Alignment tool for SME V + Shelter

Dear Dan, If this is the answer to my question then we have
the problem that one can move the arm in relation to the spindle-pivot distance as well as move the cart in relation to the 'slots' on the heashell. With 2 moving dimensiona I am not sure about the result.BTW the slots are
to provide for the distance between the stylus-tip and the fastening bolts because this distance differ by carts.Or so
I thought. I am not a technical guy but I know that the spindle-pivot distance is fundamental.
Regards,

"P2s and effective length are not dependent on the cartridge used." True. They are instead dependent on the tonearm design and must not be changed. Providing slotted headshell mounting holes therefore allows mounting the cartridge so the exact stylus-to-pivot distance required by the manufacturer can be set, regardless of the cartridge's stylus-to-mounting hole dimension. So with (most) arms you need to be able to adjust the fore/aft position of the cartridge in the headshell. The spindle-to-pivot distance is also specified by the tonearm manufacturer/designer and combined with the specified EAL (effective arm length) provides the correct arm geometry.

Nandric: "BTW the slots are to provide for the distance between the stylus-tip and the fastening bolts because this distance differ by carts. Or so I thought." That is not correct. The slots are to allow one to shift the cartridge fore or aft until the stylus tip is the PROPER DISTANCE FROM THE ARM PIVOT ;-) That distance is called the 'effective arm length', and is pre-determined by the tonearm designer.

Hello again. I realized that with the SME slide mount you can set effective length easily. I suggest people draw themselves a picture so that the relationships between these distances become clear.

Also, I suggest researching arc-style protractors. It is not necessary to check p2s every time you check cartridge alignment because the arc is drawn at the correct effective length and the arc is registered properly by the spindle hole.

Another advantage is that with this type of protractor everything is fixed in place, platter, protractor, etc., so there is no moving of the protractor (ala DB) while you are trying to hit a gnat's ass with the stylus.

Dan, the SME slide mount moves the entire tonearm (pivot and all) back and forth, pretty much toward or away from the spindle. Moving this carriage does not change the arm length, which on an SME is 233mm from pivot to the tip of the stylus (of a cartridge with standard stylus-to-mounting hole dimensions.)

Because of the fixed cartridge mounting holes, the arm length of an SME (and pretty much ONLY an SME) wiil increase/decrease by however much more or less the stylus-to-cartridge-mounting-hole dimension deviates from the standard. I.e., if the stylus is forward of the cartridge mounting holes say 2mm more than standard, the the effective length of the SME arm will be 235mm, not 233mm. It's not a disaster though, because you simply have to increase the overhang a tiny amount (according to a chart) and everything goes back into proper relationship.

Personally, I'd advise anyone using an SME IV or V to use cartridges with standard stylus-to-mounting hole dimensions. It makes life easier and still leaves a zillion cartridges to choose from ;-).

Setting up proper SME arm geometry involves two steps:
1,) checking/setting the stylus overhang (using the sliding carriage base), and
2.) adjusting the cartridge horizontally to align with the gridlines of a DB (or other conventional protractor) at the two null points (there's enough play in the mounting holes to allow this adjustment.) And that's it ;-)

Nsgarch, I hope you get the chance to try an arc-protractor and even better, a MintLp protractor. A good look and it is easy to see why there are much better tools available. Whatever works for you. :-)