A new way of adjusting anti skate!

Dear Mijo, I never said the skating force was not affected by groove modulation. In fact, I agreed that it IS affected by groove modulation, which I described as “tortuosity”. My objection was to your repeated insistence that velocity or speed affects the friction force. It does not. Not because I say so, but because the equation for friction force says so. Thus we have to find another mechanism for the effect of groove modulation on the skating force that does work with accepted theory. I described two possibilities: (1) groove tortuosity causes momentary acceleration of the cartridge moving mass that also pulls the arm inward, adding to the skating force, and (2) Groove tortuosity causes mistracking. Mistracking causes momentary variation in VTF. VTF does affect friction and the skating force.

Wally, It is my impression that underhung tonearms elicit a skating force in BOTH directions.  The force changes direction (where by "direction" I mean toward the spindle vs away from the spindle) at the single null point, where for one magical moment, there is zero skating force. So if you made a graph of the the skating force across the surface of an LP, for an underhung tonearm, you would get a straight line, give or take, that starts on the positive side of the X-axis, passes through zero at the X-axis, representing the null point, and ends up on the negative side of the X-axis.

Also, is it not the case that headshell offset angle does produce a skating force all by itself, at each of the two null points for an overhung tonearm, where the stylus is tangent to the groove but headshell offset still produces skating force?

Hi lewm,

Study the Effective Moment Arm in the download. Imagine how it would be drawn if the stylus were underhung at various radii. Your answers should be there! By the way, drop the idea of null points having a significant influence on skating force. If they did, a graph of skating force (independent of changes in coefficient of friction) would not be a parabola but more of a "W" shape with the lower Y-axis points in the graph sitting at the null points along the X axis.

So: drop thoughts of null points and offset angle. Think only in terms of Effective Moment Arm (look closely at how it is drawn/determined) and coefficient of friction.

Hi ninetynine. Measuring anti-skating force using a multivariate test as it seems you may be doing with a test record and an analysis of the electrical signal is fraught with many problems. Like a mosquito at a nudist colony beach, I'm not even sure where to begin!

Measuring crosstalk is the one and only multivariate test that I will allow done - and only because there is no alternative. This is because SO MANY things need to be right before you can trust the validity of the data you get from these multivariate analyses.

However, I have done a study of the cutterhead stylus alignments on the azimuth axis on 9 different test records and can confidently report that this industry is a bit of a mess. This industry has the technology to make styli that truly replicate the cutterhead stylus contact profile (Shibata was NEVER one of those) and equipment that can reveal the finest iota of information from the groove when all parameters are in alignment, yet the engineers making our test records - that we must trust to use to align our styli by - can't agree with each other by a factor of several magnitudes of unforgivable. We will be releasing data in our own study soon. 

I think we’re talking past each other. But I’ll take a look at your attachment.

Regards:

Published to AES, 1967: "The Skating-Force Phenomenon. What it is, how it's measured, and its influence on performance of modern, lightweight phono cartridges." JAMES H. KOGEN ...

6 pages

PDF, copy/paste Google search:  "1967 paper by Shure’s Chief Engineer James Kogen." 

Found at audio-creative.nl. 

* Skating decreases towards the spindle as centripetal force (est. influence  elsewhere @ 5%) increases.

* Downforce, stylus profile, depth of groove and groove velocity are factors. (Spindle to pivot distance is a consideration.) 

* Increasing or decreasing skating force will influence wear to either inner or outer grooves, as well as wear to either the left or right bearing surface of the stylus. 

(Wallytools- Shure devised a neat tonearm mounted device to measure skating. It's described in the Kogan paper.)

Conrad Hoffman has thoughts on the subject, http://www.conradhoffman.com/AntiSkate.htm

Descartes on First Principles: "It will accordingly be necessary thereafter to endeavor so to deduce from those principles the knowledge of the things that depend on them," Although Descartes never spun an LP it is likely the philosopher would agree that although it might fit many, one shoe doesn't fit every foot.

When skating is balanced, left and right channels are hypothetically equally amplified. The "phantom center channel" phenomena emerges. Very minor adjustments to anti-skating will move soundstage center left or right.

Through the early 1970's, VTA at 15* was typical. Sometime around 1974 (IIRC) 22* VTA as standard was agreed on. Later investigation found there was still a discrepancy of several degrees VTA/SRA from one manufacturer to another.  As with correctly aligning an advanced profile stylus, azimuth or SRA may vary. Stylus to cantilever fitting is not always precise. Setup by the book is sometimes an approximation, none the less a good place to begin. Presuming ones gear is in good condition, listening and knowing what to listen for should confirm the best practical application. 

Peace,