ABSTRACT
A microphone cannot provide sufficient voltage and current to feed a disc cutting head directly; the small signal from the microphone requires considerable amplification in order to drive the cutting apparatus. Similarly, the phonograph pickup is incapable of driving a loudspeaker. In both cases, the vacuum tube amplifier of the era provided the means of increasing the voltage and current of the electrical signal provided by the first transducer to a level sufficient to drive the second transducer. Today, solid-state amplifiers have generally replaced their tube counterparts.
