raising the volume through headphones

[CJtheBeast87]

in order to keep quiet i plug my cheap sennheiser headphones into my tv the same way as i do my surround sound. i just unplug the ss and plug in my headphones. Im only getting one volume. i have a knob on the surround sound to make the vol louder when using that. there is no such knob on the headphones.
am i stuck with this volume? going into tv settings doesn't seem to do anything. do i need volume controlled headphones to control the sound? or is there anyway i can raise it just a little. it sounds great but would be nice if it was a little louder.
is there like an extension i can buy? i dont see any other audio outs? i also have a ps3 if that helps.