All the Jelco SA-750 tonearms (9″, 10″, and 12″) are ‘S’ type arms.
The effective mass of the Jelco 750D 9″ tonearm with the standard headshell but without cartridge is 13.48g.
Here is correspondence from Jelco, Haruo Uchida/Sales Manager
SA-750D effective mass is 13.48gr without cartridge( effective mass is 19.23gr with 6.5gr cartridge). We think that the higher compliance cartridge is usable to SA-750.
The standard HS-25 headshell weight is 12g. The economy HS-50 headshell weight is 9g. So it is possible to further reduce the effective mass by using the HS-50 headshell.
Jelco offers three headshell models:
- HS-25 is the premium headshell, provides azimuth adjustment, and is the included with the SA-750 tonearms. It is 12g.
- HS-20 looks similar to the HS-25 and also offers azimuth adjustment. The main difference is that the HS-25 finger lift is secured with the same bolts for the cartridge, which is an awkward design. The HS-25 finger lift is secured to the side of the headshell, making cartridge mounting much easier. The HS-20 is also sold by Sumiko as the HS-12. It is 12g.
- HS-50 is the low cost headshell with no azimuth adjustment. It is 9g.
The premium HS-25 is included with the arm. The HS-50 does not include azimuth adjustment. Both are available in tonearm accessories.
The Linn arms are normally 211mm pivot to spindle. The Jelco SA-250ST is 210mm pivot to spindle. The Jelco SA-250, SA-750D, and SA-750DB are 214mm pivot to spindle. The small difference in length can be eliminated by making a slight (+1mm or -3mm) adjustment of the cartridge position in the headshell.
Here is the complete set of specifications for the Jelco tonearms.