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COMPONENT UNITS 205
The over-all response-frequency characteristic of this early equipment did anticipate to a degree the transfer losses encountered; the intent was correction to the release print. The low-frequency response of the amplifier was reduced by the simple expedient of reducing the capacitance of the interstage coupling capacitors ; this corrected to some degree for such factors as the difference between the recording level and the reproducing level, for voice effort, for voice quality, and the like. High-frequency losses were somewhat compensated by the resonance peak of the oildamped galvanometer which was some 6 or 8 db between the frequencies of 5000 and 6000 cps. A certain amount of "presence" was added quite unavoidably by the pressure-doubling peak of the condenser microphone cavity which produced a sharp rise in response at about 3000 cps.
Fig. 31. Unilateral variable-area sound track, unbiased — negative and print. Horizontal motion of the rectangular recording light beam across the slit provides modulation of the track.
Scanning or
reproducing light
There were no equalizers or filters to correct for nonlinearities of microphone, amplifier, or galvanometer; no means was generally available for altering the frequency range or the dynamic range as desired. In some respects, there was little need for such versatility.
There was little 16-mm sound-recording equipment in existence in this period before 1931 ; most of it was scaled-down 35-mm equipment in which the major modification was merely the substitution of 36 for 90 feet-per-minute speed for the 16-mm film.
As a practical matter, the amplifiers of this early sound-recording equipment were quite microphonic ; it Avas a few years before nonmicrophonic electron tubes first made their appearance on the market. The filament-type tubes so familiar at that time (240, 201A, 112A, and 171A) are now obsolete ; even the 864, the first nonmicrophonic tube that ap