I just got a used Bachmann  GP7 with printed letters on the tank that say on board DCC. I am looking at installing sound and noticed that when I opened it up, that the board is a H601X + PCB03A with no visible connections/pins to install a sound card and I have no manual. I also noticed that when I pulled off the fuel cover, it looks like a place for a round speaker. I also see something that looks like a visible electrical connection point for a speaker. Does this card already have sound in it and I just have to get a speaker for it and which one or do I replace the whole card and with which one?