So back to my orginal thinking remove the OEM decoder and purchase a new one with sound.

Does Bachmann sell the same decoder they use in sound equipped modeles?

Thanks

Any suggestion on choice of sound decoders?

So the decoder in the unit will not work if I just add a speaker.

Will I have to remove the old decoder and install a new one? 

Can I buy an OEM sound decoder?

I recently bought the Cavailer set with a DCC equipped Class J 4-8-4.  I would like to add sound.  After looking at the drawing for the DCC equipped and the DCC Sound, the only difference I see is a speaker added to the DCC Sound.

Both the PCB and the decoder are the same.

What do I need to do to add sound?

New to DCC...