Jun 222010

A Short History of Early Ortofon Pick-Up Cartridges

Research by Barry.D.Hunt


The Ortofon company started life as ‘Fonofilm A/S’, founded in 1918 in Copenhagen by Arnold Poulson and Axel Peterson [1], initially manufacturing equipment for the film industry. There were many groups around the world, noteably in America and Europe, all working on the development of sound-on-film. In 1919, the same year that DeForest (inventor of the triode valve) received his first (US) patents in the field, three German inventors patented the ‘Tri-Ergon’ sound system. The Tri-Ergon group gave, on 17 September 1922, a public screening of sound-on-film productions before an invited audience. By the end of the decade, Tri-Ergon would be the dominant European sound system.

In 1923, Arnold Poulsen and Axel Petersen, patented a system in which sound was recorded on a separate filmstrip running parallel with the image reel. Gaumont would license and briefly put the technology to commercial use under the name ‘Cinéphone’ [2]. In America a joint venture between the Fox film company and Western Electric (Westrex) lead to the development of the variable-area (later the stereo variable-area) sound-on-film recording system. In 1926, Fox purchased the North American rights to the Tri-Ergon system, though the company found it inferior to the Movietone system and it was virtually impossible to integrate the two different systems to advantage. Because of this, both the Tri-Ergon and Cinéphone systems gave way to the Westrex system.

In 1948 Fonofilm introduced the first monophonic moving coil pickup: the model AB. The technology for this pickup was derived from the cutter head that the company had previously developed in 1945. Ortofon also designed a rudimentary arm to be used with the Model AB cartridge. The cartridge connections consisted of two long pins that emerged from a short cylindrical stub, moulded as part of the pickup housing. The pickup simply plugged into the arm and the stub clamped by a simple collet.

The Model C

The model AB shortly evolved into the model A and model C monophonic moving coil pickups, both having a revised design of the arm coupling arrangement. Models A and C differed in the tracking weight used: the model A, intended for domestic consumers, needed a 7 gram tracking weight; whilst the model C intended for professionals, used a lower tracking weight of 3 gram. These cartridges were unique in having an extended high frequency response of around 20kHz.

At some point during this period, Fonofilm changed their name to ‘Ortofon’, (from the Greek: orthos, pure or correct + phonos, sound). Early cartridges were marked Fonofilm on the bottom rather than Ortofon (sometimes the Ortofon name is on the top of the cartridge). Ortofon supplied their monophonic cartridges to the broadcasting industry and in particular to the German company EMT. At that time EMT had no arm design of their own. To allow the cartridges to be used with the EMT 927 deck, Ortofon supplied their model RF927 (and later the RF229) arm that was designed to couple to the Model A and Model C cartridges. The coupling for this arm used a cylindrical stub with a radial alignment pin drawn in by a helical groove on the inside of a collar, which could freely rotate about the end of the arm tube. This is similar to the EIA (or SME) style used today. The contacts used two studs arranged along the stub diameter, horizontal, that is, parallel to the record surface.

SPU series

In 1957 Ortofon introduced a moving coil stereo cutter head and followed this in 1958 with the introduction of the “Stereo Pick-Up” or SPU, designed by Robert Gudmandsen. Initially Ortofon supplied these new cartridges in the Type A headshell, designed to be used in their own RMA pickup arm, to broadcast turntable manufacturers, including EMT. Being a two-channel device, an extra set of contacts was necessary, these being arranged at right angles, or vertically, to those used for monophonic heads. This configuration followed that employed by Neumann in their DST 62 head. EMT has continued to use this Neumann, or ‘diamond’, contact configuration almost uniquely amongst pickup arm manufacturers.

The SPU series, had the following specification:

Frequency response: 20 –20,000 Hz
Channel separation: better than 20dB
Compliance: 10cu

SPU generators mounted in Ortofon’s Type A headshell were denoted SPU-A, and if fitted with an elliptical stylus SPU-AE. An example is shown below.

Ortofon later made a different version of their arm to take what they called the type G headshell. This headshell was a larger (22mm longer), ‘whale’-shaped design that could take not only Ortofon’s own cartridges but also other, larger cartridges. Ortofon arms using the type G headshell were referred to as RMG arms, to distinguish them from the RMA arms designed for the Type A headshell. At that time they also changed the contact arrangement to the ‘square’ configuration used today (somewhat confusingly, the RMA arms supplied to EMT continued to employ the ‘diamond’ configuration). The pattern of the type G headshell was adopted by SME when they developed their arm. Owing to the wide acceptance of the SME arms, the headshell- arm coupling arrangement designed by Ortofon, is now more commonly referred to as an SME bayonet coupling.

Comparison of an SME / Ortofon Type G headshell (left) with the Ortofon Type A headshell (right). Photo. T. Schick

Cartridges mounted in Ortofon’s own shell would have a suffix ‘G’ attached: SPU-G. Alternatively the cartridges could be fitted into the users own headshell. The larger dimensions of the G-type shell allowed Ortofon to supply versions of the SPU with built-in step-up transformers; the assembly would have a suffix ‘T’ attached: SPU-T. The Danish company Joergen Scheu made these transformers for Ortofon. SPU versions incorporating the transformer and fitted into the type G headshell were referred to as SPU-GT, and if an elliptical stylus was used, the SPU-GTE.

Regardless of whether the transformer was fitted or not, SPU cartridges fitted into G shells were weighted to an identical 32g, to preserve the same value of effective mass and therefore resonant frequency and maintain compatibility.

Some photographs of SPU are shown below.


Ortofon SPU without integral transformer fitted with an elliptical stylus and mounted in a Bakelite Ortofon type G headshell.


Ortofon SPU (with elliptical stylus) fitted into the Ortofon headshell with an integral transformer. Note the (silver plated) ‘spring’ connections between the transformer secondary windings and the contact pins of the headshell. Ortofon claimed that this technique ‘reduced undesirable resonance’ (?)

The S 15 series

The S 15 series of cartridges were designed in the mid ‘60s and were based on the SPU. There were two versions: the S 15-T with an integral transformer, weighing 18.5g; and the ‘lightweight’ version without transformer, the SL 15, weighing 7g.

Either version could be supplied fitted with a 17um conical stylus. To distinguish these versions from those fitted with 17um x 8um elliptical styli, the latter would later have the suffix ‘E’ attached to their designation.

When fitted into the Ortofon type G headshell, (and confusingly called the S-15MT), the total mass of the S-15MT combination was 29.5g. This total mass could well have been chosen deliberately, if such a combination was intended for broadcast use. Assuming that SPU-Gs were already in use and tracking at 4g (not unusual at the time to ensure secure tracking), then in the event of an emergency failure, direct replacement of the SPU-G with an S-15MT would allow the latter to track at a recommended 1.5g.

Both the S15-T and SL15 had improved channel separation and compliance figures over that of the SPU. When introduced they were both more expensive than the SPU.

Data sheet courtesy of W. Cowen.

S15-T cartridge

The S15-T had an integral transformer that had a voltage gain of 80 (38dB). The SL15 used a separate out board transformer supplied with flying cable ends (‘kabelübertrager’) to be installed between the pickup output leads and the preamplifier. Ortofon marketed such a device the ‘2-15K transformer’, so called as it was designed to match the 2Ohm coil impedance of the SL15 to a notional 15KOhm of the RIAA equalising amplifier.


An S15-T cartridge mounted in an SME S2 headshell is shown below.


Ortofon SL15E (Photo. W. Cowen)

According to the manufacturer’s specification, the SL15 had a higher compliance (25cu) compared with the S15-T (20cu). This suggests that in the lightweight version there is a change to the suspension.

A high output voltage version of the SL15 was made available, called the SL15ELL. This had an output of 0.125mV with a coil resistance of 6 Ohm, suggesting that the higher output was obtained by increasing the number of turns in the coils. It tracked at 1.5-2.0g.

Ortofon SL15ELL (Photo. W. Cowen)


The SL15 and SL15E gained rapid acceptance, evolving through to mark II versions. Changes appear to have been made to the coil design. There is a reduction of output voltage to 0.015mV/ (cm/sec) and an increase in coil resistance to 2.5 Ohm. The SL15 II was fitted with a 15um conical stylus. There also appears to have been a change in the stylus rake angle to 20 degree. The 2-15K transformers were replaced with the STM-72, offering a step up ratio of 100 (40dB).

A ‘flip down’ stylus guard was fitted to the Mark II version of the SL15. This feature was retained on all subsequent designs up the MC30 II. The stylus guard is easily removed should there be concern over its presence causing unwanted audio resonances.

SL20 Series

Later there were versions called the SL20 and SL20E (presumably acknowledging the revised international cutting standard of 20 degree) and finally a version intended for quadraphonic use: the SL20Q. The SL20 series used square pole pieces, claimed to improve linearity.

The next generation of Ortofon moving coil cartridges starts with the MC20, then MC30 and MC25 (and its variants). These may be regarded as coming from the ‘middle’ period, and as such marks a convenient place with which to finish.


Although the S15-T design superceded the SPU, Ortofon continue to produce the SPU in small quantities (at the time of writing this article in 2010) and still in Ortofon’s factory in Denmark.  Modern SPUs are now available in a variety of variations, with a choice of stylus profile and coil material (see the Ortofon websitehttp://www.ortofon.com for details). The stylus rake angle is now 20 degrees. The majority come fitted into the type G headshell. None of them have an integrated transformer; so are best described as SPU-G and SPU-GE.

Modern SPUs may be distinguished from early samples by the colour of the plastic plate on the underside of the cartridge: original samples have a grey plate, on modern samples this is black (as shown in the photograph of an SPU-GE above). There is also a change in the badge on the top of the cartridge: early samples have the name ‘Ortofon’ written in a silver script font on a black background, modern samples have the name in black san-serif font on a silver or gold (depending on variant) background. All versions have a similar mass as the original: 32g [3]. Since they now come without the integral transformer, the mass is made up by a mounting block or weight fitted between the generator and the headshell. In early samples this weight is brass, in modern samples the weight is a silver colour (most likely nickel-plated brass).

A version of the SPU is still available fitted into the old Type A headshell. As can be seen from the photograph below this can be distinguished by the badge: black san-serif lettering on a gold background, as well as a gold-plated finger lift and arm mounting stub.

Notes and web links

[1] The names Poulson and Peterson are also spelt Poulsen and Petersen

[2] Crafton, Donald (1997). ‘The Talkies: American Cinema’s Transition to Sound, 1926–1931’, New York: Charles Scribner’s Sons, ISBN 0-684-19585-2, pp. 419 – 420.

and Crisp, Colin G. (1997). ‘The Classic French Cinema, 1930–1960’, Bloomington/London, Indiana University Press/I. B. Tauris, ISBN 0-253-21115-8, pp.97 -98.

[3] Depending on the exact variant, the mass is either 30g or 33g. See the web site below for details. It is not known why Ortofon did not maintain the original weight of 32g.

This is the offcial Ortofon web site.

This is a (difficult to read) review of the S15-T carried out by the Gramophone Magazine, October 1966, p. 125.

© Text Copyright 2010 Barry Hunt.

© Copyright of photos used in this article belong to the original named owners.

This article is republished here with the kind permission of the Author and the Art Of Sound Library (a historical audio data base, which can be accessed if you are a member of the Art of Sound Forum http://theartofsound.net/forum/index.php) The quality of material therein is of a very high standard and it is well worth joining to be able to read it and then take part in the general forum as well.


NB No part or portion of this article may be reproduced or quoted without written permission.

 Posted by at 9:46 am


  1. Hi there,

    A very nice article but I’m afraid you’re incorrect about SPU cartridges.

    They are still made in Denmark and will never be made elsewhere.

    SPUs are considered the “heart blood” of Ortofon and the Danish audio culture, and the designs will never be licensed out nor will they ever be produced outside of Denmark.

  2. Hi Dee

    The article was written by one of my contributors, so I will pass the info on and have it revised.

    Thank you for your comment.

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