I came across this simple circuit on pintrest for a 1 watt amp using a 12ax7 with an automobile ignition coil as an output transformer. Interesting, but the coil does not isolate plate voltage from speaker output. Unless this is just too risky to experiment with, I think with some mods it might be interesting to. experiment with in order to build a flea powered bedroom amp. https://www.allaboutcircuits.com/textbook/experiments/chpt-5/vacuum-tube-audio-amplifier/ Comments?