Question concerning the Mint Tractor

In case anybody wonders how I got the offset number:

• I modeled a hypothetical tonearm of 240mm in effective length.
• I marked a point where the stylus meets the record with the VTA being horizontal to the record plane.
• Another plane was added, which is 1mm higher than the original setup. This new plane represents a thicker record.
• I then measured the vertical projection of the stylus sitting on the plane that is 1mm higher.
• The overhand is now longer by 0.032485mm without VTA correction.

I don't know how relevant this number is in reference to distortion. This offset probably won't affect the sound much, but it will increase as the VTA increases or decreases from the original overhand setup using the arc protractor.

There is an excel file in this link at the bottom of the page. One can use it to verify distortion in reference to overhang.

http://www.enjoythemusic.com/freestuff.htm

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
 

I see, Tim. Thanks.

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.

If per Tim's explanation raising or lowering VTA changes overhang, as does
raising or lowering the stylus according to the thickness of an LP, then it
seems to me overhang changes a fraction every time a record is played with
thickness different than the Mint LP protractor. Adjusting VTA to compensate
for record thickness is an inexact science. After all, how is one to set perfect
overhang for each record with the precision of the Mint LP Best tractor?
According to the geometry, it's impossible.

Perhaps, the solution is to use the Mint LP Best tractor with a thin platter mat (or
a few stacked CDs, etc...), so the total height of the Mint LP+thin mat equals the
total height of a "standard" thickness LP+one's favorite platter mat. This would
eliminate one variable in the geometry if one could get the two heights
equal.