|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
71.32.154.219
In Reply to: Anti-skate force : Increase or Decrease posted by Jagdeep on May 12, 2007 at 11:01:49:
*skating* force increases (tendency for stylus to move toward the spindle) as the stylus tracks grooves closer to the spindle.therefore, anti-skating devices are generally designed to increase force as the stylus approaches the center, to counterbalance the greater skating force.
Follow Ups:
As far as I know, the stylus arc hits a zero skating point somewhere in the middle.I am not a mathematician, but the skating force is the resultant of the groove drag (one vector, tangential to the grooves) and the deviation from the true tangential point (IOW tracking error) as the other vector. The resultant of those two vectors is the skating vector, which is perpendicular (or centripetal) to the grooves.
However, that easy calculation assumes that you have either unmodulated grooves, or grooves that have a modulation in such a way that the stylus drag is constant (again, that would take some thinking for me, how a signal would need to evolve over a record to cause constant drag.)
You are aware that the skating force will increase on louder passages, and decrease on silent passages.
What was your original question again? : )
I think what you're thinking is that skating force comes from tracking error, which would be incorrect. Skating force is present all the way across the record and is due to the overhang/offset angle employed on pivoting arms.The motion of the vinyl at the point of contact is always perpendicular to a radius line from the center of the LP to that point. This is the direction of pull on the arm from friction. If you draw a line representing the direction of drag on the stylus, then draw a line from the stylus to the arm suspension, you'll see that they're not parallel. The arm will always want to swing in a direction to make the lines parallel, and thus we have skating force.
Right, I did not think that through. It's a function of the overhang, unless you have a tone arm with an underhang (some straight tone arms do that), then you have a centrifugal skate.Still my point is: the overhang is not static over the course of the record, nor is the drag of the record on the needle. Hence the skate force is chaning from moment to moment.
The biggest factor on skating force is the music itself, however. Vibrating the cantilever and producing electricity requires energy from somewhere and the only source of energy in a phonograph is the spinning platter, so the energy comes at the expense of more drag.This makes it hard to set anti-skate because there's no setting that removes the effect, but rather only one that provides the best average of cancellation. Loud test bands for setting anti-skate cause you to compensate for the worst case scenario, while setting a stylus on a grooveless area only compensates for an unrealistic 1-point contact scenario.
Bry
Yes, i believe the skating is a function of the head offset and the velocity. So, in my head, the velocity is reduced as the stylus approaches the centre, so, my confusion.In my head, one needs to have higher antiskating at the outside but, many advise it should be on the inside.
Read this topic John E pointed to above. The friction between 2 materials doesn't really change with speed, allowing for the same anti-skate setting for 33's and 45's, and theoretically for the inner and outer grooves.However, I believe there are some side-effects of the closely-spaced modulations in the inner grooves that can increase drag, by causing the stylus to climb steeper slopes to achieve the same frequencies. Someone else could probably answer this better.
-Bry
This post is made possible by the generous support of people like you and our sponsors: