If you want build hi-fi power amplifier about 30watt to 50Watt or 75 watt. Recommend use TDA2050 below, builds by the integrated circuit and PCB layout.[...]
This is a small Stereo amplifier 3W + 3W using BA5406-IC. It use 12V power supply as source of this project. and use a few part so easy to build.
No light! because of a low voltage battery. How do you increase the voltage up? You can do many ways. And, I recommend a simple step-up converter circuit using TDA2822.