Skating & Anti-Skating - The Basics
There is much confusion about skating forces and anti-skating compensation among audiophiles and even in the audiophile media. There have been respected manufacturers of tonearms claiming that skating forces are not important enough to deal with or that any anti-skating compensation will negatively affect the performance. There have been - and still are - incorrect explanations of skating/anti-skating on several audiophile and tonearm manufacturer websites.
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When the explanations have been accurate, they are often couched in terminology not familiar to those without a solid understanding of physics. WAM Engineering proposes a simple analogy that will make it easy to understand skating forces. We won't go into the REASONS for skating forces and what causes it as that is often where people fall asleep. Instead, we offer a scenario that many of you have experienced and we hope will help your understanding of what is at play here.
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THE EXAMPLE
Have you ever been water skiing or wake boarding? If so, you probably remember that while being towed by the boat the easiest place to ski that demands the lowest amount of your energy to hold your position is found right on top of a straight line defined by the direction of the boat - DIRECTLY behind the boat. When you swing out to one side of the wake or the other and try to hold your position outside the wake of the boat, you have to spend energy to resist the force that is trying to put you back on that straight line that runs directly behind the boat in the direction of its travel.
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The force that is pulling you back to the point directly behind the boat is a skating force. Your effort to turn away from that force, leaning hard to one direction so you can stay far outside of the wake is an anti-skating force.
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Significant skating force is not generated by the offset angle, as is often incorrectly claimed, but is primarily a function of the friction generated in the groove by the stylus and the location of the tonearm pivot point - which is NOT on the straight line defined by the tangent to the groove the stylus is tracking. (A tangent to a circle is a line that just touches a circle at one point and where a line drawn at that point to the center of the circle is perpendicular to the line.)
Imagine that the tonearm pivot point is the boat, the stylus is the skier and a line defined by the tonearm pivot point and the spindle is the center line of the wake of the boat. As the distance between the stylus (skier) and the straight line defined by the pivot point and the spindle (center of the boat wake) increases, skating forces also increase. As the skier moves back toward the center of the wake, skating forces decrease until they reach zero in the center of the wake.
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While the above description of skating force in vinyl playback is incomplete, it is certainly sufficient for purposes of making the general principles more accessible to the average audiophile. Videos to help you understand it in its entirety coming very soon!
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WATCH SKATING FORCE IN ACTION - *EXTREME CAUTION REQUIRED*
If you have a record with no grooves or run out grooves pressed on it you can see this force in action for yourself. (Classic Records did a few 45rpm pressings in this manner in the late 90s to early 00s). *BE FOREWARNED THAT THIS PROCEDURE COULD RESULT IN SEVERE DAMAGE TO YOUR CARTRIDGE AND WALLET IF YOU ARE NOT CAREFUL*
Turn your amplifier OFF. Re-confirm that your platter is level using a small bubble level. Initially, set your anti-skating at least mid-range in order to keep the stylus from flying too fast toward the center in this process. With the record turning no more than 33rpm, lower the stylus at the outer edge and watch it skate toward the label. Be ready to catch the arm before it gets too close to the label. Notice that the velocity slows as the stylus gets closer to the center of the record. Decrease your anti-skating a bit more and notice the difference in velocity and the change in velocity as it approaches the label.
Now disengage the anti-skating entirely and lower the stylus onto the record at a point about 1.5 inches from the label. Notice the velocity with which it approaches the label. Compare this velocity with what you see when you lower the stylus at the very outer edge of the record and watch how fast it travels the same distance of about 1.5 inches. You should notice the stylus picks up inward velocity much faster if you lower it at the outer area versus the inner area of the "playing" surface. This is happening because the skating forces are more powerful further away from the center of the record. If you don't see this in action and your anti-skating is disengaged there may be something wrong with your tonearm's horizontal bearing. Check this on a WallySkater.
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Now look at your blank record in bright light and notice the micro groove you have just etched in the record surface. CLEAN YOUR STYLUS!
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WHY DO WE NEED TO APPLY AN ANTI-SKATING FORCE?
Since skating forces generated on the stylus as it travels through the record groove cause it to lean hard toward the center of the recrod, without an opposing anti-skating force you will cause uneven stylus wear and premature stylus aging. Further, the increased likelihood of mis-tracking on the right groove (right channel) can result in damage to that groove during mis-tracking and the higher forces the left groove sees can cause its own wear problems.
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The bottom line: We apply anti-skating to preserve the stylus and our precious record collection. Do we need a better reason than that to do it and to do it with accuracy?
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HOW TO APPLY THE RIGHT AMOUNT OF ANTI-SKATING FORCE?
The perfect amount of anti-skating force varies depending upon the distance of the stylus to the center of the record, vertical tracking force, the amplitude of the music being played, the playing speed, stylus profile, the type of anti-skating mechanism being used, the alignment of the cantilever with the groove, etc. In other words, there is no PERFECT amount of anti-skating. A compromise must be struck.
By applying anti-skating as a percentage of vertical tracking force you can get to an excellent compromised "average" in your anti-skating across most of the record surface for most music at normal playing speeds.
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And so, was born, the WallySkater.
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The WallySkater is not only useful for measuring anti-skating - and is the only product of its type known to us - but is also very useful for learning about your tonearm's horizontal bearing quality and whether you have any unwanted horizontal forces on your tonearm applied by your tonearm wiring.
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IMPORTANT: Using a blank record or the groove-less area of the inner run-out on a record to adjust anti-skating so that the tonearm remains stationary is not a recommended method to adjust anti-skating as it results in about 50% too much anti-skating force applied. A FAR WORSE method is the use of "anti-skating bias tracks" found on some test records. The high amplitude such tracks are made at will result in applying far too much anti-skating force and the premature death of your stylus and precious records. At the end of the day, the final litmus test of proper anti-skating application is to have even stylus wear over time. This is one of the reasons we inspect our stylii regularly under our modified optical microscope. The wear patterns we find confirm the science behind the WallySkater!