The popular IC LM317 is used by these circuits.
For you make project easily with PCB.
Power amplifier with PCB easy to build
Small Amplifier Circuits
The multi-purpose Amplifier using TDA2030 (15Watt OTL with PCB easy build)
Power Amp Super Bridge 120W by IC TDA2030 (at 2 ohm speak)
CAR Power Amplifier