Cartridge protractors by alltheprotractors.com

[alltheprotractor page - click to enlarge]

Quick and Convenient

Product name: alltheprotractors.com Cartridge Alignment Protractor
Manufacturer: alltheprotractors.com
Cost: 3.14 Euros (Currency conversion)
(YMMV)
Reviewer: Roger McCuaig - TNT Canada
Reviewed: March, 2020

Some basics about cartridge alignment

While preparing to write this review, it rapidly became evident that yours truly's understanding of this subject had some significant holes in it. Assuming that others might be in a similar situation, it was decided to include some basic principles. Those who already have a good understanding of the subject can skip to the product review section.

Misalignment between the stylus and the groove causes distortion. Of course, everyone wants to minimize distortion so properly aligning the stylus is important. Linear tracking tonearms are designed to be tangential to the record groove at all times, thus, the angle between the stylus and the groove does not change and there is virtually no deviation from the optimal tracking angle. A pivoted tonearm, however, tracks in an arc across the record therefore the tracking angle constantly changes from the first groove to the last. Obviously, this means that it is impossible to maintain the perfect tracking angle throughout the arc of the stylus. A null point is defined as a point where the deviation from the groove tangent is zero. It turns out that it is possible to create 2 null points across the complete arc and that this strategy will produce the optimal (or smallest error) alignment. As is always the case, there are choices. Over the years several alignment strategies have been developed based on different null points.

Some commonly used include:
  1. Baerwald - a.k.a. Loefgren A: Null points are 66 and 120.9 mm
  2. Loefgren B: Null points are 70.3 and 116.6 mm.
  3. Stevenson: Null points are 60.325 and 117.42 mm
  4. Uni-Din: Null points are 63.3 and 112.5 mm

Why so many different alignment strategies? Well the answer is simply that each one results in a different deviation curve from first track to last. For example Stevenson generates much less deviation at the end of the record (the last track on an LP) compared to the others but results in higher deviation for the rest of the record. This makes Stevenson popular among 45 rpm record users. Yours truly has always used Baerwald alignment which is compromise strategy based on obtaining an equal amount of distortion at the beginning, middle and end of the record. Also worth mentioning is that Baerwald protractors are very common, thus easy to find.

There are 4 basic parameters used in cartridge alignment:
  1. Mounting Distance: The distance between the tonearm pivot and the platter spindle.
  2. Effective Length: The distance between the tonearm pivot and the tip of the stylus.
  3. Offset Angle: The angle between the cartridge cantilever and the pivot to stylus line.
  4. Overhang: the distance that the tip of the stylus extends past the platter spindle.

There is an excellent drawing of these parameters on www.vinylengine.com. Many vinyl record enthusiasts will of course already know about this excellent web site. One has to login to get access to some of the pages on this web site however it is well worth it as there is a vast amount of useful information. Given that there was no copyright information found with regards to this drawing, it has been assumed that this document is copyright free and inserted here.

[Tonearm parameters - click to enlarge]

There are basically 3 types of alignment protractors available. For this report, they have been baptized as follows: Generic, Design Specific, Manufacturer Specific.

Generic protractors contain only null point data. One can align any cartridge on any turntable with this type however the overhang has to be set separately by direct measurement or by trial and error. Many tonearms cannot swing in as far as the spindle so directly measuring the overhang is not possible. I have used a generic protractor for many years however my Dynavector tonearm comes with its own overhang gauge so no measuring or trial and error is required. If the overhang is not set to the right value it will be impossible to find an alignment setting that works for both null points. This is because the stylus tip will not be on the correct arc.

Design Specific protractors also provide the null points with the important difference that they are placed on the proper arc as required by the tonearm specifications. All tonearm specifications include the required Mounting Distance. From this number and the chosen null point settings (Bearwald etc.) it is possible to calculate the Effective Length and the Overhang. Feel free to explore the internet for the formulas, they are there. It is then possible to make a drawing that places the null points on the arc, which automatically takes care of the Overhang adjustment at the same time as the alignment.

Manufacturer Specific protractors are simply a Design Specific protractor provided for a specific turntable–tonearm combination. For example Rega has supplied alignment tools for their turntables that use their recommended null points. These will only work on Rega turntables. (or a turntable with a Rega arm on it that was installed according to Rega's specs)

Alltheprotractors.com

The protractors reviewed here were provided by alltheprotractors.com. This is a very simple but very efficient web site. One finds there a tutorial page and video, a page explaining the theory for cartridge alignment ( a bit like what has been provide above) and an order sheet for getting your own protractor. All you need to do is punch in your Mounting Distance, select the null point setting you prefer and the paper format you wish to use and place your order. For a reasonable fee of 3.14 Euros you will receive by email the link to a .pdf file download. The only thing left to do is print out the pdf and check that the scaling is OK. Then you're ready to perform the alignment. The protractors provided are, of course, the Design Specific type. The null points are drawn on the specific arc for your tonearm. Therefore overhang and alignment are done in one shot.

If you do not know the exact mounting distance for your tonearm, the tutorial page will show you a reasonably simple method for finding this number using some paper, a pencil and a ruler. Generally this is not necessary as, in my experience, the mounting data for pretty much every post 1960 tonearm is available on the internet. Of course if you have a DIY model and you forgot to write down the number when you installed it, this tutorial might come in handy.

Alltheprotractors.com sent for review pdf files for the 4 popular null point pairs listed above. Each printout includes the null points, mounting distance, overhang and offset numbers, a scaling chart and a note indicating for whom the protractor was made. The files printed out perfectly to scale so no tinkering with printer scaling was required. A hole punch kit from the local hobby shop was used to make a 4 mm hole where the printout fits over the spindle. A perfect fit for a Lenco spindle. The corner of the printout has to be folded under as it extends out to the pivot point of the tonearm and gets in the way. This corner of the printout could actually be cut off as it is not required in order to perform the alignment on an installed tonearm. A thought, one could use this printout to install a tonearm!

The Dynavector tonearm used in this experiment was already installed and aligned to the Baerwald settings. The Baerwald printout provided by alltheprotractors.com aligned exactly with the tonearm. This is, of course, as it should be. In fact, all four Baerwald protractors on hand gave the exact same result. Not surprising of course. No attempt was made to align to other null points. No doubt they would work well but Baerwald will do fine. Below is what the printout looks like. The mounting distance and null points are sufficient in order to identify for which turntable and alignment strategy the printout was made however, having more than one turntable and not a very good memory, I wrote on the bottom of my printout "Baerwald - DV507".

[Baerwald example - click to enlarge]

Conclusions

A protractor that eliminates the need to dig out an overhang gauge or resort to trial and error setting of the overhang is definitely an advantage. The protractors provided by alltheprotractors.com are convenient and quick to download, accurate, complete and easy to use. What else can one ask for.

DISCLAIMER. TNT-Audio is a 100% independent magazine that neither accepts advertising from companies nor requires readers to register or pay for subscriptions. After publication of reviews, the authors do not retain samples other than on long-term loan for further evaluation or comparison with later-received gear. Hence, all contents are written free of any “editorial” or “advertising” influence, and all reviews in this publication, positive or negative, reflect the independent opinions of their respective authors. TNT-Audio will publish all manufacturer responses, subject to the reviewer's right to reply in turn.

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© 2020 Roger McCuaig - roger@tnt-audio.com - www.tnt-audio.com