A transistorized voltage-controlled variable-gain audio amplifier including a transistor connected as a common-emitter amplifier, and a control circuit coupled to the emitter of the amplifying transistor and operative in response to a direct control signal to vary the impedance at the emitter without changing the voltage thereat. The control circuit includes a second transistor having matched collector and emitter resistors connected to a source of energizing potential and to ground respectively, and a branch circuit including at least two forward-biased semi-conductor diodes connected in series between the collector and emitter of the transistor. The junction between the diodes is connected through a capacitor to the emitter of the amplifying transistor thereby to effectively connect the impedance of the branch circuit in parallel with the emitter resistor of the amplifying stage. A direct control voltage applied to the base of the control transistor varies the current through the diodes to vary their impedance, and consequently the impedance at the emitter of the amplifying transistor, without changing the voltage at the emitter, to thereby vary the gain of the amplifying stage.