Cartridge Brushes and Skating Force
Stanton Magnetics Replies to a Reader
From BAS Volume 8, Number 3    December 1979

 In the last issue of the BAS Speaker, I came across a letter from Mr. Ven-katanarayanan from the Philippines who needed help with his turntable and Shure Type IV cartridge. Mr. Ven-katanarayanan did not know exactly how to set up the antiskating. I would like to help him.

The skating force is the result of the friction between the stylus or the brush and the record surface. While the stylus touches the sides of the groove, the brush rides over the land between the grooves and sometimes in the groove. The geometry of the conventional tone arm is such that the offset angle determines the magnitude of the skating force vector (a tangential tone arm with no offset angle has zero sideways force, at least theoretically). The brush is located in front of the stylus or to be more precise, behind it with respect to the motion of the record. Consequently the imaginary offset angle of the brush is larger than the one of the stylus, and so is the overhang. (This is true for the Stanton brush, but not for the Shure. -- Ed. )

Now comes the tricky part. In order to set the antiskating dial correctly with the brush, adjust the tone arm counterweight or tracking force so that only the brush rides the surface of the record. Normally this force downward with the Shure V15 Type IV should be about 0.5 gm. Make sure that the stylus does not touch the record. Do this while the record is turning. The tone arm will skate happily toward the spindle. Return the tone arm to the outside of the record and ad-just the antiskating until the tone arm stops skating. Now you can increase your tracking force by 1 gm to normal force required by the stylus and add another gram of antiskating on top of the existing setting. Now you are all set. If you mistrack on the outside channel you should not blame your tone arm setting but the stylus or the record. What you do using this method is set the antiskating for the brush first, then add the tracking force and antiskating for your stylus.

-- George Alexandrovich, Vice President, Field
Engineering, Stanton Magnetics Incorporated

The Manufacturer's Version
Concerning the proper antiskating force when using the Shure V15 Type IV cartridge: with the stabilizer in operation, the tracking force at the stylus tip is .5 gram less than the tracking force setting on the tone arm. For example, if the desired tracking force at the tip is 1.0 gram, the arm tracking force adjustment must be set to 1.5 grams.

The factors that cause skating forces on the record are the same for both the diamond tip and the stabilizer bristles. Just as the tracking force must be set to include both the diamond tip and the bristle forces, the antiskating force should be set to accommodate the total skating effect for both tip and bristles. Thus the correct antiskating force is that which corresponds to the tracking force setting on the tone arm. Referring to the example above, if the total tone arm tracking force setting is 1.5 grams, the antiskating force should be set to compensate for 1.5 grams. In this example, both the tracking force and the antiskating force are properly set for playing at a tracking force of 1.0 gram at the stylus tip.

The maximum tracking force that should be applied to the tip is 1.25 grams, which means that with the stabilizer in operation, the maximum tracking force setting on the tone arm should be 1.75 grams. Any additional tracking force exceeds the recommended tracking force range of the cartridge. I hope my explanation has clarified the questions concerning proper tracking force and antiskating force settings with the V15 Type IV cartridge.

-- Scott Mastricola, Product Manager, High Fidelity Products, Shure Brothers, Inc.

And the Editor's Last Word
The two previous explanations of the skating force generated by brushes are similar in concept, and for a brush located close to the stylus should yield the same setting of the antiskating control. But there is a way to determine in actual use whether the control is set correctly, and it should be used as a final check of any system, whether or not it is equipped with a brush.

The essential idea of any antiskating device is to balance the horizontal forces on the stylus assembly so that the stylus shank is centered in its support structure, thus having equal compliance in both directions. Most good cartridges are sufficiently compliant that they will exhibit a visible deviation from the center position if the horizontal forces are imbalanced. To find out whether this is the case on your system, place one eye directly in front of the cartridge body with the arm lifted just off the record and sight down past the center line, or some other convenient feature of the cartridge body, to the stylus. Then, using the cue lever if you have one, lower the arm onto the record while watching the stylus tip. If the skating force is correctly adjusted the stylus will move up toward your eye but will not shift sideways with respect to your reference mark. From this position it will be easy to vary the antiskating knob and watch the stylus deflect to either side of the center point.

One thing this technique will quickly reveal is that some antiskating systems are misdesigned. The one on the Philips 877 turntable, for instance, shares with the earlier Philips units a simple design error: the force is applied by a spring, and it increases as the arm moves toward the center of the disc. Instead of being a gentle spring which is deflected a long way at normal settings, the spring has a high constant and small deflection, and the force varies so much over the course of the side that the antiskating force goes all the way from zero at the outer edge (stylus deflected to the right as viewed from the front) through just right at the middle of the side, to too much at the inner grooves (stylus deflected to the left). With the most compliant cartridges it is even possible to see the skating force change with the modulation level on the disc. This is the reason, incidentally, why adjusting the antiskate for equal distortion on a test record like the Shure Eradiscs will result in too much antiskating force: the level at which the test signal is recorded is scarcely ever reached on actual commercial records, so that the needle drag, and therefore the inward bias for which the antiskate system is correcting, is unrealistically high.

There is, it is true, a rationale for doing things this way despite the problem I have just outlined. That is that it is most important to have the horizontal forces on the stylus assembly balance when the music is the loudest, because this is when the system's tracking ability is most severely taxed. Maybe so, but then the other 99.9% of the time the stylus will be pushing too heavily against the outer groove wall and will wear unevenly. You can, obviously, take your choice. Personally I prefer to put on a popular record with sustained levels that are high, but not extreme, such as Fleetwood Mac or Joe Walsh or Frank Zappa or whatever, and adjust the system for zero horizontal deflection of the stylus at that level.

-- Brad Meyer (Massachusetts)

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