designed amplifiers in the recorder. In recorders, there is a requirement for voltage equalization of
frequencies in the output. Earlier we said that the higher the frequency, the more the voltage output; for
the lower frequencies, the opposite is true. Therefore, the very weak, low frequencies must be boosted.
It is not enough to increase the gain of the amplifiers. The problem is to boost the low frequencies and
limit the high frequencies. In most instances, it is sufficient to add RC networks to the input signal path
of an amplifier. To attenuate the high frequencies, RC network values are selections that result in
bypassing a major portion of voltage of the higher frequencies to ground. The reduction of the higher
frequencies input voltage of an amplifier results in a relative boost of the lower frequency voltage.
Frequency-selective feedback circuits between amplifier stages may also be used to equalize the output
voltages of the high and low frequencies. Many variations of equalization circuits are used in both
playback and record amplifiers.
Figure 3-7. Typical record and bias oscillator circuits
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