What about Uni Din?

Dear @lewm  : "  They are two different phenomena.. ", agree.

Löfgren A ( example. ) distortion at 139mm is 0.19% and at 75 is 0.42%.

R.

Why doesn't anyone ever mention that the whole idea of alignment by protractor is flawed since it assumes that the Zenith of the diamond is precisely 90.0°?   Zenith being skewed by 0.3° is enough to make alignment A behave as alignment B.  If your diamond Zenith is off by 1.5° it is possible that you will completely miss both null points entirely.  

dave

Its a mess this vinyl thing that we love :)
Sure most carts are a series of imperfect connections, and even with a really good protractor its hard to see everything perfectly. So in comes software. In the end these tools get us in the zone but we use our best tool to finish. Ears.

@lewm , I think if you look at phase angles with a given tracking error the phase angle difference between the left and right channels will be three times greater at the very inside of the record than at the very outside. Because the outside is traveling three times faster the peak to trough distance at a given frequency will be three times longer. This makes sense to my meager brain.
@rauliruegas , Are you saying the label edge is at 54 mm?
@intactaudio , I examine every stylus under a microscope. If it is not dead on the cartridge goes back. The beauty of the Smart Tractor over priced as it is is that is has a really nice magnifier making it significantly more accurate than the Feikert. Does it really matter? I seriously doubt it but it makes me feel better.

Can‘t you compare on your own with the Smart tractor? The new Uni din is really worth a try ... specially with high dynamic cut records ( classic originals from the 60‘s) ... I use it.