A brief history of turntable drive systems

By Viktor A. Shapkin (translation by mrgoodsound)

This article was written by Viktor Shapkin, a very passionate and knowledgeable Russian audiophile who sadly passed away in 2017. Viktor was greatly interested in vintage audio, especially from American firms. The article below was published to his personal website where it can still be viewed. It has been translated from Russian to English by myself, with minor edits made for the sake of clarity. I hope the reader enjoys and learns something new.

To rotate a platter with a phonograph record, engineers throughout history have designed different types of drive systems.

Historically, the first type of drive system (denoted in the figure by the Roman numeral I) was one in which the motor (M) rotated the platter shaft through a reduction gear (RED). Note it is through the shaft, not the axle, because the axle does not transmit torque.

Until recently, there were no tables with such a drive in Russia, and therefore there is no common name for such a drive system, so we will call this central drive (or gear drive).

When the era of sound films (talkies) began in 1926, it was turntables with such a drive system that provided the sound accompaniment for motion pictures, using phonograms with 16" shellac discs. Since it was desirable to receive sound in sync with the image, the film spool with the image and the platter with the phonogram were rotated through a common motor unit.

In order to reduce the speed of the common motor (in the USA, most often 1800 RPM motors were equipped) to the operational speed of the platter, gearboxes were used. Western Electric used worm gearboxes, and to dampen torsional vibrations, rotation was transmitted to the disc through several springs (for RCA, worm gearboxes were used with felt pads instead). This is the same principle as in a car clutch. Another common method for leveling torsional vibrations was to increase the mass of the platter - this method was used by engineers from RCA, Fairchild, and other manufacturers.

It is curious to note that it is to the designers of these gearboxes that we owe such strange non-integer values ​​of the rotations of the records - 33 1/3 and 78. Indeed, why not exactly 33, and not exactly 80?

With acoustic recording, there was no standard for the rotational speed of the disk; it varied within wide limits. For recording and playback of electrical recordings at high speed (with high quality), a transmission (reduction) gear ratio of 23 was chosen. For low speed (longer playback time), a gear ratio of 54 was chosen. Indeed, if you divide 1800 by 54, you get 33.333333, if 23 - then 78.26.

This type of drive was used both for synchronous, i.e. drives synchronized with the image, and asynchronous playback, i.e. tables triggered manually by the operator.

Gear drive in HH Scott 710

However, the central/gear drive is an expensive and complex type of drive. It dominated turntables for the first 10 years of their existence, from the mid 1920s to the mid 1930s. It was used only once in household models - on the H.H. Scott 710 turntable from 1955.

To reduce the cost of turntables and bring them closer to the consumer, the type of drive system employed became an obstacle. Over time, it was replaced by other, simpler and cheaper drive systems. The central/gear drive would remain only in recording and broadcast machines from firms such as RCA, Presto, Scully in the USA and Neumann in Europe

The next drive system that was introduced was roller (idler) drive. It became widespread thanks to the Presto company from New York who in the mid 1930s, mastered the production of discs for the home recording market. They were aluminum discs covered with a certain substance that allowed cutting grooves and repeated playback of the resulting recording. These discs were recorded and played on tables with the help of two tonearms - a recording arm equipped with a cutting head and a reproducing one equipped with a playback head. (Ed. note: Presto record cutters are still highly sought after today and fetch high prices on eBay)

Presto K75a record cutter

To transfer torque from the motor to the disc, Presto engineers installed rollers (rubber wheels) that connected the nozzle on the motor shaft and the inner rim of the disc. Since then, the roller drive has been used by turntable designers for 40 years - from the mid-30s to the mid-70s, when the last of the "giants" - EMT 930 and Garrard 401 finally left the market.

Roller drive turntables can be divided into three subgroups:

1) The most common - where the idler contacts the platter from the inner rim. It saves space, and in this case the motor rotates counterclockwise with respect to the rotation of the platter. Examples of this subgroup include probably 95% of all idler-drive turntables, including countless consumer models whose names have long been forgotten. From famous machines, the British Garrard, German EMT, Canadian McCurdy, French Bordeau, and Australian Commonwealth.

2) A less common design - where the idler contacts the platter from the outer rim. In this case the direction of rotation of the motor and platter coincide. There are fewer representatives of this group, notably the American D&R and British Sugden (Connoisseur).

3) The rarest - the motor shaft is pressed directly against a rubber surface attached along the perimeter of the platter rim (either from the outside or inside). This can be considered a 'bandage' drive, as the rubber surface resembles a bandage along the platter. The third group includes professional units - models from Presto, Gray Research and Byer.

The number of idler wheels used by different manufacturers in their designs varied from 1 to 3, as there would sometimes be separate wheels employed for each speed (33, 45, 78). The vast majority of tables had one motor, but, for example, Presto recording machines had one motor for each speed (33, 78), and Gray actually used two motors for one speed. The axis of the idler wheel was most often vertical, but horizontal installation of the idler was also used. most famously in the Swiss Lenco.

Presto 64a featuring one motor per speed

In most cases, the idler wheel did not change the number of revolutions (rather it changes due to the difference diameters of the motor shaft nozzle). However, in some designs the idler wheel had two working surfaces with different diameters, and the ratio of these diameters provided the required gear ratio of the transmission, see American Rek-O-Kut.

Almost simultaneously with the spread of the idler wheel drive systems in the late 1930s, Western Electric engineers installed a belt drive on the 300A table for radios. The first belt drive consumer table, the Components Corporation model, reportedly appeared in the early 1950s. This type of drive became widespread in the 60s. (Ed. note, more musings on the reasons behind the widespread use of belt-drive turntables is a subject for a future article)

In the 1960s, the dominant assumption was that the belt transmits less vibration from the motor to the platter than the idler drive, and the cost of cheap belt drives was certainly less than that of cheap roller drives. Reinforced and un-reinforced rubber and synthetic threads were used as a belt. The profile of the belt was either rectangular or round, depending on the designer's philosophy.

The vast majority of tables used a single belt, however American engineers at Fairchild developed a sequential two-belt design with a countershaft. This design was later used by other manufacturers. (Ed. note see modern tables from VPI.)

For a number of reasons (one of them, a slow start-up from standstill), the belt drive has not taken root in studios, especially in recording applications. The only exception to this is the Fairchild 750 with its 25 lb platter. In consumer and 'high-end' applications, the belt drive has been widely used for 15-20 years. Both belt and idler drives existed on twin-motor tables, when both motors simultaneously rotated the disk through one belt or two rollers.

The last drive type used on turntables is direct drive, where the platter is mounted directly on the rotor of the motor itself. In the mid-1950s, engineers at the Danish company Lyrec developed a triple motor system for Neumann recording machines that rotated at all three record speeds. The torque was transmitted to the platter through an oil clutch. Such a drive was complex, large, and expensive. The appearance of such a drive in a form acceptable to consumers, without intermediate elements between the motor and the disk, became possible only in the early 70s after a number of companies (Japanese Matsushita, West German Dual) mastered the production of low-speed motors with the required torque. 

At first, turntables with such a drive were successfully used in studios, where professional users immediately their characteristic inaccessible to other drive systems - an instant start-up. Then, as the production of low-speed motors became cheaper, such turntables found more and more distribution in the domestic sector and, by the time of the arrival of other audio mediums, direct-drive on turntables was the most common.

We should also mention in some designs, the platter is driven by a drive train consisting of both the belt and the idler wheel.

The famous TD-124 drive train

The world famous model with a combined drive - Thorens TD-124. The same drive was possessed by: the now forgotten Soviet Victoria (top class), a small-circulation model Russco BID (Belt-In-Drive), a Neumann RA 2 turntable and a number of lesser-known tables.