What is more accurate: magnetic anti-skating, or barrel weight attached a fishline?

TLDR (too long, didn't read - so some of this may have been covered) ...

In general (because especially with anti-skate, there are no hard and fast rules), the smallest bit of anti-skate has worked best for me ... definitely err on the side of too little (to retain dynamics) rather than too much.

With some unipivots, a touch of anti-skate can have a secondary positive effect of stabilizing the arm a bit.

Gravity vs. magnetism?  Both are constant forces, and you can engineer a system so either one works (progressively increases as you track toward the inner groove), or alternatively is sub-optimal.

Cheers,
Thom @ Galibier Design

Lewm said:

Ralph, I am saying that when the cantilever/stylus is tangent to the groove, the friction force generated by the stylus to groove resistance has a vector directed tangent to the groove, too.  But because the headshell is offset with respect to a straight line drawn from the cantilever to the pivot, there will still be a skating force due entirely to the headshell offset angle.  Interestingly, if you use an "underhung" tonearm (no off color pun intended) with zero headshell offset, then there can be only one null point on the surface of the LP with respect to tracking angle error, but at that one null point, skating force will also be zero, because the forces will line up with the pivot.

Tangency (null points) is not enough to eliminate skating force.  Lew says it quite well, but maybe it needs to be said a different way as well.

Skating force is the vector sum of the forces of the record "dragging the stylus in a generally forward direction".  Forces sum and  cancel each other.

The amount of drag and its direction is a function of groove friction and geometry.  The friction part is what makes it tricky, because this in turn, is a function of record velocity (changes across the record), the dynamics of the musical passage (varying resistance to larger "wiggles" in the groove), the condition of the vinyl, the shape and polish of the stylus, and ... I'm probably forgetting something, but you get the picture.

Here's a visualization that might help (and spare you the vector math):

• Hold your left arm out in front of you (horizontally) with your palm facing toward the right.
• Bend your wrist so your fingers point further to the right, so it resembles the headshell/cartridge offset.
• Have someone tug on your fingertip in a direction parallel to your bent hand.

This is our null point case.  Your hand will move to the right (skating force).

So, even at the null point, there's some skating force.

As Raul and others have correctly stated, there is no single correct anti-skate setting for your rig because of the frictional factors I mentioned in the third paragraph.

Cheers,
Thom @ Galibier  Design

Hi Stringreen,

Actually, lever based (gravity) anti-skate systems vary the force across the record due to the angular change of the weight (it's distance from the fulcrum relative to the downward force of gravity).  Designs with thread (string) like the Tri-Planar can be adjusted  somewhat to change the point at which the force engages, and sufficiently for the vaguaries of the unpredictable skating environment (is it hockey season yet?).

Given the unpredictability of skating forces, you can't really do better than this.  IOW, a perfect solution for a situation which can't predicted will ultimately be no better.  I don't want to speak on behalf of VPI, but I think this has been their philosophy all along.

Somewhat related to this ... some anti-skate designs can help stabilize a unipivot tonearm to a certain extent.

Cheers,
Thom @ Galibier Design

Indeed overhang/underhang, in conjunction with the frictional forces imparted by the record groove on the stylus are the key actors in this play.

I haven’t thought about the underhang case you brought up in a while (for the pivoting, 6" arm in your example), but Indeed it would appear that its natural state is to skate outward rather than inward- this, even if one had a reverse offset angle on the the headshell.

The only underhung arms,I’ve encountered were in a used record store, years ago - some DJ rigs set up for auditioniong records.

Cheers,
Thom @ Galibier Design