Patent GB-845958-A (GB)
Title: Binaural phonograph system
IPC: H04R17/08
Filed: 1958-12-12
Abstract: 845,958. Binaural systems. ERIE RESISTOR CORPORATION. Dec. 12, 1958 [Jan. 6, 1958], No. 40120/58. Class 40 (4). In a system in which a single stylus causes the generation, from a record having two signals recorded at right angles to one another, of two signals in respective amplifier channels which are fed to respective loud-speakers, means is provided for cross-coupling from each channel a fraction of its own signal to the other channel in a subtractive sense, together with means for adjusting the amount of crosscoupling to compensate for misalignment of the pick-up with respect to the directions of the two recorded signals. Type of transducer employed.-The invention is described as applied to a binaural pick-up consisting of an elongated bar 1 (Figs. 1, 2) of barium titanate or other polarizable piezoelectric ceramic having two pairs of electrodes 2, 3 and 4, 5 mutually at right angles, the polarization of each pair being opposite. This latter may be achieved by connecting the polarizing voltage between adjacent electrodes, thus producing the field distribution indicated by the arrows 6 (Fig. 1). One end of the bar 1 is fixed in a chuck 8 (Fig. 2), as by cementing, and the other end is fixed to a cartridge structure (not shown). The stylus 10 at the free end of the chuck 8 follows the record excursions in the directions 11 and 12. If, in manufacture, the pick-up is tilted, each pair of electrodes will generate a signal which includes a proportion of the unwanted signal, which may be eliminated by subtracting a portion of the signal generated by the other pair of electrodes. Manner of compensation.-In the arrangement of Fig. 4, the electrodes 2 and 5 are connected to ground via a common adjustable resistance 17 and the electrodes 4 and 3 are respectively connected to ground via separate adjustable resistances 18 and 19. The outputs are taken from resistances 18 and 19, each being less than that appearing across the relevant pair of electrodes by the amount of the voltage drop across resistance 17. Thus the output across 19 is less than that across electrodes 3 and 2 by an amount which includes a fraction of the voltage appearing across electrodes 4 and 5. Adjustment of 18 and 19 compensates for differences in output of the pick-ups due to variations in manufacture, and adjustment of 17 varies the fraction of signal which is cross coupled to the other channel. The alternative arrangement of Fig. 5 avoids the decrease in output due to voltage division which occurs in that of Fig. 4. The electrodes 2 and 4 which have instantaneous output voltages of opposite sense are grounded and connected to the variable resistance 17a, while electrodes 3 and 5 are connected to separate variable resistances 19a and 18a which are commoned to resistance 17a, the outputs being taken from 19a and 17a in series, and 18a and 17a in series, respectively. As the voltages from the two electrode pairs are connected in opposite sense to resistance 17a, the required substraction takes place in that resistance. A push-pull arrangement based on that of Fig. 5 is described with reference to Fig. 6 (not shown). Specification 823,241 is referred to.