View Full Version : What is the anti-skate mechanism?


jm55
06-14-2009, 10:48 PM
What is the anti-skate mechanism for? How does it work? What would happen if I did not use it, or made the settings very high?

KLH9
06-14-2009, 10:56 PM
anti skate counteracts the centripetal force (http://en.wikipedia.org/wiki/Centripetal_force) exerted by the spinning record.

This force causes the needle to be pulled off center in the record groove. anti skating counteracts these forces to keep the stylus in the center of the grove.

As the arm nears the center the forces are different then at the outside. a proper working anti skate will apply a different force at the center then at the edge.

If you do not use anti skating or use too much or too little you will wear one side of the diamond.

markd51
06-14-2009, 11:08 PM
I'll try to run this down, in simple terms, as I don't consider myself any big authority, but do have mucho experience with analog.

An Anti-Skate mechanism is nothing more than a band-aid, which is required for pivotal Tonearms.

A Pivotal Tonearm has a tendency, due to physics, to wish to "skate" towards the center of the record, while the record is in play.

The Anti-Skate device "resists" this tendency, either by a tension spring, or other means, which tries to keep the arm in a neutral boyancy so to speak, in a horizontal plane.

The objective, basically, is that a Tonearm, and the Cartridge, and Stylus stay perfectly centered in a record's groove, favoring neither the inner, or outer wall of a groove. That equal force be given to each wall of a groove, so the stylus can pick up, and transmit the information from either groove wall.

To go, and explain further, many modern day gurus claim that they use as little, to no anti-skate whatsoever on a tonearm, that that "zero" setting gives the best sound, and performance per given Cartridge.

All I can say, is that I've usually used a blank track on a test lp, and some futher minor tweaking visually, by viewing a Stylus as it lands-retracts from a groove, and of course ultimately, how it sounds, and I've never ever had mistracking, or channel imbalance problems, by using these simple methods.

Generally, the method claimed by all of us analog fans, is that if the Stylus calls for a vertical tracking weight/force of 1-1/2 grams, to then of course set the Anti-Skate Dial to 1.5.

But, there's not a Tonearm made virtually, where these simple settings can be relied upon.

Anti-Skate can, and will vary from the outer lead in tracks, to the inner tracks on a record with a pivotal Tonearm, so with that being said, one can only try to find a "happy medium", where the Tonearm-Cartridge will perform its best throughout the entire side of an LP-Record.

Some experimentation is required, and I've found that this setting can enhance the performance of a Cartridge. but not quite so "critical", and important as other settings, such as VTA, VTF, Loading, Gain, Arm
compatibility, and truthfully, about another 1/2 dozen tweaks adjustments in the analog chain.

A simple layman's term, or recognizance, would be, if the stylus hits a scratch, and the stylus skates 15 grooves, and goes 1/2 way through the song, somthing is drastically off! lol I hope this helps you, with some basic understandings. Mark

jm55
06-14-2009, 11:42 PM
Yes, both posts gave me the main insights for understanding. Thanks. Of course any other thoughts from others will also be appreciated, but at least I am mainly out of the dark :)

jm55
06-14-2009, 11:46 PM
Oh, except for the fact that you have presented many new concepts for which I am in pitch black with VTA, VTF, Loading, Gain, Arm compatibility, etc. Every time I think I am getting a handle on hi fi audio systems, I learn of entirely new ways in which I know very little.

jm55
06-14-2009, 11:52 PM
All I can say, is that I've usually used a blank track on a test lp, and some futher minor tweaking visually, by viewing a Stylus as it lands-retracts from a groove...


Can you elaborate on how one does this, or rather what kind of motion you are looking for, and when exactly?

JBL GUY
06-14-2009, 11:59 PM
markd51

Very good explanation...

Back in my stereo sales guy days when stereos where steam powered:):):)

I cut a circle out of thin Plexiglas and drilled a hole in the center...then using a cart with a warn out stylus would demonstrate the inward force vector to my customers that asked about anti-skate adjustments.

And some turntables of the day used a system where by the anti-skate force changed with the position of the tone arm. I remember the swinging weight ant-skate systems where the angle of the holder of the string for the anti-skate weight changed as the tone arm move to the center of the record.

And the system using magnets and the ones that used springs...

IIRC the amount of anti-skate compensation decrease as the tone arm approaches the center of the record because the radial velocity of the record decreases resulting in a decrease in the inward force vector.`

It was so much simpler back when I was a kid with my single ended 2 tube mono record player and all I had to remember was to flip the needle in the ceramic cartridge to the correct position...either 78 rpm or LP and set the correct speed.:):):)

wilkes85
06-15-2009, 12:54 AM
It basically keeps the stylus from sliding across the record when you set it down on the run-in groove.

I've also used the anti-skate for when i'm dubbing a record and there's a part where I know is gonna skip or get a lock groove. This sometimes works.

Not that many of my records are full of skips and lock grooves.

lini
06-15-2009, 01:57 AM
Sorry, but antiskating has nothing to do with centripetal force - and radial tracking arms per se don't have a tendency to skate towards the spindle centre either. The skating is simply caused by the deviation between where the groove pulls the needle to and the effective arm axis (i.e. the virtual line between the tip of the needle and the arm pivot point). I.e., as soon as the drag on the needle isn't perfectly in line with that axis, the arm will try to turn and reduce that angle - and that rotational momentum is the skating force, which the antiskating function tries to compensate. Well, and that the skating always goes inward on usual hifi arms is mainly caused by using long arms with overhang and cropped headshells. But that's not a must. If you'd make youself a drawing with a shorter and completely straight arm, you could see that with this geometry the skating force could even reverse its direction while the arm moves over the record...

Greetings from Munich!

Manfred / lini

jm55
06-15-2009, 02:30 AM
I have to confess that I had reservations about the introduction of the term "centripital force". I am not questioning the phenomenon of the stylus tending toward the center under certain conditions, only its real cause.

Your post contains some interesting insights, but I will have to study it for a while in order to fully understand it. I might have a clarification question or two tomorrow.

I am quickly realizing the turntable probably has more connection with mechanics than any other audio component. I had no idea of its complexity the last time I actually owned one (some 15 years ago, up until a few days ago).

JBL GUY
06-15-2009, 02:51 AM
lini

Sorry, but antiskating has nothing to do with centripetal force

Yes quite true...and as stated it actually results from the friction of the stylus in the record groove pulling on the tone arm and because of the geometry of the tone arm an inward force is created.

I have to confess that I had reservations about the introduction of the term "centripital force".


Yes in fact it is not centripetal force ...however the net result is similar to the pix at the Wiki site...only the force is in general as applied to TTs is inward not outward as it centripetal force. and it is not the result of the law of physics that states that an object in motion in a strait line will tend to stay moving in a strait line unless acted upon by an outside force...It actually has nothing to do with angular momentum.

I hope that I am typing this the way I am thinking of it because it is way late(early) here...:):):)

lini
06-15-2009, 03:30 AM
jm55: The simplest way to get it might be to look at the special case of a linear tracker first. Here you ideally have zero tracking angle error and skating force, as the arm should ideally always be in the correct position so that the drag of the groove is perfectly in line with the arm. I.e., in this case the needle ideally should simply get drawn along the radius of the platter/record and the cart should be positioned perpedicular to that. Next step: Imagine this linear tracking arm again, but now we fix it in "middle of the record" position and equip it with a radial pivot instead. Now you should easily be able to imagine that for the first half of the record the deviation between arm axis and groove drag vector has a maximum at the beginning, then becomes smaller and smaller, until it reaches null in the middle and then changes its direction for the second half and gets bigger an bigger again, until it reaches its second maximum at the end. I.e., with a geometry like this we'd indeed need an antiskating device that pulls outward less and less for the first half and then pushes inward more and more for the second half. Well, and the next step would then be to imagine the whole affair with a longer rotational arm with overhang and cropped headshell, but that's quite hard to imagine... ;)

Greetings from Munich!

Manfred / lini

Karma16
06-15-2009, 07:44 AM
HI,
Yes, lini has it right. One more thing should be mentioned. Skating force cannot be properly compensated. Because one of the primary factors in the creation of skating force is stylus to groove friction, skating force is constantly changing. This is because the friction element is constantly changing due to groove modulation. Any antiskating compensation can never be better than an average value which is rarely correct.

It should also be noted that one can completely remove antiskating and increase the tracking force to compensate. The skating force will still be there but tracking will remain good because of the increased VTF. Some tone arm manufacturers have followed this philosophy. AR is an example. IOW, skating force and VTF interact.

This subject is among the most misunderstood in hi fi.

Sparky

Doug G.
06-15-2009, 01:04 PM
No matter how much you increase the VTF, though, there will still be more force applied to the inner groove than the outer because of the skating force.

This is why styli wear unevenly without antiskate.

It may only be an approximation but it is better than nothing.

Doug