GB825338A - Method of recording sound and device for carrying out this method - Google Patents

Abstract

825,338. Recording sound. TELDEC TELEFUNKEN-DECCA SCHALLPLATTEN G.m.b.H. March 19, 1958 [March 26, 1957], No. 8783/58. Class 40 (2). An arrangement for grooved sound recording by a heated stylus in which the average depth of cut of the stylus is increased with increases of the amplitude of the signal, is characterized in that means are provided to regulate the heating of the stylus in dependence on the depth of cut such that temperature variations of the stylus resulting from the different depths of penetration are compensated. The embodiment is described with reference to an apparatus for recording two signals in a separate groove, such as for stereophonic recording. In this case the one signal is conveyed by hill-and-dale recording and the other by lateral recording. The signals are taken from twin tracks pre-recorded on a magnetic tape 11. The signals from the particular track to be recorded by the lateral method is picked up by a head 12 and fed via an amplifier 14 to a recording head 4 cutting a groove on a record disc 3. Advance signals from the same track are picked up by a head 16, amplified by amplifier 18, rectified by a device 21 to produce a voltage which by means of a motor 24 varies the pitch of the traverse of the recording head 4 in accordance with the strength of the signal. Similarly, signals from the other track on tape 11 are also fed to recording head 4 via head 13 and amplifier 15. Advance signals from the same track are picked up by head 17, are amplified by amplifier 19 and also control the pitch of the traverse of head 4 via device 21 and motor 24. At the same time a branched-off lead through a device 23 applies a correction voltage to an electromagnet 28 which causes the depth of cut by the head 4 to be varied in accordance with the strength of the signal. A feeler 33 is provided which rests in contact with the record surface in advance of the head 4 and forms part of a transducer 32 which generates a voltage in accordance with surface variations and applies a depth setting correction via device 23 and electromagnet 28. An alternating current source 30 provides a stylus heating current which is varied by a choke 29 in accordance with the strength of the signals handled by device 23 and compensates for the greater heat dissipation which occurs during a deeper cut. Specification 770,465 is referred to.