Antiskating .... The last analog secret

It may strike some of you as strange, but when I think of what takes place with (and without) antiskating force applied, and the benefits to playback (or lack of them ;-) my attention is not on the interaction of the stylus and groove, simply because the range of forces we're talking about w/ or w/o AS is minuscule.

It is my assertion that when someone perceives different playback qualities w/ or w/o AS, it's due not to the very slight differences in the stylus-groovewall pressure, but rather the accuracy with which the coils (or MM) are in alignment with the stationery parts of the cartridge: the magnetic pole pieces (MC) or the field coils (MM).

In the case of a MM cartridge, the magnet has a very small force field, and if it is being held slightly off-center by some skating force pushing sideways on the cantilever (see Thomas' picture;-), then its force field will not penetrate the coils equally.

Similarly, moving coil cartridges are designed with a little "English" on the suspension, so that at the optimum VTF, the coil/armature is at a perfect right angle to the (very powerful) magnetic force field created by the pole pieces. In fact if you search the vdH website, you'll find that A.J. himself recommends setting the VTF visually -- applying just enough VTF so that when the stylus is placed on the record, and the cartridge viewed from the front, the cantilever passes "right through the center" of the hole in the front pole piece! According to him, that's how you know the coils are lined up with the magnetic field and will produce the most output.

My point, is that different cartridges, due to their coil/magnet configuration, the strength of the magnets, the layout of the pole pieces, etc., may not all exhibit the same sensitivity to the slight misalignment resulting from a little skating force (or too much antiskating force!) And that it's not really about the stylus in the groove.

Doug also touched on an important point when he mentioned that correct AS will (these days) be much less than equal to the VTF! This is because that (old) standard was based on spherical and elliptical styli which develop much more friction in the groove than modern line contact or micro-ridge styli.

By the way, trying to set AS using a blank record surface is like testing your brakes on a frozen lake! If the stylus can't develop any friction (which it can't on a blank surface) then there will be NO skating force produced. Yes I KNOW, if you set the stylus on a blank record, the tonearm literally FLIES toward the label! But that's not due to skating force. In most cases, it's due to the twisting of the internal tonearm wiring -- something that causes even tangential arms to move across blank records! If you try and set AS using a blank track, you will be applying WAY too much AS!
.

Could you clarify please if in general more antiskating (or less antiskating) is needed with high VTF (and high tonearm effective mass). I have a SPU Anniversary 85 cartridge with a recommended VTF of 3.5 grams. The tonearm is a Fidelity Research FR-66S, made from stainless steel with 38 grams of effective mass! I can imagine that because of this combined high tonearm + cartridge "inertia" + high VTF you need less AS (at least no more than let's say 1.5 or 2.0), but I'm not an expert in this field.

To Raul Iruegas: Raul, could you also take a look at the thread about MC vs MM cartridges please?

Chris

Very good description Nsgarch! My thinking has been along the same lines regarding VTF and AS. If we get beyond the obvious need to have enough force to keep mistracking from occurring, then it has to be the interaction of the generator parts that gives us the differences with small changes in these settings.

The better I can get cartridge alignment (better tools, whatever) the more I do not need to rely on countermeasures such as AS to make things sound good.

Ok, break time from the weather is over. Not ice this time, just snow. I'll take that over ice any day!

I would like to add that the existance of skating forces, and their ill effects, are absolutely NOT in question! They are simple and Newtonian, and can be calculated and compensated for with reasonable accuracy . . . but getting it right in the real world is not a simple matter.

From the years I spent setting up a handful of high-end turntables every month, with myriad cartridges, tonearms, etc. I can attest to the accuracy and repeatability of using test records, and equalizing the trackability between both channels . . . but for good results, a consensus of SEVERAL different test records is necessary, as is a good 'feel' for any measurement equipment used. This is complicated by the fact that many cartridges simply don't track well, or may have tracking problems on one channel, independent of correct anti-skating adjustment, and a good many tonearms don't have consistent, repeatable anti-skating compensation mechanisms -- so experience is necessary to know when to stop measuring, and leave well enough alone . . . or to replace the defective part - usually, the cartridge.

I agree very much with Raul and Nsgarch in that the sensitivity of various cartridge/tonearm combinations to anti-skating is huge, and that it affects many other factors other than the groove/stylus relative pressure. Doug's setup methodology is pretty close . . . but anti-skating adjustment CANNOT be properly made at anything other than the final tracking force, as they interact quite a bit.

I also find some correlation between those who prefer no anti-skating, and those tonearms that have really silly, poorly-engineered anti-skating mechanisms. In my experience, virtually anything that uses fishing-line is highly inconsistent . . . and it's really a shame that many otherwise fine tonearms (SME, etc.) use this arrangement. And the whole "twist the tonearm leads" thing . . . seems obvious why the proponents of this method don't "believe" in anti-skating.

But with a good magnetic or temperature-compensated spring arrangement on a low-friction gimballed tonearm, it's been my experience that the measured/test record results have usually been pretty close to the manufacturer's scale indication. So my recommendation for the novice is this:

1. Get all of the geometry absolutely as spot-on as you can, set the VTF on the high side of the cartridge manufacturer's recommendations.
2. Set the anti-skating in accordance to the tonearm manufacturer's instructions. If you find their anti-skating methodology too vague and hokey for your taste, then get another tonearm . . . as you will probably always find the whole tonearm too tweaky and fussy. If tweaky/fussy is your thing, then enjoy.
3. If you find that you consistently hear more mistracking on the left channel, slightly reduce your anti-skating. The opposite applies for the right-channel. If you don't hear any mistracking problems, then don't worry about it. Listen to music.
4. If the tracking performance is always poor, or a well-engineered anti-skating system can't correct a channel-tracking bias . . . and you're sure about #1 above . . . then there's probably something wrong with the cartridge.

As for Thomasheisig's picture - I simply don't believe that this was caused by incorrect antiskating adjustment . . . the tonearm would simply fly across the record WAY before this would happen to the cartridge. If this occured over time, then maybe the tonearm had a problem with its lateral bearing, but that's still unlikely. Probably somebody bashed it. Duh.

Dazz, well you barely make it! Go to http://www.cartridgedb.com and go to their resonance calculator. Enter your FR tonearm name and model, the mass (use 48gm to account for cartridge weight and mounting hardware) and hit calculate. You'll see that at a compliance of 8 (for that cartridge) you're still in the 'preferred resonance' range at 8Hz.