VTA setting for 'parabolic' and 'elliptical' styli

Interesting. Of course, the oft quoted 21-25d usually means parallel or slightly positive vta. I don't think there is a rule: mostly a combo of urban legend and different specs/ manufacturer.
I'm not being helpful, but the problem usually lies not only in how the record was cut (about which one can only speculate, or generalise), but also on how the stylus was cut (as you note) & attached to the cantilever -- i.e. at what angle is the stylus expected to reach optimum tracking? It is a lovely example of hi-end imprecision: manufacturers raise the point and conveniently let it "float" without a solution...
I remember a V15 & Pickering 5k I had both "allowed" for negative vta. OTOH, IIRC, a VdH mc20 (OK it was mc) recommended slightly positive vta... "particularly for older records".
Other than the legends that parabolic was more tolerant of vta (hence negative) but shiabata allowed better info retrieval & longer life, I have never seen actual steadfast rule about this.

Dear Axel, the needed VTA is a result of the record and the angle of the cutting head used to engrave the groove. It changes with various LPs made with various angle cutting heads. Try - to name the extremes - OPUS3 vs. Mercury SR LPs and you will notice that the VTA (i.e. heights of tonearm base) needs to be changed by almost 8 mm in a 9" tonearm. The size and form of the polished contact area may again vary these results, but to a MUCH smaller degree compared to the requirements set by the various cutting angles.
This was common knowledge by all seasoned audiophile collectors of vintage stereo-LPs back in the late 1980ies.
Cheers,
D.

Dear All,
thank you for those details shedding some light on all of this. I say SOME because now I'm in some turmoil about VTA, even accepting a fair degree of compromise I start to see why some arm manufactures come out with what others consider ridiculous, the VTA micrometer screw...
The range is now from -1.5mm to +5 or even 6mm up from level tone arm depending on the record plus stylus! That prospect seems plain awful :-(

Also, it becomes clear (to me) that the better the stylus' retrieval rate/mechanism the more in need of CONSTANT fiddling in order to maintain this now achieved high level of play-back standard!?

Put in an late 70s EMI, go up, put an early 60s London go down, put a re-issue RCA Plum-Dog go where?
Rainer's Chicago violins often are some sort of an 'ear-flossing' so go down? etc. etc.

In the 70s and 80s we had next to no such an issue ---- who ever talked about VTA then?
Nobody I know, including my hi-fi dealer...

I can start to see that this is becoming like the tyre changing rituals of Formula 1, each track in need of a different 'optimum' tyre? And never mind the weather, eish.

So now we can only pick some records we know, of sorts, and then find out if a cart, or the arm/cart sounds right.

I'm thrown, time I get back to some old elliptical cart and kiss all this hi-end thing good bye if every batch of different records needs a VTA change to maintain some hi-end standard.

OK, I'll enjoy the music, never mind if it shines out the last corner, or what ever... This could be a relieve like at Myth Busters.

Greetings,
Axel
PS: Maybe next is, we need an electronically VTA adjusted arm including level detection :-)

Dear Axel: The " pain " on all this is that even records ( on the same manufacturer ) on the same " times " come with differences because the whole cutting process is not perfect.

I know at least to persons ( perfecionist ones in this regard. ) that change the VTA on almost every single record and I see them that some times in different same record tracks, my friend Doug is one of them and I undertand him ( and Paul ) because they like to achieve the best of what they are hearing.

I don't have the patience ( maybe I'm wrong because I like too to obtain the best on it. ) for this so I focus and give more time to the music.

Regards and enjoy the music,
Raul.

Dear Raul, see - once again - I totally agree with you on this matter. I do alter my VTA several times during each session - depending on the record playing and the cutting angle used to engrave its groove. I started doing this in 1987 after my first visit to Sid Marks in Brooklyn/NY.
I think its vital.
Many sonic judgements regarding cartridges or tonearms may well be just a matter of a momentary "VTA sweet spot" on one combo and missing it again on the next.
You are always concerned about the circumstances of a given test/comparism - and right so.
This here is the maybe most important point in the cartridge/tonearm evaluation. Missing the correct VTA for the given record is dangerous in a serious test set-up.
Cheers,
D.