Hi Giovanni,

Uhm... which is the SM309 tonearm mass, anyway? I can't find that.
I think the effective mass of the 309 is around 10.5-11g, so it's certainly not a high-mass tonearm. It'll definitely need plenty of added mass on the headshell to work properly with a DL-103SA, but aside from that, it should make for a decent combination.

So my final question is:
the DL 103 SA fits, mechanically speaking, the SME 309 ?
Has anyone around ever tested that combo?
To be brutally honest, I wouldn't choose any modern SME arm to use with a DL-103, as in my opinion they work best on classic 'S'-shaped tonearms with detachable headshells, where one can then use something really high-mass, (such as the Ortofon or FR headshell I use), without the need for spacers.

I'm not a fan of using spacers, unless absolutely necessary, as they alter the resonant behaviour of the headshell (and arm). It's far better, in my experience, to have, say, a 17.5g headshell designed that way in the first place, than a 10g one 'modified' with a 7.5g spacer, if you see my meaning.....

The important question I'd ask you is if the DL-103SA is going to be your cartridge of choice for some time, and if it is, then you should buy a Jelco SA-750, as that's the best modern tonearm for any DL-103.

If, however, you're intending to use other cartridges in the near future, then the SME would be more flexible in that respect. A DL-304, for example, would work better on the 309 than on the Jelco.

Basically, it boils down to what your future intentions are, cartridge-wise

Marco.