GB745095A - Improvements in electric apparatus for reproducing sound from a sound record - Google Patents

Abstract

745,095. Sound recording apparatus. STONE, L. Nov. 24, 1954 [Aug. 29, 1953], No. 23912/53. Class 40(2) The amplifier electric power supply, or part thereof, is derived from, or through, one or more windings 27 of a motor 13 of an apparatus for reproducing sound from a sound record, e.g., a gramophone record disc or a magnetic tape record; the apparatus comprises a record carrier, e.g. a gramophone record disc turntable 12 or a magnetic tape record spool arrangement, the electric motor 13 for driving the record carrier, a pick-up, e.g., a stylus operated pick-up 15 for co-operating with a gramophone record disc or an electromagnetic transducer head for co-operating with a magnetic tape record, and an electric amplifier 17 for amplifying the signal produced by the pick-up. As shown applied to a gramophone unit, the cathodes or cathode heaters 32, 33 of amplifier valves 18, 19 take their L.T. supply from between one end 28 and a tapping 38 of the motor winding 27 while the amplified H.T. supply is taken from between tapping 38 and the other end 39 of the winding, said winding acting as an autotransformer. In other embodiments the H.T. supply is taken from the A.C. supply leads 25, the cathode heaters together with that of an additional valve are serially connected across a part of the winding, or the cathode heaters are serially connected with the winding which then constitutes a voltage dropping impedance. To avoid the turntable turning continuously between records or the delay of the cathodes warming up, the invention provides means for declutching the turntable from the motor at positions of a, speed control knob 16 intermediate 33, 45 and 78 r.p.m. positions. The unit may be part of a television or sound radio receiver and connected to a common loudspeaker. The pick-up may be of the piezo-electric crystal or of the magnetic type and if of low output a pre-amplifier may be employed.