I wanted to make a headphone amplifier with a crossfeed like this one, elsewhere on the net I saw that some people where using the LM317 voltage regulator as output devices, I had a couple spare ones laying around so I figured, why not?

After some thinking and experimenting I finally settled on this schematic:



R1 and R2 simulate a headphone load, because the headphone output of my receiver is connected to the outputs of the amplifiers with a 390 ohm series resistor. That's fine for driving a pair of headphones but it can destroy an opamp if it's directly connected to its input.
Without R8 and R9 the amplifier oscillates, the 10k resistor forms a lowpass with the input capacitance of the opamp, this attenuates the feedback signal at high frequencies.

If you want an amplifier that can handle a line level input, you can use this schematic:



This is what it looks like, the power supply is in a separate casing.