Control circuit for a matrixed four channel audio reproducing system

摘要

A gain controlled audio amplifier for each channel which includes a differential to single ended converter fed by a differential amplifier, the common emitters of which are coupled to balance and volume control circuitry for controlling the amount of current flowing in the amplifier relative to the other three amplifiers. A pair of diodes are connected in back-to-back relationship between the control electrodes of the differential amplifier and receive a signal from an enhancement circuit which controls the amount of signal being applied to the input of the differential amplifier. The enhancement circuit includes a pair of amplifier sections which are connected together so that the output voltage of one increases as the other decreases and vice versa and the decrease of output voltage in either section occurs substantially more rapidly than the increase of output voltage in the other section. The balance and volume control circuitry controls the total amount of current flowing into the four amplifiers, the amount of the total current flowing into either of two pairs of the amplifiers relative to the other pair of amplifiers and the amount of the total current flowing into each of the amplifiers in the two pairs relative to the other amplifier in the pairs.