The TX-1000 sold in the USA for approximately $8,000 and the Dragon CT
for approximately $2,000 (including a good tone arm). Estimates of the total
number of these turntables sold worldwide range from 200 to 500 for the TX-1000
and 2,000 to 5,000 for the Dragon CT. These numbers are guesstimates as no one
really knows for sure. While the TX-1000 and the Dragon CT are both Nakamichi
turntables, they actually are quite different from one another in both design,
appearance, and materials (cast metal versus wood.)
Despite being so different from each other
the TX-1000 and the Dragon CT share one incredible feature. Both turntables
have a self-centering mechanism that eliminates the wow caused by the spindle
hole being punched off center. All of us who play vinyl
records have seen the effect of an LP with an off-center spindle hole—the
cartridge and arm swings horizontally from side to side with each revolution of
the platter. Likewise, we have heard the pitch of a sustained note rise and
fall with each revolution of the turntable. This is particularly noticeable on
sustained piano notes contained in the last grooves of a side.
Among turntable aficionados the Nakamichi TX-1000 turntable and its smaller brother,
the Dragon Computing Turntable (CT), are legendary. These turntables, like most
classics, are rare. Both turntables were sold from roughly 1983 to 1987 before
being killed off by the ascendancy of the CD. These differences are
understandable when you realize that the TX-1000 was designed by Etsuro
Nakamichi and built by Micro-Seiki, while the Dragon CT was designed by Junichi
Okumura and built by Fujiya Audio Ltd.
"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. 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."
To summarize, even if your LP is
made with the spindle hole dead-centered, if your spindle hole is .1 mm larger
in diameter than your spindle you will most likely have audible wow. Wow at
this level will probably not be audible as a rising and falling pitch unless
you are very sensitive to pitch instability. However, most people will notice
that the inner details of the music will be blurred or indistinct. Also
consider what is happening to your stereo image as the stylus is forced against
first one side of the groove and then against the other side of the groove with
each rotation of the LP—essentially anti-skating gone crazy.
For those of us
that listen to vinyl on a regular basis we are accustomed to hearing the
consequences of pitch instability caused by off-centeredness. We just chalk
these detriments up as just some of the inherent differences between digital
and vinyl playback.
With
the TX-1000 you can play an LP without using the self-centering feature—this is
called nominal centering. And you can switch back and forth between nominal and
self-centered. Thus, it is easy to hear the difference self-centering makes.
With an LP that is .5 mm off-center, the improvement in sound is very
noticeable—more detail, a more natural, relaxed sound, and none of that
annoying undulating wow on sustained notes.
With LPs that are less than .1
mm off-centered, the sonic difference between nominal and self-centered is not
very audible. However, the TX-1000 gives a digital readout of the off-centeredness of each LP
that it centers. Very few of the hundreds of LPs that I have centered on TX-1000 are off-center by less than .1 mm. Thus, almost all LPs that I play on
my TX-1000 sound better for having been self-centered. There is no doubt that self-centering an LP can significantly improve the quality of the
sound during playback. However, self-centering is meaningless if the turntable
itself is not a good sounding turntable. After all, putting delicious frosting
on a mediocre tasting cake is waste of good frosting.
The
specifications of the TX-1000 as published by Nakamichi in early 1984 (via a
Google translated Japanese sales brochure) stated the signal to noise ratio as
"above 78dB DIN-B". Wow and flutter were stated at "0.003%
(WRMS/FG direct reading method) 0.02% (after WRMS and the center search)".
I am not an engineer and I don't know what these numbers really mean. TX-1000 is currently set up, with a Van den Hul Colibri XPW
mkIII mounted on a Schroeder Reference 9" jacoba tonearm and with the
turntable supported on Stillpoints rather than on its original air bladders,
the sound with nominal centering is wonderful. The sound is detailed, smooth,
musical, has rhythmic drive and arises from a black, black background. With
self-centering, things get even better. I have heard both the
Certus and the Proscenium turntables at audio shows. I suspect that both
turntables sound better than the TX-1000 with nominal centering.
For rock, heavy metal and certain percussive soundtracks pitch stability
or instability is not really that noticeable. For this type of music I use my
Garrard 401turntable with Moerch DP-6 12" arm and Empire 750LTD (moving
magnet) cartridge. I find that this combination of table, arm and cartridge to
be highly synergistic and produces music that has more pace and rhythmic drive
than the TX-1000, Schroeder, Colibri combination. On the other hand, for
classical music, small ensembles, and vocals the TX-1000 combination is, the only way to go.
Besides
how many of you readers ever see a TX-1000 in the flesh let alone
be able to purchase one? The answer is - not many. Vinyl is making a resurgence. New
turntables are coming to market and many of them are quite expensive—much more
expensive than either the TX-1000 or the Dragon CT, which would have cost
roughly $16,000 and $4000, respectively, when their original purchase price is
adjusted for twenty years of inflation. Modern day turntable manufacturers are
reluctant to publish the flutter and wow specifications for their turntables.
However, the rule of thumb is that current belt drive turntables have flutter
and wow of less than .1% and current direct drive turntables have flutter and
wow of less than .05%. The inexpensive ($399 street) Technics SL1200 has
published flutter and wow of .035%. Let us say that your
new $30,000 turntable has flutter and wow of only .015%—an incredibly low
number. Now you put your audiophile approved $40 LP (with the spindle hole
being .25mm off center) on your new turntable. Per figures above,
your flutter and wow just went up to .345% (.015% from the turntable and .33%
from the off centered spindle hole).
The manufacturer of your turntable just
spent $1 million in research and development to bring the flutter and wow down
to an incredibly low .015% and you just paid a portion of that R & D with
your purchase.
A question to you and the manufacturer is: Who cares if flutter
and wow of the turntable is .015%?
What is important is not the flutter and wow
of the turntable by itself, but the flutter and wow of the turntable and LP
combined.
If the flutter and wow of the turntable was .05% that would mean the
flutter and wow of the turntable with the LP would be .380% (.05% + .33%).
Audibly, .380% is not much different from .345%. The difference between .380%
and .345% may not even be audible because the .035% difference is being swamped
by the .33% LP wow.
To my way of thinking, the purchaser of a turntable would
be far better off if the turntable manufacturer spent his R & D money on
developing a self-centering mechanism for his turntable. That would
dramatically lower flutter and wow on playback for the purchaser of the
turntable. Who listens to a turntable spin with no record on it?
What is
important is the flutter and wow with the LP spinning and the stylus in the
groove. Even if all of our LPs were off
center by only .1 mm and all spindle holes were the exact diameter of the
spindle, neither of which is the case, the .380% versus .345% flutter and wow
would only drop to .180% versus .145%. This is still audible and the LP flutter
and wow is still dominating the turntable flutter and wow.
So what
does all this mean for the average vinyl lover. It means nothing if you are not
going to buy a new turntable at some time in the future. However, if you might
be buying that one last turntable some time in the future you might want to
have a little chat on the phone or at the next audio show with your favorite
turntable manufacturer. You might want to give him copy of this article and point out to him that while Manufacturer is spending all his time
trying to drop his flutter and wow from .05% to .04%, there is a 400 kg gorilla
rampaging though the listening room that is making so much noise that all of Manufacturer's time and money spent on achieving a .04% flutter and wow is
meaningless and wasted. If enough of us talk about self-centering, maybe one
manufacturer will actually do it. And if one manufacturer does it, many more
will follow due to competitive pressure. If a dealer is demoing a
self-centering turntable and a non-self-centering table and the tables are
anywhere close in price, the customer will choose the self-centering
turntable the majority of the time. Building a self-centering mechanism is not
as difficult or as expensive as it was in the 1980s. With current micro
processors and servo motors the design and manufacturing of a self-centering
turntable is easier and cheaper (in inflation adjusted dollars) than ever
before.
Both the TX-1000 and the Dragon CT have a
glass top platter on top of a metal sub-platter. A sensor arm is used by both
turntables to measure the off-centeredness of the LP. The top platter is then
automatically moved relative to the sub-platter to correct for the off-centeredness
of the LP. The two turntables make the correction in different ways.
I have never seen a Dragon CT perform its self centering feature.
However, from descriptions of it that I have read on the Web it seems you push
down on the spindle which manually brings the glass top platter into alignment
with the sub-platter and starts the self-centering process. In the picture of the Dragon CT the arm at the back of it is not a tone arm. It is
the sensor arm. Once the self-centering process has been initiated, the sensor
arm moves over to the lead-out groove area of the LP and slowly drops down. The
sensor arm has a stylus at the end of the arm. Once the stylus is caught in the
lead out groove, the sensor arm moves to the lead out lockout groove.
The lead
out lockout groove is in almost all cases, particularly for modern LPs, a
perfect circle. As the LP spins, the sensor arm measures the horizontal
movement of the stylus caused by the off-centeredness of the spindle hole. A
small plunger then comes out of housing next to the platter. The plunger gently
nudges the glass top platter. You may have done something similar to this when
you tried to center an LP with an oversize spindle hole by gently nudging on
the rim of the LP as it spun on the plate. The Dragon CT, however, is very precise
and accurate. After nudging the top platter the Dragon CT measures again,
applies another nudge and continues to measure and nudge until the LP is centered.
Once centering is complete the sensor arm lifts up and retracts to its rest
position.
For the TX-1000 the process is essentially the same.
An LP is
placed on the glass top platter and the 'center search' button is pressed. A
2" x 9" housing to the left of the platter rises up about 2.5",
a brass rod (the sensor arm) rotates out, moves over to the lead out groove
area and drops down. The stylus at the end of the brass rod drops into the lead
out groove and moves the rod to the lead out lockout groove. The turntable
measures the horizontal movement of the stylus and by means of two servo motors
in the sub-platter adjusts the position of the top platter relative to the
bottom platter. After moving the top platter the off-centeredness is again
measured and additional correction applied. For most LPs, the self-centering
measuring and adjusting process takes about ten seconds. On a few LPs, which
are very off-centered, it can take up to thirty seconds. Once the LP is
correctly centered the brass sensor arm lifts up, rotates back into its housing
and the housing drops back into the turntable.
Schematic
Click on the pictures to magnify
Adjustments
Universal Remote Control Codes, Setup procedure, Circuit diagrams and more ....
