adding sound

[blsky73]

adding sound to already dcc equipped bachman trains. which decoders should i use

[SteamGene]

Not the decoder that comes on the locomotive.  It would be a great help if we were to know what locomotives you wish to convert.  BTW, a "train" is a rail unit with motive power and rear marker light(s).  A locomotive is "motive power."
Gene

[blsky73]

i have a gp40 diesel that came with the ez command controller. the controller broke ?? replaced it with prodigy express