Audio Power Indicator


This is audio level indicator which can be used to measure the audio level output of your amplifier. Simply connect the output of your amplifier to the input of this circuit, then you will know the average value of your amplifier's power.

Audio Power Indicator circuit diagram

R1_____________220R  1/2W Resistor
R2,R5,R6,R8____100R 1/4W Resistors
R10,R12,R14____100R 1/4W Resistors
R3_____________220R 1/4W Resistor
R4,R7__________330R 1/2W Resistors
R9_____________560R 1/2W Resistor
R11____________820R 1/2W Resistor
R13______________1K2 1/2W Resistor

D1___________1N4004 400V 1A Diode
D2,D4,D6__BZX79C2V7 2.7V 500mW Zener Diodes
D3,D5,D7,D8,D9,D10 Red LEDs (Any dimension and shape) (See Notes)


  • The output power indicated by each LED must be doubled when 4 Ohms loads are driven.
  • The circuit can be adapted to suit less powerful amplifiers by reducing the number of LEDs and related voltage dividers.
  • LEDs of any dimension can be used, but rectangular shaped devices will be more suitable to be compacted in bars or columns.
  • For a stereo amplifier, two identical circuits are required.