I am wondering why you are considering the TCS M1 specifically or is this your standard decoder? My DD40AX (new version) runs acceptably with the supplied decoder, unfortunately my Zephyr cannot see the engine and so I am stuck with it on address 03. I have about 3 of the original DD40's with the split gears out of which we produced one functioning unit using F-unit gears. When I replace the decoder in the new DD40 I would like to find a sound decoder that would fit. QSI has the appropriate sound files, ie. 2X16 cylinder prime movers and the correct horn but their sound files are specific to their decoders and none of theirs fits. Does anyone know which sound decoder Bachmann had in mind when they called this loco sound ready?