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  • Audio Equalizer Circuit

  • Created: Mar 17, 2014

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IC UM66 is used in the circuit to alter the melody which is produced by the melody generator. Oscillation is generated by the voltage controlled oscillator at the time when constant voltage is applied. For the purpose of the VCOs phase locked loop IC (i.e. 4046) which is IC1 and IC2 in the circuit is used. PLL chip comprises of VCO as well as Phase comparator.

By the help of the potentiometer, the voltage which is given to VCOs can be changed. To modify the VCO input voltage potentiometer of value 5K and 10K are attached in the circuit. This voltage is taken by IC1 and IC2. The output of VCOs at the pin 4 of IC CD4046 is a time-multiplexed by a CD4051 multiplexer IC (which IC 4 in the circuit diagram).

The signal which is selected for the multiplexer is produced by 555 timer(IC3) which is working as a astable multivibrator. 4.7 is the time taken by the each high as well as low pulse which is upcoming from 555 timer. The duty cycle is produce surely to be 50% by bringing a IN4148 a small signal diode. The output is then applied to the NPN transistor at the base terminal by a 40K ohm resistor.

The input for melody generator UM66 (Various other IC for the purpose of melody generation can also be used) is taken from the collector terminal. The output of the melody generator is then supplied at one terminal of the 4 ohm speaker(SP) and the left terminal of the speaker is linked with 5 volt power supply.

With the minute alterations in the locations of the potentiometer, the same tune can listen to the many distinct tones, height as well as pitch. In the same manner variety of melodies can be changed by just putting that particular melody IC at the place of UM66 in the above circuit.



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