Graham Phantom Anti-Skate. Is it effective at all?

Because unipivot arms are balanced on the point of a pin, if the arm is set up properly it will compensate for any nonlinearity elsewhere.

My vinyl experience over the years has not included LOMC's or other cartridges having relatively low compliance, such as I presume most of those participating in this discussion are using. FWIW, though, using MM's and MI's having relatively high compliance (primarily Grace F9-E variants, including non-Ruby, Ruby, and Soundsmith re-tipped Ruby versions), primarily on a Magnepan Unitrac unipivot arm, with VTF generally set in the upper part of the recommended range for the particular cartridge, I have over the years consistently found that:

1)Left or right deflection of the cantilever, as viewed from the front of the cartridge when playing a record, will closely match the corresponding angle (nominally straight ahead) that is assumed by the cantilever when the stylus is raised above the record if anti-skating is set to approximately 50 to 65% of the amount recommended for the particular tonearm at the particular VTF.

2)A setting can be found in that range which will result in imperceptible left or right cantilever deflection at ALL points on the record.

3)Modest deviations from that amount of anti-skating force (either higher or lower) will ALWAYS (IME, as described) produce clearly perceivable sideways deflection of the cantilever while playing a record, which will NOT vary perceptibly as a function of what part of the record is being played.

4)I have never tried an anti-skating setting approaching zero, because given the foregoing it would seem absurd to do so in these particular circumstances.

Hopefully that datapoint will be of some usefulness in the discussion. Best regards,
-- Al

Dougs point about the anti skate been applied to one end of the cantilever and the skating force being applied to the other is quite correct. However IF one has checked that the cantilever is straight, and not being pulled in one direction or the other whilst playing ( assuming one can find a record that is not eccentric ) then this argument has less weight. In terms of the physics then the effective mass and cartridge compliance come into the calculation. The issue here is that not many cartridge manufacturers specify the lateral compliance, and in my experience some low compliance cartridges are quite compliant in the horizontal plane and vice versa.

Furthermore if a cantilever is leaning one way or the other, then clearly the magnets or coils could be sitting in a position where there is more non linearity within the electrical/magnetic fields.

Many arms have inbuilt anti skate anyway. In the case of the VPI's the twisted loop of tonearm wire is far too stiff in my view and exerts both an anti skate and a rotating force affecting azimuth. In other arms the tonearm wire is often impeding free movement in the bearings as John pointed out.

Antiskate systems themselves can be problematical - spring, hanging weight, elastomer thread, weighted lever - they all have their pros and cons. It is a horses for courses scenario where you end up, but the process for determining the optimum ( or "none" ) anti skate should be consistent.

As an aside, whilst having a hiatus from audio, I used a Shure V15Vxmr ( with stabiliser brush removed ) for about 10 years on an ET2 linear tracker ( high horizontal mass, no skating forces ). I had added a little magnetic damping to the bearing tube motion using the eddy fields generated from the motion of the tube across the magnets. After 10 years the original cantilever was still dead straight and the cartage was sold for more than I originally paid.

Doug:
I don't expect you to defend Stringreen. I addressed you and him as you were both in the no- antiskate camp, and you had agreed with his point.

You said

Skating forces put an inward bias on the stylus. The stylus wants to skate inward but is constrained by the inner groovewall.

This is incorrect. It is the arm that pivots inwards because of the resultant force produced by stylus friction in the direction tangent to the groove and the restraining force in the direction of the arm pivot. The stylus, on the other hand, is actually being pushed upwards and outwards against the compliance of the suspension as the cantilever pivot moves inwards.

However, so long as steady contact is maintained with both groovewalls, no distortion will occur. If the stylus traces the grooves accurately, it will reproduce accurately (for its part).

As the stylus is pushed up the 45 degree slope of the groove, the VTF on the opposite face decreases.
Applying antiskate pulls the arm (and therefore the cantilever pivot) outwards thus equalising the VTF on both channels. The inward and outward forces are then equal at both the stylus and the cantilever pivot, as they are joined by the cantilever, and the plane of movement of the cantilever is therefore vertical. If there is no antiskate (intentional, or otherwise via wiring) then the forces must be unequal, and with enough VTF, while the stylus may track correctly without the distortion due to low VTF on the right channel, that channel will have appreciably more tracking force than the left. And any alteration of VTF will still vary downforce disproportionately.

Arms are designed to have a mechanism to allow some form of compensation for skating force, as the force cannot be wished away. It is what designers do. It is good basic arm design, like having variable VTF. It is for designers who don't wish to include it to try to explain their decision.

Whether is is well implemented, or compromised by wiring torque, or the user wishes to use it, is another matter.

Stringreen:

In my previous post the last sentence was wrong - it was a typo.

To the OP, Mulveling:

If all set up parameters are correct, and an arm cannot supply sufficient antiskate to eliminate right channel distortion, then there may be stiffness in the bearing (not usually the case with unipivots) or drag in the internal wiring.

John

.

Regardless of whether you choose Baerwald, Lofgren, or Stevenson, the alignment is based on 3 parameters or measurements:  PivotToSpindle, PivotToStylus, and OffsetAngle.  Fix any two, and proper alignment will require you adjust the third. 

If you have an arm with a fixed mounting position on the table then the first is set as well as the OffsetAngle. This leaves only the abiity to change PivotToStylus unless you don't mind varying the OffsetAngle in the headshell.

Let's say you have an arm mount which allows you to vary the PivotToSpindle. In such a case you should be able to pick a good position for your cartridge in the headshell slot, with the cartridge straight (not rotated), thus fixing two of the three parameters. Then you could achieve proper alignment by sliding the arm mounting position. 

Sometimes, the specified PivotToSpindle distance is not optimum.  My old Fidelity FR64 allowed for easy rotation of the cartridge in the headshell. This was useful since when mounted using the template, fixing the PivotToSpindle, and installing the cartridge, fixing the PivotToStylus, only the offsetAngle could be adjusted.  The old Fidelity arm mounting posiiton was not specified with Baerwald in mind.  But, if you can move the arm mount, you could set the cartridge square in the shell and then move the arm base as needed.

Thankfully, the current VPI JMW PivotToSpindle spec seems to be correct for easy alignment using any of the 3 Alignments (Baerwald etc.)

It seems to me that the choice of which optimization to use (Baerwald etc) can be informed by the predominant type of record played.  I prefer the Baerwald's more gentle degradation of the tracking angle error at the record center  since I listen to much classical music which often runs to the limits of the inner radius and will often have crescendos at the end of a side.

As far as anti-skating being unimportant: It seems to me that is nonsense since a lack of anti-skating force is easily heard in highly modulated groove passages as gross distortion/breakup.