Just as
Nakamichi made great-sounding
cassette decks by addressing the vagaries of
magnetic tape, they also made a lesser-known series of
turntables that did the same thing for
vinyl.
Among the many analog noise phenomena, record groove tracking is one of the worst, and also one of the most difficult to handle. Created by a master engraving stylus in the record blank, the groove in an album represents the analog waveform of the music. To properly reproduce the music contained within it, the playback stylus should fit the groove as tightly and as close to the angle of the cutting stylus as possible. Any variation in tracking angle on any axis creates noise and prevents the record player from recovering music from the groove. Since analog has potentially infinite resolution, the closer you got to following the groove, the better the sound you got.
Audiophiles (myself included) would spend hours adjusting the tracking angle of the record player's stylus by turning the cartridge in the headshell, adding shims to raise or lower it, and even changing its tilt. Records with test tones and templates with spirit levels, calipers, and measurement grids were used to gauge the changes to ensure that they were correct. However, there was one factor involved that no audiophile could address - the record's inherent manufactured accuracy. If the record had a hole in it that was slightly off-center, all the preparations by the audiophile were reduced, as the record was incapable of true alignment since the grooves didn't even rotate properly about the record's center.
Enter Nakamichi. Their TX-1000 and Dragon-CT turntables had what they referred to as the "absolute center search system". A measuring arm tested the record for circular accuracy, and the turntable would then adjust the record's rotation so that the grooves would revolve around the album's true center. A record sat on a heavy glass platter, which in turn sat on a thick felt pad, so a pushrod arm could tap the disk into alignment as it rotated. The TX-1000 could carry two tonearms, so one could either have two different cartridges on identical tonearms, or two completely different tonearms. This was because many audiophiles like to use different cartridges or styli for different records (Thorens used to offer quick-change tonarm "wands" for this purpose) or tonearms with different weight or tracking characteristics. The dragon "only" carried one tonearm.
These turntables are extremely rare and highly prized, and represent audiophile fanaticism at it finest.
A photo of the devices can be found at
http://www.niji.or.jp/home/k-nisi/tx-1000.htm