All transistors except BC556C, should be mounted on a suitable heatsink to prevent overheating. It would also be ideal to mount the plate in a metal cabinet to prevent unwanted noise.
This power amplifier circuit uses complementary transistors in order to achieve the desired power. It is powered by a dual polarity power supply circuit of +/- 45V and consumes 4 amperes. ALL diodes labeled A, B and C in the amplifier circuit diagram are 1N4001 and also be mounted on the heat sink but with silicone grease. The entry should be 1 Volt to deliver full power.
The power supply circuit can not be regulated, but the filter must be very good to avoid “hum” in the speakers.
In this case the transformer has a secondary with midpoint of 32V / 0V / 32V (center tap). For mono amplifier circuit configuration must have a current of 4A, 8A stereo. The diodes must be at least 100V by 6A (mono) to 12A 100V (stereo), you may use bridge amplifier circuit for the rectifier diode. The capacitor should be minimum of 4700μF x 63V each.