This is Audio Clipping Indicator electro suite, serves to provide an indicator in case of clipping for the audio signal. This case should be avoided because it will cause the reproduction of defect sound.
This Audio Clipping Indicator electro suite is built with 2 op-amp as the main component (IC TL062), that arranged to detect two side peaks of negatif and positif audio signal.
Generated with source voltage 9-30 Volt DC, the sensitiveness in case of audio signal clipping we can set the Trimpot. The peak of Positive audio signal is controlled by Op-Amp IC1A, and the negative side audio signal is controlled by Op-Amp IC1B.
If the level peak of positive and negative signal exceeds the reference, so that the both of Op-Amp will give the output and will be used to give the current input to C4, and if there is an element clipping, then the charge processing of C4 will be exceeds and finally the signal is forwarded to LED via Q1.
Source : wihans.info