Variable gain circuit with coupled frequency band pass - adds signal with selected frequency band to output signal to improve sound quality using frequency sensitive impedances

摘要

The circuit frequency characteristic varies with gain and is automatically set by the l.f. level. A control voltage derived from the l.f. signal is applied to a circuit with frequency sensitive impedances. It delivers signal(s) whose frequency characteristic is varied by the control voltage. They are added to the output signal. In order to achieve aurally correct volume control, pref. for t.v. or radio receivers, the circuit has at least three switches of which the first delivers an amplified output signal with a certain fundamental frequency variation, while the second switch adds to the output signal through a circuit with frequency sensitive impedances a signal with a selected frequency band. This switch is controlled by a further switch to which the control voltage is applied.