Philips Belt-Drive 1950

The engineers of the Physics Research Laboratory (Natlab) of the Philips Company - in fact Philips Gloeilampenfabrieken in Eindhoven, Netherlands - always had the liberty to research, invent and design whatever idea they had. There are many inventions and patents registered on their name, and many are being used by other leading manufacturers. Also in Audio. When in 1950 Philips started its record company named Philips Phonographische Industrie, there should be of course a proper machine for the playback of the 33 rpm vinyl discs with newly recorded performances of conductors Willem van Otterloo and Paul van Kempen, pianists Clara Haskil and Cor de Groot, violinists Herman Krebbers and Theo Olof - to mention a few names in the classical music section. It was engineer Louis Christiaan Kalff who came up with a new turntable of modern design and a revolutionary transmission of the turning of the motor to the platter, a system that broke completely with the motors and transmission of the common 78 rpm worm wheel concepts. It is, as we now know, the first belt drive turntable ever. It was the Philips HX301a.

HX301a Belt Drive

Since many music lovers would also continue to play 78 rpm shellac records in those days, the turntable (in fact a simple small record player), had two speeds: 78 and 33.33 rpm. RCA's 45 rpm 7 inch disc had been introduced in the US in 1949, but it would take some four years before it was adopted by the European record manufacturers. Therefor the Philips label had introduced a 78 RPM Minigroove vinyl disc with the size of the RCA 45 rpm disc (7"). Both popular and classical music was pressed on this format. In this way many people could get acquainted with vinyl records and could be persuaded to buy LP records instead of continuing to listen to the 78 RPM old shellac discs which were still manufactured in the early 1950s.
The Philips machine worked with an idler wheel. But it was not the familiar wheel that shifted up and down a pulley with diameters for 33 and for 78 RPM. No, it was the motor, mounted on a separate triangular chassis, that was shifted from the left transmission wheel to the right and vise versa. Another peculiarity of the construction of the Philips is that the belt does not run over the entire periphery of the platter, but touches only about a quarter of the platter and that may be some 10 cm in all.

Philips Featherweight Pick Up

Equally revolutionary was the Philips featherweight pick up arm with matching cartridge, and that in a time when tonearms were heavy objects and cartridges playing at a mere 10 gr. of down force on heavy vinyl platters.
At left the arm as it was portrayed on a 78 rpm record sleeve.

1953: Components 3-Speed Belt Drive + 25 lb. platter

While most manufacturers of turntables were designing their products along the principles of wormwheels (Thorens), idler wheels (Rek-O-Kut, Garrard, Collaro, a.o.), there was a small and hardly noticed company which produced a turntable that turned a heavy platter via a belt. That company was Components Corp., located in Denville, New Jersey. The design was quite revolutionnary. Apparently the engineers had discovered that only a heavy platter (in this case weighing 11.3 kg.) can procure a steady turning without being held back for not even one micron by strong dynamics and modulations in the recorded signal - equal to the performance of the idler wheel transmission. So smearing of transients was out of the question. To eliminate the transfer of vibrations from motor to chassis, they carefully suspended the motor. They also supported the turntable by long dampened springs to eliminate extraneous mechanical shocks and vibrations. Mechanical and acoustical feedback was practically non existent. In order to change the speed of the Components Corp. turntable, one had to lift the large cover hiding the motor and belt and slip the belt to the desired section of the pulley. In his report in High Fidelty Magazine (Vol. 3, No. 6 / January-February 1954) reviewer Roy Allison considered this a drawback. Strangely enough it took some 20 years before the importance of the technique of this design was fully recognized and found its application in heavy high-end turntables.

Professional Features

The design and construction of the Components Turntable was well thought over and the denomination "professional" was fully justified. In order to minimize mechanical feedback, the motor had double shock mounting. The isolation was twofold. First the motor was de-coupled from its own, small chassis by four blocks as shown in the image at right and in the drawing below at right. Then this chassis was de-coupled from the main base plate by another four, round rubber blocks. Then there were of course the other important features. The spindle was designed in such a way that records with large holes could be played without trouble. The long springs had felt damping. The shaft with single ball bearing was held in place by nylon sleeves. On top of the platter was a thick cork turntable mat for good protection of the surfaces. And there was the stepped pulley with the slightly rounded sections which kept the relatively wide belt from shifting during play.

Acoustical 3100 and All Balance Tonearm

The Acoustical 3100 turntable was also a belt drive turntable. The motor was a black Pabst Aussenlaufer type and there was a big capacitor which, when loaded, gave the platter a quick start. That was also possible because the platter was of high density chipboard and very light. Therefor the rumble frequency was rather high if compared to the rumble values of heavy platters, and did not interfere with the sound. Also magnetic attraction to Moving Coil cartridges was avoided. By pulling or pushing the chrome plated knob at the left corner, the speed - 33 or 45 RPM - was selected.

Early Type All Balance Tonearm

The tonearm was of the balanced type which uses a spring for creating the down force. Such an arm does not jump out of the groove in case of a mild warp, but just keeps on tracking. If the side thrust (bias) has been set perfectly right, the turntable will play records correctly in practically every position. It does not need to be level. At right the early arm with headshell. The contacts were spring loaded. Below the Jobo 2800 with the later All Balance tonearm.

Acoustic Research and Thorens

The Philips HX301a, the Components construction, the designs of the later turntables by manufacturers Thorens (TD-124), Perpetuum Ebner, and Dutch trade company and the turntable manufacturer Acoustical (Triotrack and Jobophone) all were using a belt. The Triotrack had an idler wheel that touched a pulley, but from the idler wheel there ran a belt around the platter. These were all designed in the 1950s. These examples show that it was not such a big step for Edgar Villchur and Roy Allison (and it is said that Mitchel A. Cotter was involved as well) of Acoustic Research to design the floating chassis (independent sub chassis), the construction used for the Acoustic Research turntable. This drive system was copied first by Thorens and applied in their TD-150. Later Ariston and again much later Linn copied the principle. At right the original chassis of the Thorens TD-150 with the interchangeable arm board which they omitted later in the TD 160, 166 and subsequent models. The chassis plate on which the motor was mounted was well decoupled from the floating metal cross with the three springs.

Unstable

A disadvantage of the floating chassis is that it can easily move in the horizontal plane. This is provoked by external shock. Specifically the drive belt is responsible for this unstability because it has a pulling effect on the platter and chassis. In most turntables this unstability is counteracted by filling the vertical springs with plastic foam. But this dampening has its effect on the general sound quality and in particular on the transient performance. In the Philips 202 Electronic turntable the movement caused by the drive belt is counteracted by a small spring mounted opposite the motor on the other side of the platter. This spring can be adjusted. It balances the chassis. The result is the desired stability.

Heavy Platters

But the light floating chassis was a swinging affair especially when the springs were not damped well with pieces of plastic foam and this prompted The Audio Critic to say about the 1970s Linn LP-12 that it was "a banjo". This qualification was of course not valid for the later improved editions. The point was made: a turntable with a suspended chassis which is separated from the motor is only working well if the suspension does not interfere with the performance: linearity of phase and a perfect transient response.
So several audiophiles and manufacturers started thinking of further developing the performance of the belt drive turntable. The next logical step was to improve the transient response by giving the platter a larger mass. In the mid 1970s designers started to use heavy platters as Components Corporation had shown already in 1953. The avanced technical production methods even more improved speed accuracy and bettered the rumble values as well. And now there was no smeering out of sudden and complex, loud signals featured by light weight platters.

Platine Verdier

Already in 1977 the first Melco turntable was presented at the Japanese Audio Fair. Micro Seiki introduced heavy turntables and by 1979 Jean-Constant Verdier - who is known for his involvement in the French ERA turntables in the 1970s - had his first Platine Verdier ready, initially proposed as a DIY kit in the French high-end magazine L'Audiophile. But lateron he started to manufacture the table in series and it evolved to the grand "Platine Verdier" which became the wanted item on the list of several serious audiophiles. At right the earliest Platine Verdier, already with its unique spring suspension and the 20 kg. heavy platter, supported by magnets incorporated in the base and platter.

Thorens Reference

Other manufacturers built heavy turntables too. Thorens designed the Reference (Referenz) turntable. It had a relatively heavy platter of 6.5 kg but an extremely heavy plinth filled with iron granulate which brought the entire turntable weight to 90 kg. The plinth was hanging on four steel cables connected to four leaf springs concealed in four cylinders (towers). The frequency of the suspension was tunable by 4 knobs on the sides of the pilars.
Now many direct drive turntables were also adorned with heavy platters, sometimes as heavy as 50 kg! But these tables were only produced in small quantities or were just manufactured as one of a kind.
Heavy platters became fashionable. Not only in belt-drive turntables. In 1981 the Technics SP-10 Mk3 was introduced with a platter three times the weight of the platter of the Mk2. Another heavy direct drive turntable was the Kenwood L-07. These turntables became an inspiration to many a hobbyist and remained so even after the introduction of the Digital Audio Compact Disc. That was when I designed the Basic 1 Turntable in 1980.

The Basic Turntable 1980

Inspired by this new trend, we designed the Basic Turntable. A few specifications:

* Platter machined from aluminum.
* Platter weight: 9.25 kg.
* Spindle: TD-124 bearing and bearing housing with ceramic thrust plate.
* Motor: TD 160 AC motor with added light bulb indicating if the motor is on.
* Precision pulley with 2 carefully calculated steps for 33 and 45 rpm respectively. Much later the motor and electronics of a Thorens TD-125 with variable speed replaced the simple AC motor.
* Plinth: rectangular box made of polished plates of serpentino (amorphous stone), filled with a mixture of sand and lead particles (grain). The motor was housed in a separate box of serpentino, but no filling was added.
* The total weight of the turntable was 40 kg.
* After much experimentation the suspension was on 4 heavy springs. The springs were made by a specialized manufacturer taking into account the weight of the turntable. Furthermore a specific diameter of the springs was chosen as well as the shape and the amount of torsion needed to arrive at the desired strength for the best decoupling and the fundamental resonance frequency of 5 Hz.
* Individual arm supports were machined for a variety of arms: SME Series IIIS, Micro Seiki MA505, Mission 774, etc.

The result is a turntable that reproduces the music with an uncanny silence, lowest distortion, a black background, and extremely high precision, as if the music signal originates from a studio master tape being played on a professional reel to reel tape recorder. This description is valid for all turnttables with heavy plinths which support more or less heavy platters, although there can be subtle differences between the various concepts. Even relatively cheap tonearms performed much better with the Basic Turntable.

The mention of these data is to let hobbyists know that it is quite possible to design a high quality turntable oneself.

Audio Fairs

One of the interesting things of visiting high fidelity shows is that you can learn a lot from other knowledgeable visitors, but above all from manufacturers, importers and also designers of loudspeaker systems, amplifiers, turntables, CD players, and all sorts of paraphernalia that matter. During visits to the 'Festival du Son' and 'Les Journées de la Haute Fidelité' in Paris in the late nineteen seventies and nineteen eighties, and visits to Munich in Germany (High End Association) and other places, there were always many products that would spark the interest of visitors, dealers and distributors alike and all for a variety of reasons. When visiting a show in Paris in the late 1980s, I witnessed the introduction of the Confluence loudspeakers designed by Christian Gerhards. In all of his loudspeaker designs he used passive filters with 6 dB slopes and as you know, 6 dB slopes provide phase coherence. It was possible because he carefully calculated the volume of the low-mid driver in relation to the tweeter. Remarkable was that he also made 3-way systems and he succeeded in creating a wonderful sound. Hearing his designs in conjunction with Rowland Research amplifiers was a sheer pleasure.

Extraordinary 'Mercure'

In an adjacent room another remarkable design was demonstrated: the 'Mercure' turntable ('platine tourne disque' or 'platine td' as the French say). It was an exceptional belt drive design. A basin was filled with mercury (quicksilver) and the platter was supported by this heavy liquid which has no crystal structure but a very high density. The platter had no axis, spindle and bearing housing. It was held in place by the belt which was guided via four wheels. The strong, round belt had a grip on the platter on four "sides" and thus the platter was kept well centered. The turntable was equipped with an arm which was built along the same principle: a mercury bearing. In the arm a Denon DL-103 was mounted. The amplifier was a professional Tannoy. The loudspeakers were Tannoy Dual Concentric Westminsters. The demonstration was extraordinary. The tonal balance, the absence of mechanical noise gave an uncanny realistic sound and lifelike atmosphere to the piano, drums and bass of the jazz players. The toxic mercury in the first edition was eventually replaced by oil of a certain thickness chosen in relation to the weight of the platter.

Above an edited image originally from "La Nouvelle Revue Du Son" as it also appeared in 1995 in "Het Beste uit Audiopinie".
The drawings illustrate the principle of the 'Mercure' turntable.

Mr. Yamamura and Melco

A few years earlier, in 1981, I stumbled upon the Melco turntables which were for the first time on display in Paris. I had an interesting conversation with Mr. Yamamura. With his firm Belco in London he imported these heavy turntables which boasted on platters weighing 20 kg, the same weight as the platter of the Verdier. He gave me the specifications and an image of the Melco 3560. When I showed him pictures of the Basic Turntable which I had designed and built together with Alexander Smit from Amsterdam, a fervent audio enthusiast like myself, Mr. Yamamura and I talked about the various aspects of building a turntable. In the process of building, Alexander and I had experienced all sorts of construction problems that needed solutions: damping, decoupling, mechanical and acoustical feedback, constant speed, etc. Mr. Yamamura told me that the damping of the heavy platters of the Melco turntables was achieved by applying a coat of resin to the inside of the platter. Alexander and I had used a very thin layer of bituminous sheet and carefully had put this on the inside. We were always listening to what the effect even of a minor alteration was. It became clear that by using this material, not the entire surface should be covered but that gluing four strips of a certain width brought about the desired effect, keeping the speed of the sound but at the same time eliminating the effect of a bell.

Micro Seiki

Micro Seiki proposed a similar belt drive turntable on 3 feet: RX 3000. And later also the more heavily constructed specimen and the extreme ponderous tables in the 1500, 5000, 555 and 8000 series. At right the simpler Micro RX 3000 which used the motor, pulley and speed selector of the BL-51. The platter was heavier than that of the BL-51 but did not reach the 20 kg mark as in the Melco turntables.

Mr. Iwata

Mr. Yamamura also talked to me about the idea of improving the accuracy of speed by means of a flywheel. In principle the speed accuracy could be bettered by topping the pulley of the motor with a thin and light weight but large flywheel. But since it is not advised to put extra weight on the spindles of turntable motors, the solution would be to put the flywheel which acts as a large pulley, not too far from the motor and drive it with a belt. From there a belt or thread is used for the transmission to the platter. That was exactly what I had seen in the French magazine L'Audiophile (First Series, No. 3 from 1978) where the system of Mr. Iwata of Osaka was shown. Mr. Iwata had build gigantic loudspeaker systems with 36 speaker units in the lower register and all sorts of horns for mid and treble, all driven by a multitude of valve amplifiers. The evaluation of the loudspeaker system was that it may be less correct as regards to a linear frequency response, but the listening experience was impressive and it was reported that it gave a display of a large space where performer, singer and orchestra were present in an extremely realistic way.

Flywheel

Mr. Iwata had built a heavy turntable and had used a lot of lead, at least in the platter. On top of it he had built a peculiar tonearm. The image in L'Audiophile showed that Mr. Iwata's turntable was obviously in continuous flux and had not yet reached its definitive state. Despite that the transmission of the motor led via a belt to a larger "pulley" which stabilized the speed. And from there a string drove the platter. A flywheel can have all sorts of shapes and sizes. Today this principle is incorporated in various high end designs like a few tables of VPI. It goes without saying that also for the flywheel a high quality spindle and bearing has to be used.