Moving coil pickup cartridge with diaphragm coupling

A pickup cartridge comprising signal conversion means and replaceable signal transmission means, the signal transmission means including a cantilever having a stylus at one end thereof adapted to scan the sound grooves of a record disc and to produce mechanical vibrations corresponding to sound groove signals;

• and an arm mechanically coupled at one end thereof to said cantilever at a position remote from said stylus, said arm being bidirectionally displaced in direct relation to said mechanical vibrations of said cantilever;
• and the signal conversion means including a first magnetic yoke having an end plate and a projection therefrom so as to be of substantially T-shaped cross-section;
• permanent magnet means having spaced apart north and south poles, one of said poles being in contact with said end plate, said permanent magnet means and said projection defining a gap;
• a second magnetic yoke having one end thereof in contact with the other of said poles of said permanent magnet means, thereby forming a magnetic circuit for direct magnetic flux originating from said permanent magnet means, said circuit comprising said one pole of said permanent magnet means, said end plate of said first magnetic yoke, said projection of said first magnetic yoke, said gap, said second magnetic yoke and said other pole of said permanent magnet means;
• a diaphragm coupled to the other end of said second magnetic yoke and having a surface thereof in contact with the other end of said arm such that said diaphragm is displaced in response to the bidirectional displacement of said arm;
• and a coil coupled to the other surface of said diaphragm, the entirety of said coil being disposed in the magnetic field and having its longitudinal axis substantially perpendicular to said magnetic flux in said gap, whereby a voltage is induced in said coil in response to the movement thereof caused by the displacement of said diaphragm.