Model Railroading > Athearn DDA40X sound to non sound

I recently acquired a sound equipped Centennial that I want to convert to DC power. What do I need to remove to have it run as a straight DC unit? According to the owners manual it will run as a sound unit on DC but it only runs at a crawl at 75% power and up from there. No way it can keep up with the rest of the fleet. And I am not a fan of sound units anyway. Thanks for any help. I'm guessing I might have a couple of sound units available if anyone is interested.

The sound board is using some of the DC power so the loco will always run slower than if it was not there.    To make it run the way you want you will have to remove the board.

Many DCC control boards have a plug that leads to the decoder; replacing the decoder with a dummy plug will connect the track wires to the motor leads.  
I think that will also put DC track power onto the head and rear lights.
You should find out who made the decoder and to to their tech support site for the best information.