The Korf Blog

The inside story: our research,
development and opinions

22 February 2022
Antiskating, Part I
As we are waiting for the CNC tonearm parts to arrive, we have some time for another practical study. We've done Azimuth Adjustment, Tonearm and Cartridge Matching, Wow and Flutter. Let's look into antiskating now, shall we?

Why Does the Tonearm Want to Skate?
For something so simple and straightforward as antiskating, there's an amazing amount of misinformation online. How can so many people be so consistently wrong without realizing it?
Antiskating isn't a precision adjustment
The answer is surprising: antiskating isn't a precision adjustment. Its presence is a lot more important than its extent, and one can often do without it at all. Get it wildly wrong, and most of your records would still play just fine. They might not sound their best, but there will be no mistracking or gross audible distortion.

But why is it so? Let's first see how the skating force appears.

The skating force is there because the stylus drag, which is always at a tangent to the groove, is acting on a line that does not go through the tonearm's vertical axis A.

It's "pulling" at some imaginary point A' to the right of it instead.

The resulting skating torque T is simply a product of the stylus drag D and the lever L. D varies a lot with the amplitude of the grove modulation. It's lower in the quiet passages, higher in the louder ones, highest when there's significant low frequency content.

This is why any attempt to counter the skating torque T will always be an approximation.
Note: this means that skating force exists in any arm configuration where A and A' are not one and the same. Setting the offset angle α to zero does not fully eliminate skating, no matter what Yamaha and VIV Laboratory say.

This also means that pivoting linear tracking tonearms like Garrard Zero or Thales generate the same skating forces as a regular pivoting tonearm.
Ok, so this skating torque T is there. But why do we need to counteract it, what happens if we don't? The side force acting on the cantilever compresses one side of the cartridge's suspension and extends the other. Stylus's response to a deflection to the left and to a deflection to the right becomes different. The cartridge's suspension now has different compliance left and right.

And... this difference is largely benign. It would skew the very low frequency response in left and right channels — but on an LP, these frequencies are anyway recorded in mono. To actually cause mistracking, the asymmetry between suspension hardness left and right must be huge.
This is very clearly seen on an oscilloscope set to X-Y mode, with one stereo channel going into X and the other into Y. Playing back a "hot" mono record or a test LP, this is an effective way to highlight the differences between the channels.

The bottom left "hook" in the picture is the difference in tracking between channels caused by insufficient antiskating. As we add antiskating, the "hook" shrinks and finally disappears. The signal in both channels becomes exactly the same.

It usually is enough to add a tiny little bit of antiskating to return to perfect tracking. And then we have a huge range of antiskating force setting that does not cause any mistracking.

This also means that it's possible to build a cartridge that doesn't need antiskating at all. An asymmetric suspension, having different elasticity for when the stylus moves left and for when it moves right is enough.

Ortofon did just that. The cartridge was called S-120 because it could accurately track a 120 micron groove deflection on the LP. A typical good cartridge tracks 80 micron, and not a lot more. Unfortunately, S-120 was a DJ cartridge with a crude bonded conical stylus, and it didn't sound special at all. No wonder Ortofon discontinued it.

How to Stop the Skate?
This is all good, you say, but how do we set the antiskating right on our tonearms?

This would be the subject of our next posts. First, we'll try to figure out exactly how much opposite torque do we need. Then we'll see how can we set it for consistently good playback and peace of mind.

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