For some years I've had a transformer, bridge rectifier, and large electrolytic caps from some sort of power supply rescued out of scientific garbage, because I couldn't bear to see it discarded, and I never really figured out what to do with a 30 V supply that could maybe do 1-2A judging by the size of the transformer. Not big enough for a huge audio amp.
I often listen to music on my computer and am frustrated by the pitiful headroom of the built in headphone output. It's actually impossible to listen to anything with more dynamics than pop music because if the quiet passages are audible, the loud ones are distorted. I bet it runs off the +5 motherboard supply and just doesn't have any volts to spare.
Anyway here's an idea I had tonight - the incredibly self-indulgent class A headphone amp. Single channel schematic shown:
At least in simulation, looks linear, plenty of gain and clean headroom. Totally discrete for that awesome point-to-point buildability should I choose to do so. 300 mA idle current to suffice the lowest-impedance 32 ohm pair of earbuds out there, and an easy 20 V p-p swing for the 600 ohm console phones out there. Wonder, though, if this is just going to be some monstrous huge thing that blows out phones and eardrums. Yeah, it's a bit big. But for some reason I am so tempted to build it.
Phones reference to Vcc and not to ground because the PSRR is just a whole lot better that way. At the risk, of course, of some idiot connecting the headphone output to a grounded input jack and creating smoke. It'd probably have a fuse in it if I built it.