Circuit diagram of 18W audio amplifier

This is the circuit diagram of the 18W audio amplifier. This circuit is very simple and cheap to build. It uses a pair of power transistors TIP41A and TIP42A for single-channel operation. The power supply used in this circuit is a bipolar (split) power supply, which is constructed using a center-tapped transformer.

18W audio amplifier circuit diagram

Parts List:

Power supply part:

18W audio amplifier circuit notes:

CD players, tuners and recorders can be connected directly.

Do not exceed 23+23V power supply.

Q3 and Q4 must be mounted on the heat sink.

D1 must be in thermal contact with Q1.

Quiescent current (best measured with an Avo meter in series with the Q3 transmitter) is not critical.

Adjust R3 to read between 20 and 30mA without an input signal.

Add R8 (optional) to facilitate current setup.

Proper grounding is important to eliminate hum and ground loops. Connect the ground terminals of J1, P1, C2, C3 and C4 at the same point. Connect C6 to output ground.

Then connect the input and output grounds of the power supply ground respectively.