High school design and technology, (Now I think called 'resistant materials?), I was allowed to build a guitar amp but it had to be battery powered.
Mine was, a pair of EL34s, lead acid cyclons for the heaters and 60 PP3 in series for the plate. They were nicads and I learned a lot about fusing HVDC on that project.
We will gloss over the charging harness (1200V bridge off the mains with a series resistor) for the B battery.