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
\frac{1}{2}
to
\frac{1}{3}
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.