Alright, this is one I wired up today:
As you can see, this thing can get pretty tiny.
Note: Don't use a GC slider for your 10k pot, it sounded terribad. The 10k pot actually affects how the sound, uh, sounds, I had to change to a different one, then finally a trimmer. That said, all of mine were scrap ones, so if you actually buy a good one then you'll be fine.
Now then, if you were to, oh, I don't know, wire up a headphone jack straight to this amp?
You'd blast your ears out.
The amp is designed to drive a speaker, not headphones.
It's best to have a resistor on the headphone jack in order to make it quieter, but you can't just add one, because you'd be adding a resistor to the speaker as well, making it quieter. You have to take advantage of the switching that goes on in the headphone jack.
I figured this out at MR CT, then Wyatt ate the amp and I didn't build one of those amps again till recently I guess.
The resistor shown is a 10k one, but I stepped it waaay down to a 100 Ohm and it sounded fine. It depends on your preference, you can make it as regulated or unregulated as you want, Heck, you could ever have another pot on this line so you can adjust it at will. XD
This only works for mono input, I think. It's wired so you get mono sound in both ears though.
Do exactly that, and you get full amp output to the speaker, and regulated output to the headphones.