I model in HO and HOn3. Recently I bought a Walthers Alco PA1/PB1 set in straight DC. I already have a PA1 with DCC and sound. Since I will always be operating these units together, I want to get decoders which do not have sound. What decoders can I get which have 21-pin settings but do not have sound? Will these work with all three units as DCC?