Here’s my circuit now, for future ref. I might need to move some parts around, because it’s totally not working at the moment.
I spent three and a half hours testing the “clipping” stage of the circuit. There was no current on the oscilloscope at first — turns out we’d used the wrong resistor. I should probably learn to read resistor bands.
Plus, the transistor was funky. Even after we’d identified the collector, base, and emitter.
Thankfully, we found out why. NPN transistors only work at a certain voltage, at 0.7V. Our resistor resisted too much of it, and left 0.3-0.4V. Which was quite odd, since the schematic specifically called for a 510k Ω resistor.