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From: rdp@teddy.UUCP
Newsgroups: net.audio
Subject: Re: Anti-skating
Message-ID: <1225@teddy.UUCP>
Date: Thu, 29-Aug-85 10:04:55 EDT
Article-I.D.: teddy.1225
Posted: Thu Aug 29 10:04:55 1985
Date-Received: Sat, 31-Aug-85 06:47:13 EDT
References: <310@ubvax.UUCP>
Reply-To: rdp@teddy.UUCP (Richard D. Pierce)
Organization: GenRad, Inc., Concord, Mass.
Lines: 91
Summary: 

In article <310@ubvax.UUCP> scott@ubvax.UUCP (Scott Scheiman) writes:
>
>What this is about is a new (?) technique I developed a while back for
>adjusting anti-skating with traditional pivoted tonearms.  
>try posting my analysis of skating/anti-skating!)
>
>    >>>>>>much stuff here<<<<<<<
>
>So here it is:  With a record spinning on the turntable, cue the tonearm
>over the record somewhere and then sight along the length of the
>stylus cantilever.  Then alternately cue the tonearm onto the record and
>back up.  The anti-skating is NOT adjusted correctly if you notice any
>apparent bending of the cantilever from straight toward you as it
>settles onto and leaves the record (horizontally, that is--it will, of
>course, be seen to "bend" vertically due to the VTF).  That's all there
>is to it.  Adjust your anti-skating until you see no horizontal bending
>as you cue up and down.  (If it bends such that the cartridge body seems
>to move toward the center of the record as the tonearm settles onto 
>the record you need more anti-skating compensation, and vice-versa.)
>
>	>>>>> an example of why id didn't work <<<<<
>
>So here are my questions:
>
>1) I've subscribed to many of the major audio magazines for years now
>and I have never seen any reference to this technique.  Have any of you
>heard of it before?
>

This technique is QUITE old. I remember seeing references to it back
in the 50's, when people first started thinking of these things. Many
installers use this as a quick empirical check of things.

>2) Does this method have validity, or have I made a mistake in my
>analysis somewhere?
>

This method has some validity, presuming the following:

    1.	The cantilever is straight to begin with, and the suspension
	is linear (or at least symmetrical!)

    2.	The tone arm is not suffering from significant amount of
	friction. In the case where it didn't work, I suspect that
	this might have been a problem.

    3.	The whole assembly is level.

The problem is, as you have alluded to, that the forces are dynamic in
nature (by this I guess you mean varying).

>3) Just how much difference does the precision of anti-skating
>compensation make, anyway?  Maybe the calibration on my turntable is
>good enough as it is!
>

See below:

>4) With the last two questions in mind, is this new technique good
>enough?  It might be, for example, that the typical stylus' compliance
>is stiff enough that the amount of anti-skating variation needed to get
>a visible deflection might be much greater than the refinement I'd
>really need to achieve.
>

This is the real bugaboo of your technique. The skating forces, compared
to vertical tracking forces are very small, on the order of a few percent.
To get a visible deflection, you are playing with forces that are probably
an order of magnitude to high, and you will end up masking other things
that may be effecting the stylus (friction, etc).

I had performed several experiments, using piezo-electric cartridges mounted
in such a way that I could measure directly the skating forces. Those
forces varied wildly, due to the following:

    1.	Stylus geometry
    2.	Tracking force
    3.	Modulation level on the record.
    4.	Radius at which the stylus was tracking
    5.	Humidity
    6.	Temperature (extremely non-linear!)
    7.	Cleanliness of the record
    8.	How the record had been previously cleaned
    9.	Tracking error
   10.  etc.

So the method you mention can be fraught with all sorts of errors, and is
I suspect, no better than the anti-skating force gauge. At best, they are
all a compromise.

Dick Pierce