GB634586A - Improvements in or relating to method and apparatus for recording sound waves - Google Patents

Abstract

634,586. Sound-recording apparatus. SOUNDSCRIBER CORPORATION. June 19, 1947, No. 16199. Convention date, June 12, 1939. [Class 40 (ii)] [Also in Group XXXIX] In an apparatus for recording sound on a track having a progressively decreasing linear speed such as the spiral track on a disc rotating at constant angular velocity, the attenuation of the higher frequencies which occurs at the lower track speeds is compensated by subjecting the sound signals to a distortion in which the ratio of the amplitude of the higher frequencies to that of the lower frequencies is progressively increased to an optimum value determined by the limit of ability of the stylus to follow accurately the steep wave-fronts at the higher frequencies, and then either widening the said higher frequency band without further increase of the said ratio of frequencies, or continuing to increase said ratio but recording at a lower level. In the embodiment described with reference to the Figure, the required attenuation is obtained by varying the amount of negative feedback in an amplifier A2 by means of a variable frequency-discriminating network 26, 27 which is connected in shunt with a feedback resistance 18, and which is mechanically coupled to the carriage supporting the recording head 5.