The AC source the 5R resistor bridge rectifier and 2200uF cap can be an unregulated wallwart power supply. The 100R resistor and 12V zener provide a steady voltage for the potentiometer which sets the output voltage. The transistors just provide lots of current gain, they could be substituted with a Darlington live TIP102, a heatsink is needed. Output is from around 400mV to 10V @ around 100mA max, though higher currents can be drawn at reduced output voltage and more ripple. Before anyone points out that an lm317 could do a better job, I already know that, just thought this would be fun.
