Stylus, bi-radial elliptical  --  The major radius which sits across the groove is similar to that of the spherical stylus and so it maintains the correct position on the groove walls; but the minor radius can trace shorter wavelengths. For a 0.3 mil minor radius the contact span is 0.42 mil. Corresponding half-wavelength frequencies are 23.6 Hz for the start and 11.4 Hz for the end of the disc, at which it will trace amplitudes up to 0.084 mil. As the styli are closer to the shape of the cutter there is less pinch effect. Second harmonic distortion is thereby lower, averaging 4.0% at 8 KHz with 5 cm/sec recorded velocity. While pinch effect is less and high frequency tracing is better with a smaller minor radius, the area of contact is also smaller, and this puts greater pressure on the groove wall for a given tracking force. Small radii should thus only be used with cartridges having low tracking force. 

 Send new term definitions proposals to info71@presrec.com