3 Level Audio Power Indicator

This circuit is designed to indicate the power level output of any audio amplifier. Its simple, portable, and displays three power levels can be adjusted to any desired value. For a standard power amplifier hi-fi stereo, the output values ​​suggested are:

• D5 illuminates at 2W
• D4 illuminates at 12.5W
• D3 illuminates at 24.5W

The above values ​​were selected for easy setup, but other options are possible. IC1A is the input buffer, feeding 3 voltage comparators and LEDs drivers by means of a variable DC voltage obtained by R5 and C4 smoothing action. In order to achieve stability of adjustment, the supply of IC1 and trimmers R6 and R7 is reduced and is subject to 5.1V by Zener diode D1.