You who like to build project power supply, May ever use the integrated circuit LM723 It can work in the circuit, there is integrated this circuit with can change voltage output get 0-25V with VR1 And control current get moderately tall about 25A by fine at VR2. For transistor at do infront enlarge the trend tallly go up. Arrive at 25A that ,he chooses to use 2N6776 numbers s have been canning wasp parallel then enhance to enlarge the trend tall very , and may more than 2N3055 numbers with. For other detail , see in original website better
http://www.seits.org/features/pwrsup.htm