Music LED light level

This is a simple circuit. Music can change the LED light level gamut.

Operation of this circuit is a circuit op amp IC1 / 1-IC1 / 5 compared to the characteristics of the circuit voltage.It has one pin acts as a voltage reference pin.That the pressure from the supply voltage and divide between R1 and R7 pressure used in this circuit will be compared with the pressure drop across R7.

Music LED light level

As the 2V input side, it will be R2, R3, R4, R5, R6 series, keeping the pressure drop across.Each R as well.

If there is pressure to 5Vp-p is the voltage across R2 = R3 = R4 = R5 = R6 = 1V.The voltage reference, we have 2V. IC4 circuit compares the measured voltage at the input pin of IC4 is 2V.Which is equal pressure on the leg or legs plus the output of IC4 will not flow to drive the LED light will be more pressure input into this.IC4 to make work. The next LED arranged in the order of the input voltage.
source : http://www.eleccircuit.com/simple-led-light-based-music-using-lm318/