Two years ago I got an idea to build myself an audio amplifier. I made one based on TPA3118 from TI. Then I made a cd player/bluetooth reciver using raspberry pi. To case it all I designed a wood+plastic enclosure to print and assemble with M3 bolts and 4mm ply wood sheet. Currently I'm focusing mainly on software side (https://github.com/trybula/RpiPythonCDPlayer/tree/main). 

I do attach more important pdfs, and Gerber of my amp PCB, however you need to remember that I'm not a professional so its not the best design. For example you need to short two pins while soldering, because i couldn't fit it correctly on the PCB. Apart of what i attached the amp box consists of 230V→35V 80W transformer, linear voltage regulator with big capacitors and full bridge rectifier, and ofc voltage control with 2 input mixer.