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The Clearaudio Alignment Tool

This paper is the fourth one of a series dedicated to the analysis of alignment tools offered by various manufacturers or offered for free on the Internet. We’re here offering an analysis of the Clearaudio alignment tool.

This tool is rather unconventional by offering various settings depending of the innermost groove you’d like to consider. If you understand alignment issues, you certainly know that problems arise at the end of the record. The closer you are from the spindle centre, the more a given tracking error will create distortion.

The value of 60.325 (IEC standard) is generally used but we all know that records with an innermost groove at 60.325mm from the spindle centre are rather scarce… using 60.325 mm is having strong consequences. See this drawing:

By considering an innermost groove of 75mm, if you’re really having no music after 75 mm from the spindle centre (in fact before…), you can calculate a new pair of null points that clearly overstated the classical Lofgren A (Baerwald) null points (66mm and 120.9mm).

Now, there is a danger! If you having music recorded on grooves between 60 and 75mm, you’ll understand what IS distortion…

But, you certainly understand now why the position of the innermost groove is important: it’s conditioning seriously the null points you’re using and the overall distortion results you could obtain.

Let’s take a look at the Clearaudio tool

The documentation of the Clearaudio tool is saying to provide (almost) perfect and easy alignment for every tonearm mounted between 222 and 327mm from the spindle centre. In fact, our analysis of the Clearaudio tool will be based on this sentence (taken from the documentation, page 6):

Data: The overhang adjustment is absolutely correct for any pivot distance.

The value of the offset angle is medium for pivot distances between 222mm and 327mm with a maximal deviation from optimum of only 0,17° with optimization for IEC inner groove radius and only 0,12° with optimization for inner groove radius according Clearaudio-Recommendation (r=75mm). These deviations are far below reading precision. The offset angle medium value for pivot distances within the o.m. range is absolutely correct for a distance of 264mm

We’re considering that the designer wanted to minimize peak distortions. Why? Because on the drawing presented on the manual, page 7, the null points associated to the pink curve are the Lofgren A (Baerwald) null points.

First step : looking at a scan of the Clearaudio tool

At a first glance, the Clearaudio tool looks like a Denessen aligment tool: you need to point the pivot of the tonearm and move the cartridge to have the stylus at the centre of a grid and to have the cartridge body parallel to the lines of the grid.

In facts, it is not a Denessen tool: the stuff supporting the graduated bar is passing through the spindle centre. This is not the case with the Denessen tool.

Second difference

Not very easy to see on this scan (I’m having a super size scan in fact – thanks to The Professor from the Crossover Network forum) but the vertical lines are not in fact vertical (perpendicular to an horizontal line) : there is an angle. Now, the centre of the grid is exactly at the vertical of the spindle centre.

Third difference: the grid is not positioned at a conventional distance.

I first measure the angle, it’s something like -0.9° (clockwise from a vertical line) and the position of the grid compared to the spindle centre: 89.3 mm

Why those values?

Brainy time…

Ok, I’ve got it : 89.3 mm is very close to the groove where occurs the maximal tracking error when you’re considering an innermost grove at 60.325 and an outermost groove at 146.05 (IEC standards). (The second grid, the one with an innermost groove at 75 is positioned the same way).

The position of that groove is given by this formula (as usual, given by Graeme Dennes paper):

Groove max = d =

With R1=60,625 and R2=146.05, you’re obtaining 89,32302

(My reading of the scan was quite good!)

Let’s now understand that -0.9° angle…

And read again the last part of the sentence:

The offset angle medium value for pivot distances within the o.m. range is absolutely correct for a distance of 264mm

Ok, let’s assume that this distance is a mounting distance and let’s calculate using Lofgren A (Baerwald) equations the tracking error for the 89.32302 groove… (you can use John Elison Excel spreadsheet) – you’ll find : -0,896952°

Hooray!

Let’s now check if we can understand the first part of the sentence:

The value of the offset angle is medium for pivot distances between 222mm and 327mm with a maximal deviation from optimum of only 0,17° with optimization forIEC inner groove radius and only 0,12° with optimization for inner groove radius according Clearaudio-Recommendation (r=75mm)

If you calculate the tracking error at the 89.32302 groove for a tonearm mounted at 222mm, you’ll find -1.068° (and 1.068-0.896952 is 0.171°)

If you calculate the same tracking error for a tonearm mounted at 327mm, you’ll find -0.723° and 0.896952-0.723 is 0.174°).

So, we understand that max error of 0.17° : it is the maximum difference between the pure Lofgren A (Baerwald) offset angle and the one you’ll obtain using the Clearaudio tool.

There is a sentence we didn’t comment yet :

These deviations are far below reading precision

This is the important point…. Even if those deviations are small, they could have important consequences in terms of distortion… I need to check that…

The next drawing is resuming the functioning of the Clearaudio tool.

We exaggerated the 0.89..° angle, this drawing is not on scale (I use this drawing while writing this note to check that the formulas I’m given are exact)

We need to find the effective length and the offset angle forced by the use of this tool. Once we’ll have those measurements, we’ll then deduce the null points forced by the use of the tool.

The effective length is given by this formula (I like geometry…)

Effective Length = [[MD]²+[d²]]0.5

Where MD is the mounting distance,

d is the distance between the spindle centre and the centre of the grid (fixed at 89.3…mm)

Let’s take another look at this sentence:

The offset angle medium value for pivot distances within the o.m. range is absolutely correct for a distance of 264mm

If we impose a mounting distance of 264 mm, what effective length are we obtaining?

Using the formula, you’re obtaining an effective length of 278.70 mm –which is the correct Baerwald value). In fact as indicated by Clearaudio, whatever the mounting distance, the effective length forced by the tool (and the overhang) is always equal to its Lofgren A (Baerwald) value.

This can be easily demonstrated using some results presented by Graeme Dennes in his paper. See page 15.

What we’re calling here d is in fact Ra in his paper (and what is called d in Graeme Dennes paper is the overhang) – let’s adapt the equation 4 to our notations:

OV = L – (L²-d²)0.5

With d =

OV is the overhang and L the effective length.

That first equation becomes:

L - OV = (L²-d²)0.5

M = (L²-d²)0.5

M² = L²-d²

M is the mounting distance.

Conclusion: whatever the mounting distance, since d is fixed (determined by the innermost and outermost grooves), if you use the Clearaudio tool, a given mounting distance will always be associated to the correct Lofgren A (Baerwald) effective length.

Splendid!

What about the angular offset?

The offset angle is the angle formed by the line BA and the line symbolizing the grid lines.

The angle OAB is given by ArcCos(d / effective length)

DAB is then OAB-0.89…

The angular offset is then 90 – DAB.

For our tonearm mounted at 264mm

OAB is 71.30°

DAB is 70.41°

Angular offset is 19.59° which is the good Lofgren A (Baerwald) value.

From the measures where having, we can deduce de null points associated - we already know that those null points are the classics 66 mm – 120.9 mm but we need to present the formulas we’ll use in the next section.

The formulas we use are taken from Graeme Dennes paper (page 174, equation (3)).

with

L: effective length

b: angular offset

M: mounting distance

You’ll obtain 120.891475 and 65.998047 (with are in fact the exact values of Lofgren A (Baerwald) null points).

Generalisation

If the tool is providing a perfect Lofgren A (Baerwald) alignment when the mounting distance is 264 mm, what happen if the mounting distance is different?

In the next table, we’re providing the pairs of null points you’ll obtain for various mounting distance. We include in this table a little number of mounting distances close to the minimum and maximum values stated by the manual (since this is where the largest “errors” will occur).

 

innermost groove

60,325

           

outermost groove

146,05

           

mouting distance

264

222

230

240

310

320

327

D

89,32

89,32

89,32

89,32

89,32

89,32

89,32

alpha

-0,90

-0,90

-0,90

-0,90

-0,90

-0,90

-0,90

               

effective Length

278,70

239,30

246,74

256,08

322,61

332,23

338,98

angular offset

19,590

22,815

22,121

21,311

16,971

16,493

16,175

               

inner null point

66,00

67,67

67,34

66,93

64,36

64,02

63,79

outer null point

120,89

117,90

118,49

119,21

123,97

124,62

125,07

 

In the first column, d and alpha are recalculated and the value we obtain are used in the next columns.

The null points are slightly different from the classical Lofgren A (Baerwald) pair of null points (66 / 120.89). To me, this is not that important (I saw tools forcing some null points to be out of the LP so, the little differences you could see in the table are not a problem).

This first graph is indicating the characteristics of the alignment provided by the Clearaudio tool with a tonearm mounted at 222mm. It provides a comparison with the classical Lofgren A (Baerwald), B and Stevenson alignment:

There is almost no difference between the Clearaudio alignment and Lofgren A (Baerwald) alignment.

The next one is for a tonearm mounted at 327mm:

The differences are less subtle but, since the tonearm is longer, the peak distortion is only of 0.5% between the two null points - this should not be considered as something important – the peak distortion is equivalent to the one you “stand” at the beginning of the LP with a Lofgren A (Baerwald) alignment... (and I never heard that a Lofgren A Baerwald alignment is providing a high distortion at the beginning of the LP... )

This tool is having the advantage of being very simple to use. I believe you can accurate set up your cartridge with it but there is no free lunch in this cruel world: simplicity, accuracy are paid by those little differences (with, in my opinion, no consequence on the sound you’ll hear).

Another advantage of that tool is that it is equilibrated! If you’re using a suspended deck, since the spindle centre is right in the middle of the plate where the grids are engraved, no special weight is added to one side or the other of the platter. This is a good point!

My opinion? A good tool !

A big hat off to the designer of that tool at the Clearaudio plant!

Some alignment device designers don’t know what they are doing, at Clearaudio, that clever design indicates that this is not the case.

I contacted Clearaudio prior to the publishing of this paper. I wanted to have details on some ‘Clearaudio findings’ (they recommend to use the 75mm innermost groove setting – I’d like to know the source of this recommendation) – I received until now no answer to my queries....

 

Appendix

(same as table 1 for the various innermost grooves possible for the tool)

 

innermost groove

65,000

         

outermost groove

146,05

         

mouting distance

264

222

230

310

320

327

d

93,47

93,47

93,47

93,47

93,47

93,47

alpha

-0,79

-0,79

-0,79

-0,79

-0,79

-0,79

             

Effective Length

280,06

240,88

248,27

323,79

333,37

340,10

angular offset

20,292

23,628

22,911

17,574

17,078

16,747

             

inner null point

70,75

72,40

72,07

69,13

68,80

68,57

outer null point

123,50

120,68

121,24

126,39

127,00

127,42

 

innermost groove

70,000

         

outermost groove

146,05

         

mouting distance

264

222

230

310

320

327

d

97,72

97,72

97,72

97,72

97,72

97,72

alpha

-0,69

-0,69

-0,69

-0,69

-0,69

-0,69

             

Effective Length

281,50

242,55

249,90

325,04

334,59

341,29

angular offset

21,002

24,448

23,709

18,186

17,671

17,328

             

inner null point

75,78

77,39

77,07

74,19

73,87

73,64

outer null point

126,00

123,38

123,89

128,70

129,27

129,66

 

innermost groove

75,000

         

outermost groove

146,05

         

mouting distance

264

222

230

310

320

327

d

101,77

101,77

101,77

101,77

101,77

101,77

alpha

-0,59

-0,59

-0,59

-0,59

-0,59

-0,59

             

Effective Length

282,94

244,22

251,51

326,28

335,79

342,47

angular offset

21,676

25,223

24,463

18,769

18,237

17,882

             

inner null point

80,75

82,32

82,00

79,21

78,89

78,68

outer null point

128,26

125,82

126,30

130,75

131,28

131,64

Comments

stylus tip allignment tolerance?

i've seen some tips that were visibly out of alignment (under a microscope) i.e. edges not 90 deg. to the cantilever. obviously, as you go from spherical thru the various ellipticals to line contact, aligning the contact footprint with the groove features becomes increasingly important for realizing a cartridge's potential performance. what tolerances do manufacturers hold as regards rake angle, tip orthogonality,etc. any clever test records that allow empirical allignment(s) using ears and simple test equipment ? just curious.

good point!

you raised a good point. In all the papers I wrote about alignment tools, I'm always considering that I'm living in a perfect world... the cantilevers and the tips are always like they should be and we know that in the real world, things are not that simple. For instance, most of us are considering when aligning a cartridge in the real life that the cantilever is aligned with the cartridge body - this is not true most of the time. (some vinylusers are not disengaging antiskating when aligning their cartridge.. wrong again..)

I discussed recently with Yosh, our man from Japan about the fact that there is always a gap between the alignment you're trying to impose to your cartridge (and the theoretical distortion figures associated) and the reality you're seeing with a good test record and an oscilloscope... Yosh could certainly add things about that...

take a look at his website :
http://www7a.biglobe.ne.jp/~yosh/sitemap.htm
(only some pages are in english)

best regards

Seb

Only a few explanations

Only a few explanations about a good test record and an oscilloscope.
In my understanding and tests:
Lateral tracking error distortion cannot be specified in these tests since even maximum distortion due to an extreme mis-alignment on normal arm&cartridge is anyway under 10%. We are often unable to see deformed wave on a oscilloscope when playing back test record, but note that distortion rate ascertainable on a oscilloscope shoud be more than 10% otherwise not easy to find as a distortion. Meanwhile any radical mistracking is evident on a oscilloscope.
Every test or testing equipment is useful for specific purpose.
About a oscilloscope: you do not need to buy it if you have a current computer.
There are many good free softs working as signal generator or oscilloscope using soundcard on a computer.

I will repeat a passage from my HP:
My personal note on lateral tracking error distortion: The most popular simulation graph is given by Mr. Elison
where corresponding distortion is indicated based on the reference velocity of modulation 10cm/s
which is much louder than normal recorded level. Moreover, tracing distortion for such high level modulation is more than 4 times of normal lateral tracking distortion.
The audiophiles are putting too much importance on subtle distinctions and would not have the broader view. I compared theoretical rates of distortions in my page based on velocity 5cm/s. FRANKLY SPEAKING THE MEASURED DISTORTIONS ON RECORDS CANNOT BE CLASSIFIED AS "WHICH DISTORTION IS FROM WHICH" RESPECTIVELY. They can be shown only as accumulated harmonic and non-harmonic distortions. I have never seen the test result indicating lateral tracking angle error.

I have no idea about a good test record or equipment suitable for alignment matters.
I am content with playing analog record as it is, and not worry so much about subtle matters such as alignment , adjustment, tweaks now - even though every analog system sounds different each other on our hearing.

Regards
Yosh