i think it is one or the other,when you plug in the headphones it takes the signal from the speakers and redirects to the headphones,if you hook up another sound mod and use the headphone jack as the inputs it should work but you will have to have twice the wireing and leds that you have now,as far as i remember if you try to hook both up to one set of leds it shorts something and dont work right.i could be wrong though