Well, Robert, you make some good points in this discussion. But you are
in error on some as well. First, what you term "azimuth" error is more
commonly called "lateral tracking angle error" or LTA by the tonearm
engineers. It was widely discussed and debated, particularly at the dawn of
the stereo LP with many learned papers written about it in the audio
engineering press. This tracking error became more of an issue with stereo
records because it is associated with a slight phase misalignment of the two
walls of the groove (thus the two stereo signals) as the cartridge tangency
changes. (This is a separate issue from vertical tracking angle error VTA
which was also an issue with stereo records but has no significance to
lateral monophonic recordings.) The result of a lot of "sturm und drang"
over LTA error was that, yes, it exists, and yes, it can be reduced to a
minimum with the choice of the proper offset angle of the head of the
tonearm as a function of the distance of the tonearm pivot to the platter
spindle. You are correct that the shorter this arm pivot to spindle
distance, the more the LTA error. You are also correct that this error
results in the steel needle turning with respect to groove tangency as the
record is played from one diameter to another. It is reasonable to assume
at first blush that this turning will present a sharp edge of the previously
flatted side of the needle to the groove wall and thereby do some gouging of
the wall. However, you are forgetting that the groove is not without
wiggles in it which represent the audio modulation. Which means that the
groove wall is continuously changing in its instantaneous tangency with the
needle. This means that the needle does not have purely FLAT spots worn on
its sides, but rather slightly curved (convex) spots as the sharp edges are
continuously worn down by the modulation in the groove. The higher the
modulation, the more this curvature will present. Therefore, the additional
slight turning of the needle in its tangency with the groove caused by LTA
error is probably insignificant in its effect on groove wear as the needle
doesn't present but statistically a very tiny amount of additional rotation
beyond the curvature of the flats caused by the previous record modulation.
In other words, the effect of LTA on causing additional record wear is
probably negligible. The effect might be more noticeable on records with
very low modulation such as some classical chamber music or similar.
Your statement that vinyl record cannot and do not wear diamond styli is
not correct. I was engaged in doing a lot of record compound wear testing
when I worked at the RCA Records manufacturing labs in Indianapolis. We
were developing two radically new record compound formulations at the time.
One was needed for the new CD-4 quadraphonic audio records which contained
supersonic signals up to 45kHz and the other was needed for the RCA
Capacitance Electronic Disc (CED) video disc system that was still in
development (it was vertical modulation, you might be interested to learn).
Consequently, we had installed a scanning electron microscope (SEM) to
evaluate the effects of wear both on styli and on records. The SEM allows
remarkably detailed views of the minutest surface irregularities with
extremely high magnification and extremely long depth of field view (sharp
focus over a wide range of depth in the specimen) that is not possible with
optical microscopes. I did wear testing of the audio record formulations
using several stylus shapes and tracking forces that represented the typical
users of the day, about 1975. We checked the amount of wear that could be
seen at intervals of 25 plays from 0 to 200 plays using players operating
typical high quality stereo cartridges operating elliptical diamond styli at
2 grams, Shibata diamond styli (line contact) operating at 2 grams, and
conical diamond styli operating at 5 grams which represented a good consumer
type player of the day. The results were frightening! The typical stereo
vinyl record compound exhibited quite noticeable "trenching" of the
sidewalls of the groove with the 5 gram conical in as little as 25 plays.
When auditioned, especially after 50 plays, these records sounded well worn
with much noise and crackling. The 2 gram elliptical fared better, but at
100 plays it produced noticeable trenching as well. The Shibata at 2 grams
would show very little wear of the sidewalls at 200 plays.
What's more pertinent to this discussion, however, is that the styli had
to be changed at regular intervals as they ALSO exhibited noticeable
flattening of their contact surfaces. I could get upwards of about 1000
plays from the 5 gram conical diamonds before I decided that they had gotten
too flatted. And, as I have stated above, the "flats" weren't actually flat
but rather broadly convex flatted portions at the contact points. 2000 to
3000 plays were about where I changed the 2 gram ellipticals, and the
Shibatas could last for 5000 plays or more. And these vinyl record
formulations contained no abrasives. But they DID wear the styli.
Lastly, I think you need to take another look at the LTA issue with the
Edison DD player. Yes, the Edison tonearm is pivoted in front of the pickup
as opposed to being pivoted at the back as with all conventional lateral
players. But it is still a pivoted tonearm and it DOES exhibit LTA error.
It just occurs with the reversed tangency arc to that of the back-pivoted
arm. In the typical DD player, the LTA is fairly low at the outside record
diameter but becomes quite high at the inside music ending diameter. In
fact, the LTA error was deliberately used to advantage in the development of
the Duncan electric stop. The fact that the LTA is very high at the inner
diameter of the DD player causes the stylus to skate toward the spindle with
considerable force. When the stylus falls out of the groove at the inside
end of play, the stylus and weight assembly swing inward until the weight
limit pin hits the limit loop which makes the electrical contact that the
Duncan stop relies on to close the circuit and operate the solenoid which
stops the DD motor. If there were no or very little LTA error, the skating
force would be minimal and the weight would not swing to the edge of the
limit loop.
Of interest here is that this LTA error on the DD player is basically
irrelevant, assuming the stylus is in good condition. The Edison as well as
the Pathe system relies on the conically shaped stylus tip sitting directly
on the bottom of the groove to properly trace the vertical modulation. It
can do this properly REGARDLESS of the tangency of the pickup head to the
groove. You will note that some record players designed to play both
vertical and lateral discs with their adjustable reproducers often present
the Pathe stylus to the record groove at quite a radical angle to the
tangent. The Brunswick Ultona comes to mind. Yet the system works because
the LTA is irrelevant for purely vertical modulation. Also note that Pathe
tonearms are often quite short. But the LTA that this causes poses no
problem to the reproduction.
Back to the case of record wear: The Edison DDs were specifically
designed to have quite a hard surface compared with the shellac material
that was used in lateral records of the day. That's why Edison chose the
condensite material. The playback theory of the lateral records was to have
the abrasive in the record material (which by the way was not diamond dust
which was much too expensive - the abrasive was a combination of the cheap
clay filler and pulverized limestone) wear the needle rapidly so that the
"flats" developed which VASTLY increased the contact surface area and
thereby quickly reduced the pressure on the sidewalls which reduced further
record wear. If you were to play a shellac record with a new steel needle
every few turns of the record (quite a tedious operation), you would find
the record very quickly wearing out because you would not be allowing the
use of a properly worn in steel needle with the right size flats. You may
have noticed that some records sound particularly noisy during the first few
revolutions of the starting grooves. This is because the use of a new steel
needle causes excessive wear in this portion of the record.
Contrary to this theory of operation, Edison wanted to wear the diamond
stylus rather than the record surface. So he used a stylus shape that had a
fairly big radius, AND which sat on the groove bottom with a large
percentage of its circumference supported by the matching radius in the
groove. This spread out the high tracking force over a fairly large contact
patch at all times. There was no need to wear flats on the stylus. Note
that even if the point of tangency changes due to the LTA error of the
Edison tonearm, the spherical stylus tip merely rotates in the groove but
STILL presents the same curved contact surface with the record which does
not have any additional effect on record wear. The choice of the condensite
material was such that it's elastic yield point (permanent deformation) was
higher than the pressure presented to it by the rounded stylus sitting in
the rounded groove. All is well and good until the stylus becomes chipped.
When this happens, the sharp edge of the chipped area presents a much
smaller contact patch to the groove which very quickly yields the condensite
under this very high localized pressure and results in a very visible
brownish-looking scratched appearance. The record surface has now been
permanently damaged and the record will play that area with much increased
noise. Regardless of whether you call it wear or damage, it's been ruined.
Greg Bogantz
----- Original Message -----
From: "Robert Wright" <[email protected]>
To: "Antique Phonograph List" <[email protected]>
Sent: Thursday, March 06, 2008 2:19 PM
Subject: Re: [Phono-L] Shellac records and damage from steel needles
> "I don't think anyone ever said that no wear (not damage-the choice of
> terms
> shows a prejudice) to a record occurs."
>
> Au contraire, dear Ron, it is eBay seller "nickjay" (or that's what he
> used to go by) who has said in no uncertain terms that he believes ZERO
> damage (or wear) happens with a single playback with a new steel needle.
> So yes, I'm afraid someone has said it, and I'm sure he's not the only
> "true believer" out there, as Rich pointed out.
>
> I'm suprised by the strongly defensive stance you take on behalf of steel
> needles, though I know you must have your reasons. But no amount of
> positive semantics replacing my negatively prejudiced choice of terms is
> going to reduce the amount of shellac dust I find all over the tip of
> every brand new soft-tone steel needle I play a shellac record with, so
> the terms really don't make any difference in the real world.
>
> I absolutely agree that optimal set-up on any machine reduces wear to a
> minimum (that's most of what the set-up is for, as minimum wear often
> equals optimum sound), but I was pointing out the one aspect of pivoted
> playback that the purveyors of this myth seem to be either ignorant or
> unaware: that azimuth error reduces the "new needles wear down to
> precisely match the groove and cause little to no wear after the first few
> grooves" theory to bunk.
>
> I also agree some machines had better designs than others. I know a lot
> of earlier, outside-horn machines had tonearms that were pretty darn long;
> every millimeter of added distance between the pivot point and the needle
> tip helps correct the azimuth error by some degree. I don't know how much
> heavier or lighter these older machines register at the needle tip, but
> I'd be willing to bet records suffered less wear played on them with new
> needles than on newer, shorter-tonearm'd models. (Unless, of course,
> there was very little compliance at the needle shank pivot on the older
> machines... I wouldn't know, I've never messed with any of them.)
>
> What I don't agree with is there being some great difference between wear
> and damage -- wear IS damage as far as I'm concerned, whether expected or
> not. Frankly, who among us makes such a distinction when considering
> buying a record that we later find out has almost completely greyed-out
> grooves? Who among us minds the occasional edge chip or flake? I fully
> expect those with shellac discs, as a part of "normal use" involves
> handling, and normal handling includes the occasional, accidental chipping
> of a record edge. No, I say it's a matter of simple semantics, none of
> which make any real difference -- but by all means, use whatever terms
> suit you, as will I.
>
> Lastly, a bit of quick clarification: regarding Edison DD's and the
> reasons for their relative lack of wear through playing, Pathe discs,
> unlike Edison DD's, are made of the same stuff as lateral shellac discs
> (minus the diamond dust, I'm assuming), and the only Pathe's I find with
> groove damage have obviously been played on a lateral machine with a steel
> needle at least once (it's a very obvious "look" the surface has when
> subjected to such numbskullery). As I said, Pathe's sapphire ball stylus
> machines offered exactly the same tip profile to the groove regardless of
> position and/or angle of the soundbox, because it was spherical; as such,
> I've never seen a clean vertical Pathe disc in the middle -- it has either
> been shredded to nothing by misuse, or its playing surface looks -- and
> sounds -- pristine.
>
> Final point (so to speak, ha ha): you won't get me to believe that the
> world's hardest substance can be altered by one of the world's most
> pliant. Modern cartridges are not "retipped" because of wear to the
> diamond; the entire cantilever is replaced, along with the cantilever's
> suspension. When burning in a new stylus, it is this cantilever
> suspension that is being broken in, and when the stylus needs replacing,
> it is because of the cantilever suspension, which cannot support the
> recommended Vertical Tracking Force after so many hours of use, making the
> magnets attached to the cantilever become misaligned with the coils inside
> the cartridge. Plastic does not wear down a diamond. (Playing shellac
> discs with diamond dust in them is, however, another story completely, as
> a diamond will obviously be reshaped by grinding against diamond dust --
> that's how jewelers shape them to begin with.)
>
> Don't let wear OR damage stop you from playing your records, but do know
> what you're signing up for and act accordingly.
>
> Best as always,
> Robert
>
>
> ----- Original Message -----
> From: "Ron L" <[email protected]>
> To: "'Antique Phonograph List'" <[email protected]>
> Sent: Thursday, March 06, 2008 9:01 AM
> Subject: RE: [Phono-L] Shellac records and damage from steel needles
>
>
>>I don't think anyone ever said that no wear (not damage-the choice of
>>terms
>> shows a prejudice) to a record occurs. That is clearly wrong for the
>> reasons you have stated. Wear to the needle continues throughout the
>> play
>> of the record. If a machine is properly maintained and the reproducer
>> has
>> compliant parts, when a new steel needle(not a nail - see comment in
>> parentheses above) is used, wear is kept to a minimum. Having said that,
>> further qualification should be made. Some machines had better designs
>> than
>> others. Steel needles are ground to a point and tumbled to create a
>> particular radius on the tip they are not merely, "headless nails."
>> What
>> has happened over time is that the whole playback system has become
>> refined.
>> Even diamond styli are worn by vinyl records and the records themselves
>> are
>> worn (degraded) every time they are played. No contact system of
>> playback
>> will eliminate this. If you have a super-valuable/rare record, should
>> you
>> play it repeatedly with a steel needle? No. But then again, you probably
>> shouldn't play it repeatedly with any needle/stylus.
>>
>> I think Greg Boganz mentioned the lack of wear on DDs on the Electrola
>> list
>> recently. It is not entirely because of the tone arm and has to do with
>> vertical grooves and the nature of the DD surface.
>>
>> Ron L
>
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