Automatic measurement of phonograph reproducers

A stereophonic test record has been designed for measurement of pickup response on a curve recorder. The principles of stereophonic disk recording which have governed the design of this record, are reviewed. The new test record contains two sweep-frequency bands for the left and right channels, the signal frequency varying logarithmically with time at a rate of 1 decade each 24 seconds covering a range of 40-20,000 cps. Left and right spot-frequency tones with voice announcements have also been provided covering a range of 20-20,000 cps. Automatic recording of pickup response has been estimated to save to of manpower used in pickup and phonograph development. For automatic measurement of preamplifier characteristics, an RC RIAA generating network has been designed. A circuit for automatic starting of recorder by keying tones on the record is described.