GB1473531A - Control of crosstalk in multiple frequency recording - Google Patents

Abstract

1473531 Quadraphonic systems D H COOPER 7 May 1974 [10 May 1973] 20051/74 Heading H4R In a quadraphonic recording system where each groove wall is recorded with a base band signal and an angle modulated sub carrier signal, cross talk from the base band signal to the sub carrier signal which is caused by tracing distortion during record reproduction is cancelled by introducing into the sub carrier modulation a proportion of the base band signal, the proportion being dependent on the groove position on the recorded disc. As described the system is a modification of acknowledged prior art of Fig. 1 (not shown) in which the two base band signals TL and TR and two signals TT and TQ modulated on a sub carriers are related to the left front SLF, right front SRF, left back SLB and right back SRB signals by the relations As shown in Fig. 8 the base band signals are as in the prior art and the two signals to angle modulate the sub-carriers are TT+kTQ and TT-kTQ, where TT and TQ are as set out above and k is preferably 0À33. The sub carrier signals are passed through an equalizer, of characteristic similar to the R1AA characteristic as described in Specification 1,473,532, before having a proportion of the respective base band signal added thereto. The resulting composite signals angle modulate respective carriers before being added to the respective base band signals and application to the recording cutter amplifier 7. The proportion of the base band signal added to the sub carrier signal is dependent on the recording cutter position on the record disc and the stylus tip radius and follows the relation m= (rvw/S<SP>2</SP>) where m is the gain index of the base band signal; r the stylus tip radius; w is the carrier frequency; v the peak velocity of the main channel signal; and S the stylus velocity in the groove = #DN/60 where D is the groove diameter and N is the record speed in r.p.m.