For the later SL-15E Ortofon developped a smaller and more affordable transformer, type STM 72 with a frequency range from 20 - 50.000 Hz., pick up impedance 2 Ohms, and load impedance 10 - 15 kOhm. The coils were double screened with mu-metal. This transformer could also be used with the MC20 and MC10.

Although Garrard was a big name in turntables, the company never made a great effort to conquer the hearts of the music lovers with a cartridge line. And if they manufactured a few cartridges or had a few made by other manufacturers and put their name on them, the impression is that this concerned ceramic or crystal pick ups.

Some may be surprised to know that Garrard did market a moving coil design, GMC5. It was a mono turnover design capable of reading 78 rpm shellac and vinyl Lp records. The frequency response was 20 to 16.000 Hz. The cartridge was meant for mounting in the TPA-10 transcription arm. The low compliance of 6 x 10-6 cm/dyne was of course in accordance with the heavy mass of that arm. This combination made it necessary to apply a down force of 5 gr. The transformer to which the GMC5 was to be connected should have a load impedance of 500 Ohm.

The GMC5 was reviewed in conjunction with the TPA10 tonearm in the May 1957 issue of the monthly magazine "The Gramophone". The reviewer was Percy Wilson. This is what he said about the GMC5:

"This is virtually two complete moving coil pickups placed back to back as to give a turnover arrangement. Each moving coil is operated by its stylus through a cantilever which has appreciable vertical compliance to deal with "pinch effect" and avoid "needle chatter".

Percy Wilson praised the skill of the engineers who succeeded in constructing this turnover design, but saw also the downside of it: a heavy cartridge.

This is the Garrard TPA12 tonearm which adorns the 4HF and 5HF motor decks and portable gramophones and the Type A record changer. Stylus pressure was adjusted by turning a wheel positioned at the rear end of the arm. In other versions adjustment was done by turning a bolt instead of a wheel.

The TPA 10 was a more sophisticated arm, although it too was of the rather heavy type. This most certainly had to do with Garrard's own GMC cartridge and probably also with the heavier Decca and Tannoy cartridges which were in use in Geat Britain at the time. The TPA-10 could be changed in length and the offset angle could be adjusted accordingly. This in order to achieve the least lateral tracking error. Unscrewing and tightening the large bolt made this possible. This adjustment was necessary if the (effective) length of the arm was changed. Only of course if the turntable base did permit the positioning of the arm's pivot somewhat further away from the spindle. This arm was specifically designed for the Garrard 301 turntable.

Note: Stylus pressure was adjusted by turning a small wheel (screw) positioned on the inside of the arm base, rather than by turning a wheel as in the case of the simpler TPA-12. When the Garrard 401 motor unit was introduced in 1964, six years into the stereo era, then other arms, like SME and Ortofon, were used.

In the early stereo days, some odd, but very remarkable designs were introduced. One of these were the moving iron cartridges made by Decca Special Products. The design was derived from the earlier cartridges in the Series 4, developed in the mono era.
The first stereo cartridges were designed especially for playing the new Decca Full Frequency Stereo Sound recordings (FFSS). The later Garrott versions were Deccas, modified by the Garrot Brothers in Australia. Aalt Jouk van den Hul re-tipped several Decca Gold cartridges with a long, nude version of the special Van Den Hul tip.

Different

The engineers of Decca followed a completely different track than Ortofon (MC), Shure (MM) and Garrard of course. Knowing that the signal will deteriorate somewhat if a long cantilever is used, they devised a way to practically retrieve the signal just above the groove. To achieve this, the Decca engineers positioned the generator (coils and magnets) as close to the surface of the record as possible, only leaving the necessary room for the diamond tip, but not more than approximately one millimeter but always in such a way to prevent the housing from touching the groove guard or the record's surface.
The first cartridges were mono cartridges with one coil.

Did Ortofon connect a long vertical coil to the cantilever to move in between the poles of a magnet, and did Shure connect a tiny magnet to the end of the cantilever to move in between coils, Decca's men choose as generator a piece of iron to move between magnetic poles close to or within a fixed coil. They choose for this concept right from the start when they designed their first ffss cartridge.
They gave the iron piece an angled shape. Slight flexing was possible in both the horizontal and the vertical plane. By clamping the rear end in a block, it stayed firmly in place to guarantee a correct azimuth at all instances (if the cartridge had been precisely adjusted in the arm in the first place).
In that way they avoided the small piece of rubber that in MM and MC cartridges constitutes the pivot and at the same time functions as a damper to control the movements and resonances of the cantilever and its tip and of the coils wound on the tiny core. It is this rubber that greatly influences the signal and is responsible for a certain weakness in the lower mid region. If this small piece of rubber can be left out, than the signal can be as pure as it possibly can be.

Note: There is just a very thin piece of rubber glued on the horizontal part of the iron. This is to prevent that the tie back cord pulls the iron against the horizontal coil when the diamond tip is not in the groove, i.c. is not scanning. But it is not altering or deteriorating the signal.
The early Deccas generated some hum if the coils are close to iron platters and in case the motors were not well screened off.
The Decca engineers did master this problem. They also looked for better magnetic materials and they made the armature extremely stable by forming it and cooling it at - 196 degrees Celsius. They even lowered the weight of the cartridge to a mere 4 grams, which extremely low.

Hysteresis

There is a second aspect of great importance. The core of the coils in a Moving Coil Cartridge should be very light. Problems occur when thin and light pieces of metal are used for the core. The downside of this is that it will have hysteresis, which means that the coil interacts with the core and will become a motor with a changing hysteresis and the subsequent distortion (though minute) which has a changing and unwanted effect on the signal. Hence in a few designs of some manufacturers a tiny plastic cross was used on which the coil wire was wound.
Cartridges with moving magnets do not have this problem but show other weak points. A moving iron cartridge just makes use of the effect which a piece of iron in a coil has.