I was trying to find a suitable headphone amplifier to go with the signal digger regen circuit. It needs to have a high input impedance. reasonable gain and some kind of audio limiting to limit the effect of impulse noise etc.
This circuit is working well for me:
The most R2 can pull the emitter voltage of Q2 up to is 2 base emitter voltage drops. That is about 1.4 V less than the supply rail. The saturation voltage of Q2 might be around 0.2 V. The maximum voltage swing available at the collectors of Q1 and Q2 then is 1.4-0.2=1.2 V which provides some audio level limiting. Probably you could put a resistor in series with the headphones to limit that further but I haven't worked that through yet.
Anyway, practically it works well. I would kind of compare it to Selenium's TL431 audio amplifer circuits but a bit better it seems.
It's a long time since I did a permanent build of a radio circuit or anything really. I kind of have finalized on the Signal Digger regen since I'm getting good results with it. I have to do a permanent build of some audio amplifiers as well. The LM386 is absolutely out because it is very destablizing to sensitive regens.
I'll give you a report on your headphone amplifier at some stage.
I've posted this elsewhere. It might be too complicated for your needs, but it works extremely well. At low voltage it draws very little. Very HiFi too, and doesn't load down my rf circuits