Ok, this probably isn't going to be the smartest post ever but I have been tinkering with building several engines using Williams off-the-shelf motors, reverse boards and their sound systems, relying on the GP30 set because it's the closest to what I want. For my SD9 their unit seems acceptable, for example. There are only a few places I can order these from and inventories are very thin. I noticed that Williams also offers a GP38 sound system. For the life of me I can't imagine how much different that could sound from their GP30 sound unit (which incidentally doesn't exactly hit a home run anyway). If anyone out there has a clue, please enlighten me.
thanks, Phil