Tracking error distortion audibility

Dertonarm,
one more thing :-)
Done my pivot / spindle measurement on the SME-V and it is: 215.35 mm give or take 0.0... something!
The adjustments with a PW, Dorian, DV X20-L are minute actually, all changing this distance value by some few 100th of a millimetre, hallo!
So it looks like we are making one BIG elephant out of a fly here.
So, all's in butter, right?
Now, if we still have IGD, then what?!
Greetings,
Axel

Dear Axelwahl,
I will keep it as short as possible.
1) it is possible to adjust teh overhang by moving the whole tonearm. But if you do so, your specified mounting distance is gone unless you move your tonearm on a circle segment always amintaining the very same spindle-bearing distance. This is a simple geometric fact. A sheet of paper and a pair of dividers will nicely illustrate the point.
2) The geometry depends on the mounting distance of the tonearm as the first NON-variable parameter of the basic calculation. If you adjust the overhang (which depends on the spindle-bearing distance founded geometry...) by altering the basic parameter, the overhang you just adjusted to is no longer the overhang you tried to align to..... because you moved the tonearm.....
3) the overhang DEPENDS on the mounting distance - not vice versa....
4) It is a BIG difference, whether you adjust the overhang with oblonged holes in the headshell (because the mounting distance remains, as you do not move the tonearm.... only the stylus) or by moving the tonearm. To adjust the overhang is a movement RELATIVE to the FIXED tonearm. You move the stylus relative to the bearing pivot and the spindle - not the tonearm!!
The spindle and the pivot bearing are FIXED PARAMETERS because their distance is the FOUNDATION of your tonearms geometry.
You can choose different zero-error points on the arc of the tonearm/stylus movement over the LP's surface and by doing so you can - for instance - bring the 2nd zero-error point closer to the inner grooves.
However - the basic geometry of your tonearm remains the same.
The nice alignment tool provided with every Graham tonearm gives a nice idea. You can align your cartridge to either Loefgren or Baerwald geometry, but you do so without moving the Grahams base - you align at the headshell only.........
The groove modulations in any LP are VERY small. A "bit" derivation results in HUGE errors in de-modulating because the VERY TINY polished areas of your stylus are no longer aligned.
Thats the difference in playback between distortion-free High-end and "so so" sound with inner groove distortion.
1-2 mm........ well, your polished flanks on the stylus are 2-8 µm (thats 1000th of a millimeter).....
1-2 mm here are 10 - 20 miles in real world playback.
So - in metapher, you are "still in the same county or district, but you are no longer in the same block, you are in a different part of the city - and you will never find the address the Lady gave you to meet her...."
In analog playback all quality starts here - at the demodulation in the grooves of the LP. If you do not precisely align 100% here - you will have an endless (and futile...) journey trying to fix problems in your system which you never can locate or solve.

Dear Axelwahl, the pivot bearing to spindle distance does NOT determine were your zero-error points are located. Again - see the Graham alignment tool with 2 options to adjust to either Baerwald or Loefgren - the zero-errors are on different points on the arc, but the spindle-bearing pivot distance is of course the very same on both, as the base of the Graham is not moved, but the adjustment takes place at the headshell ONLY.
I guess the point is clear now - isn't it?

Dear Axelwahl, good to learn your mounting distance is fine. If you had checked that earlier, we could have spared some time and space here...
Anyway - if you still have inner groove distortion when the tonearm geometry itself is fine, then this can be related to several points:

a) lateral azimuth of the cartridge/stylus
b) horizontal azimuth of the cartridge/stylus
c) antiskating
d) 2nd zero-error point already long passed when you reached the inner grooves (the SME uses an IEC-standard when calculating the zero-error-points. The 2nd point is pretty close to the 1st and in the inner grooves you are close to the maximum error - why this IEC-standard was used and favoured by SME and Ortofon was explained in the "Prices for Oldskool tonearms"-thread. It has to do with the new way to master and cut LPs in the early 1980ies.

a) and b) can hardly be altered in the SME V, but you can try - usually there is a small degree of free movement. Both do have direct impact of the position of the stylus contact area to the groove walls.
c) antiskating or skating force as the source of distortion will apply, when the distortion is pre-dominant in one channel only.

Hallo Herr Tonearm :-) and who ever is still with us…

As I said, my tonearm pivot to spindle centre is to SME spec. as it turns out, (with my current cart, Per Windfeld).
I thought THAT was the salient point of YOUR departure on the –DEFINITIVE- tracking error as a result, if this measurement is out of spec.

So now as this is right on spec, I try to understand why this should yet also be a problem?

Baerwald or Loefgren have THEIR best interpretation about where the null-points aught to be, Linn has theirs, SME theirs and so on. There is no FINAL and ONLY position where these null-points aught to be, else e.g. Linn and SME would have it ALL wrong the last 50 years --- is what I understand you try to relate, no?

Every 'template maestro' has his own sweet intuition about how to get there, so as to have the least distortion as a result. No problem with that at all, but as always more than one way leads to Rom (and many of course do not, also true).

I just think, if your first point is not the case here (spindle / pivot right on spec. in this here situation) why question the manufacturers 'preferred' set-up, and go on about other set-ups?

The exact arm-pivot to spindle with an e.g. Linn 9" arm is different to SME 9" arm and so is their resulting overhang and therefore their exact set-up. I guess you only let me off if I go with some set-up other than SME's, no? :-)

There is one still relevant item that was not even mentioned this far, that at both null-points, where ever they are picked to be, the cart's cantilever aught to be as close to 90 deg., as can possible be, in order to have at least at these two points 0 deg. tangential tracking error.
It seems to me, that it here where the SME (and Linn) arm can cause a problem with a cart's skewed cantileve. The SME arms (just as Linn's) have next to NO play to allow for the cart's cantilever skewness to be compensated, true.
With older cart designs it’s less of an issue, since they have no threaded mounting holes but need rather a longer screw and nut for fastening. This allowed (allows) for a slightly bigger margin for twisting the cart body to get the cantilever (rather than cart body only) aligned. And I would agree further, that the method used by Graham seems just about the best to achieve that also!
So not all is lost.
My last point: I do question greatly whether e.g. Graham arms (any other arm) are mounted, spindle / pivot, to the 100th of a millimetre correct! Never in all your live!

And it was THIS distance's absolute need for TOTAL correctness that stared this dialogue – Egyptian geometry and all – so at least my take. I might have missed something though.

SME also Linn assume that the cantilevers of the carts mounted are not out of true. Experience shows that this is of course not so, but it is a question of the degree of skewness relative to the cart body, with 1-2 deg. seeming the acceptable tolerance, so my understanding by Ortofon’s techies.
Now I may only wish that or discourse will be of some edification not just to the two of us :-)
Mit bestem Gruss,
Axel