It can be modified up to 150v dc supply with 30amp of current..and for that you need to change somthing like..chang final driver transistor to ttc5200 and tta1943..chnage the input transistor to mpsa92,,change the bias transistor to mje340 and mje350..change the 47ohm resistor to 100ohm 5watt..and also chnage the 470pf to 680..then it will be capable to handle 150vdc supply..and remember..use 1watt resistor in order resist heat👍👍
