Seagrave, the author, and to Audiocraft (may it rest in peace).

There was something else in our first article that needs emendation. We erroneously credited Benjamin B. Bauer and Dr. John D. Seagrave for the original work on the mathematical analysis of tracking error. Actually, their articles added nothing substantially new to the considerably more detailed and profound study of the subject by H. G. Baerwald, an obviously brilliant man who worked for The Brush Development Company in Cleveland, Ohio, and published his massive paper on tracking error and optimal pickup design in the December 1941 issue of the Journal of the Society of Motion Picture Engineers, years ahead of anyone else. This is the classic work and the most complete solution of the mathematical problems posed by the subject; the computer program that resulted in our new alignment table is based on the Baerwald equations.

When you look at the table, please note that as the arm length is changed, the optimum overhang changes very, very gradually, whereas the optimum offset angle changes much more rapidly. This is the most important thing to understand in order to develop a good feel for the alignment procedure; it explains, among other things, why you can't just move the cartridge straight back and forth to trim in the overhang, no matter how small an adjustment you're making.

Let's track through the essential steps in using the table.

First, install the cartridge in the arm, but don't tighten the screws all the way. Allow the cartridge to be just barely movable when pushed. For openers, you might as well locate the stylus tip approximately where the instructions tell you to.

Now measure the effective arm length, from lateral swing axis to stylus tip, with an accurate ruler, such a machinist's scale. You don't have to agonize over this measurement, but try to get it right within 0.5 mm (0.02 in.).

Look up the optimum overhang corresponding to this arm length in the table. You may interpolate without any fear of inaccuracy.

(For example, if the effective arm length is 238.5 mm, take the halfway point between the 17.398 and 17.319 mm overhangs, i.e., 17.3585 mm, which you'll never measure more accurately than 17 1/3 mm.) Set this overhang (measured from the stylus tip to the center of the turntable spindle and coinciding with the effective arm length) either by moving the cartridge in the head shell (in which case you'll change the arm length slightly) or by moving the entire arm.

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Table of Optimum Overhang and Offset Angle Alignments for Pivoted Tone Arms

Optimized for a 12-inch LP record with a recorded area between the IEC Standard maximum and minimum radii of 146.050 mm (5.750 in) and 60.325 mm (2.375 in). Zero tracking error in all cases at radii of 120.90 mm (4.76 in) and 66.04 mm (2.60 in). For in-between values of arm length, interpolation error will be smaller than the least possible measurement error.

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The overhang can be measured with a short and narrow machinist's scale or ruler; a good way to do it is by measuring up to the outside of the spindle only and then adding the spindle radius, which is half of the standard spindle diameter of 7.163 to 7.214 mm (0.282 to 0.284 in). Thus, in the example above, you'd set the stylus tip 13% mm from the outside of the spindle.

Now comes the crucial part. Prepare a piece of cardboard (a file card of the right size will do) by punching a spindle hole in it and marking off radial distances of 66.04 mm (2.60 in) and 120.90 mm (4.76 in). You could also do this with one of those convenient (and in correctly marked) paper protractors furnished by tone arm manufacturers. Then twist the cartridge in the headshell so that you can see absolutely no tracking error at those two points. Keep playing with the cartridge until you get this right. The offset angle will then be automatically correct for your overhang.

After that, set the vertical tracking force to the highest value allowed in the cartridge specs and adjust the antiskating bias. The easiest and most accurate way to do this is by ignoring the bias calibrations on the arm (except as a general guideline) and setting the bias by observing the stylus with a small magnifier or loupe. When tracking a low-level passage, there should be absolutely no difference in the centered (neutral) position of the stylus on or off the record. If you see the tiniest snap as you lift the cartridge off the record, the bias is incorrectly set.

And now comes the most annoying part.

After you've done all this, everything is probably slightly off, since all these alignments interact. The antiskating adjustment could quite conceivably have misaligned the two zero-error points, in which case you'll have to trim those in again. Then the over hang will probably be off, and the effective arm length in turn. Keep going around in a circle, from one to the other, until everything is right on the button and in accordance with the table as well as the alignment card. The end result will be worth the trouble.

Please note that these alignments optimize your record player for 12-inch LP records only.

Mr. R. R. Mills, the managing director of J. H. Reproducers in Australia, took us to task for not recommending in our first article a dual purpose optimization for both LP's and 45 RPM doughnut singles. We think that's a preposterous idea: spending in the upper hundreds of dollars for a fine cartridge/arm/turn table combination and then getting more distortion than necessary on your best LP's just so that the bubble-gum cheapies can be played with a little less distortion. Pure LP optimization is barely good enough in our opinion; optimizing for the much smaller minimum radius of the recorded area on 45's carries the pivoted-arm compromise a bit too far for any serious audiophile's comfort.

What about the vertical tracking angle? Here the going gets a bit rough. We find that deviations of as little as 20 minutes of arc from the correct vertical tracking angle are audible, yet there are modern LP records, none of them more than ten years old, cut with angles as small as 15° and as large as 18.5°. Go back a little further in time and the spread becomes 13° to 22°. In the earliest days of stereo there were even a few records cut with a negative vertical tracking angle. (You'd have to twist your cartridge around 180° and reverse your left/right leads to play those correctly!) And the angle is never, never labeled on the record. What do you do? We suggest that you align your cartridge/ arm vertically to make the latest state-of-the art records cut with the Neumann SX 74 head sound their best. That's probably a 17.5° or 18° cut, and you're unlikely to run into anything higher. The Mark Levinson records are a very good example. After having performed every step of the lateral tracking alignment, put on such a record and play with the arm height adjustment until the sound can't be made any cleaner and more transparent. Generally speaking, if the sound is hard and over-bright, you've raised the arm too much; if it's muddy and mid rangy, you've lowered it too much. Try to get it just right; it isn't so hard with good associated equipment-the right alignment almost clicks into place. And don't look at the arm tube. Its position is meaningless except as an indication of where you've been and where you're going.

Once your vertical tracking alignment is set for the largest angles currently used in the business, you're ahead of the game, since you

can always make the angle smaller by shimming up the record (say, with another record) but you can make it larger only by readjusting the arm height. You can even make a series of calibrated cardboard discs and mark on the album cover how many of them you need for shimming up that particular record. Just don't give up because the whole thing is too much bother. Once you've developed a routine, you'll waste very little time and you'll enjoy your record collection a great deal more. Remember, the difference isn't trivial.

A word about our tone arm and turntable reviews.

Phono cartridges are very special active devices and will be getting very special consideration beginning in Part II of this series.

Tone arms and turntables, on the other hand, are passive vehicles for the cartridge; their performance is defined by their mechanical excellence as tools or machinery. Once you understand the stylus/groove interface, the mystique of purely subjective testing (''the highs are grainy and the midrange is hooded') begins to appear singularly inappropriate to tone arms and turntables. Not that their ultimate proof of quality isn't in the sound. Of course it is. But you don't have to test a hammer that has a five-inch handle by vigorously hammering nails with it for two days. You say, "This hammer doesn't have a decent handle; give me another one." Since the world of tone arms and turntables is full of hammers with five-inch handles, simple inspection often suffices to make a "first cut" in a test program whose sole concern is finding the best. In some cases a few minutes of use will reveal all the necessary information. In other cases it may take weeks or months.

We've taken this completely pragmatic, common-sense approach to evaluating tone arms and turntables. It's entirely possible that in the end a few super-subtle finalists will require careful A-B listening comparisons under con trolled conditions. We're far from that point yet. We're still looking for equipment that, right up front, doesn't seem to threaten the stylus/groove relationship in any way whatsoever.

Nor do we want to make any broad generalizations, at this juncture, about design criteria for the ideal tone arm or turntable, other than the integrity of the stylus/groove geometry itself. Under each particular model, we're commenting on whatever specific design problem that unit poses; when the time comes, after we've reviewed a sufficient number of different designs, we'll summarize the lessons to be learned.

Before we get into the reviews, however, we'd like to bring up one amusing example, which will serve to illustrate some of the technical points we're trying to make. Somebody we know made a truly superb tone arm some time ago for a special laboratory project. It consisted of a plastic soda straw, pivoted on four ordinary household pins in a gimbals con figuration. Consider this ultra-sophisticated de vice: it had very low mass, great axial rigidity, low Q because of the relative deadness of the plasticized material, only the correct two degrees of freedom in the gimbals (not able to twist every which way like a unipivot), quite adequately low bearing friction at the four points of suspension, and of course no silicone gunk or other damping at the pivot to modulate the vertical tracking force on warps. Of course, the experimental cartridge it was made for was extremely low in mass and high in compliance; for your normal cartridge the straw could be replaced with, say, a straight section of balsa wood or some other heavier material that's rigid and dead. How about that, Dynavector? Oh yes, just one more thing. The Duxseal we keep referring to in the reviews is the acoustically deadest material known to us, originally made as a sealant for plumbers, electricians, appliance installers, etc., by Johns Manville. You can buy it from suppliers to that trade. It will damp some of the most stubborn resonances.

Dual CS721

United Audio, 120 South Columbus Ave., Mount Vernon, NY 10553.

Dual CS721 automatic single-play turntable, 3400. One-year warranty; distributor pays return freight. Tested #052570, on loan from distributor.

This is Dual's top-of-the-line turntable/ arm model, with electronically controlled direct drive DC motor. We don't find anything seriously wrong with it, except that the combination of the Kenwood KD-500 turntable and Grace G-707 tone arm is even better and costs $60 less (but isn't automatic, of course). Other wise the Dual CS721 would be our current top recommendation as the record player for a medium-priced stereo system.

Dual is particularly proud of the arm, and it isn't a bad arm at all. The bearings are deployed in an ideal gimbals configuration and appear to be correctly preloaded. We could detect no play or wobble whatsoever. The arm tube is straight, rigid and quite dead. The offset angle of the nonremovable headshell is almost correct, requiring minimal twisting of the cartridge for fully optimized alignment. With those advantages, you're already way ahead of the game. We also like the continuously adjust able arm height (i.e., vertical tracking angle) feature, which makes this all-important alignment truly painless by means of a simple knurled knob control. Now if only the control could be used during play . . . but no such luck.

The two weak spots of the arm, in our opinion, are the headshell and the counter weight. The mechanism that clips the removable cartridge holder into the fixed headshell isn't quite positive enough; there remains the possibility of not only play but also a lack of positional repeatability under worst-case conditions (such as frequent removal and reinsertion).

You can imagine how much that disturbs a tracking-error fanatic. Nor is the entire head shell assembly dead enough for our taste. As for the counterweight, we question the anti resonant mechanical filters built into it for the purpose of tuning out arm and chassis resonances. The jellylike bobbling of the counter balance breaks up a resonant peak into several smaller ones (just a few dB lower in amplitude) instead of dissipating it resistively (like carbon fiber, balsa wood or even silicone gunk), which would be definitely more desirable. We aren't suggesting that this is a totally wrong headed solution, given the design constraints of a very compact, practical, easy-to-use, automatic turntable at a price-but a purist's approach it isn't.

The turntable itself is also of basically good design, without disqualifying faults. We'd like to see a platter that doesn't ring at all when struck; the Dual's isn't quite dead enough.

The resonant frequency of the chassis on its suspension could also be a few Hz lower for best results. All in all, though, this is a competent, well thought-out job, and it doesn't appear to suffer from the horrible things direct drive turntables are sometimes accused of, such as cogging.

The only thing we can't figure out is where the CS721 fits into the audiophile scheme of things, since it's neither the ultimate nor (in view of Kenwood/Grace) the best for the money. How about best for the money if you must have an automatic?

Dynavector DV-505

Onlife Research, Inc., Tokyo, Japan. Distributed in the U.S.A. by Audioanalyst, Inc., PO Box 262, Brookfield, CT 06804. Dynavector DV-505 tone arm, $575.

Tested #510880, owned by The Audio Critic.

Since we've already discussed this ""ultimate" arm (its name in Japan is Ultimo) at some length in two previous issues, we only want to summarize our conclusions here.

Despite its sci-fi appearance and mind boggling price tag, it isn't the ultimate arm.

It suffers both from errors of design and from errors of execution. The massive, heavily damped main arm, pivoted to move only later ally, and the much lighter, undamped sub-arm, pivoted to move only vertically, constitute an erroneous design concept in our opinion.

Regardless of the convoluted rationale presented in Onlife's technical brochure, such a gross difference between the lateral and vertical motional impedances will tend to resolve vectors with a strong upward bias, thus falsifying the information cut into the groove. Further more, the sensitivity of the short sub-arm to warp wow is inevitably greater than that of any normal arm.

The greatest boo-boo in the physical execution of the DV-505 is the way the arm height adjustment mechanism is slotted and keyed.

Every time you change the arm height with this beautifully convenient device, the play between the key and the slot results in a shift of the lateral swing axis of the arm, completely negating the overhang alignment. Once you're aware of this unbelievable defect, you can push the damn thing back to the end point of the play, hoping that at least that point is stable. But for $575? Come on, Onlife.

We think we have figured out the reason why this arm so often appears to improve the sound when inserted into a known system. The unusually large mass of the entire structure tends to act as an anchor or inertial platform, dissipating some of the grosser extraneous disturbances of the stylus/groove relationship that afflict the typical installation. As soon as purposeful and meticulous care is taken to eliminate these disturbances (better mechanical and acoustic feedback isolation of the turn table, for example, or a dab of deading material such as Duxseal in the right places), correctly designed arms such as the Grace G-707 begin to sound better. It's as simple as that.

There are more ways to skin a cat than hanging a $575 anchor around its neck.

Grace G-707 Sumiko Incorporated, PO Box 5046, Berkeley, CA 94705. Grace G-707 tone arm, $140. One-year warranty;

customer pays all freight. Tested sample owned by The Audio Critic.

We consider this simple, un-gimmicky arm to be virtually unexceptionable in design; refinements would be possible, of course, but mainly in execution rather than concept. It's the best all-around workhorse arm we've been able to find so far. You must keep in mind, however, that it has a fixed headshell, so that frequent cartridge changes are a nuisnce. And, needless to say, you still have to twist the cartridge in the headshell every time, since the lateral geometry still isn't right on the money.

Interestingly enough, this is also a straight tube, gimbals-suspension design, like the Dual arm, and there's really no better approach.

The Grace is a little longer and a little simpler, both of which are fundamental advantages; its headshell and arm tube seem to be reasonably dead, although two little dabs of Duxseal (one between the cartridge screws on top and one on the arm fairly close to the pivot) resulted in an ever-so-slight increase in sonic clarity, proving that there was room for improvement even in that department. The slight extra mass also brought the G-707 right in line with the compliance of our Denon DL-103S cartridge; overall, however, the arm appears to be accept ably compatible in mass with a wide range of modern cartridges and is certainly not too heavy for any that we know of. As for the bearings, they appear to be eminently free from play and wobble, which probably accounts for a significant part of the arm's audible performance.

We could wish for generally more rugged construction, a more convenient antiskating adjustment, a cueing mechanism with more positive feel, etc., etc.; but the fact remains that this is the arm we're currently using in our reference system, even though we can't help wondering why there isn't this kind of intelligent design available along with SAEC-like construction-for those who are willing to pay the price.

Grace G-940 Sumiko Incorporated, PO Box 5046, Berkeley, CA 94705. Grace G-940 tone arm, $150. One-year warranty; customer pays all freight. Tested sample owned by The Audio Critic.

This isn't exactly our cup of tea: a uni-pivot design (i.e., free to move in various un desirable ways that would be impossible with a gimbals-type suspension); fluid-damped at the pivot, which is far from the ideal place; and without antiskating bias, so that there will be lots of tracking error (among other things), no matter how carefully the overhang and offset angle are aligned. What's more, the arm is on the heavy side for some of the latest high-compliance cartridges.

The fact that the G-940 still sounds a lot better than most other arms tells a great deal about most other arms.

Harman Kardon Rabco ST-7

Harman Kardon, 55 Ames Court, Plainview, NY 11803.

Rabco ST-7 straight-line tracking turntable, $430.

Tested #2423689 and #3000927, owned by The Audio Critic.

If this were a successfully executed product, more than half of our preceding article, including the overhang and offset-angle table, would be unnecessary or at least academic.

The ST-7 has a straight-line tracking arm, and that means no overhang and no offset (and therefore no skating force, either). The ideal lateral geometry. And it's a fully automated single-play turntable, with universal arm and two-speed table lovingly made for each other--obviously the ultimate fruition of the original Rabco idea, right? Wrong.

Our tests of two different samples were nipped in the bud by an absolutely intolerable and disqualifying defect common to both, which we must therefore assume to be a design characteristic. The carriage of the arm trans port mechanism is so loose and wobbly that the theoretically ideal stylus/groove relation ship made possible by straight-line tracking is totally negated, indeed made worse than with Just about any conventional arm. The result is a big resonance in the upper-bass/lower-mid range region, adding an insistent coloration to the sound that we don't find at all accept able in advanced audio equipment.

The overall construction of the ST-7 seemed much too flimsy to us from the beginning, but this we didn't expect. Next! Infinity 'Black Widow' Infinity Systems, Inc., 7930 Deering Avenue, Canoga Park, CA 91304. 'Black Widow' tone arm, 3200. One year warranty; customer pays all freight. Tested #11216, on loan from manufacturer.

Aside from its Bongiornoesque name, we found this slender and not particularly lethal looking tone arm quite livable with on first acquaintance, even though twisting the cartridge for optimum geometry in the tiny (and, of course, not quite correctly offset) vestige of a headshell took some doing. Then we discovered that damping this half-shell as well as the bearing housing with some Duxseal resulted in a substantial improvement in transparency and definition, so it's an inescapable conclusion that the arm rings to some degree. Closer examination of the bearings indicates some proneness to jitter; what's more, the little half headshell can be plucked to twang ever so slightly; both of which resonant conditions may have been helped by the damping.

Overall, the arm seems even a little flimsier than the Grace G-707, which for 30% less offers substantially the same virtues without the same vices.

Kenwood KD-500

Kenwood, 15777 South Broadway, Gardena, CA 90248.

KD-500 direct-drive turntable, $199.95. One-year warranty, customer pays all freight. Tested #430148, on loan from owner.

Although we haven't tested some of the top contenders yet (for example, the Linn Sondek LP12 and the Thorens TD-126 Mk II are among those next in line), we doubt if we'll ever find a better value among turntables than this excellent and remarkably low-priced Ken wood unit. There really isn't all that much to say about it, except that it's entirely trouble free and makes good cartridges and tone arms sound their best. For example, we like the sound of our Denon DL-103S/Grace G-707 combination much better on the Kenwood than on the Luxman, which costs three times as much.

The KD-500 is living proof that what makes a turntable sound good isn't exotic engineering, super specs or fancy features, but simply a design that allows the stylus/groove relationship to remain undisturbed at all times.

The "resin concrete" chassis on which all parts are mounted is probably a strong contributing factor; it seems to be nice and dead. The platter itself is rather live (it rings like a bell when struck) and could probably benefit from a liberally applied layer of Duxseal underneath.

(Unfortunately, we don't own ours, so we can't mess with it.) The adjustable legs of the Ken wood aren't the most sophisticated kind either, and we had to place ours on a marble slab to improve the mechanical feedback isolation.

Furthermore, the direct-drive DC motor doesn't have much torque. But who cares? Properly set up, the Kenwood seems to be more stable and feed less crud to the cartridge and arm than any other turntable we've tried so far.

As one of the old perfume ads used to say, it's unfair but it works.

Luxman PD-121

Lux Audio of America, Ltd., 200 Aerial Way, Syosset, NY 11791. Model PD-121 direct-drive turntable, $595.

Three-year warranty; manufacturer pays all freight.

Tested #E6901267 and #F6901268, owned by The Audio Critic.

This was our reference turntable for many months, mainly because nothing more precise and beautiful had ever been built, and it worked very reliably. All right, the mechanical feed back isolation wasn't the greatest, but a marble slab took care of that. (What do you think marble was invented for? Michelangelo?) Deep down we always knew, however, that there was something subtly wrong with the sound. A kind of thickness in the upper bass and lower midrange. We tried to blame every thing-record, cartridge, arm, etc.-except this gorgeous machine. But the day of reckoning finally came. The unspeakable truth: the PD-121 drums. Like a real live drum. That large, flat base just isn't dead enough. The main cause of excitation is airborne acoustic feedback, but you can verify the character of the resonance by tapping on the turntable just so, with the record playing and the volume control up. The coloration of the resulting undamped transient is the same as the coloration we heard in the music. And the drumming isn't curable by any simple means. Goodbye, PD-121.

(And you thought it would be something really sophisticated, like cogging or some other fashionable direct-drive vice, didn't you?) Mayware Formula 4 Mayware, England, distributed in the U.S.A. by Polk Audio, 1205 South Carey Street, Baltimore, MD 21230.

Formula 4 PLS4/D tonearm, $149.95.

Tested sample owned by The Audio Critic.

This is a unipivot arm, with silicone damping applied right at the pivot (i.e., in series with the stylus compliance), and you know from our Grace G-940 review above how we feel about both of those design approaches.

The Formula 4 also has a somewhat wobbly sliding weight between the pivot and the head shell, so that not only the vertical tracking force but also the dynamic mass of the arm can be varied. An interesting idea, but we aren't convinced that the slight play between this cursor weight and the arm tube isn't audible.

Nor that the very light, fixed headshell doesn't ring. Nor that the ultrathin arm tube is rigid enough. Nor that eccentric counterweight doesn't set up some torsional forces that aren't completely balanced out.

Since the Grace G-707 is a simpler and more effective design, as well as quite compatible with the same high-compliance cartridges that the low-mass Formula 4 was designed for, there's really no need to belabor the above points. The Formula 4 also costs a few dollars more and is even less rugged in construction.

J. H. Reproducers Co., an Australian manufacturer, claims that the Mayware Formula 4 is an inferior rip-off of their original design. We're reporting this merely as a partisan allegation, since we haven't been able to get our hands on the J. H. version thus far to form our own opinion. Needless to say, how ever-once a fluid-damped unipivot, always a fluid-damped unipivot.

SAEC WE-308 NEW Audio Engineering Corp., Tokyo, Japan. Distributed in the US. A. by C. M. International, 4131 Calle de Primera, Torrance, CA 90505. SAEC WE-308 NEW double-knife-edge tone arm, $195. Tested #FJT4955, owned by The Audio Critic.

This incredibly frustrating combination of precision workmanship and geometrical blundering, which we can only liken to a superb Swiss timepiece with an 11-hour dial, was already discussed in sufficient detail in our CES report (May/June 1977, page 17) to constitute a review; we really don't feel like beating up on these obviously dedicated though misguided people all over again. We must add, however, that we finally succeeded in twisting the Denon DL-103S cartridge into the correctly aligned position on the SAEC; if the offset angle of the arm had been just half a degree smaller yet, it would have been impossible- and probably is impossible with certain other cartridge configurations.

And what do you know, the correctly aligned SAEC/Denon combination still didn't work properly. The mass of the arm was much too high; the subsonic resonance went way down to the point where it coincided with the slight warp excitations produced by the record, and the stylus bobbled like very slow jelly in the groove. Now the Denon isn't a particularly high-compliance cartridge; it can live happily with some fairly massive arms.

So it seems that the SAEC is designed only for the very lowest compliances to be found today. Of course who says it was designed at all? (Sorry. There we go again.) One nice feature of the SAEC, though, is the optional arm stabilizer accessory (AS-500), a large cylindrical weight that threads right onto the arm post under the turntable. It's again the anchor or inertial platform concept, but a lot cheaper and more convenient than in the case of the Dynavector.

Let's be thankful for a good idea even if we can't be for a good arm.

Recommendations

It's much too early in the game to categorize any tone arm or turntable as the best, even with qualifications. We just haven't looked into enough of them. But at least two excellent and relatively low-priced pieces of equipment emerge from our investigation so far. To those who are unwilling to wait for our reports in the next few issues, we can recommend them unhesitatingly.

Tonearm: Grace G-707.

Turntable: Kenwood KD-500.

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[adapted from TAC, Vol.1, No.4: July/August /Sept 1977]

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Also see:

A Comparative Survey of Power Amplifiers: Part II

The Present State of CD Player Technology: Who Is Doing It Right? By David A. Rich, Ph.D. Senior VLSI Design Engineer, TLSI, Inc. Adjunct Assistant Professor, Polytechnic University

Various audio and high-fidelity magazines