About The Circuit
Given below is the desription of an audio circuit using a single transistor. This is the simplest of all the audio mixer circuits and very easy to make as it has only one transistor. The diodes D1 and D2 are used to bias the base-emitter junction of the transistor. The signals to be mixed are coupled directly to the base of the transistor Q1. 33K Ohm resistors are used to limit the current to the input lines. A 10k POT can be added in series to the lines so as to adjust the gain of the induvidual channels. The input power needed for the circuit is 15V dc. A total of 1mA is calculated to be the collector current of the transistor Q1. It would be better if the whole circuit is properly assembled on a Vero board.