Thursday, January 20, 2011
Audio Peak Level Indicator by Op-Amp LM324
This circuit was designed to provide a valuable test equipment tool for sound reinforcement systems like guitar amplifiers and the like. Used in conjunction with a signal generator it can be of considerable help in setting and controlling levels through any amplifying chain.
Audio Peak Level Indicator Circuit |
The circuit is formed by an input buffer and ac to dc voltage converter (IC1A) feeding a window comparator (IC2A, IC2B, IC2C) which illuminates one of three LEDs at a time. No setup is required: if correct values are used for resistors R3 to R7, LED D1 will illuminate at 0dB input (0.775V RMS), LED D2 at +5dB input (1.378V RMS) and LED D3 at +10dB (2.451V RMS).
Note:
- Maximum current drawing: 12mA when one of the three LEDs is illuminated and less than 4.5mA when the input level is below 0.775V.
- LEDs of different colors can be used to mark any of the three different levels.
- Input pins of unused op-amps must be tied to negative ground. Output pins must be left open (see the upper left corner of the drawing).
R1 : 300K 1/4W Resistor
R2 : 1M2 1/4W Resistor
R3 : 510K 1/4W Resistor
R4 : 220K 1/4W Resistor
R5 : 91K 1/4W Resistor
R6 : 160K 1/4W Resistor
R7 : 56K 1/4W Resistor
R8,R9 : 100R 1/4W Resistors
R10 : 220R 1/4W Resistor
C1 : 100nF
C2 : 1µF/63V
C3 : 10µF/25V
D1,D2,D3 : LEDs (Any coloring at will)
IC1 : LM393
IC2 : LM324
IC3 : 78L05
SW1 : SPST Toggle or Slider Switch
Circuit From: www.redcircuits.com
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