Certainly ’On the Fly’ is needed for perfectionism.
On the Fly VTA (Cantilever Angle) is actually On the Fly SRA (Stylus Rake Angle).
Angle of stylus tip is primary, angle of cantilever is just a guide, a starting place, ’good enough’ if not a perfectionist. You can see the cantilever, thus see VTA; very hard to see SRA, especially the refined miniature stylus tips, ML, Shibata, SAS .... So we start with specs, then listen!
This pre-supposes perfectionism regarding arm tube vertical mounting, tt level, pivot distance, arm/pivot height, overhang, null points alignment, tracking and anti-skating.
SRA, I have read, should be 92 degrees (view from side): top of stylus diamond 2 degrees forward of the tip of the diamond in the groove at the LP surface. Because, ’generally’ the cutter blade is cutting at 92 degrees, top of cutting blade 2 degrees forward.
Others: please jump on this if I have wrongly understood and stated this goal of 92 degrees!!!
Cantilever angles (VTA) vary, cantilevers are shaped differently, tips are mounted different methods/angles, degree of production accuracy vary ... in the end ’this tip’ is the one to align.
i.e. the Shure V15 are named for their 15 degree VTA. When new, that should get you close to SRA. Close, now perfectionism begins.
Old, suspension strength changes, angle changes. Cantilever shafts get bent, sometimes twisted.
Tightening after slight adjustments is required for proper evaluation, some ’on the fly’ systems are not easy to tighten/loosen/tighten.
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Now, thin/thick LPs, i.e. lower or higher groove surface,
IF SRA is correct for thin LP, then, to play a thick LP, the rear of the arm needs to be raised a speck to maintain perfect 92 degrees into the groove. How much typically? Or, set 92 degrees for an average thickness and enjoy.
The problem with averages, like chair or desk height, is that average only fits a small percentage of people, most people (lp thickness) are taller or shorter than numerical average.
My Acos Lustre 801 arm, removable headshell, has the easiest On the Fly system I can imagine, easily adjusted lp to lp if desired. Loosen lock with two fingers, raise/lower with 1 finger, re-tighten with two finders, repeat. Thick LP, change. Back to thin LP, change, takes a few seconds. Mono cartridge typically, or, easily change to an alternate stereo cartridge.
My Russian Blackbird arm includes a built in micrometer lift, wonderful, HOWEVER, the method of tightening/loosening/tightening the vertical post is a nasty and awkwardly positioned allen-head set screw, so it’s tedious bit by bit, PITA, that one get’s set and stays put. It is fixed, not a replaceable headshell, my primary stereo cartridge.
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Removable Headshells allow use of different cartridges (via multiple headshells, multiple cartridges pre-aligned for that arm) . Now, besides resetting tracking and anti-skate, verifying azimuth, we need to consider SRA of that cartridges stylus tip. Mt 801 both allows and excels at that.
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BTW, I happen to believe choice of null points makes more difference than perfection of a very close SRA. When deciding, you must listen to all tracks, outer to inner, and a few LP’s with a variety of frequencies here and there to decide which pair of null points to use. The 3 primarily recognized null point systems vary by their designer’s approach/conclusions.
Oh Yeah, easily adjustable Azimuth (and retention of Azimuth while tightening) is important, especially replaceable headshell use.
