The low-frequency amplifier assembled on an integrated circuit is convenient in that it does not require adjustment after assembly. One of the most common ICs for use in these amplifiers is the LM386.
Instructions
Step 1
Connect the second and fourth pins of the LM386 microcircuit to the common wire.
Step 2
Connect the sixth pin of the microcircuit to the power bus (+6 volts), but do not apply power to this bus yet.
Step 3
Take a ten kilo-ohm variable resistor. Place it with the handle up, with the leads facing you. Connect the left terminal of the resistor to the common wire, connect the middle one to the third terminal of the microcircuit, and the right one to the output of the signal source. The result is a volume control.
Step 4
Assemble the so-called correction chain. To do this, connect in series a capacitor with a capacity of about 0.05 μF and a resistor with a resistance of about 10 ohms. Connect this chain between the fifth pin of the microcircuit and the common wire.
Step 5
Connect one of the speaker terminals with a resistance of 8 ohms to the fifth pin of the microcircuit through an electrolytic capacitor with a capacity of 100 to 500 μF (plus to the microcircuit), and the other to the common wire.
Step 6
This amplifier has a gain of 20. To increase it tenfold, you need two more capacitors. One of them, with a capacity of 0.1 μF, connect between the seventh pin of the microcircuit and the common wire. The second, electrolytic, with a capacity of 10 μF, connect between the first and eighth terminals (plus to the first).
Step 7
If the 200X gain is too high and the 20X gain is too low, set it to 50. To do this, connect a 1K resistor in series with the 10uF capacitor.
Step 8
Add additional bass boost to the amplifier if desired. To do this, replace the 10 μF capacitor with another, with a capacity of 0.02 to 0.05 μF, and increase the resistance of the resistor connected in series with it tenfold.
Step 9
Set the volume control to minimum, apply power and input signal to the amplifier, and then gradually increase the volume to the desired level.
