Phonograph Needle Drag Distortion

In the following paper are included: the graphical synthesis which originally led to the belief that the tangential motion of a phonograph playback needle would cause distortion of the output signal; the mathematical analysis of the forces which would tend to cause such motion; and descriptions of equipment, tests, and conclusions reached.These conclusions are, in brief, as follows: In a common type of crystal pick‐up, equipped with the usual steel needle, tangential motion of the stylus tip does occur as postulated, ranging in amplitude up to 0.0012″, the amplitude of the motion being a function of the recorded frequency, the amplitude of recording, the radius of the groove in which the signal is recorded, recording speed, record and needle wear, and needle pressure. In addition to the tangential motion caused by the recorded signal, a vertical resonance occurring in the needle‐pick‐up arm system causes low frequency tangential motions of the needle tip (24 cps) with amplitudes of up to 0.0015″. Attempts...