Difficult to say without a schematic or looking at it. It may simply require you to run a wire from some point on the board or Jack to one of the terminals (probably the negative) on the speaker. I would suggest putting a small toggle switch in series with it so you could take the mod in or out of the circuit. The speaker will be in parallel with the voltage divider for the line out/ headphone jack. One thing for sure. You don't want to accidentally short output amp.