TT speed

lewn,

Yes, of course this has nothing to do with pitch. 

Larry, You wrote, ...."at some point slowly moving forward (retarding, in terms of time), then at the top of the arc, it starts to retreat (speeding up)"  I think you would agree that although the velocity of the stylus tip does decrease as it moves from the outer grooves toward the inner grooves, just because path length is getting progressively shorter per revolution of the platter, this has zero effect on pitch, assuming a perfectly created test LP and a turntable with perfectly constant speed.

I think that what he is saying is that the stylus tracks an arc across the record, which means it is at some point slowly moving forward (retarding, in terms of time), then at the top of the arc, it starts to retreat (speeding up).  Both the slowing of time and the speeding up covers the entire side of the record and covers such a small number of degrees of arc (hence small fraction of one cycle of the record) that it has nothing to do with what can be perceived in terms of pitch change or timing.

You are connecting two parameters that are not related. The stylus tip does not need to know where it is on the surface of the LP in order to reproduce the frequency accurately. It’s essentially a point in space.

For any pivoted tonearm, the stylus will describe an arc starting at the outermost grooves and swerving inward to the right of the spindle as it heads toward the lead-out grooves.  When you use a typical 2-point protractor, like the Feickert, you can see this effect, because the protractor is helping you to locate the stylus and cantilever at each of the two null points defined by any of the 3 standard alignment algorithms.  By definition, the stylus tip and cantilever should be parallel to the groove or perpendicular to the center of the spindle, at a null point.  You have to rotate the protractor to set each of the two null points because the tonearm pivot defines one and only one arc upon which the null points have to be set.  Please try to visualize that if my words are insufficient.  Alignment can affect distortion characteristics, but it does NOT affect fundamental frequency.  Because no matter where you are on the arc, the cartridge is reproducing what is encoded in the grooves at that point.  When a test LP with a 1000Hz tone is created, it is done with a lathe that ideally automatically compensates for the changes in groove length (a spiral with an ever diminishing radius, heading toward the lead-out grooves).  Your rotating the protractor is just to locate each of the two null points, has nothing at all to do with speed accuracy.  So long as the platter maintains constant speed, 1000Hz is 1000Hz everywhere on the LP surface.

Use an arc protractor.

Align stylus tip to arc for full sweep. Make parallel to only 1 grid, inside or outside, your choice. DONE. No guessing. No trial and error, no back and forth. The 2-point protractor is archaic and very inaccurate. 
 

I have 123 cartridges, so doing alignments is common. Takes about 5 minutes. I use Lofgren B DIN mostly. Sometimes Stevenson DIN. The Arc protractor is deadly accurate and quick. I use it for conical, elliptical, HE, LC, MR tips. I get no IGD. Haven’t heard that in years. 
 

For printing your free arc protractor, you need your pivot to spindle distance; it’s a spec for your turntable or you can measure it. Choose your alignment (Lofgren A/Baerwald, Stevenson, Lofgren B) EIC/DIN/RIAA null points, and print. Easy peasy!

Any alignment of a radial arm is a compromise. The alignment procedure is supposed to achieve the least amount of distortion across the entire record surface, not eliminate distortion. So, to fuss over it excessively is futile.

At least it is not a large number, but maybe it accounts for a tiny perception of tonality in people with pitch perfect hearing?
(Not me)

 I am still thinking tracking error, but the aspect of speed throws me off that idea. 

Sorry, you will need to restate your question as I don"t have a clue what you are asking.  Also, state the type of protractor, single point, arc etc.

@testpilot It is a paper protector for a 9” arm which has 13mm of overhang. Maybe Baerwald? I don’t know for sure.

@lewm I am saying that when aI go from the outside to the inside, I need to rotate the platter somewhat… maybe 20 degrees, but probably less. 

So I am saying that the arm moves in a way that makes it advance or retard with respect to the platter spreed. I need to remove some rotation the platter more going from the inside to the outside. (Add rotation if going form outside to inside) 

The stylus is not moving linearly along a fixed line radially inwards. It is moving in an arc that is not perpendicular to the track’s direction.

Ditto to what testpilot said.  I think you are saying that the two alignment points afforded by some types of protractors are typically separated by 20 degrees, using the arm wand and the pivot as the definers of the angle. But tone is about the constancy of turntable speed, not a factor much affected by alignment. The custom of checking alignment at two points is to improve the accuracy of the process vs just aligning to one point, which typically used to be the inner null point of a particular alignment algorithm.  The classic Dennesen protractor used one alignment point, for example.  Anyway, tone is speed.  A 1000Hz tone recorded at the location of the inner null point will look different, if you could see it, from the same tone recorded at the outer one.  So ideally the record cutting process accounts for the accuracy of the frequency, and then we need an ideal turntable with constant speed.  Then you would hear 1000Hz at both locations on the surface of the LP.

Sorry, you will need to restate your question as I don"t have a clue what you are asking.  Also, state the type of protractor, single point, arc etc.