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BELL SYSTEM TECHNICAL JOURNAL 



watts, for the three channels. Ei and E2 are equalizers to compensate 

 for any amplitude distortion that would cause a listener to obtain a 

 different tone effect from the loud speakers than he would from the 



Fig. 2^Ainplifying equipment used at Philadelphia. The taller racks are 8 ft. high 

 and contain A\ and A-, amplifiers, volume indicators, and various controls. 



actual orchestra. These equalizers are loss networks and principally 

 equalize for the acoustic characteristic of the loud speakers in the 

 particular hall, but they are placed in a low energy part of the ampli- 

 fication circuit so as not to waste the energy of the final power stage. 

 In view of the inclusion of the equalizers in the'amplification system, 

 and particularly because of the fact that the amplification of the Az 

 amplifier deliberately was made to increase with frequency in order 

 to compensate in part for acoustic losses in the overall system, the 

 actual amplification-frequency curves of the amplifiers are of little 

 importance. The equalizers of the system are discussed in the paper 

 by Bedell and Kerney. 



