PLAYBACK NEEDLES
To minimise wear and secure the maximum useful life from a recording, a properly shaped needle, Fig. 8.22, must be used. A properly shaped needle will also minimise background noise.
The difference in shape between the cutting stylus and playback needle causes trackability distortion and pinch distortion. Trackability distortion is overcome by use of an elliptically shaped needle. When an elliptically shaped needle tracks the groove, its points of contact nearly coincide with the original points of cutting stylus contact at any given position. Pinch-effect distortion is caused by the changing width of the groove as the angle of groove sides and line of excursion of the cutting stylus change. As the groove width narrows, the round ...
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