This is a mini amplifier(4x4x4cm), which I called it Magic Cube. I prepared the case in 3D-printing and installed the following components inside the case. Although the PCB board features only 3Wx2 output, but for my tests it can drive any bookshelf speakers at ease.

3Wx2 PCB board x 1
Speaker jack x 4
3.5mm jack x 1
DC jack x 1
Power and signal cable x 4

https://youtu.be/dgsR5FtU3kU