Switching circuit for audio amplifier in HI=FI system - has preamplifier connected to common supply line and to positive HT supply via switch

摘要

The switching circuit is for use with audio amplifiers in car radio and cassette recording equipment and in mains supply "hi-fi" equipment. The circuit incorporates a supply line with a direct voltage and an output amplifier stage between the supply lines. The output amplifier is fed from a pre-amplifier with a switch controlling the circuit. One side of the pre-amplifier (1) is connected to the common supply line and the other side of the pre-amplifier is connected to the positive side of the supply line via switch. The switch can have a relatively large series resistance because the relatively low quiescent current of the pre-amplifier will cause very little voltage drop.