Reed 2G magnetic antiskate

For AS devices that are not simply a weight on a string, they use either a spring or magnets. Both magnetic and spring force vary with distance between the surfaces affected. So I have always wondered how they’re designed. Absent the information, it’s possible that the AS force in both cases is changing as the arm traverses the LP, because distance is changing. But it would be in a linear fashion or a mathematical fashion at least. Whereas the skating force is only partly predictable.

jw944ts OP

"Skating forces are max on the outer LP, and decrease"

The dude at WAM (WallyTools) says it is a Parabola, i.e.

Highest Inward Skate at the Outer Edge; 

Lowers as it goes near 90mm radius

Increases again as it moves closer to the center

It’s your fault that I watched a lot of his videos this am. I met this dude at the NY Audio Show recently.

https://www.youtube.com/watch?v=5mAK8f2g0x4

when there, top right, click 'from wally tools'

He sums it up, Anti-Skate, what we can do is "At Best An Approximation"

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He recaps the advantages when all is done right:

"will sound much more relaxed; non-mechanical sounding; Improved Imaging and Sound Staging come into better focus; overall clarity will improve; sibilancy will often decrease; chances of hearing mis-tracking will be near zero"

Yep. It's a parabola of sorts.  And if AS is virtually constant, it can be represented as a straight horizontal line on a graph of distance across the LP surface vs force (AS vs Skating on the same graph).  So you can visualize that a straight line can only intersect a parabola at two points on the curve. Like a stopped clock, AS can only be precisely correct for two instances in the course of playing a record. Why I stopped fretting.

this pattern of highest, decrease and then increase in skating force as the arm tracks across the record is why, I imagine, the magnetic, varying systems have been developed, as opposed to a constant force....but still, just an approximation at best, as every LP/cartridge/stylus  will be slightly different....and, practically speaking, there is certainly a difference between physics theory and what is audibly noticeable

a brainiac, was involved

so Reed’s ’attract for a while’ (magnet forward of the pivot pulls arm out) then reduce (to zero? arm pivoted/centered between the +/- magnets), ’repel for a while’ (magnet behind the pivot pushes arm out) is it’s own parabola? That’s supposing I am guessing right, which I wouldn’t put money on.

I can’t wait to find out what OP learns from Reed.

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WAM quantifies AVERAGE (data from the hundreds of arms/cartridges they have worked on) anti-skate needed as a small Percentage of Tracking Force

long arms , they say outer avg needed is 9% of VTF; inner avg needed is 7% of VTF, thus try for an average of 8%

shorter arms, the average needed is 11%

It’s tempting to say 12" 8%; 11" 9%; 10" 10%; 9" 11%, just because it fits the averages and imagined logic, 

reminder, averages, like shoe size, or desk height, is wrong for everyone above or below that make the computed average, i.e. averages are wrong for most of us.

He sums it up, Anti-Skate, what we can do is "At Best An Approximation"

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I think, using my ears and the 3 guitarists, I am now going to use only the last track which is the inner location, and that is by average close to the outer, a speck more rather than less if in doubt.

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Just to repeat: Steve and Ray Leung at VAS told me a few times, and Peter at Soundsmith has stated that the MAJORITY of the cartridges they rebuild have excessive wear on one side, most often the outer edge, thus the MAJORITY have too much anti-skate. 

I agree the SME 3009/3012 seem to get it right, but all other arms I have messed with, both the tracking dials and anti-skate dials have been proven inaccurate by more accurate or revealing tools/methods.