Setting anti-skate

Nsgarch, thank you for your detailed technical analysis, but your understanding of coefficient of friction is wrong in EXACTLY the way it brings you to the wrong conclusion. Your analysis utilizes your personal logic instead of an application of physics. So, all of your 3 numbered points fall apart from an incorrect primary assumption. Your problem is that friction is actually INDEPENDANT of contact area. If you don't believe me, look up the equation for friction on the internet: F=uN. frictional Force = coefficient of friction times Normal force. Nothing about contact area. Diamond touching vinyl has the same coefficient of friction whether touching by the "bottom tippity tip" or the entire playing surface of the groove. And, the normal force is determined only by VTF, again independant of contact area. 1) vinyl has no coeff by itself 2) diamond has no coeff by itself -- they have a coeff TOGETHER that is constant and (3) INDEPENDANT of contact area. The smaller contact area of a blank record just means the same force becomes a much higher psi (surface pressure). So there IS definitly a frictional force, it is close to the force in a groove, and it is adjustable by anti-skaing. THAT is why the arm will go racing towards the center unless an equal and opposite force in applied by the anti-skating feature. If you set a needle down on a stationary blank record it will NOT slide towards the middle. But it may slide towards the outside, because now the anti-skate is unopposed.

Warjarret, some of your assertions are correct. A coefficient of friction is indeed just a scalar number. It's used to calculate both static and moving (kinetic) frictional forces.

Kinetic coefficients are lower than static coefficients for the same material(s) and don't depend on the area of contact (once the two surfaces are moving.) And you are quite right that the frictional coefficient(s) between diamond/vinyl are constant. I should have said frictional force(s), my mistake.

In any case, the TOTAL force (or drag) exerted on the diamond is far more when it's sliding in a groove than when it's sliding across a smooth vinyl surface. Much of this increase is due I suppose to the tortuous interaction of the stylus with the groove -- a kind of mechanical (as opposed to frictional) resistance created by the diamond trying to get through that obastacle course, IN WHICH CASE you'd have to calulate a kind of EFFECTIVE coefficient of friction for stylus-in-groove.

Nevertheless, I'd be very interested in your explanation of why, at the same VTF, some cartridges require very little AS and some require much much more. According to your view of the matter, AS should be the same for all cartridges at the same VTF -- and I must admit, most tonearm makers think so too, but it just ain't so, as anyone who has played around with AS can attest -- and the reason why I prefer doing it visually first and then by ear. BTW, years ago, I used the blank vinyl method, and ALWAYS wound up with a far higher setting than recommended by either the arm or cartridge manufacturer or by my visual inspection --I don't know why THAT is but I quit doing it a long time ago. I suppose there are definative electonic ways of calibrating proper AS, but I never explored those.

Changing the subject, I saw a stylus/arm slide across a stationary platter (no AS applied) because the whole table was tilted slightly -- a good reason to make sure everything is perfectly level before attempting any adjustments. I level my table with the clamp and a record in place and the arm over (not touching) middle of the record. (Very important if the table is a suspended type.)

Nsgarch and I are getting closer to agreement now, because I agree that different stylus shapes require different anti-skating force, and that a blank record must also be different than a real groove. The interaction of the stylus with groove undulations definitely makes a difference in skating force, which agrees with other comments heard here that skating force varies with groove modulation. I just think a blank record is a good starting point, before fine tuning of the anti-skating. I think its about as accurate as trying to observe motion of the needle upon dropping it into a groove. Its a lot more difficult to see the needle move a little, than seeing an arm skaing across a smooth record! Plus keep in mind that many cueing devices don't exactly set the arm down straight AND many records have a little out-of-round wabble. These will give the stylus some sideways motion also. Furthermore, we need to figure out a final step which ACCURATLY provides the real adjustment. I think the only way to do this right, is by playing various test tones, and comparing right and left channel distortion on a distortion analyzer. Without this equipment, I agree that listening is the next best way.

Warjarret, as I said earlier, years ago I used the blank vinyl method, and I ALWAYS wound up with a far higher AS setting than recommended by either the arm or cartridge manufacturer, or by my visual inspection. It consistently yields AS values that are WAY overkill -- I'm not sure why that is (I quit doing it a long time ago) but it may simply be that the unconstrained diamond tip on a highly polished surface is too unstable a mechanical assembly, sucseptable to air currents, TA internal wiring, irregularities in the vinyl surface or whatever, but it always took two to three times the nominal AS force to keep the arm in place.
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...we need to figure out a final step which ACCURATLY provides the real adjustment.

Warjarret,
I think you're engaging in antiskate overkill. As I said above, there is no such thing as a perfect antiskate setting. The very notion is impossible and you've described the reasons why yourself. This search for ultimate "accuracy" is more hopeless than the search for the Holy Grail. It simply doesn't exist. It can't exist.

I think the only way to do this right, is by playing various test tones, and comparing right and left channel distortion on a distortion analyzer.

No test tones can accurately emulate the variable vinyl formulations, variable groove modulations and variable arm positions we encounter on real records. Why measure some theoretical value that bears only an accidental and occasional relationship to constantly changing real world conditions? What's the point?

Without this equipment, I agree that listening is the next best way.

No, it is a better way. The subtlest effects of excess antiskate would not even be detected by a distortion analyzer, since they have nothing to do with distortion or mistracking.

The physical effect of excess antiskate is a constraining lateral pressure on the cantilever/suspension interface. This dampens HF response and muffles microdynamics. Nothing to do with distortion. You'd have to set antiskate far WORSE before distortion began to occur.

Your ears and brain are capable of very subtle "measurements" if you trust them and train them. You may not be able to quantify the results, which I sense might bother you, but with practice you will hear the results and you will be able to repeat them. All the "roughing in" methods we've discussed tend to set antiskate too high. From there, reduce it until you get full HF extension and maximum microdynamics.

Then relax and enjoy the music. :-)
Doug