About cartridge alignment and the various tonearm geometries
A few of the most important aspects of cartridge alignment:
• First things first: In order to avoid damaging your cartridge, make sure the tracking force is close the one recommended by the cartridge manufacturer:
• Good lighting and a 10x loupe are essential:
• The following two steps (alignment on the arc and offset angle) are extremely critical for optimal results. Take your time and get as close as you can to perfection. If the cartridge is not aligned properly, all other adjustments will be useless.
You need a protractor for the alignment. We favor the arc protractor because it is the most faithful representation of the trajectory of the stylus on the record. Make sure you perform your alignment in at least two places on the arc, one at the beginning and one toward the end. (Note: you do not need to do this procedure at the null points--in fact, it is preferable to be outside the null points because you will see errors more readily.)
• Do it again until the stylus is on the arc in both places. Be patient... practice makes perfect. Once the alignment is finished, you’ll need to get the offset angle as close to perfect as possible.
not good at all...
... there we are
• Make sure you verify the alignment again once the offset angle is correct.
Finally check the VTF again. If you moved the cartridge forward or backward in the alignment procedure, the tracking force will have changed too.
• Finally, you’ll need to adjust the azimuth and the Vertical Tracking Angle (VTA). You’re almost done…
There is a lot of additional information on the subject on the internet. Here are some other sources of reading:
• If you want to calculate all the parameters for alignment in Löfgren A and B geometries, here is the link to the Enjoythemusic webpage where you can download the famous John Elison's spreadsheet. You'll also find a stroboscope image to download and a two-point protractor; all free!
• Here is another calculator for alignment, from the Vinyl Engine. You can compare Stevenson, Lofgren A and B against anything you’d like to experiment with.
If you'd like to better understand the difference between Vertical Tracking Angle (VTA) and Stylus Rake Angle (SRA), there is a nice graphic representation of this geometry on this page of The Analog Dept. (Note that the Vertical Tracking Angle is properly displayed in the graphic as the angle between the record surface and the line formed between the contact point of the stylus with the record and the cantilever pivot point--it's not the angle between the cantilever and the record surface.)
• On the Analog Dept website, you’ll find more interesting ideas, as well User Manuals for Thorens turntables, SME tonearms, etc
Note that we prefer the arc protractor over the traditional two-point protractor mentioned in this and other sites.
The question of azimuth is also a source of great confusion; we address it more specifically here
If you’d like to dive deeper into the questions of tonearm geometry, here are some reference texts:
• Some historical papers on turntable and tonearm geometry (Baerwald, Bauer, Löfgren--see below for the English translation--, and Stevenson in pdf downloads)...
• Thanks to Klaus Rampelmann, we have an English translation of the original paper by Löfgren, On the Non-Linear Distortion in the Reproduction of Phonograph Records Caused by Angular Deviation of the Pickup Needle. You can download it as pdf: Loefgren_English_2008
• Another interesting post by John Elison, on the subject of the supposed downsides of 12" tonearms. It's fascinating to see the small differences between the two tonearms when the offset angle is wrong, in particular; it turns out that the 9" arm will still create more distortion than the longer one. I completely agree with him about the questions of rigidity and structural resonances: it entirely depends on the material used, the specific construction (everywhere, from headshell to counterweights), including the cross section at various points on the armwand etc.