/udic Azimuth tonearm VTA cartridge ruler

Azimuth refers to the horizontal balance of the cartridge when viewed from the front. This, in turn, determines at which angle the stylus sits on the record groove.

​The theoretical assumption is that when the Cartridge is perfectly perpendicular to the record groove, the stylus will sit perfectly in the record grooves.

​All cartridges are made by hand and therefore, the stylus may not actually be perfectly perpendicular to the cantilever, the coil assembly at the of the cantilever or the cartridge body.  

This means visual methods, can only provide you with an approximation.    As soon as the record spins, whether your stylus is sitting at the optimal spot is unknown,  so it is impossible to achieve an accurate setup by eyesight.

​If azimuth is set incorrectly, the Stylus will not sit perfectly in the record groove, signals recorded on the Left Channel will leak to the Right Channel, (or vice versa), this is leakage between Channels is called Crosstalk,

and it is expressed as a negative decibel number. The higher the negative number, the lower the crosstalk, the better the channel separation.

Incorrect azimuth will also lead to degradation in other measurements such as %THD between L and R channel, as well as IMD% (Intermodulation Distortions).