The above is a stereo amplifier circuit based on IC STK4191 with 2 X 50Watt output power 8 ohm impedance. And besides that you can use some ...

In this video B688 DIY Bass Amplifier with Volume, i'm showing, a way to make a Class-A effective bass amplifier with magnetic coil.

If you want build hi-fi power amplifier about 30watt to 50Watt or 75 watt. Recommend use TDA2050 below, builds by the integrated circuit and PCB layout.

This is the pre-amplifier circuit diagram for an amplifier. it's a mono-circuit diagram. every amplifier used this type of diagram.

See figure below its power amplifier using transistor mosfet as amplifier. Mosfet Amplifier with power output 400W