[GP49000]

The ultimate Zero Tracking Error models: GT-55

The Zero Tracking Error tonearm in the Zero 100 and its offspring was higher in mass than tonearms on many competitive turntables. This was at a time when ultra-high compliance cartridges had to be matched to ultra-low mass tonearms. Garrard responded to this issue by slightly reducing the mass of the arm on the Z2000B, but the real reduction in mass was achieved on the last Zero Tracking Error models, the GT-55 and GT-55P.

Tonearm mass was reduced substantially, to a level competitive with other contemporary tonearms and suitable for the most compliant cartridges, by reducing the cross section of the tonearm beam and manufacturing the arm and pivoting headshell of magnesium instead of aluminum. The new C6 cartridge slide was reduced in mass from the C3 in the prior models, too. Further improvements in bearings reduced friction in the arm's four pivots.

Although the GT-55 models were built on a familiar-looking steel unit plate fitting the same plinth cutout as the Zero 100 and SL95 models, there were even more sweeping changes underneath. The platter was driven by a belt but gone was the Synchro-Lab motor. In its place was a 1000rpm DC servo motor from Matsushita, speed-controlled by an integrated circuit governor built by Garrard using a Matsushita integrated circuit. Speed adjustment was wholly electronic, ±3%. An illuminated stroboscope, identical to that in the Zero 100, was provided.

Although record changing on the multiple-play GT-55 model was done with a pusher-type spindle and a side platform almost identical to that of the earlier models, the works that operated the machine were totally new. The metal levers, and the cam gear that drove them, meshed with a pinion on the hub of the platter, were all banished. Replacing them was a modular mechanical assembly mounted under the tonearm. A plastic slide reached to the bottom of the spindle to trigger the record-changing spindle. A cogged belt extended from the platter's hub to the mechanical module, providing the drive to cycle the tonearm and change records. Careful design and tensioning of the belt resulted in its contributing infinitesimal noise and vibration to record playback.

Moving parts in the new modular mechanism were made of low-friction, self-lubricating plastics. It required no lubrication for life (cleaning out hardened, dried-up grease on the old metal mechanisms and relubricating them were an every-few-years maintenance task on the older models). Their operation was near-silent. The modular mechanism, in one form or another, would be incorporated in future Garrards but in one aspect of operation, that in the GT-55 models was unique: their tonearm cueing was accomplished by a back-and-forth motion of the main operating cam within the module. A dial on top of the chassis adjusted a brake, to provide for adjustment of the rate of descent of the cueing system.

The GT-55 model with provision for playing multiple records was supplemented by the GT-55P single play unit, which had the same inverted thrust bearing design as the single play models AP75, AP76, Zero 100S, SB and SC. Other than the different bearing, the lack of a side platform and of a multiple-play spindle, the GT-55P was the same as the GT-55.

The GT-55 models were built with their steel chassis painted in both a silver colour, and in black.

Unfortunately, while the GT-55 tonearms have performed splendidly, their motor/governor system has not aged well. Many units have been discarded because of severe speed variations which developed as units aged. The fault was in the Matsushita-design motor and governor, which would lose its speed stability as certain parts aged. Most can be fixed by replacing all the electrolytic capacitors on the governor board; some have had problems with the Matsushita integrated circuit itself. Garrard also used this same drive system in the GT-35 and GT-35P (to be discussed later), Matsushita itself put it into many Panasonic and Technics models, and several other makers used it, too. The same problems afflict every single model using this particular motor and integrated circuit governor. Matsushita itself ran out of supplies of the integrated circuit, the UPC1003, years ago.

Photos:

GT55, black
GT55, silver
GT55 magnesium Zero Tracking Error tonearm
GT55P single record player (note lack of record side support platform)
GT55P underneath, showing modular mechanism at upper left, and its cogged belt drive. Slide to operate record-changing spindle is not installed on single-play model, but the lever on the mechanism to operate it on the GT55, still exists.