Amplifier for Musical ICs

We use musical IC UM66, UM3456, M3481 etc for many applications like for door bell, as an indicator for reversing car, for vehicle turning indicator, burglar alarms, intruder alarm and many more. Sometime it happen that sound from the IC is very slow and you are not able to hear it properly because of various kind of noise around your home or offices. Therefore to amplify sound signal you can use this simple amplifier circuit. This will amplify the musical sound so that you can hear it properly and from distance also.

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Fig. 1: Prototype of Amplifier for Musical IC Circuit on Breadboard

In this amplifier circuit we have amplify the musical sound of UM66 IC you can use any other IC also. And to amplify the sound signals we have used a LM358 IC . LM386 is a very popular and widely use 8 pin audio amplifiers used to amplify sound signals.

To understand the working of circuit first we should understand its pin description-

Pin 1 and pin 8 is used for gain control of the amplifier.

Pin 2 and pin 3 is used to feed the input signal which is required to be amplified. Pin 2 is used for negative input and pin 3 is for positive signal.

Pin 4 is used as ground.

Pin 6 is used to connect DC power supply.

Pin 5 is used as output.

Pin 7 is used as bypass terminal with a capacitor to prevent oscillation.

Working of the circuit is very simple when power supply is provided musical IC UM66 start producing musical sound, output can be obtain from pin 1 of IC1. You can directly attach the speaker between pin 1 and ground and hear the musical sound. We have connected a Zener diode at pin 2 of IC1 because excess voltage more than 3.3V will harm the UM66 IC.

Now to amplify the signals first we have to adjust its gain factor through pin 1 and 8 if it is left open the gain will be 20dB as it is internally set in IC but it can be vary by adding a resistor and a capacitor between pin 1 and 8 up to 200dB. Now feed the required signals to pin 3 of IC2. A variable resistor is connected to pin 3 to adjust the sensitivity of input signal and we will get output on pin 5.

Capacitor C2 act as a coupling capacitor remove DC signals and passes only AC signals through it. And we will get the amplified signals through speaker.