For anyone who love transistor circuits, here you can find small wattage discrete amplifier. Building discrete amplifier is much more fun and some people say it’s involve more artworks than building the ones with integrated circuit. Look at the figure below for the circuit’s schematic diagram.

2watt transistor amplifier circuit schematic

A variable resistor 470 Ohm is provided in series with two 1N4148 diodes to set the minimum stationary current, when your circuit is not fed by any signal. To set this stationary current, insert an ampere meter between power supply and circuit, short the input to ground, and adjust the variable resistor until the current decreased minimum value. If you have a harmonic distortion meter, you can optimize between low stationary current and low harmonic distortion, since minimizing the stationary current will increase the total harmonic distortion.