Here is the circuit diagram of a 10W audio amplifier using the popular TDA2003 IC from SGS Thomson. The IC can easily deliver 10W to a 4 Ohms load at 18V DC supply voltage. The IC can be also operated from 12V and that makes it applicable in car audio systems. The useful features of TDA2003 includes short circuit protection between all pins, thermal overload protection, low harmonic distortion, low cross over distortion etc.
The circuit given here is designed as per the datasheet from the manufacturer and found to be working fine. Capacitor C7 performs the job of input DC decoupling.R2 and R3 is used to set the gain of the amplifier.C3 and R1 determines the upper cut off frequency.C6 and R4 and meant for increasing stability at high frequencies. Capacitor C5 couples the output to the speaker.