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Protractor User Guide

Phew, so many protractors in the set-up tools section !!!

Which one I should use?

In fact, it depends on the Turntable / Tonearm combo you’re using…

Some of the protractors posted on the Vinyl Engine are specific, some of them are generic. Some of them are Baerwald type, one is Loefgren and two are Stevenson

Baerwald? Loefgren? Stevenson? Which should I choose?

Which is the best?

I won’t tell you there is one better than the others. Make your own opinion.

Simply, the equation you need to solve to find optimal alignment is undetermined: there are too many unknown parameters. Baerwald, Loefgren and Stevenson apply different objective constraints to the problem to allow a solution:

  • 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)

What is a null point?

The path of the stylus follows an arc. As a matter of consequence, the stylus is not always orthogonal to the groove: it’s only orthogonal for two points named the null points. The main goal of alignment is to set up these null points at specific point’s dependant on the objective.

Conclusion: null point pairs (measured from the centre of the record) are different because of the added constraints:

  • For Baerwald null points are 66.0 and 120.9 mm
  • For Loefgren null points are 70.3 and 116.6 mm
  • For Stevenson null points are 60.325 and 117.42 mm

When you align a cartridge (using a particular technique) by setting the null points, you’ll obtain the ‘correct’ effective length (distance between pivot and the stylus) according to your mounting distance, the ‘correct’ overhang (difference between the effective length and the mounting distance) and the ‘correct’ offset angle (the angle between a line going from the pivot of the tonearm to the stylus and the axis of the cantilever/cartridge body (assuming that the cartridge body is parallel to the cantilever).

A simple drawing will explain everything

Which protractor for my combo?

Baerwald is the more common alignment technique

Loefgren is less popular but it makes sense.

Now, Stevenson. (not very common)

To me (my personal opinion), the protractor offered by Rega with their TT and tonearms is the Stevenson type. The unique null point proposed by this protractor is very close to the 60.325mm stated by Stevenson. But aligning a cartridge perfectly a with a unique null point is almost impossible, except if you’re using the third hole of the headshell (the one in the front) with a Rega cartridge. In that case, you force the effective length to the correct value stated by Rega (to me, it’s 237.44 mm) and you only need one null point.

Now, with other cartridges, the second null point is necessary to obtain a good alignment (by the way, if you bought the turntable basic’s protractor, you may feel that this tool is not as precise as expected)

The first thing to do is to check if you can use a specific protractor since they are easier to use.

A specific protractor will only be good for a TT equipped with a specific tonearm:

TT Specific Protractors

Rega Baerwald and Stevenson protractors

The Rega Baerwald protractor and the Rega Stevenson protractor are only of use with Rega turntables equipped with Rega tonearms. It may be useful too if your arms mounting distance is EXACTLY 222 mm (as for every Rega turntable). For instance, the NAD 533 turntable can use this protractor since they are a copy of the Rega TT sold under another brand name.

Using these protractors is very simple: be sure that the stylus follows the arc and align the cartridge with one set of lines. Why one? Because you only need one.

What is the point of the other line? It’s just a way for you to check that your mounting distance is correct. If the stylus follows the arc, if the cartridge body is aligned with a set of lines, if your mounting distance is the one specified by the protractor, then, the cartridge body must be aligned with the second set of lines. If it’s not, there is a problem (and specially, if the mounting distance is not the one indicated, you won’t observe a perfect alignment using the second set of lines).

The Rega Stevenson protractor may be used by people who would like to align their cartridge the Rega way without using the protractor provided by Rega.

Thorens Baerwald arc protractor

The ‘Thorens Baerwald arc’ protractor is only for use with the following turntables equipped with stock arm:

Ambiance, TD 125-II, TD 125-II, TD 126-I, TD 126-I, TD 126-II, TD 126-III, TD 126-IV, TD 145, TD 145-II, TD 146, TD 146-II, TD 146-IV, TD 160-I, TD 160-I, TD 160-IV, TD 160-V, TD 165-I, TD 165-II, TD 166-I, TD 166-II, TD 166-V, TD 280, TD 280-II, TD 316, TD 316-II, TD 318, TD 318-II, TD 320, TD 520

Stock arm : TP11 I, II & III, TP16 I, II, III & IV, TP21 and TP28 mounted at 215.6mm from the spindle centre.

Again, the stylus must follow the arc and you must align the cartridge body with one set of lines. If it’s not aligned using the second set of lines, it’s because the mounting distance is not the one indicated here (215.6). In that case, use a generic protractor.

Generic Protractors

Stupid protractors

The “Stupid protractors” file proposes two generic protractors: One based on Baerwald theory and the other on Loefgren. The “Stevenson protractor” file proposes a generic Stevenson protractor.

A novice should go for the Baerwald version, people who know what they’re doing will choose the one they want (since they are big boys).

How to use this kind of protractor?

Two grids and a hole: the aim is to obtain a perfect alignment with the two sets of lines and the cartridge body.

First use the grid closest to the spindle hole. Put the cartridge in the middle of the headshell; twist the cartridge clockwise or anti-clockwise in order for you to observe the alignment with the grid. When it’s right, go to the second grid.

If the cartridge must be rotated clockwise (or anti-clockwise) to be aligned with the second grid, move the cartridge forwards (or backwards) in the headshell, then go back to the first grid. Align the cartridge and check with the second grid; repeat until alignment is achieved at both points.

Kearn’s universal arc protractor

Now for the “Kearns universal arc protractor”. Not for the novice! Here the trick is to ascertain which arc should be followed by the stylus. You must first know (measure) the mounting distance of your tonearm, check a table to know the effective Baerwald length and then choose which arc to follow and align the cartridge body with the grid. Once the set-up is complete, you can check with the B hole that you’re correct: using that B hole, the cartridge body must be aligned with the grid – if it’s not, you followed the wrong arc.’

Stuff protractor

Finally, the “stuff protractor”. When using a standard protractor we make the assumption that the cantilever is parallel to the cartridge body, that’s why we align the cartridge body with the grid. But the correct thing to do is to align the cantilever with the grid. Hmm, not that easy. The stuff protractor describes a way to align the cantilever using a mirror (you must be able to drill a mirror and to engrave it with lines). Again, not for the novice!

Please post in the forum if you have any questions.

Regards, Seb

Comments

cartridge alignment

hi to all you vinyl lovers

i have just got my self a gemini pdt-6000 to just play a few of my vinyls on. i was wondering what protractor i should use to setup cartridge etc. it has a pickering np/ac cartridge and a pd07-c stylus .plus is this going to be an ok setup or should i invest in something else when i have got the funds.
thank you

regards john

Which Protractor for SONY PS-X65 ?

I've recently purchased a Sony PS-X65 in pristine conditions. There's an alignment drawing under the platter cover… But I wonder if it's really precise since all you have to do is to place the arm and align it with the horizontal lines, and then move the cartridge so that the stylus 's placed exactly on a cross…

Tonearm: universal electronic
Effective length: 235mm
Overhang: 13mm

I would like to make a more precise setting of my GRADO Gold1c cart. (No hum by the way).

Which protractor would be the most useful to me ?

Thank you in advance

JP

Fixed headshell alignment - FR-64S

I'm going to install an FR-64S tonearm equipped with an FR-7 fixed headshell cartridge. I've been advised to drill the mounting hole 3 mm larger than actually required to allow some 'play' in the alignment procedure. It seems to me that the effective length will be nevertheless fixed. What effect would sliding the arm back and forth have? What is the proper alignment procedure with a fixed headshell cartridge? Thanks.

Regards.

overhang and offset angle

Hi,
With a fixed headshell you can't adjust the overhang or offset angle so you are usually stuck with the original alignment geometry and null points. In theory mounting the arm very accurately at the recommended mounting distance should get you close, then if the arm has a sliding base you can adjust the mounting distance using an overhang gauge to achieve 15mm overhang.

Regards,
JaS

Which protractor to use with sl 1700 and shure cart m97xe?

there is a bundled protector with the cart, but I am not sure which one should I use. Pls guide with any specific tuning wrt to VTF, VTA (I am a noob, and I think it can not be easily adjusted on this technics, pls confirm).

regards

Geometry for 10" 78's

I should like to put together a turntable for exclusive use with 10"78's.
With an outer radius of 120mm and an inner of about 54 mm the "usual" null points do not appear brilliant, and i believe null points around 100 mm and 60 mm might be advantageous.
I have an old Transcriptor Fluid arm (http://www.vinylengine.com/library/transcriptors/fluid.shtml) and a Thorens TD 146 arm (http://www.vinylengine.com/library/thorens/td146.shtml) for this.
Could you possibly point me to a calculation/protractor i might use?

Thank you,
Werner

Alignment Calculator

Hi,
You can use my Alignment Calculator to calculate null points for alternative inner and outer groove radii using either Stevenson, Lofgren A (Baerwald) or Lofgren B geometry. Baerwald calculated null points of 59 and 102mm should give the lowest average RMS distortion across the playing surface.

You could then mark the null points on a piece of card for a custom two-point protractor. Alternatively, if you are certain of the mounting distance Conrad Hoffman's Arc Protractor Generator is an excellent tool.

Regards,
JaS

Thank you, that is exactly

Thank you, that is exactly what i was looking for.

advice for LP12 + sumiko MMT

Hello
Could you please advise which protractor would be best for the Linn Sondek LP12 with Sumiko MMT arm and for the moment an Ortofon OM5E cartridge, please. Thankyou for a great resource.

Sumiko MMT

Hi,
The MMT is a classic 'Baerwald' design with original geometry designed to align to Baerwald IEC null points.

If you have the arm mounted as per original spec (221.7mm mounting distance) the two-point 'Stupid' protractor would be ideal.

Regards,
JaS

SME 309 w/Rek-O-Kut

Any suggestion on what to use for a project I'm building? Is the standard SME protractor the way to go?

SME 309

Hi,
If you have the protractor that came with the 309 then I'd use that. You could use the two-point 'Stupid' Baerwald protractor but I'm guessing there would be little to no benefit in this case as the alignments and distortion plots are so close?

Regards,
JaS

What happens to the sound,

What happens to the sound, if i use other protractor other than the Stevenson with the rega like the geodisc or one generic

Rega geometry

Hi,
Aligning accurately to alternative geometries will result in a change in the maximum level of tracking distortion and the pattern of distortion across the playing surface.

For example, a Geodisc will give the same alignment as the Stupid protractor (ie Lofgren A / Baerwald) and reduce the maximum and average distortion levels.

However, the difference is only a fraction of a percent in distortion levels and varies across the record. The main advantage to using an alternative protractor to the original Rega type is having two points to align to for increased accuracy. IME it's unlikely you'll hear a repeatable audible difference between a cartridge properly aligned to a two-point Stevenson protractor vs a Baerwald or Lofgren B version.

Regards,
JaS

Which kind of protractor are

Which kind of protractor are the one that came with the Hi-Fi news test record?

HFN Protractor

Hi,
The two-point version bundled with the HFN 002 is Baerwald for IEC grooves ie null points at 66.0 and 120.9mm from the spindle centre. I haven't used the linear offset technique but it should align to the same nulls if the designer knew his stuff. FWIW you can check the geometry used with any two-point protractor with a ruler.

FWIW the instructions say that the two-point version is 'suitable for 9" arms' which is misleading at best - the protractor is actually universal and will align any length arm (headshell slots permitting) to Baerwald IEC geometry.

Regards,
JaS

EPA-100 MKIII TONEARM

I have recently bought an TECHNICS SP-10 MKIII with the EPA-100MKII black boron arm.
The turntable is all original and weighing some 44kg/97pounds.

Would you please help me with an alingnment protractor for my BENZ-MICRO ACE LS low output
MC cartridge.
I am using a Sumiko headshell with this arm the one from the Sumiko MMT arm.
The overhang is 15mm,but i need some alignment protractor.
Unfortuneately the owner didn't have the original 9.5g Technics headshell.