GB860767A - Binaural pickup - Google Patents

Abstract

860,767. Pick-ups. ERIE RESISTOR CORPORATION. March 23, 1959 [April 3, 1958], No. 9916/59. Class 40 (4). [Also in Group XL (b)] A pick-up comprises a rod of piezo-electric material having a coaxially-extending stylus arm mounted on one end and being mounted as a cantilever at the other end so as to lie along the axis of a bore in a surrounding casing, a compliant damping member being placed between the transducer and the bore. As shown in Fig. 1 a barium titanate rod 9 with the crosssection, polarization, and electrodes of Fig. 2, is secured at one end in a rubber bung 20 located in a bore 2 of a moulded plastic casing 1. Connecting-wires are pressed against the concave surfaces of the electrodes by the bung 20 which is apertured in conformity with the cross-section of the rod 9. At its other end the rod 9 sockets into and is secured to a magnesium, beryllium or glass reinforced plastic stylus arm 7 which projects into a narrower bore 3 in the casing. The cross-sectional areas of rod 9 and stylus arm 7 are in such proportion as to provide a match for propagation of shear waves across the junction. At the junction between the bores 2 and 3 lies a rubber damping member 27 which is cemented to the stylus arm at 29 and provides a dilatable seal for damping liquid in the space surrounding the piezo-electric rod 9. As shown in Fig. 15 the pick-up may be constructed by clamping and cementing a bung 89 and damping collar 94 between two moulded halves of a casing which define a central bore for a piezoelectric rod 88 and stylus arm 85. Also clamped between the halves of the casing are a terminal disc 106 carrying four pins 107. The sides 118, 119 of a spring U-clip engage flats on a portion of the casing so as to locate the casing with one or other of two styli facing towards the record. These positions are selected by rotating the cartridge through 180 degrees in a mounting cylinder 116 containing a solder-tag board 111 with contact-plates 114 as best seen in Fig. 16. The piezo-electric rods may take the crosssections shown in Figs. 7 and 8 with an electrode coated and earthed centre-bore and the polarizations shown. The output from across each pair of opposed electrodes may be fed to separate push-pull amplifiers energizing two loudspeakers of a stereophonic system, see Fig. 9, not shown. If the polarization is as shown in Fig. 11, with one pair of electrodes earthed no push-pull stages are necessary. Push-pull amplifiers may also be avoided if input transformers with centre-taps, or balanced potentiometers are used, see Figs. 18 and 19 (not shown). Specification 823,241 is referred to.