A very simple and useful stereo balance indicator circuit that is based on few common external  components is presented in this circuit diagram . The schematic circuit is very simple to build and will provide an visual indication with LEDs for left , right and center balance  . Outputs from each channel are fed to the two inputs of IC1 connected as a differential amplifier . Output of the IC1 is connected to the noninverting  inputs of the IC2 and IC3 . If the outputs of the IC1 approaches  the supply rail , the outputs of the IC2 and IC3 will go high illuminating the LED 3 , this will show that the right channel is dominating . If the sound is balanced to the left channel , the Ic2 and IC3 will go low and the LED1 will light . If both channels are equal in amplitude the outputs of the IC2 and IC3 would be low and high respectively , lighting up LED2 .

This sound balance audio circuit diagram need to be powered by a 15 volts power supply . The operational amplifier circuit diagram it is a common 741 operational amplifier .