Okay. Open the player. In the rear left corner of the MK2s are two rectangular connectors. One is labeled "Analogue" and the other "Digital."

Pull the one labeled analogue from the board. Use a very fine flat bladed screw driver and remove the gray/black striped wire from the connector located on the far left of this connector. This wire will carry the sub signal across the mic in cable. I don't remember what color the ground half of the cable is, but you can get ground from almost anywhere. Connect the sub board output cable to that pulled wire by some means such as soldering or some sort of connector (what I will be doing). Connect the ground half of the output from the sub board to the cable ground. Put everything back together and connect your cables using an appropriate adapter. Enjoy.

DISCLAIMER. This ia all from memory and I've never actually done this, so this post could be riddled with errors.

Stu