Isn’t this about setting the two null points
Far from it, from my point of view. I was trying to point out the absurd lengths audiophiles go to in order to adjust for the optimal Vertical Tracking Angle, while completely ignoring the equally important Horizontal Tracking Angle for pivoted tonearms playing stereo records.
I am open to having my argument demolished, preferably by the application of physics or engineering principles!
Simple geometry shows that for a 9-inch tonearm with a 2-degree tracking error, the adjustment required to correct the error is about 8-mm at the tonearm pivot. I was a bit surprised at my calculated result but I have triple checked it.
I’ve since found out that my calculation is supported by this hour-long video posted in another thread:.TURNTABLE SETUP BY A SCIENTIST - YouTube
He is not a fan of Rega, especially their use of one of the tonearm signal wires for grounding.
He is a great supporter of AnalogMagik Cartridge Alignment Software & Test LPs for actually measuring the critical setup variables. @billstevenson no doubt agrees! As you pointed out, there are production tolerances involved especially when you consider the microscopic dimensions of a stylus and cantilever.
Personally I am reluctant to spend significant amounts on AnalogMagik because my main deck, the Holbo air-bearing tangential tracking system, does not involve a pivoted tonearm, has a null point at every playing position, and creates near-zero skating force. It also allows VTA to be adjusted on-the-fly. I have not got around to using an oscilloscope and test record (I do have both) to do this properly.