Dear customer, first of all let us thank you for your confidence in our products. The Protractor you hold in your hands is a precision device that enables you to adjust cartridges and tonearms with an effective length from 8,6 up to 17,7 inches for correct overhang and offest.
The calculation of parameters were carefully carried out according Lofgren’s (frontside) and Baerwald’s (backside) equations aiming in reduction of the overall RMS distortion level caused by deviations from the perfect linear tracking position of your cartridge. Please read this manual carefully to have full benefit from this unique tool. In terms of perfect azimuth calibration we reffer to our innovative software ADJUST+ (www.adjust-plus.com).
A little bit of theory
The general geometrical correlation of a tracking device based on a fixed pivot point are well known since the fundamental publications of Baerwald and Lofgren back in the first half of the 20th century. The conclusion of both papers was that such a tracking device must have an angular offset with a defined overhang. The offset and the overhang vary with the effective length of the tonearm itself.
While tracking the record the stylus matches tangential position in the groove in two points – the inner and outer Null points (linear tracking position).