There are many opinions on cartridge alignment, and disagreement is common, even among experts. The setup procedure and the parameters outlined here have been studied and tested by both Durand Tonearms and Found Music.
Attention to fine details with a proper protractor is paramount to getting good alignment results. A mirrored protractor made especially for the tonearm geometry in question is our current preference. It should allow the user to align offset angle and azimuth at a minimum of two points along a proscribed arc.
In broad terms,
deviation of the cartridge stylus from "alignment" in any axis results in audible distortion due to extraneous forces being exerted on the cartridge mechanism. The better the alignment, the freer the cartridge is to trace the groove properly. This makes for a better signal at the source.
There are seven parameters that we have access to in tonearm/cartridge setup. They are all directly responsible for sound quality and are interactive and interdependent to some degree:
-pivot to spindle distance (P-S)
-vertical tracking force (VTF)
-effective length (overhang)
-offset angle (zenith),
-azimuth (vertical orientation of stylus when viewed from front),
-vertical tracking angle (VTA) or stylus rake angle (SRA)
Again, these parameters rely on one another. If one parameter is adjusted far off the mark, it can take others out of tolerance with it. It is usually necessary to go through a setup procedure more than once in order to get it right.
The phonograph cartridge
is designed to function:
- with stylus (and cantilever) pulled through the record groove normal to the groove centerline (when viewed from the front of the cartridge)
- with stylus tip raked slightly toward the incoming vinyl
- within a manufacturer's recommended tracking force range
The purpose of alignment is to provide the cartridge an environment where the above criteria are met on the play surface of the record. Note that even in an ideal condition, this requirement is not quite met on pivoted arm designs except at two carefully chosen null points; the locations of which are specified by alignment type (Lofgren A, B, etc.). See link to diagram below where you can see examples of deviations from the null points.
In the .pdf drawing below, the null points are the two locations on the arc where the stylus follows a line exactly tangent to the record groove. There are three other points on the drawing where you can see that the direction of the stylus deviates from the tangent, and these are marked with their deviation from tangent in degrees.
In practice, this deviation is usually much less significant than setup errors!