Для любознательных. Что такое, и окуда Пинч эффект. Из первоисточника.

ENGINEERING BREAKTHROUGH Now the long ac- knowledged supe- rior elliptical stylus is a reality, made possible by Ortofon Engineering in con- junction with its diamond supplier. This most dramatic design improve- ment in years mini- mizes pinch effect, inner groove distor- tion, bottoming and reduces phase dis- tortion -long major problems of Pick -Up Manufacturers.

PINCH EFFECT ...occurs when as illus- trated in the drawings at left, the cutter, while mov- ing from side to side in plotting a wave form, left a groove of varying width, which literally forces he playback stylus upward at the narrower portion of the groove. Since stereo cartridges have vertica as well as horizontal com- pliance, this undesirab e motion creates an output by the cartridge which manifests itself as "second harmonic distortion." Since the elliptical stylus essentially has the same shape as the cutter, it traces the actual path made by the cutter with the sides of the record. The playback stylus maintains the same tangential contact with the groove walls as the side of the cutter did while cutting the groove. This is not true with a spherical stylus, since its tangential angle of contact with the record grooves will vary as illustrated in opening paragraph.