Technical data:

 - supply voltage 12-15V;

 - minimum level of the audible signal applied at the input> 6Vrms;

 - adjustment of tilting thresholds.

Circuit description

At the base of the application is the LM324 operational amplifier, mounted either in a differential amplifier configuration or by a comparator, depending on the topological position in the circuit. If we refer to the input, LM324 is mounted in differential AO configuration; it amplifies the difference between the signals applied to the INL and INR inputs. If at the output, the amplified signal exceeds the set tilt threshold, the LEDs light up, as follows: if the Right channel predominates, the red LED (D5) mounted with the cathode on the ground lights up, U1C is with the output 'High'. If the Left channel is predominant, the other red LED (D3) lights up, U1D is with the 'Low' output. In case of equal signals on the two channels, the AO outputs U1D and U1C are in 'High' state and the green LED in the middle (D2) lights up.

In the tests, it will be noticed that in the situation of balance of the signals, often two LEDs will light up, sometimes, the practical balance, depending on the tolerance of the components used and the adjustments.

Bill of materials available in the download section.