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VPI tonearm geometry

An attempt to understand the geometry of VPI tonearms

The geometry used by VPI tonearms is presently undefined and this article will attempt to provide a better understanding of VPI’s tonearm geometry. I’m not the first to have questioned VPI’s tonearms. John Elison, for instance, contacted Harry Weisfeld several times over past years requesting VPI’s geometry parameters. Except for the numbers provided on VPI’s website, John never received an answer to his questions concerning the second null point or his request for more precise and exact data.

My point is not to criticize VPI because all vinyl fans know the high quality of VPI products.  In fact, I am a very happy user of a VPI 16.5 RCM imported from the United States at a time when VPI didn’t have distributors in Europe.  However, I would love to own a VPI turntable in the future.  Therefore, my approach is one that any customer aware of tonearm geometry theory might have when looking at the rather unconventional data provided by VPI.

We will discover (if you can finish this long and boring paper) that, finally, the alignment proposed by VPI and by their jigs is really interesting.

Harry, why didn’t you tell us before!

VPI data

Official data for VPI tonearms can be found here


  JMW 9 JMW 9 + JMW 9 Sig JMW 10 JMW 10.5 JMW 10.5i
Headshell offset 23.5° 23.5° 23.5° 22° 22° 22°
Spindle to pivot 223mm 223mm 223mm 250mm 250mm 262mm
Overhang 15mm 15mm 15mm 15mm 15mm 15mm
Null points 66mm 66mm 66mm 66mm 66mm 66mm


What is the problem with this data?

The problem is that when you combine data to calculate the null points, you’re not obtaining the first null point at 66 mm.

With the JMW-9, JMW-9 PLUS and JMW-9 SIGNATURE, following the indicated mounting distance, angular offset and overhang, you’ll obtain null points at 49.16mm and 140.6mm.

With the JMW-10 and JMW10.5, the pair of null points you’ll obtain will be 53mm and 145.4mm. With the JMW10.5i, the null points will be at 52mm and 155.5mm (out of the LP).

Since the first null point is declared to be 66mm, the real data behind VPI tonearms are not the data provided by VPI.

In fact, this is not that important since VPI provides a jig to help users align their cartridge. This jig is rather unconventional since there is a unique null point but, when using the jig, you must point it to the pivot of the tonearm. Two jigs were evaluated in this report—a black one and a white one.

Let’s now understand certain issues regarding alignment.

We’re about to present some calculations. These calculations are not related to any assumptions made by Löfgren, Baerwald and others who provided various pairs of null points we’re usually using. This is just simple geometry.

Let’s begin with this first question: “What is a null point?”

At a null point, the projection of the cantilever onto the record’s surface is exactly perpendicular to a line passing through the platter’s spindle and the stylus.  In other words, tracking error is zero at a null point and there can be a maximum of two null points for pivotal tonearms.

Let’s make a drawing to visualize the null points:

Null points are measured by their distance to the spindle centre i.e. AC (NP2) and CB (NP1). The angle formed by the line passing through the stylus and the pivot of the tonearm and the projection of the cantilever onto the record’s surface is named the offset angle (AOffset). Once set up, the offset angle is fixed. 

Linear offset.

The linear offset is given by OA* Sin (offset angle) = OB* Sin (offset angle) (since OA and OB are equal to the effective length).

This linear offset is equal to DB and AE.  Therefore, it follows that:
Linear offset = NP1+DC
Linear offset = NP2-CE

Let’s now take a look at the triangles ODC and OEC with right angles at D and E. Those triangles share one common side, OC. and OD = OE = OA * Cos (offset angle) =OB * Cos (offset angle). It follows that DC=CE

And then the linear offset is (NP1+NP2) / 2
DC = CE = (NP2-NP1) / 2

Whatever the effective length, if you choose a pair a null points, the linear offset is simply a function of the pair of null points you choose.

I asked VPI jig users to measure the angle OCB on their jig. What is the theoretical value of this angle?

Let’s begin with the DCO angle – once we have this angle, OCB will be 180-DCO.

DCO is given by: ArcCos ((NP2-NP1) / (2OC))
And then, OCB is 180 - ArcCos ((NP2-NP1) / (2OC))

Remember that OC is the mounting distance and for a given pair of null points, the angle OCB is a function of the mounting distance.

Let’s call the angle measured by users, Alpha.

Our goal here is to obtain the value of the second null point (since it’s not provided by VPI). Let’s consider the mounting distance as known. We now need to resolve this equation:

Alpha = 180 – ArcCos ((NP2-NP1) / (2OC))

180 – Alpha = ArcCos ((NP2-NP1) / (2OC))

Cos (180 – Alpha) = ((NP2-NP1) / (2OC))

NP2 = 2OC * Cos (180 – Alpha) + NP1

Once we know the second null point, all other data relating to the geometry of the tonearm alignment can be calculated from the following equations:

Effective length = (OC² +NP1*NP2)0.5

Angular offset = ArcSin ((NP1+NP2) / (2*Effective length))

Overhang = Effective length – mounting distance

Measurements of the VPI jigs

I asked users of the VPI jigs on various vinyl forums (Vinyl Engine, Vinyl Asylum and the LS3-5a French forum to take their jigs and measure the inner null point as well as the angle of the grid to the stylus/pivot line. (And I would like to thank those users: John Elison (VA), Musikmike (VE & VA), Lanny (VE), Naturalman, bbill (;-)) (LS3-5a))

There is no real doubt about the position of the null point on the black VPI jig, which is 68.75mm. About the white one, I have only one measurement of 68.0 mm.

Now, the grid angle for the white jig has been measured at 96.2°. For the black jig, things are rather complicated. Most users measured that angle to be 96°. Now, John Elison indicated to me that the spindle hole is closer to the edge than the centre of V by about 2.2 mm. Because of this, John Elison measured his black jig’s grid angle to be 95.5°. I’ll provide numbers for those two values.

The black jig is supposed to work with JMW 9, 10 and 10.5 tonearms; the white jig is supposed to work with 10 and 10.5 series. We supposed in our previous calculations that the mounting distance is known. For the JMW 9, a mounting distance of 223 mm is given by VPI on their website. Now, on VPI turntable, this arm is mounted at 222mm (measured by users with a Feikaert jig). Since, our results depend on the mounting distance, this explains why, in the next tables, we’ll indicated the second null points and so on for various mounting distances.

In the center column of the table there are three columns of numbers.  The first two columns represent the black jig while the last column (with an angle of 96.2°) represents the white jig.  There are no values for the white jig with the JMW-9 because it was applicable only to the longer tonearms.

First result: there is no clear outer null point. This is a direct consequence of the construction of the jig.

Please understand that the data is determined by the VPI jig.


Let’s now compare the pairs of null points we obtained with more traditional approaches (Löfgren A (aka Baerwald) and Löfgren B).

For the 9” tonearm, I took the mean value of the outer null point (113,43) and a mounting distance of 223 mm.

In the two last lines of the table, I calculate the average %RMS distortion over the record length and over the last third of the LP. Our idea here is to have a single number represent the distortion caused by one or another pair of null points. I’m providing the %RMS for the last third of the LP side because, when searching on the Internet about VPI geometry, Bbill (LS3-5a forum) found this text:

Harry Weisfeld once said: "I use a Mitch Cotter system described by Peter Axcel in The Audio Critic. I find it to be the best sounding of the bunch. On the JMW-9 the jig we supply will give you lower distortion in the final third of the record. Just a point of view difference but they sound a bit different. Listen to both and you decide in your system with your cartridge which matches better. Both work, but they are different. We don't publish the specs because we want you to use our jig! No matter what anyone says cartridge alignment is a matter of taste." 

I do agree with the later affirmation!

The overall measure of distortion is very good and comparable to that obtained with Löfgren B alignment (whose aim is to minimize overall distortion). Now, one can even considerer this alignment better than the Löfgren B since the distortion at the end of the LP (the weakness of Löfgren B null points) is lower with the VPI null points.  On the other hand, one could also consider VPI’s alignment to be worse than Löfgren B since VPI simply traded lower inner groove distortion for higher outer groove distortion.  The next drawing confirms this fact.

Here’s something interesting to consider:

All LPs have outer grooves that start at approximately the same place—somewhere between 144-mm and 146-mm.  However, the position of the innermost groove seems to vary considerably among LPs—anywhere from 60-mm to 70-mm.  Therefore, by shifting the alignment curve to favour inner grooves at the expense of outer grooves, you will always be listening to more distortion if you always begin playing the LP at its outermost groove.  Just a thought!


The data used to build this drawing can be seen in the previous table.

The distortion curves pictured above are called weighted tracking error curves.  They are weighted in order show the audible effect of tracking error distortion across the entire grooved area.  For example, the blue Baerwald curve shows approximately 0.6% distortion at the innermost groove, in-between the null points, and at the outermost groove.  The audible effect of this distortion will be the same regardless of groove position.  The Löfgren and VPI alignments produce lower distortion in the middle of the LP at the expense of higher distortion at the inner and outer grooves.  Some people prefer this type of alignment because even thought distortion is audibly higher at the beginning and end, it is lower for a longer period of time in the middle of the LP.

If you’re now using the jig with a 10” tonearm, things could be a little different.

Distortion for the last third of the LP is now lower with Löfgren B than with VPI’s alignment. Now, if the real angle is 95.5°, the distortion for the final third of the LP remains inferior to the distortion obtained with Löfgren B null points.

The next drawing shows the distortion curves.

Finally, for the longer 10.5, even if I’m using the value of the outer null point obtained by an angle of 95.5°, the lowest average %RMS distortion will always be given by a Löfgren B alignment. That is the definition of Löfgren B.

In this later case, the VPI alignment forced by the jig is similar to Löfgren A (Baerwald) alignment during the first 50% of the LP side.  At the end, it is very similar to a Löfgren B alignment.


Well, you’ll certainly think that I’m crazy but I had a great time analyzing the geometry of VPI tonearms forced by the use of the VPI jig. The solution proposed for the 9” series tonearm is quite interesting due to its very low distortion in the middle of the LP.  The outer null point moves out farther for the 10 and especially for the 10.5i.

Now, regarding the jig by itself, I think that VPI is providing a very good tool.  We generally align our cartridge with some piece of paper and our eyes. Both those tools have their limitations and between the real null points and the null points presented by the paper protractor, there is always a gap.

You say you’re using a basic protractor (like the “stupid protractor” you can download here)? Well, are you sure that you’re able to see a 0.5° difference between your cartridge body and the lines printed on the piece of paper?

You say you’re using an arc protractor (like a WallyTractor, one of mine or one made by Stephlouv from the ls3-5a forum)? Are you sure that the mounting distance stated by the drawing is the one you actually have on your turntable? Are you able to accurately measure the mounting distance? Are you sure that you’re really following the arc?

You say you’re using something like a Geodisk for which you need to point toward the pivot of the tonearm. Are you sure that you’re pointing exactly that pivot?

So there will always be a gap between your null points and the ones indicated on your protractor. Most of the time, there won’t be any consequences because misalignment problems arise only in some extreme cases and you’re guessing that alignment is not that important as long as set-up is done properly and accurately.

Some people don’t like Löfgren alignment for instance. They’re hearing a tracking problem at the end of the LP side. To me, this is because Löfgren alignment is more “risky” than the more standard Löfgren A alignment, better known today as Baerwald’s alignment. The gap between your real null point and the Löfgren null points certainly explains that mistracking. If accurately set up, I’m not sure you could hear a real difference (but I don’t have golden ears).

Now, should we burn all our paper protractors? Certainly not! But if you choose to use this kind of protractor, please have in mind that, when it is said, for instance, the cartridge body must be parallel at the two grids, this means: the cartridge body MUST be parallel at the two grids, not “almost”.

And that VPI jig? By its construction, the effective length will be quite accurately set up. Now, regarding the offset angle, you’re still having one pair of eyes but the gap between the actual and the theoretical null point will be minimized by the fact that you’re controlling the effective length.

There is always a unique outer null point with the VPI jig based on its inner null point, mounting distance, and grid angle.  I tried to show that average distortion is quite good and comparable to what the other popular alignments could theoretically provide (but things could be improved for the 10 and 10.5i tonearms).  In my opinion, VPI’s alignments are comparable to other, more popular alignments, especially in the case of the JMW-9.  Furthermore, the alignment method employed by VPI is certainly far superior to flimsy paper protractors, arc protractors and sight-line protractors.  It is therefore clear to me why VPI customers are generally happy with their VPI tonearms.

A special note to Harry Weisfeld who may read this article

You have provided some very interesting answers to alignment issues by the construction of you alignment jig.  Please understand that this paper is an attempt to understand what was on your mind. Your choice was to not communicate much about the specific data relating to your tonearms.  In fact, you chose to actually publish proxies (some might say erroneous data) on your website.  Well, this is your choice, but now, you know that some customers want to know more.

I know that this kind of analysis is not your cup of tea. Please understand that the tools I’m using are the ones used by people interested in understanding tonearm geometry and issues regarding cartridge alignment. Those tools are as old as geometry and trigonometry.

Löfgren’s paper (published in 1938) is the base of all subsequent papers published on the subject including Baerwald (1941), Bauer (1945), Seagrave (1956), Stevenson (1966) and Kessler & Pisha (1980). Interested reader will find an excellent paper by Graeme Dennes reviewing and analyzing those historical papers here

If I have presented any incorrect data in this paper, I take pride in knowing that I am in good company.  However, if you would like to provide more accurate data that can be verified mathematically, I will be happy to improve my analysis to reflect the greater truth.

My deepest thanks to John Elison who checked my very bad English and to Graeme Dennes who accepted to read preliminary versions of this paper.

All errors in this paper remain mine.



Many thanks to sjg for the corrections


VPI arm info

Hi Seb,

I am gathering specs to provide to a plinth builder (SP-10 Mk 2) to allow mounting for my JMW 10.5 arm. I see you utilized a S2P distance of 250 mm. I bought this arm used and it did not come with a manual or VPI jig.

However in my correspondence with VPI, Mike (customer service rep) stated the S2P distance is 252 mm. I was able to borrow a white VPI jig from a friend and careful measurement of that confirmed the 252 mm distance, assuming the 15 mm overhang is correct. So if the printed specification is wrong for the 10/10.5, it might be possible for the other VPI arms as well.

How much difference would this make in your calculations?

Thanks, Pryso


Hopefully, you PM so and I then discover your question ;-)

problem is that the data I used in 2008 to write this paper came from the VPI website. At this time, the mounting distance was said to be 250mm and the aim of this paper was to understand the very strange data VPI gave (as the functioning of the VPI jig).

I never received any comment form VPI (and I sent them a draft version of the paper prior to its publication here) and VPI didn't communicate very much about their toneram geometry.

If the mounting distance is 252 mm, assuming a first null point of 68.75mm, the second null point will be something like 120.3mm (I cannot be precise here as explained in the paper). Overhang is then 15.9mm.

distortion curves should be like that in this case:

hope it helps ;-)

best regards


The fastest spinnig portion of the record sounds best

We all know that 45 rpm records sound better than 33 1/3 don't we? Those high priced records that are today recorded in 45 are done that way for a purpose. The 45 is the superior medium. 16rpm is reserved for speech and low fidelity applications. 78 was needed for higher fidelity until new technology drove the need for high speeds irrelevant. So why is Harry's theory the best. Because you are taking the fastest spinning portion of the record and adjusting for lowest distortion. And we all know that the finale is important. Cannon shots be damned.

But if this technology is to advance we should be aiming for the highest fidelity at the lowest speed. I support a limited number of 45rpm records to show what the medium is capable of but let's move this technology along. If it is to have a future, then we must continually strive to put the most information on the smallest amount of disc surface. Despite digital. They haven't replaced the automobile have they?

To err is normal. To royally screw things up is divine.

JMW 10.5i geometry

I suppose to have a JMW 10.5i tonearm.
However, after reading your fine article about VPI tonearms I am not sure anymore about the model.
Do I have the 10.5i or the 10.5?
The reason for questioning is the different tonearm data I measured in comparison to the data shown in your tables.

E.g. I measured spindle to pivot 256mm and effectivelength 271mm!?

How can I determine that I do have a 10.5i without having a 10.5 for comparison??

thnks vm in advance for ur help

You probably know by now but

You probably know by now but indeed, the 10.5i has a S2P distance of 256mm.

VPI 12.6 geometry

The 12.6 comes w/the black jig. I have adjusted the portion w/the V that slides on the piece that goes on the spindle. All that said, has the same math been applied to the 12" arms and results published?

- John

VPI Jigs


I have both the with and the black jigs and I can say that the white jig has a null point of 66mm while the black on is closer to 69mm, which I guess is 68.75. I also agree with John Elison that the spindle whole is closer to the edge than the center of the "V" (on the black jig), therefore, am wary of that as if one lines up the V to be dead center with the Jig screws, then try to line it up with the spindle and V center, they are not a straightline from Spindle to V to Pivot...

Ugh...more frustrations on setting up my shelter 501 with the JMW 10...


Mounting a Shelter Cartrige on a VPI 10.5 arm

Hi there, I am a long time owner of a VPI Aries II with all of the HRX goodies, along with now a VPI 10.5i arm. Yes, I too had problems mounting a Shelter cartrige and (get this) a Grado too. The problem with both of these cartridges is their compliance is too high, thus, when combined with the VPI arm, you get a resonant frequecny of under 9hz which is bad for record warps, footfalls, and other resonance issues. Unless you are willing to move up to the VPI 10.5i arm or step down to the JMW 9 arm you will always have a problem mounting these cartridges on this arm. My suggestion is get a Benz (which is what I use) if you want the MC warm, or if you are looking for speed go with the Helikon (though I didn't like it). Harry won't give a clear effective mass for his tonearms which does bug, and makes it hard to match up his arms with cartridges unless you are willing to mix and match. There are my thoughts. I hope they help.



Stanley Wallen I am still using this alignment tool , I use to sell them when I was an audio dealer years ago. At the time they were well regarded, what is their current reputation? My eyes are no longer as good as they use to be and I am not as good at sighting in the exact center of the pivot. Short of getting someone with younger eyes to align the arm which is the best tool available at a reasonable price?

I've use the Dennessen

I've use the Dennessen Soundtractor for decades now, and the VPI sure seems to be similar, though because its meant for a specific arm, the VPI doesn't need the complex pivot locating arm that the Dennessen has. Anyone know if they are the same in their function?

the dennessen tool is

the dennessen tool is different.

it's rather complicated to explain but, with a dennessen, whatever the mounting distance, you'll always obtain the same pair of null points (not with the vpi jig)

the complex pivot locating procedure is the price to pay to obtain an very accurate setting. (and keep that tool! IMO, this is the best tool to have to set up a TT!)

best regards



Vinyl Forever!!!


I am difficulties in regulating the JMW-9 Signature
of the VPI Scout! I request aid! some tutorial… manual one for me
he is very vacant… I am vinyl aprendiz! and taste very. Thak You!

regulating ? what if the

regulating ?

what if the problem exactly ? positioning the cartridge ?

best regards


antiskating ? on a VPI tonearm ? ;-)

I don't know anything about that antiskating mecanism but it seems that there is an antiskating mecanism (first thing to check with VPI tonearms)

The simpler way to set it up is to obtain an HFN test record and set up the antiskating force with it... (nothing in the manual ?)

hope this helps !

best regards


Antiskating ...

The manual does not indicate how to do this adjustment!

Thank you!

Vinyl Forever!!!


The manual only shows how to set-up the anti-skating mech.,and does that badly.It does not show how to adjust it.I guess you have to listen,but it does discourage the use of a test record without groves.
By the date on this post,I would assume that you have probably figured it out.
From what I have found out is that you set-up the anti-skating with no weight or just one o-ring to give the arm a little resistance and none on the side with the groves where the line from the tone arm attaches.
This should do for cartridges with between 1.8 and 2.2 grams of VTF.
I have the Wally anti-skate set-up device as seen in the Michael Fremer video,and with no twist in the tone arm wire,this is dead on for my set-up.

Vinyl Forever!!! Was

Vinyl Forever!!!

Was difficult and laborious! But I can assure you that the mechanism of Antiskating well adjusted brings a significant difference. No conception despite guidance for not used to do without. I use and I recommend its use by experience.

Tonearm null points and tracking error

I found your article very interresting. Particularly when you mention (accurately!) that the null points are out of the record surface!

I have created an Excel spreadsheet that computes and traces the graph of a tonearm of any lenght, overhang and offset angle. Given an effective lenght and overhang, it also calculates the optimum offset angle. It is not based on any "official" method but on simple geometry and trigonometry. If you would like to have a copy of it, just tell me : geometry is of public domain and I would be pleased to send it to you.

There is one thing I do not really understand about the usual null points that most tonearm manufacturers use. I would tend to aim for a minimum tracking angle error, which is only obtainable if the error at the last groove equals that at the first groove. By the way, I use 145mm as the first groove and 63mm as the last one. For these, for a 12 inch tonearm (304.8mm), I obtain an overhang of 15.373mm and an offset angle of 19.113 degrees. With these settings, the null points are at 71.077 and 128.523mm. The maximum tracking angle errors are +0.8377 degrees at the first and last grooves, and -0.8378 at 95.3mm.

However, I notice that, for most arms of similar lenghts, the suggested null points are around 66 and 121 mm. For illustration purposes, I looked on the Net and found a Simon Yorke desing that is 308.8mm long (effective lenght), which is just a little over 12 inches. They suggest a distance from axle of 295.6mm (for an overhang of 13.2mm. The offset angle is 17.63 degrees. Then mention null points at 66.00 and 120.9 mm (for these settings, I get 65.795 and 121.275. which are damn close). These settings give tracking errors of +1.267 degree at 145mm ; -0.8169 at 89.1mm and +0.252 at 63mm. According to my program, the optimum offset angle for this overhang should be 17.855 degrees. That is not much difference, but it does reduce the maximum tracking error by almost 22%! For an arm of this lenght, my program would recommend an overhang of 15.16mm and an offset angle of 18.86 degrees. The maximum tracking errors are +0.826 degrees at 145mm, -0.826 at 95.5mm, and +0.824 at the inner groove (63mm).

Let us put that in a table form
Arm.................Simon Yorke.......My program
Lenght................308.8............308.8 mm
Overhang..............13.2.............15.16 mm
Offset..................17.63............18.86 degrees
Max positive.........+1.267...........+0.826 degree
At.....................145.00...........145.00 mm
Max negative........-0.8169..........-0.826 degree
At.......................89.1..............95.5 mm
Inner groove.........+0.252..........+0.824 degrees
Inner null..............66.0...............71.06 mm
Outer null............120.9.............128.52 mm

We notice that the maximum tracking error (which is at the outer groove) is reduced from 1.267 to 0.826 degree, which is a 53% improvement! We notice also that the error at the inner groove has grown from 0.252 to 0.824 degree.

I did not "pick" the Simon Yorke desing on purpose ; I could have used any other 12-inch arm and results would have been quite close to those of the Simon Yorke.

What I do not understand is why don't these arms aim at the smallest possible maximum tracking angle (which is always at the outer groove)? There is always a large difference between the outer and the inner groove, at the expense of a significant increase of the error at the outer groove. I understand that, at the inner groove, the signal is more compressed since the linear speed is smaller. If anyone could explain that to me, I would be gratefull!

>What I do not understand is

>What I do not understand is why don't these arms aim at the smallest possible maximum tracking angle (which is always at the outer groove)? There is always a large difference between the outer and the inner groove, at the expense of a significant increase of the error at the outer groove. I understand that, at the inner groove, the signal is more compressed since the linear speed is smaller. If anyone could explain that to me, I would be gratefull!

Hello (and thanks for your interest).

I'm having problems to recalculate the tracking angle errors you indicated - the ones I'm obtaining are different from the ones you indicated (and I'm very interested by for excel file ;-))

Now, there is a problem when you only analyse the tracking error (groove tangent-angular offset) because the consequences of a given tracking error depends on the radius where you are. It is more usefull to analyse the % tracking distortion in this case.

to illustrate this, take a look at this drawing.

three curves are represented and the idea of the % tracking distortion is to having a idea of the impact of a given tracking error independantly of where you are on the record.

As you can see, the impact of a given tracking error is multiplied by 2.4 from the outest groove to the innest groove.

you can easily recalculate the %tracking distortion by using the John Elison Excel file.

for this second drawing, I supposed a identical % tracking distortion wherever you are on the record. this is only possible if the tracking error is moving accross the record side a certain way :

now, if I take a look at the data you calculated, I'm obtaining this with tracking error :

and this with the %tracking distortion :

an another question : by choosing different innermost and outermost grooves, you pointed a very interesting problems - the standards values we're using are the IEC standard values (60.325 and 146.05). We all know that the innermost groove is rarely 60.325 and things could be improved if we could have an idea of the distribution of the innermost groove across a significative sample of LP.

Where did you get that 63mm value ?

best regards


(PS : and you're guessing that John Elison did a splendid work in his correcting of my very bad english)

Tracking Error

I'm sure Seb will be able to give a better explanation than me, but the Simon Yorke design uses Baerwald null points which are designed to give a certain spread of distortion across a record.

From Seb's Protractor User Guide:

Baerwald - The distortion at the beginning, the middle (where it’s high) and the end of the record must be equal

Loefgren - Alignment must minimize the distortion across the record

Stevenson - Distortion is more important at the end of the record so let’s minimize it by assuming a null point at the end of the record, i.e. at 60.325 mm (IEC standard end of the record)

You can see from this graph of the data you have supplied, compared to Baerwald and Loefgren alignment, that their is no such thing as a free lunch.

Graph of tracking error and distortion

You can also see why Seb is such a fan of Loefgren B null points!


Variation of tracking error across a record

Quite a few of my Deutsche Gramophon classical recordings only have music down to 70 mm from the record center. I'd be interested in a cartridge alignment that didn't try to accommodate those last 10 mm (down to 60 mm) but instead gave the lowest errors from 145 mm downto 70 mm.

By the way, what does cartridge alignment error actually sound like?