How best to eliminate LP warps

Actually, this whole discussion leads me to the conclusion that we are chasing a ghost. As @optimize notes, there are irregularities in LP manufacturing, whereas we are treating the LP as identical precision instruments that just need to be set up via the cartridge.

Instead, we should be looking for a tonearm that can be easily and finely adjusted on the fly to suit each LP as it is played. Preferably, the tonearm should have a precise measuring system built into it’s adjustment mechanism, so that these numbers can be noted on the record sleeve, and the adjustment made in two or three seconds prior to each play.

And, of course, we should remove warps and dishes from the equation, coming back to Lewm's point.

All of this discussion about azimuth involving USB microscopes, test disks, oscilloscopes, Fozgometers, hour glasses, adjustment for each disk and such leaves me LOL. Better to put more faith in one’s hearing.

Assuming you have easy adjustment for azimuth, and if your stylus is symmetrically placed, adjust roughly for level by matching your cartridge parallel to its reflection on a disk. It doesn’t take much of an eye too get very close. Use a flashlight and/or thin mirror if that helps. If the stylus is a bit crooked, use a mirror and do the best you can to have the stylus as vertical as possible.

Then put on your disk with the best, widest, soundstage in your collection. Listen carefully as you adjust azimuth just a bit, first one way than the other. If the soundstage widens, continue slowly in that direction. If it doesn’t widen you’re done. If it does widen continue in that direction to the max soundstage.

it's scary to see your expensive cartridge and stylus on a badly warped record.

@terry9 , we already established that the two channels can have very different cross talks. (Peter Ledermann) So, by taking measurements you can assure that your stylus is digging into your records. If you want to do it this way then confirm it with a visual inspection, OK. I think it is a waste of time and money. Money that would be better spent on a USB microscope.

@melm , you are a little late with that idea but you are right on except with a good eye you are far more accurate visually than your hearing. If it make you happy.

I have made recordings with the arm set up correctly and with the stylus 2 degrees off and no one can reliably identify the right set up switching back and forth.