The circuit is a gem; a TDA1554 IC is the heart of an amplifier that will output up to 22 watts per channel with excellent sound quality. (Typical THD less than 0.1%!). Originally intended for automobile use; but can be used as a home amplifier if you have a good power supply. Operates on 13 to 14.4 volts (typical automobile voltages with engine on) and can draw as much as five amps at 13.8 V DC.