COMPLETE REPRODUCING SYSTEMS 



315 



STUDIO 



ACOUSTICS OF STUDIO 



MICROPHONES 



AMPLIFIERS 



MONITOR 



ACOUSTICS OF 

 MONITORING ROOM 



LOUD SPEAKER 



ATTENUATOR 



ATTENUATOR 



AMPLIFIER 



CUTTER 



WAX RECORD 



TURNTABLE 



frequency oscillator and fed to the first detector. The output of the first 

 detector is amplified by the intermediate frequency amplifier and then fed 

 to the second detector. The audio frequency output of the detector is 

 followed by an attenuator and power amplifier which drives the loud 

 speaker. The action of a radio 

 reproducer in a living room has 

 been discussed in Sec. 12. 2 J. 



F. Phonograph Reproducing 

 System. — A complete phono- 

 graph recording and reproducing 

 system is shown in Fig. 12.22. 

 The general studio equipment is 

 quite similar to that of a broad- 

 casting studio except for the 

 equalizers and filters. An equal- 

 izer is used to attenuate the out- 

 put fed to the cutter below 600 

 cycles to yield approximately uni- 

 form amplitude below 600 cycles. 

 The high frequency response is 

 accentuated in recording so that 

 a corresponding attenuation in 

 the high frequency response in 

 reproduction will efi^ect a reduc- 

 tion in ground noise without 

 frequency discrimination in the 

 reproduced sound. The cutter 

 actuated by the amplifier cuts 

 a spiral wavy path in the revolv- 

 ing record corresponding to the 

 undulations in the original sound 

 wave striking the microphone. 



PLANT 



MASTER MATRIX OBTAINED BY METALIZING 

 AND ELECTOPLATING ORIGINAL WAX RECORD 

 METAL MOLD OBTAINED BY ELECTROPLATING 

 MASTER MATRIX 



PRESSING MATRIX OBTAINED BY ELECTRO- 

 PLATING METAL MOLD 



RECORDS PRESSED IN THERMOPLASTIC 

 MATERIAL BY PRS SING MATRIX 



HOME 



PICK UP 

 RECORD 

 TURNTABLE 



EQUALIZER 

 AND FILTERS 



ATTENUATOR 

 AMPLIFIER 



LOUD SPEAKER 

 ACOUSTICS OF ROOM 



Fig. 12.22. Complete phonograph recording, 

 record pressing and reproducing system. 



In the record plant the original wax is metalized by sputtering with gold 

 and electroplating with copper. The resulting plating is separated from 

 the wax and backed by solid metal plate and is termed the master matrix. 

 The master matrix is electroplated with copper. This plating is separated 

 from the master matrix and backed by a solid plate and is termed the metal 

 mold. The metal mold in turn is electroplated with copper. This plating 

 is separated from the metal mold and backed by a solid metal plate and is 

 termed the pressing matrix. By means of a hydraulic press the final records 



