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Thread: A short history of early Ortofon pickups

  1. #1
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    Default A short history of early Ortofon pickups

    A short history of early Ortofon pick-up cartridges


    History

    The Ortofon company started life as ‘Fonofilm A/S’, founded in 1918 by Arnold Poulson and Axel Peterson, initially manufacturing equipment for the film industry. In 1948 they 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.



    Ortofon Model C monophonic pickup fitted with a coupling stub designed to be used with the Ortofon RF297 arm. Photo. R. A. Bruil

    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 EMT. At that time EMT had no arm. 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



    The photograph (by R. A. Bruil) above shows the generator assembly of an early Ortofon SPU cartridge. A later version is shown below. Note that at this time the distance between stylus tip and cartridge mounting points had not been standardised, hence the two sets of fixing holes.


    Photo. R. A. Bruil


    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) 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 Shou 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.


    Photo by R. A. Bruil.

    The photo above shows an SPU-T with elliptical stylus (and so has the suffix ‘E’ attached: SPU-TE) fitted into, what looks like, an SME S3 headshell.

    Some photographs of SPU are shown below.

    SPU-GE



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

    SPU-GTE



    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.



    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.


    S-15MT






    An ST-15 cartridge mounted in an SME S2 headshell is shown below.




    According to the manufacture’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.


    SL15E

    Ortofon SL15E (Photo. W. Cowen)

    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 elevated output was obtained by increasing the number of turns in the coils. It tracked at 1.5-2.0g.


    Ortofon SL15ELL (Photo. W. Cowen)


    SL15 II

    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.
    Last edited by Dalek Supreme D L; 20-04-2009 at 10:06. Reason: Replacing old item with new as per Barry D Hunt's request.

  2. #2
    Join Date: May 2008

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    Wow. Another fantastic write-up Barry. Thank you very much for sharing this. I find this sort of feature fascinating. It's items like this that would be excellent to save and make visible within the AOS Library, which is a little reference area we hope to get off the ground in the near future. As long as Neil doesn't mind sharing it as 'Strokes Of Genius' mod
    Nick
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  3. #3
    Join Date: Nov 2008

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    NO Nick, I don't mind sharing it. I agree an item like this should be in SOG and in the library as well. As long as thats okay with Barry ?

    Well done Barry no more photo problems now. Well worth the slight wait and what an excellent write up. I am glad you choose to join AOS, its information like this that makes AOS so unlike the 2D light weight stuff you mostly get elsewhere.


    Regards D S D L
    Last edited by Dalek Supreme D L; 10-04-2009 at 09:27.
    Regards Neil

  4. #4
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    Great stuff Barry. Very interesting, very informative and stunning pics.

    Many thanks,
    David

  5. #5
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    There once was a time when SL15E's were being traded in or chucked away for the latest model. SPU's were fairly cheap and judged not good on tracking modern vinyl, probably because the arms weren't solid enough... Of course now, even SL15e's go for over a ton in half decent condition.
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  6. #6
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    Nice write-up Barry

    The SL15-ELL shown has different specs to the SL15,
    the output is 0.125mv, output imp. 6ohms
    and stylus pressure is 1.5-2.00 grams.

  7. #7
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    The level of knowledge and interest some people have in this hobby never ceases to amaze me. I do not have a decent T/T and I still found the write up very interesting, many thanks Barry!
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  8. #8
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    Quote Originally Posted by aquapiranha View Post
    The level of knowledge and interest some people have in this hobby never ceases to amaze me. I do not have a decent T/T and I still found the write up very interesting, many thanks Barry!
    Thats because you don't get out very often

    Nice article Barry,you must be thirsty after all that work,have a drink on me
    Paul

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  9. #9
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    Quote Originally Posted by Dalek Supreme D L View Post
    NO Nick, I don't mind sharing it. I agree an item like this should be in SOG and in the library as well. As long as thats okay with Barry ?

    Regards D S D L
    First of all apologies for the tardy reply - I have been away from my PC over Easter and have only now returned.

    I am glad that you all seem to have found it interesting and thank you for the words of appreciation. One of my interests, apart from actually using music reproducing equipment, is finding out about the history behind some of the more famous or landmark items that have been, or are still being, used. In the present case I have to thank Will for his posting on the sale of his SL15E. This started me looking at the, then contemporary, S-15E, and I'm afraid I got a bit caught up with it all.

    As to the posting being included in the 'Library' - well I have no real objections, however the piece is not definitive and on re-reading contains some small errors, factual as well as grammatical. I would be happier if, Neil you could let me re-edit the piece (is this allowed / possible?)

    Finally Will, thanks for that information. It was new to me. The photo was the best (sharpest) I could find of an SL15, though I would have preferred a shot of the front showing the 'script' Ortofon logo. I was puzzelled by the reference to high output. You have now explained this; looks like Ortofon increased the number of turns on the coils to provide the higher output. If you are agreeable, I'll include this information in a re-edited posting.

    Regards

    Barry

  10. #10
    Join Date: Nov 2008

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    Hi Barry

    No problem if you want to re submit the item with new bits or tell me where you want the new edits to go in the old version and I can do it. However the best and cleanest way is if you resubmit the full finished piece (with new bits in place as you want them ) and I can cut and paste it into the spot left by the old and remove the old totally and cleanly leaving the final finished item.

    Ring me when you want to do this and you can let me know which way and I will do it for you. Not tonight though as I am of to bed now. I will be at home tomorrow from 11.30am onwards.


    Regards D S D L
    Last edited by Dalek Supreme D L; 14-04-2009 at 23:36.
    Regards Neil

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