Originally Posted by
Barry
The Mk. I SME used a very thick bedplate as well as 'tall' locking nuts, compared with those parts of the Mk. II arms. The Mk. I also had a very wide adjustment of azimuth, allowing the headshell socket to be rotated at least 45 degrees so that EMT/Neumann cartridges could be used. The Mk. I's also used a different 5-way connector at the arm base, whereas the Mk. IIs used a modified 4-way Belling & Lee 'Unitor' connector.
In those days, there was no standardisation of the position of the stylus relative the to cartridge fixing. So the designation 9" or 12" was only notional. The original SME arm was designed by ARA for his own use and with Ortofon SPUs in mind (that is why SME adopted Ortofon's headshell coupling, and originally the arm was sold without a headshell; that came later as an optional extra), the effective arm length was not quoted at all. Likewise the spindle to pivot distance was only nominal because this distance is adjusted to achieve the desired overhang, where again in those days, the only concern was to achieve a null-point at the end of a 12" diameter record, to try and minimise end of side distortion.