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SEMI-PORTABLE EQUIPMENT
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weighs 60 lb. The power supply is in a separate case that is connected to it by a cable. The two units are separated to reduce the " stray" hum fields "sprayed" about by the power transformers and by the reactors of the power supply. The maximum over-all gain of the amplifier from the microphone input to the recording machine galvanometer input is in the order of 100 db. The power output is in the order of 250 milliwatts. The total harmonic distortion under operating conditions is well below 2% at full modulation level of the galvanometer. Figures 63A and 63B describe the over-all electrical performance of the Maurer amplifier with different control settings. Figure 64 is the RCA MI10238 (PA-142) amplifier; this unit is somewhat comparable. The captions associated with the figures provide the pertinent characteristics; the design differences will become apparent when the legends are compared.
CYCLES PER SECOND
CYCLES PER SECOND
Fig. 63A. Over-all electrical responsefrequency characteristic of Maurer 162B amplifier. Film equalizer is on ' ' + 3 ' ' ; the three different settings of the low frequency equalizer are shown.
Fig. 63B. Over-all electrical responsefrequency characteristic of Maurer 162B amplifier. Low frequency equalizer is on ' ' high ' ' ; the three different settings of the film equalizer are shown.
General Characteristics of Amplifiers
It must be recognized that the more versatile an equipment is intended to be, the more costly it will be. Two general classes of equipment are available commercially: permanently installed equipment and semiportable equipment. In the former, portability and compactness are sacrificed for versatility and superior performance; in the latter, versatility, and — to a degree — performance, are sacrificed for portability and compactness.
Both classes of equipment have many circuit elements in common; in fact, a block diagram representing one is usually applicable to the other. It should be noted, however, that mere size and complexity of itself is no assurance of either versatility or of superior performance in terms of the attributes such as: