It's worth mentioning that skating forces are a function of groove friction
(tangent to the groove) and the angle formed by the stylus, tonearm pivot,
and the disc spindle. A linear tracking arm has no skating forces because
the angle is zero (instead, the forces are air bearing friction and how
level the arm is).
Groove friction is a function of (1) VTF, (2) stylus geometry, (3) groove
modulation, and (4) groove speed.
The blank disc models a silent groove, so you can at least set your
anti-skate to account for VTF and groove speed. But even then, the
friction for a blank disc models a different point of contact and doesn't
capture the stylus geometry (i.e. stylus tip vs stylus sides).
It's also worth noting that the outer groove is faster (therefore more
friction and more skating) than the inner groove. That said, I would
calibrate anti-skate using the center of the grooved area as a
representation of the average skating force (as you note with the AES
calibration disc). And rather than have the tonearm remain stationary
(constant radius) when setting the anti-skate, I'd set the anti-skate so
that the tonearm moves slowly OUTWARDS (not inwards) to counter-balance the
additional skating forces generated by real-world groove modulation.
If you find little or no skating force difference between the inner and
outer grooves, that might be because of tonearm pivot friction,
tonearm/cartridge mass (high rotational inertia), or very low friction
between the blank disc surface and the stylus.
Anti-skate settings will be different for 33 RPM and 78 RPM, even with the
same cartridge and VTF due to the higher groove speed and increased groove
friction, and hence increased skating force. Styli for 78s tend to have
more groove wall contact (yet more friction), combined with more groove
speed... so significantly more anti-skate is needed for 78s, not just due
to increased speed.
Once you have an understanding of groove friction (and the interaction of
VTF, stylus friction, groove speed, and groove modulation), not only can
you properly set your anti-skating (i.e. 33 vs 78 rpm), but this can inform
your disc transfers. A common misconception is to increase VTF when a
groove skips, but this can actually make things worse since you are
increasing groove friction and thereby increasing the skating force.
Increased VTF, on the other hand, can help with a repeating groove. And,
of course, there's using slow-speed transfers to reduce skating forces.
* Eric Jacobs*, *Principal*
*The Audio Archive*
1325 Howard Ave, #906, Burlingame, CA 94010
Tel: 408-221-2128 | [log in to unmask]
On Tue, Dec 22, 2020 at 1:08 PM Corey Bailey <[log in to unmask]>
> Hi All,
> OK, I’m going to open up a can of worms here…………………
> Most turntables have an anti-skate adjustment. Some do not & some have a
> counterweight suspended from a thread (which, is surprisingly accurate).
> I learned years ago that the anti-skate (A-S) adjustment should be 9 to
> 11 % of the vertical tracking force (VTF).
> Once the turntable is set up & with everything properly adjusted, my
> method has been to adjust the A-S by playing a blank disc (usually a
> lacquer) & set the A-S so that the tonearm tracks steadily in the middle
> of the disc. A slight drift towards the center is desirable but
> generally difficult to achieve. When digital recording became the norm,
> I began visually & audibly checking the fades for all of the material
> being transferred from disc to make sure the modulation is equal (unless
> it is intended otherwise). When I purchased my 1^st set of AES Coarse
> Groove Calibration discs, (AES-S001-064) I was pleasantly surprised to
> find a generous band of no modulation in the center of the discs
> although there is no mention that it is to be used for A-S adjustment.
> I recently read that an easy way to adjust A-S is to adjust it so that
> the tone arm stays steady in the dead wax area of the record to be
> played. I tried this & found that when the tone arm is placed in the
> center of a blank disc, the tone arm travels to the outside of the disc.
> So, what’s the correct adjustment? I thought I’d ask the experts on this
> forum: How do you adjust anti-skate? Do you use sophisticated
> measurement tools? Comments? Opinions?
> Happy Holidays,
> Corey Bailey Audio Engineering