Reproduction in Auditory Perspective

A C U U M tube amplifiers have been closely identified with the extension of the channels of communication since, with completion of the initial transcontinental telephone line 20 years ago, they first enabled New York to converse with San Francisco. There are now thousands of audio frequency amplifiers in telephone circuits and in sound picture theaters, public address systems, and other similar services as well as in the millions of radio receiving sets. Along with the extension of the field of usefulness of audio amplifiers there has been continuing progress toward more faithful reproduction, better transmitters, better receivers, and better amplifiers. Those first telephone repeaters, although quite adequate for their immediate purpose, transmitted a frequency band only a few octaves wide. Very few radio sets even now cover a range above 3,000 c.p.s. without distortion, and the most up-to-date sound picture installation rarely can be depended upon for accurate reproduction of frequencies above 7000 or 8000 c.p.s. The requirements as to frequency range and freedom from distortion for any particular service are, in the last analysis, determined by public demand. However, when one undertakes to reproduce an orchestra like the Philadelphia Symphony and to reproduce it in such a manner as to satisfy the critical ear of the director, or that of the devotee of symphonic concerts, one has to provide something out of the ordinary in audio amplifiers. In his paper, which forms a part of this symposium, Dr.