When asked to pinpoint the single fundamental element of violin technique, he replied; "Absolute pitch first of all. Many a player has the facility, but without perfect intonation he can never attain the highest perfection. On the other hand, anyone who can play a single phrase in absolute pitch has the first great essential. "1
With these remarks, Mischa Elman, one of the greatest violinists, put his finger precisely on a crucial point, that exact pitch lies at the foundation of Western music. 2 This point tends to be taken for granted by musicians. Indeed, it is taken as so obvious that when a musician says of a colleague that he or she has a "good ear", what is invariably meant is a good ear for pitch--not for dynamics, not for inner detail, not for upper-octave frequencies, not for location, but for pitch. (Musicians also treasure rhythmic sensitivity but do not usually think of that as a hearing ability but rather as a separate "sense of rhythm".)
Music history shows that musicians have held pitch considerations to be at the heart of things for many centuries. The first great theoretical discovery in music was Pythagoras's discovery of the harmonic series. Ever since then (Sixth Century BC), tunings and scale temperaments have been a matter of obsessive theoretical concern to musicians; probably they were a practical obsession from even longer ago! The rise of the uniform, even-tempered (well-tempered) scale has seemingly settled the pitch question for keyboard instruments, but performers on instruments with continuously variable pitch (strings, singers, winds to an extent) continue to regard refined pitch selection as an indispensable element of their art.
Under these circumstances, it seems clear that pitch stability and accuracy should be one of the primary goals of high fidelity musical reproduction. Yet pitch has been treated with an indifference almost amounting to contempt by the audio industry. I refer to the fact that virtually no records are center-punched with an accuracy sufficient to give stable pitch. You have no doubt noticed this audibly--fluctuating pitch of sustained notes or, in less severe cases, a sort of general wateriness to the sound--as well as visually--the sideways oscillation of the tone arm, back and forth with each revolution. But probably you have not had the opportunity to hear what records sound like when they are truly accurately centered.
Neither had I until I recently purchased a Nakamichi TX-1000 turntable, which centers the records automatically to an accuracy greater than .01 mm. The result of this centering is quite simply a musical revelation. Once heard, it cannot be forgotten nor easily done without. For me, to return to the world of off-centered, uncorrected records 3 would amount to expulsion from a musical Garden of Eden.
Before I continue with my musical reactions in detail, let's think about numbers for a moment. Suppose we are listening to a groove that is, say, 75 mm from the center of the record; typically, this is still in the music groove region, but near the end of it. (Seventy-five millimeters is about three inches.) Since the record goes around once in 1/(33 1/3) minutes = 1.8 seconds, the velocity of this groove past the stylus is 2 pi (75mm)/1.8 sec. which equals 261.8 mm/sec.
Now suppose the record is 0.5 mm off center. (This is the limit of the correcting motion of the Nakamichi TX1000. Records further off-center than that have to be roughly hand centered before the TX1000 is applied. Most records that do not have badly worn spindle holes meet this standard of 0.5 mm.) Then when we are hearing the part of the 75 mm groove that is furthest from the platter center, the effective radius of the groove is 75.5 mm and the velocity goes up to 263.5 mm/sec. At the closest part of the groove, the radius is effectively 74.5 mm and the velocity goes down to 260.1. The ratio between the maximum and minimum velocities is 75.5/74.5 = 1.0134. Thus the pitch of a note recorded in this groove is a little more than 1.3 percent higher at the part farthest from the platter center than it is at the part closest. In another viewpoint, the wow is ±0.66 percent. Proportionately, smaller center errors give smaller pitch wow, with .25 mm giving about 0.33 percent, 0.1 mm giving .13 percent, etc. Smaller groove radii would give larger wow percentage (inverse proportion) for a given off-centeredness. Off-center wow is worst at the end of the side.
A usually accepted standard for audibility of wow is 0.1 percent. This of course varies from person to person. The pitch discrimination level for A/B matching can be as low as 0.01 percent in people highly sensitive to pitch.4 This is of course a different, probably more sensitive kind of pitch audibility than wow, but in fact the repeated periodic pitch variations of off-center wow are seemingly quite close in nature to the A/B test.
The TX-1000, in the process of centering the records, gives read-outs of how far the records are off-center before the correction. While most meet the 0.5 mm standard, few are centered within 0.1 mm and almost none at the level of, say, 0.03 mm or less. Moreover, spindle-hole looseness generates ambiguities that are often on the order of a tenth of a millimeter, varying with how you put the record on. And, as noted, better than 0.1 mm centering is needed to meet the nominal ± 0.1 percent wow threshold. (Precisely, at 75 mm groove radius, ±0.1 percent wow corresponds to .075 mm centering.) In short, it is numerically clear that some correction process is needed for the vast majority of records, if they are to be audibly pitch stable.
The TX-1000 also gives one the opportunity to compare center-corrected play with non-corrected play, since it can be operated without activating the correction mechanism. At the level of 0.02 mm or so, residual warp wow and out-of-roundness seem to have roughly the same order of magnitude as any off-center wow, and the benefits of centering become not very obvious. But for as little as 0.05 mm-and records rarely are that well center-punched--off-center wow becomes consistently more significant than the other residuals, and the benefits of centering are completely, even glaringly apparent.
It is paradoxical that turntable manufacturers vie with each other for low "wow" figures when in fact the wow from the off-centeredness of the records is much larger, often of a higher order of magnitude or more. After all, .20 mm center error, which is common, causes at 75 mm radius more than ± 0.25 percent wow, which is not a very impressive turntable figure. In practice, not even test records are well enough centered to give meaningful wow figures for really low-wow turntables. Accurate wow figures can then be obtained only by recording a test signal on a magnetizable plate already in situ on the turntable and playing that signal back, or by some other such process not involving a pre-punched record. In short, almost everybody knows that the records themselves are the problem, not the turntables, but nobody does anything about it-except Nakamichi.
The evidence is inescapable numerically that, for steady tones, the off-center generated wow is audible. But how bad is it in practice, with musical material, not test tones? My experience in pre-Nakamichi days was that it is very bad, indeed, that it is one of the principal faults of the playback of vinyl records. Its elimination was almost the only argument in favor of CD that was musically meaningful. But for me that one argument was beginning to seem almost enough, regardless of CD's other problems (which I find severe). I judge from conversations that many people shared this feeling of despair over the pitch instability of records. I speculate that for many musicians, for example--and many do like CD-pitch stability was a decisive factor, whether formulated explicitly or not.
With most audio nuisances, one tends not to realize how annoying they really were until they are eliminated. And, annoyed though I was explicitly by wow from off-centeredness, I was not completely prepared for how marvelous records can sound when properly centered. Of course, there is still warp wow 5, but the geometry of the Mørch DP-6 tonearm that I am using minimizes that, and pitch stability becomes excellent altogether. But such a prosaic phrase as "pitch stability" doesn't do justice to the glories revealed. All of a sudden, there is music, where before there was a wary, pitch-blurred pale imitation. The effect is spectacular on piano recordings, which are notorious for revealing wow. But in fact, the gain is enormous on all musical material with any sustained pitch content, that is to say, all music except the purely percussive.
As a bonus, imaging is also made much more precise and stable. It surely stands to reason, and it can easily be verified by calculation, that sideways motions of the tonearm are going to degrade the relationship between the two channels and hence the image. This borne out in practice, I assure you.
Some comment is needed on arm geometry in relation to off-centeredness. The strange theory has been given some currency that linear tracking arms will all but eliminate off-center wow. This theory seems to have arisen as an analogy of the fact, and it is a fact, that an arm like the Morch, with its vertical pivot in the plane of the record, does virtually eliminate warp wow, provided the resonance frequency is properly chosen (depending on effective mass relative to cartridge compliance), and provided of course that the warps are not insanely severe. But the analogy with the off - center problem is false. Regardless of arm geometry, the groove velocity past a fixed point is higher at larger radii. If the record is off center, the effective groove radius increases and decreases with the record's rotation. Ergo, the velocity goes up and down and so does the pitch. Arm geometry cannot fix this. 6
The question has perhaps arisen in your mind: How good is the Nakamichi TX-1000 turntable otherwise, beyond its centering capabilities? The gain in musicality from centering is so great that, unless the TX-1000 were somehow truly disastrous, otherwise, I feel it would still be superior. But the fact is that the TX-1000 is an excellent turntable in general. I wasn't entirely happy with the glass platter, which seemed to give a bright sound. (Apparently neither was Nakamichi so happy; a soft mat to go on top of the glass platter was offered as an option.7) By putting on top of the glass platter the superbly absorbent Sorbothane mat from AudioQuest, I obtained excellent vinyl damping and very fine sound, at once detailed and tonally neutral-and still blessedly, indispensably pitch-pure.
I am not going to attempt a review comparing the Nakamichi's excellent sound (with the AudioQuest mat, but independent of centering) with the current state of the art. Without all the contenders available in house, how could I? But I can say this: If I had a choice between, on the one hand, literal master tape sound with off-center pitch wow superimposed and, on the other hand, the sound of the Nakamichi TX-1 000 including centering, I would unhesitatingly choose the latter. Pitch stability and accuracy really is that important to me musically. It would be doctrinaire to insist that you will have the same priorities, but that is the situation for me.
Such praise for equipment that is no longer available no doubt makes frustrating reading. But I bring up these matters for a serious purpose, unrelated to whether or not you can somehow locate a TX-1 000 or the less expensive Nakamichi Dragon CT turntable, which also centers. In our age of microprocessors, the whole business of centering is apparently not terribly hard to handle. The TX-1000 at $7500.00 was expensive, of course, but the Dragon CT cost only $1750 including an arm of decent quality. Clearly it was, and still is, possible to handle the centering problem in a fairly low-cost way. Considering this, I find it disappointing that the manufacturers of the multi-thousand dollar turntables of today are not addressing the ubiquitous and serious problem of off-centeredness.8
I urge them to do so, and I think you should exert pressure on them, too, in whatever ways are available. Complain to the turntable manufacturers! You are being treated as if you were tone deaf. Don't take it lying down.
Meanwhile, until some other manufacturer addresses the problem, Nakamichis are really the only turntables for me.9 I wish that audiophiles, including me, had had the wisdom to make the Nakamichi turntables a success at the time. We owe an apology, in my view, to the memory of E. Nakamichi. If the chance comes again, if any manufacturer ever offers a precision automatic centering device with a tumtable again, I hope we'll do better.
I would be remiss in the context of all this not to mention the Center-a-Disc, from HVH Designs, 7647 Densmore Avenue, Van Nuys, California 91406 (price $68). This is a device for centering records by hand. Once the center is found, there is a way to lock a holder on the record so that you don't have to relocate the center for subsequent plays. Obviously, I am entirely in favor of the intention here, and the Center-a-Disc is effective in extreme cases. I can't think of a better thing you could do for your system for anywhere near the price. But in all honesty, it is no substitute for the automatic centering. It is slow, it is tricky, and, though it helps the bad ones, it really isn't accurate enough, at least in my hands, to do the job completely. I don't think I can even move an object only .02 mm, say, on a consistent basis. In the end, this is a job for microprocessors and machinery. Still, the Center-a-Disc is a lot better than the nothing else that is available, now that the Nakamichis are gone. Buy it.
We omit the usual manufacturer's information because the unit is out of production. Nakamichi's address, however, may be pertinent:
Nakamichi USA 19701 South Vermont Avenue Torrance, California 90502
1 Quoted from Master Violinists in Performance by Henry Roth, TSH Publishers, Neptune, New Jersey, 1982. Later context makes it clear that what Elman meant by "absolute pitch" was not pitch memory, as in contemporary usage, but complete pitch sensitivity in a harmonic context.
2 And some Eastern music as well. I understand that classical Indian musicians are at least as careful of pitch as Western musicians.
3 The Nakamichi centers records by moving a top platter assembly relative to a subplatter.
4 I have verified this experimentally in doubleblind tests involving myself and my UCLA acoustics students.
5 Earlier, I praised the vacuum damping of the Sota for virtually eliminating warp wow; but as it turns out, the off-center wow is a much worse problem.
6 Some radial trackers, e.g., the Souther, have remarkable abilities to track regardless of off-centeredness. But they don't and can't eliminate the pitch wow.
7 A vacuum mat add-on was also offered, but DAW found that this damaged the back sides of the records (in Issue 31, p. 39).
8 Ubiquitous it is, too. If you think audiophile records or old classics are immune, look and listen again. The good record companies try, no doubt, but the pressing plants are not controlled by their audiophile company customers, apparently.
9 I might be tempted to have a back-up table of some current audiophile sort, but there would be very few records centered well enough to play on it.
TAS issue 54 July/August 1988