BJT transistor amplifier circuit 400w output transistors 4 tip41c quite strong and tip42c 4pcs 2 × 46 volts DC supply voltage + – symmetric power supply.
Output power supply AC 12 amp amp 2x33v proposed for transformer circuit connecting to the audio input volume control stereo potentiometer 10 … from 20k to do.

The transformer used in the prototype that we showed in the video is a 33-0-33 volt AC transformer, center TAP, and measure end to end brand 66 volt AC. This gives us a total power of 300W (150W) per channel. If we get the actual 400W (200W per channel), we use a 40-0-40 volt AC transformer. The reason we did the project with a lower transformer voltage was thinking of people who do not have enough money. So there would be an economic and a more expensive version that provides more performance.
Should get a transformer of a high voltage of over 45 +45 V AC and want to condition it may take a few turns of wire until you are of the appropriate voltage for this amp or better yet, build another amplifier that uses more voltage as our 500W stereo amplifier , using a transformer 55 +55 V. The ideal way to achieve a good performance of this amplifier current is 12 amps. Remember that this also depends on the transistors that use the exit. When using transistors 2SC5200 and 2SA1943, they need a minimum current of 1 amp, so we recommend using a transformer of at least 8 or 10 amps.

400W Power Amplifier Circuit
Source: videorockola.com Power Amplifier Circuit schematic pcb files alternative link: