Turns out it *does* work with the IRF510. However, it's just not
powerful enough to drive a speaker. After switching a few speakers
around (went from 8ohm to 4ohm) i got brave and plugged a set of
headphones into it. It amplifies, but it's only 'audible' with
headphones. I put a single BJT booster stage in front of it, and while
it distorted a little bit, it didn't really get any louder, so it's a
'headroom' thing, i presume.
Would increasing the supply voltage from 9V up to say, 12V or 18V give
it more 'power', or should I look elsewhere? Will higher voltages
change the biasing requirements?
I expected this to be roughly the same volume level as the LM386 1/2W
chipamp (a fun little device, IMHO). Is that about right?