Fine-tuning the tonearm anti-skating.
For those who prefer theory, here's a response from SoundSmith stylus manufacturer Peter Ledermann.
Make sure the anti-skating is set correctly; there are many ways to check this, but we wholeheartedly endorse Frank Schroeder's method. Note: it may not match, or work at all, with test records designed for anti-skating adjustments. Frank Schroeder's reasoning is as follows: the level of anti-skating used should create equal pressure on each groove wall for the MOST of the record. Since this force depends on the level of modulation (how loud the music is recorded on the disc), setting it "to maximum" for the "loudest passage" is completely inappropriate. It's better to ensure equal pressure on the groove walls where 80-90% of the musical information is concentrated (and these are recorded with approximately 30-40% modulation); this makes much more sense for both listening and wear. When you've adjusted everything correctly, the tonearm will move along the SMOOTH SURFACE of the record (not in the groove) near the label, where the runout groove is, slowly INWARDS TOWARDS THE CENTER; MUCH SLOWER than if the stylus were simply following the runout groove. If you've achieved this, then the best average anti-skating is set correctly.
The following information is useful, but not exhaustive. With a cartridge with medium to high compliance (most MC cartridges don't), LOOK at the cantilever position: when it's in the air, and when it's on the record: both at the beginning and end of the record. Look for changes in position both initially when seated and after 1-2 minutes. If you do this BEFORE the adjustments described above, you'll get a general idea of whether you have anti-skating problems. The cantilever shouldn't change position; If this happens, your anti-skating is WRONG. But the best way to determine this is to observe how the cartridge behaves on a flat surface, as described above.
DETAILS...
Almost always, turntables are set up so that they have too much anti-skating, or they have an adjustment that can't be turned down properly, or the adjustment range and fine control are terrible, or you have none at all.
Typically, people use too much anti-skating, as evidenced by the thousands of cartridges I've restored over the past 40+ years: typically, the outer (right) side of the diamond (right channel) is worn much more than the inner (left channel).
Properly designed anti-skating is nonlinear, as it should, of course, automatically increase as the cartridge approaches the inner grooves. Frank Schroeder and I share this opinion, and therefore consider MOST records with a track for adjusting anti-skating to be incorrect: they are recorded with modulation levels of around 80-90% or even HIGHER – and yet you are asked to set the anti-skating strength so that there is no distortion (or so that it is equal in both channels if the cartridge tracks poorly).
The problem with these tracks is that, since the required anti-skating strength depends on the amount of modulation, they force you to adjust the anti-skating level too high. This would be fine if you were listening to music that, by its nature, constantly builds to maximum crescendo, without the usual musical dynamics, i.e., transitions from loud to soft. But very few pieces of music sound like this. When you tune at this level using a "test record," it means you're greatly "overcompensating" with a large amount of anti-skating, as you're setting it to a level that's EXTREMELY rare in your recordings. Typically, modulation is around 30-40%, and adjusting the anti-skating using these "test" records leads to an "overdose": the stylus applies too much pressure to the right channel and too little to the left.
Since there's no properly recorded track yet that would allow for proper anti-skating adjustments, the method Frank Schroeder discovered through careful reverse engineering works without tools or a special record.
If you place the stylus on the smooth surface of the record (at the end, between the grooves), the tip of the stylus will experience resistance on the surface similar to what it would experience if it were in the groove. This involves calculating the "force per unit area" taking into account vinyl rheology.
It's safe to say that this resistance is SIMILAR ENOUGH for the method to work well. Especially since it was developed and calibrated by Frank Schroeder specifically for records with 30-40% modulation. Now it's easy to set the anti-skate and observe the tonearm movement. Set the desired tracking force, then the anti-skate so that the tonearm drifts very slowly inward when the stylus is resting on a smooth surface (not in the groove) at the end of the record. You'll have a moment to do this before the stylus "catches" the run-out groove.