Dave usually uses a Gibson Chet Atkins SST.
That model was designed by the same guy who designed all of the Godin multiacs and solid-top acoustic guitars.
I am not certain on this, but I believe I read somewhere that he plugs turns the volume and both tone wheels on his guitar all the way up and puts black duct tape over them. He plugs into a Mackie 1404 before going into his amp. I can't remember what amp he usually uses. But, I have a friend that has a Chet SST and uses a Crate acoustic amp and the sound is virtually identical. It is really nice. You also need to be a very percussive player to get that DMB sound.
Anyway, hope I could help a little.
MIKE