Hi Anthony,
I don't think an expansion board can be added to the piano.
The kn7 has 4 slots built in, where you plug these boards into. ( ie I had to remove the underneath panel on the keyboard, plug the boards in , then put it back together.

Your manual should tell you if expansion boards are an option ( but unfortunately I doubt it).

The boards add new samples to the kn.

best wishes
rikki
[QUOTE]Originally posted by AnthonyCian:
[B]That's what I'm asking. Like to know if these expansion boards are able to work on the PR804. How does it connect?