This circuit was found in a Electronics Handbook (1989). The shown amplifier provides a few hundred milliwatts of output when powered by a 9 V battery. Changes to the original circuit are to recommend if most modern transistors like the BC548 and BC558 are used. The transformer can be obtained from an old radio transistor out of use. P1 is the volume control. The speaker is 8 Ω small. If power supply is used, it should have good filtration and provide a current of at least 100 mA. The circuit has a high impedance input. The circuit can be used in experimental receptors, intercoms, multimedia sound, etc.
