Sound Level Meter

This nifty sound level meter is a perfect one chip replacement for the standard analog meters. It is completely solid state and will never wear out. The whole circuit is based on the LM3915 audio level IC and uses only a few external components. This circuit can also be integrated into audio amp projects. 
Circuit Schematic


Total Qty.


C112.2uF 25V Electrolytic Capacitor
C2, C310.1uF Ceramic Disc Capacitor
R1, R321K 1/4W Resistor
R2110K 1/4W Resistor
R41100K 1/4W Resistor
R511M 1/4W Resistor
D111N914 Silicon Diode
Q112N3906 PNP Transistor
LED1-LED1010Standard LED or LED Array
U11LM3915 Audio Level IC
MISC1Board, Wire, Socket For U1


  1. V+ can be anywhere from 3V to 20V.
  2. The input is designed for standard audio line voltage (1V P-P) and has a maximum input voltage of 1.3V.
  3. Pin 9 can be disconnected from +V to make the circuit use a moving dot display instead of a bar graph display.
  4. Thanks to help from the forum, this circuit has been improved from the original version to include a peak detector for a more stable and viewable output. This page has been updated with the new circuit.
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