Question concerning the Mint Tractor

I don't understand how changing VTA would alter/affect the Best Tractor's alignment.

Tvad, kindly bear with my somewhat leaden prose as I try to walk through it.

As an example, imagine changing SRA/VTA by moving the post of the tonearm up or down. Imagine the center of the arm's pivot fixed at the center of the post. (Some tonearms do not match this hypothetical.) Imagine the cartridge is correctly aligned to some known standard such as Baerwald.

Start with the stylus at a 90 degree angle to the horizontal plane of the record and the tonearm happens to be parallel to the record. Mentally put a stake in the exact spot where the stylus point sits.

Now, raise the arm on its post, which causes its pivot point to raise. The distance from the pivot to the stake has increased - the 'effective distance' (Pivot-to-Spindle + Overhang relative to stake) - has increased.

The length of the arm is fixed, so something has to give. The stylus point does not simply pivot at the point of the stake - it is moved/pulled rearward from the spot marked by the stake as the arm is raised. This changes its effective length relative to the presumably correct alignment marked by the stake, and thus changes alignment. Its not protractor specific.

The smaller the VTA change, the smaller the change to effective length, so whether a VTA change is worth a new alignment is up to your ears.

I think that's right.
 
Tim
 

Tim's geometry clarification was excellent.

In addition, changing VTA on most arms alters VTF, so the cantilever wouldn't be sitting at the same angle as it does during play.

True observation, Tvad. Overhang will surely change every time one plays an LP differing in height from the Mint (or whatever protractor was used).

Adjusting VTA/SRA is indeed an inexact science, but fortunately it's a very exact art. :-) We adjust by ear, for every record. Accurate sound is the goal. Accurate geometry is just a means to that end.

FWIW, most of our VTA adjustments are far less than the thickness of any mat, less than a sheet of paper even. I've posted it a zillion times and everyone thinks we're crazed - until they visit and hear the difference for themselves. Ask Dan_Ed or Swampwalker or Raul. They've all watched me raise or lower the arm by a hair's thickness and heard the sound snap into focus.

Whether its worth the effort is up to each of us of course, but for me it's become second nature and takes literally no playing time. We record the height for each LP so replay setups are instant.

Thom and others have suggested that Paul and I may become less particular about this after Mint-ing. That hasn't happened and isn't likely too. Why should improved stylus alignment in one plane encourage sloppiness in another? My lazy backside understands the appeal, but my ears don't.