Being that you already know what colors are what, you will just need to make sure that the amp accepts a low level input, instead of a high level, if it takes a high level, none of this will work. If it does accept a low level input, then cut the headphone cable there should be 2 wires a shield. the wires are the left/rightpair, and the shield is ground. the ground will need to be wired to both negative speaker leads, and the left / right should be to the positive leads. wire colors change between manufacturers, so it would be best to check which is which before hard wiring anything.