Jason.....Thanks for that info on the digitrax decoders.
The ZIMO MX620 engine decoder that I installed, after modifying the plug-in part, comes with sound built into it, but it only has enough capacity to give the steamer either a sound chuff or a whistle. I'm going for the chuff.
The pins on the ZIMO MX620 plug-in decoder are way too small to fit in the receptacle in the Con-Cor 2-10-2 tender. Your Zepher would probably have the same problem.
With the large Con-Cor tender (unlike anything CNR used) all you'd need to do is run one wire from the MX620 decoder installed in the tender, to an amplifier and then to the speaker and then a ground wire. That's what the ZIMO rep told me.
I'd sure like to see how big the standard plug on the Digitrax plug in decoder is. I was told that if the if the digitrax plug-in decoder fits the plug in the Con-Cor 2-10-2 tender, then it is an HO sized pin plug.
I thought all this decoder stuff was standardized. From what I've seen, it looks like the Europeans are building their decoder parts a lot smaller than the North Americans are.
I'm trying to find some small amplifiers and speakers now. Apparently, ZIMO will be coming out with their own in a while to augment the MX620 that has the sound in it.