MintLP arc protractor


I'm talking to Yip about a protractor for a Rega RB-300 mounted on a VPI HW-19 Mark III. To verify the desired 222mm spindle to pivot distance I cut a piece of cardboard 222mm in length. I measured from the spindle to the center of the armboard mounting hole. It looks to be spot on at 222mm. Is there a more accurate way to measure so that I can confirm my initial findings?

Wendell
narrod

Showing 1 response by thom_at_galibier_design

Greetings,

The problem here is that the turntable in question has already had its tonearm mounted, and save some potential play in the mounting hole, its pivot-spindle distance is fixed.

Normally, you establish a pivot-spindle distance from the effective length before mounting the tonearm, but using (for example) the Ellison spreadsheet, you can work this backwards.

So, assuming it's an accurate Rega Stevenson mount, you have a 222mm pivot to spindle distance which resolves to ~ 237mm eff. len. for Stevenson and ~239.3mm for Baerwaald.

This 2.3mm (approx.) difference is what Doug was referring to when he said you might run into problems with a "short" cantilever - meaning a cartridge whose stylus is positioned considerably closer to the mounting bolts than the 9.0mm statistical norm.

There's a potential for your not being able to slide the cartridge forward enough in the headshell slots to achieve the 239.3mm effective length. This is why Yip is being so persnickety.

As Johnbrown wisely suggests, you can do a proof of concept by printing out a Hoffman protractor. This will set your mind at ease.

Cheers,
Thom @ Galibier