This is OCL 150 W mono audio amplifier circuit , with impedance 8 Ohms. The supply voltage using 25 volt DC with triple voltage + ,- ,ground. see below this circuit : Buffer amplifier use PNP transistor is A564 / A733 /A1013 and NPN use D400 / D438. Driver Amplifier use NPN transistor is TIP31 / TIP41 / D401, and PNP transistor use TIP32 / TIP42 / B546. For the transistor booster or end , here I use a 2 x 20355 and MJ2955 . This anplifier is recomended to full range speakers. See pcb line and construction audio amplifier below : Click to view larger PCB line Components are already installed The booster amplifier already installed.