AnalogMagik Tutorial No. 5: How to Optimize Anti-Skating
(On both Version 1 & Version 2)
Anti-Skating
The market has no shortage of controversies on the existence, definition and setup methods when it comes to anti-skating. Some manufacturers do not believe in Anti-skating.
Here is a good paper we found on the subject: Anti-Skating
AnalogMagik is more interested in how the "skating" force will show up on a distortion analyzer and how to compensation can be adjusted on your tonearm instead of debating about the cause or existence of anti-skating. We are more interested in finding a solution for it in cases where distortions are detected on the distortion analyzer.
As the turntable spins, the cartridge stylus of pivoted tonearms may experience uneven pressures on the groove walls, a side-thrust which makes the stylus lean harder against one side of the groove than the other. This side-thrust - normally compensated by an anti-skating adjustment - is caused by the offset angle for headshell, groove modulation, and other factors. If there is no compensation for the skating force, the distribution on the vertical tracking force on the groove walls is increased in the Left Channel (Inner Groove Walls, resulting in distortion in the Right Channel, and vice versa.
Not all tonearms provide for an anti-skating adjustment. On a 12" tonearms, anti-skating is sometimes not required, but on a 9" arms some anti-skating force is usually needed.
There are many bizarre methods advocated by many people on setting Anti-skating.
Some suggest using a blank record groove and "to eyeball" the speed at which the cartridge slides across the surface. Some use a Mirror cut into the shape of an LP, and anti-skating is determined by watching the cartridge slide across the surface. Some employ the use of torture tracks, some use complex DIY devices which measures bearing friction. Some use test tracks such as the "Esther" LP and their ear to detect audible distortions, on the track closest to the spindle.
However, none of these bizarre methods bears any correlation with what you are trying to measure, and will result in an arbitrary anti-skating force which may not correlate to what you are actually trying to compensate.
In our opinion, any tool which attempts to measure anti-skating force without the stylus sitting on the LP grooves while the record is spinning introduces a different friction coefficient experienced by the stylus which bears no correlation with the actual level of pressure and frictional force experienced by the stylus in real time play.
For example, if you use a mirror or a blank/grooveless record, the friction coefficient will be different from a normal LP with actual groves. They bear no correlation to one another so they will lead to inaccurate results. Torture tracks are just that, they are torture, and does not reflect the normal grooves and normal signals of a regular Music LP.
We need to take a step back to see what anti-skating actually does.
When there is too little anti-skating force, the stylus will apply more pressures to the left or inner groove walls, causing a higher level of distortion on the R channel. When there is too much anti-skating force, it will cause too much pressure to be applied to the right or outer groove walls, causing a higher level of distortion on the L channel. This can only be measured while the stylus is sitting in the grooves with the LP playing. Our theory of optimizing anti-skating is to equalize the level of distortions between the right and the left channel.
Play the anti-skating test track on the AnalogMagik Test LP, and use the Anti-Skating function on the AnalogMagik software. Repeat the measurements with increased or decreased anti-skating force.. The anti-skating force is optimized when the distortion figures between the Left and the Right channel is balanced or as close together as possible. We also believe a distortion analyzer is much more accurate than utilizing our ears to detect audible distortions.
Again, meaningful results are highly dependent upon the VTF, the cartridge, as well as the design of the tonearm. On good setups, we have observed a distortion percentage difference of approx. 0.05% between channels, while the net number should be below 1% on good setups.
Some tonearm and cartridge combination will require different methods of measuring Anti-skating (such as using pulse modulation, sine wave observation, etc), but is beyond the method we have chosen which we believe will work most tonearm combinations.
Establishing Correlation & Obtaining Meaningful Results
In some setups we are able to establish a very strong correlation with Anti-skating adjustments. On the Schroder Reference tonearm for instance, you can detect a change in numbers with the slightest change in anti-skating. But on some tonearms we are simply unable to observe a correlation no matter what we do, and the numbers do not change regardless of your adjustments.
We believe Anti-Skating is so controversial precisely because of this reason.
The effects of Antis-kating is dependent on many factors:
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Mass of the armwand
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Vertical Tracking Force
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Cartridge suspension
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Stylus Shape
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VTA/Azimuth/Alignment Geometry
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Bearing chatter
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Vinyl Materials
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etc......
If you are able to observe a correlation, it means the anti-skating adjustment falls within the range where anti-skating will matter. In such cases, you will be able to optimize Anti-Skating using the AnalogMagik Anti-Skating THD% analysis.
On 12" tonearms tracking at 2g or above, you may notice a number where the L and R channel distortion is already very close, or you may observe that numbers do not correspond to anti-skating changes. In such cases, the anti-skating force is not required.
Some tonearm designs have inherent imbalances and will register numbers which will be skewed towards one channel, in such cases, nothing can be done. Some tonearms have too much anti-skating force even at the lowest setting, so the results are highly dependent upon equipment quality.
One must realize that the force exerted on the stylus is not linear, therefore the amount of anti-skating force required will be different depending on the relative location of the cartridge towards the record spindle. The curve is somewhat of a parabolic shape, with the skating force higher at the outer groove than at the inner groove, and lowest in the middle. Some tonearms designs have a mechanism which will increase anti-skating force gradually to counteract the non-linear nature of the centripetal force.
Optimizing anti-skating adjustment at the outer grooves where the skating force is the strongest will cause over-compensation across the inner groves. This is why the anti-skating track is placed near the inner grooves.
Anti-skating affects crosstalk measurements. We have observed that when anti-skating is set incorrectly, the imbalance will sometimes (but not always) cause crosstalk readings to be skewed so that in an optimal number can never be achieved. Therefore it is important to go back and forth between Anti-skating and Azimuth, as well as VTF and VTA to achieve an optimal set of numbers.
Again, we emphasize that no setup parameter can be optimized in isolation. One must try to achieve optimal settings in as many setup parameters as possible. For example, when meaningful numbers cannot be achieved under the Anti-Skating test, it could be caused by an incorrect VTF, Azimuth or even alignment. You may have to go back and forth different parameters to achieve meaningful results and optimal setting.
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