Why use a super accurate cartridge protractor

Hi Dan_ed
The Mint Protractor you refer to,

accurate to the 2nd digit of a millimeter

does that mean to 1/100 of a mm? And what did you mean by

...aligning horizontal azimuth and effective length with any precision

This is one of my points that, while there are figures for how precise the protractors are made regarding linear dimensions, there is nothing regarding angular ones. Even in the case of the Graham jigs mentioned by Moonglum, there are no numbers, so we don't know by how much things are improved by using the jig, ie how much angular adjustment is required. Or ultimately, by how much the stylus is out of alignment on the cantilever, how much the cantilever is out of alignment with the generator, and how far that is out re the body. Of course that is a big ask...!

You are totally right regarding the rest of the adjustments - I agree that a protractor is only part of the set up process - and the other parameters can have big effects.
John
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Hi John,

Yes, I understand that to be the precision of the protractor in all regards. Maybe a good question for Yip. I assume that the lines orthogonal to the groove are drawn to the same precision by a computer.

When I align on a Mint I am not concerned at all with the orientation of the cantilever, within common sense. ;-) What I mean is that I align the stylus to the lines and not anything else. The lines, as tiny as they are, are still a bit wider than the stylus so I'm twisting ever so slightly while staying within the bounds of the line. Whether the stylus may need a bit more twist to the right or left is a pretty tough call. Perhaps this is the angle you refer to? I admit I am still at the mercy of how precisely the protractor is drawn as well as printed.

To the thread question. Even though there may not be good tools for setting all of the parameters I do find that using those that are available do indeed give me better results. I think it is possible to get just as good of results with most protractors, but I find that the extra precision does help me get repeatable results as I do switch cartridges and arms fairly often.

I read the very interesting article about cartridge setup. One critical factor mentioned is aligning the cantilever to the headshell because the cantilever was found not to be parallel to the cartridge body. So my question is, how can the cantilever alignment be gaged on an SME tonearm independent of the cartridge body?

That's easy with a mirrored protractor like the MintLp.
There are (thicker) perpendicular lines on the arc at the two null points.

Using a magnifier - and with the stylus resting precisely on the marked null point - align so the cantilever is parallel in-between the two guidlines when the latter are aligned with their mirrored reflection (thus accounting for parallax error).

Hi Tonywinsc

As Tobes says, you would have to use a mirrored protractor for the reasons he states.

For the SME 309, it should be LofgrenA/Baerwald DIN.

But importantly, it should be a TWO point protractor, not an arc, as you will have to make adjustments at the arm base rather than the headshell.

As an aside, this actually is interesting because it raises the possibility of using the SME base for measuring the variation in cantilever/cartridge body alignment. as the alteration in overhang/mounting distance for a given effective length means a specific change in offset angle. It also offers a practical way to measure typical accuracies by comparing the difference in base position for repeated setups by different users without altering the cartridge position.

The accuracy that the stylus can be positioned independently on an arc can be measured, and the variation from that position in the alignments can give a number for the offset accuracy...

Anyway, back to work...