After quite a bit of testing, I decided to bite the bullet and add a South West Digital DCC sound decoder to the Prairie. I picked up their 2-cylinder GWR Group 3 decoder, which includes generic sounds which are suitable for a range of larger 2-cylinder engines. This was my first hardwired sound installation so I had to summon up a bit of courage to snip the 8-pin DCC plug from the wires, after testing it of course, but I reasoned that if for some reason it didn't work in the Prairie, I could always find a use for it in another GWR loco.

Incidentally, I opened up a Hornby 28XX with a view to possibly putting sound in that, and I was surprised at how little room there is in the tender - not a straightforward job at all.

Fortunately there is a lot of room in a Prairie. Since I'd already filled the bunker with lead, the speaker had to go in the cab, but it'll be all but invisible once crew are added. I mounted the decoder slightly forward/over the gearbox. The only modification I had to do was remove two small pieces of lead I'd added inside the body, which interfered with the decoder. The cab floor is a piece of plastikard with holes drilled in it to allow the sound to escape.

Department of cruel close-ups:

I kept all the decoder leads long, including those I haven't used, just in case I want to try adding extra functions at some point.

Initial running was a bit hesitant, but a wheel clean and some tweaks to the pickups sorted that out. You have to play around with a couple of configuration variables to get the chuff rate properly optimised, and I still need to work on those. The SWD chip has a lot of play value, with plenty of sounds and modes to keep you occupied.

Here's a link to a short YouTube clip showing the Prairie moving about a bit.

DCC sound is very much a personal thing, and I'm sure there will be differing views on the realism of the supplied sounds, but I find that it helps to make a small-ish layout seem bigger, as it encourages you to drive slower.