Stereo volume control in headphone amplifier
This is a Class A amplifier - the output transistor is always conducting until the amplifier reaches negative clip. 

It doesn't have much output power and worse yet, the amount of available negative current becomes less as the amp output swings negative. 

It should drive headphones just fine but that's about it. 

If you want to use a pair of these as a stereo pair, you will want to use an audio-taper dual pot for the volume control.