Kuzma Stogi Reference - Manual (Page 11)

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STOGI/STOGI REFERENCE 11 KUZMA
E. Tangentional Cartridge geometry adjustment
Once the cartridge has been mounted, it is necessary to ensure that the cartridge is
tangentional to the record grooves in order to minimise tracking distortion during playing. As
the cartridge moves in an arc across the record, tracking distortion occurs and is minimised
by the tonearm geometry and the angle of the cartridge in the headshell.
With optimum tonearm geometry very low distortion levels (below 1 %) can be obtained
across the entire playing surface. Cartridges have zero distortion at two points on a record
and these points are used when aligning the cartridge. In practise these points lie at 66 mm
and 121 mm from the record centre (see protractor). Other protractors make use of different
zero points due to the use of different parameters in calculation. In this case 60 mm has been
chosen as the inner groove and 146 mm as the outer groove which still has optimum tracking
distortion.
(Fig. 16)
For a distance of 212 mm from record centre to centre of tonearms horizontal rotation the
optimum overhang is 18 mm and the effective length, ie. distance from the centre of tonearm
horizontal to the tip of the cartridge is 230 mm. This is gained with offset angle of 24°, and
gives a maximum tracking error of under 2° and distortion of under 1 %. These are harmonics
of the second order which are not so irritating as the third which are very common in
amplifiers. (Fig. 16 a)