AnalogMagik Tutorial No. 5:
How to Optimize Anti-Skating
As the turntable spins, the centripetal force will pull the tonearm and cartridge towards the center of the LP. Microscopically, this force will cause the stylus to have more pressure on the inner walls of grooves versus the outer walls, resulting in distortions. To counteract this force, most tonearms will have an anti-skating dial which will apply a counteracting centrifugal force, so that the stylus will have equal pressure on both side walls of the groove.
Not all tonearms provide for an anti-skating adjustment. On a 12" tonearm, anti-skating is usually not required in some cases, but on a 9" arm some anti-skating force is usually needed. The market has no shortage of controversies and setup methods when it comes to 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 or complex DIY devices.
In our opinion, any tools which attempt to measure anti-skating force without the stylus sitting on the LP groove 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 in real time play settings. For example, if you use a mirror or a blank/grooveless record, the friction co-efficient will be different than a normal LP with actual groves. They bear no correlation to one another, so they will lead to inaccurate results.
e need to take a step back to see what anti-skating actually does.
hen there is too little anti-skating force, the centripetal force will cause the stylus to apply too much force 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. When anti-skating is optimized, the level of distortion between the right and channel should be balanced.
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 optimised when the distortion figures between the Left and the Right channel are balanced or as close together as possible.
Again, meaningful results are highly dependent upon the VTF, the cartridge quality as well as the design of the tonearm. On good setups, AnalogMagik have observed a distortion percentage difference of approx. 0.05% between channels, while the net number should be below 1% on good setups.
On 12" tonearms tracking at 2g or above, you may notice a number where the L and R channel distortion is already very close, this is because 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 realise that the centripetal 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. Usually, more force is required towards the center. Some tonearms designs have a mechanism which will increase anti-skating force gradually to counteract the non-linear nature of the centripetal force.
The alignment geometry of your choice produces the lowest tracking error at the null points, then the tracking error gradually increasing as the stylus moves away from the null point. Antiskating works the same way where the optimised anti-skating force is only optimised on that specific point on the LP.
Anti-skating affects Azimuth. We have observed that when anti-skating is set incorrectly, the imbalance will 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, AnalogMagik emphasize that no setup parameter can be optimised 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.