|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
122.59.215.219
In Reply to: RE: Anti skating is pissing me off posted by Biff on April 21, 2015 at 09:37:32
Two of your respondents are right - skating force is the resultant of vector addition of non-aligned forces. Those who state (wrongly) that skating force results from interaction between stylus and grooves should observe the behaviour of a stylus on an ungrooved LP side. They should learn the principles of vector algebra. It might improve their inelegantly-expressed mood.
It is true that the counteracting bias force that one sets (if one chooses to set it) is a compromise. It is correct at only one radius on the disc. I can think of nothing better to do than to set it for the mid-radius of a typical LP.
Follow Ups:
You wrote, "Two of your respondents are right - skating force is the resultant of vector addition of non-aligned forces. Those who state (wrongly) that skating force results from interaction between stylus and grooves…."
No problem with your first sentence. But I don't know whom you have in mind when you write, "Those who state wrongly", and I think you're missing something. The skating force is an indirect result of the friction between the stylus and vinyl. (Think about it; if there were no friction, there would be no equal and opposite force to create the skating force.) Since we only care about reproducing music, it can further be said accurately that what we care about in calculating the skating force at any moment in time is the friction between the stylus and vinyl plus the groove effect. The need for the stylus to traverse groove modulations at an ever decreasing velocity from outer to inner, regardless of their tortuosity, must have an additive effect on the friction force, and therefore it must affect the skating force on a moment to moment basis. So, in my opinion, if you think that the groove has no additional effect on skating force, you should think some more about it. If you can agree that groove modulations do play a role in determining the magnitude of the skating force, then it stands to reason that setting AS using a groove-less LP will not give you a result that really reflects what is happening when you play music. However, it probable gives a best-case scenario, i.e., the apparent skating force on smooth vinyl is probably at least slightly less than it ever is when playing music.
I find it far simpler to just state that the outer radius of the groove is ALWAYS larger than the inner radius, so the relative speed on the outer groove is larger resulting in more friction (more material exposure per unit time) and so, the stylus gets pushed along towards the center AND starts traveling that way, as well, UNLESS we counteract that force.
The groove is not responsible for skating force. If you put a nail through a wooden dowel, placed it on a flat spinning disc, and loosely held the back end, it would still drift left or right until it aligned itself with the direction of drag. The groove prevents the arm from aligning itself with the drag, so the force remains.The difference in the length of the inner and outer groove is negligibly small, and travel speed doesn't affect the drag anyway.
Edits: 04/22/15 04/22/15
Now I see. It is the DRAG vector causing all the problem! Vectors are useful, afterall ;-)
Skate force is NOT due to the outer groove versus inner groove friction. It is entirely based on geometry from an offset headshell which is required due to overhang. Otherwise the same problem would plague linear tracking tonearms.
As for a unique piloting arm that was designed primarily to avoid skate, I offer the following read:
http://www.stereotimes.com/post/viv-lab-rigid-tonearm/
nt
Thanks for posting the link.
Regards,
Andy
Well, for the skating force to occur it takes both the geometrical deviation (i.e. the groove drag vector not being in-line with the virtual arm axis) and the friction. The latter will be different for "tip of tip on blank disc" compared to "flanks of tip in groove", though - 'cause for the former the normal force equals the actual tracking force (which should be a bit lower than the set tracking force due to vertical skating...), whereas for the latter it'll be 2^0.5 the actual tracking force, so that friction for "tip in groove" should be ca. 41 % higher than friction for "tip on blank" due to the different normal forces.
However, the actual coefficient of friction would seem pretty likely to also differ between blank disc and modulated groove - but the influence of that factor would seem pretty hard to guesstimate (for me, at least), so it would be nice to have something like the Dual Skate-o-meter at hand to get a better idea about that...
Greetings from Munich!
Manfred / lini
"Those who state (wrongly) that skating force results from interaction between stylus and grooves should observe the behaviour of a stylus on an ungrooved LP side."
What does this sentence mean? Where do forces on the arm come from if not from the stylus in the groove? A stylus on an ungrooved side is also pulled in toward the label if anti-skate is 0.
I think what they're saying is that the friction of a stylus in a groove is different from the friction of a stylus on a flat grooveless surface. However, it is often close enough that the flat grooveless surface can be used successfully to set antiskating. In my opinion, it is probably just about as good as any other method. I have yet to find a perfect method for setting antiskating.
Best regards,
John Elison
LT arms :)...That is a whole different bean bowl. I think what Logan really means that the Skating force is a multiplier of the drag force and the vector strictly resultant of the geometry of the arm, not a result of some unequal friction caused by grove modulation. Also since the vector will change along the curved path the algebraic change of the vector is very predictable, one could devise some compensation that follows that change exactly. I have not plotted it, but here is what i think; the change to the vector is directly proportional to the tracking error at a specific point, since the drag force is always tangential to the groove. If that is really true the change in the skating force is most likely be within the percentage of change in tracking angle error.Is it really worth getting upset over a couple percent change of a minuscule force?
There is nothing you can do about the change in drag force due to increased modulation, but that has nothing to do with the arm geometry caused vector. Theoretically even drag force can be calculated based on the dynamic compliance of the cartridge and the change in velocity of the modulation. Since it is assumed that a properly tracking stylus never leaves the grove wall, the force of friction is the same as the friction agains an unmodulated grove wall, the additional drag force comes from moving the assembly along the modulation and that is just the force needed to work against the compliance, once you have that force in the direction of the travel of the stylus, then you just have to calculate the vector that falls into the tangential direction of the disk at the point of stylus contact. There you have your drag force based on modulation :). Simple ay?
dee
;-D
True terror is to wake up one morning and discover that your high school class is running the country.
quote by Kurt Vonnegut
Edits: 04/22/15 04/22/15
> Also since the vector will change along the curved path the algebraic change of the vector is very predictable
>
> I have not plotted it
If you have my tonearm alignment spreadsheet, the angle of the vector is described in Column B labeled Groove Tangent . It shows that skating force will decrease as the tonearm moves inward to the middle of the record (89.3-mm groove radius) and then increase slightly as it continues inward to the innermost groove. For a 230-mm effective length tonearm aligned to null-points of 66-mm and 120.9-mm, skating force is 4.3% lower on the innermost groove than on the outermost groove. In the middle of the record, skating force is 11.6% lower than on the outermost groove. The magnitude of skating force follows a path like the blue tracking error line on the graph.
Best regards,
John Elison
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: