Here is the 22 watt stereo audio power amplifier circuit diagram based on TDA1554 and integrated circuit from NXP semiconductors (formerly PHILIPS semiconductors). It is very simple and useful circuit for amplify the stereo signals .The circuit dissipates roughly 28 watts of heat, so a good heatsink is necessary. The chip should run cool enough to touch with the proper heatsink installed .the circuit operates at 12 Volts at about 5 Amps at full volume. Lower volumes use less current, and therefore produce less heat. R1 is also a 5% resistor.