Proto sound 2

Hi all. I live in the UK and have an extensive 0 gauge model railway, using dc power voltage regulated controllers. with a track voltage variable from 1.5 to 20 Volts dc I am looking for help please

Question

all My locos use dc direct from the track, however I have three MTH desiels with Protosound 2 installed. and use ac track voltage up to 18 v ,

how can I rewire to use variable dc voltage input and still use protosound. at present the electronics have been bypassed with dc track current lead directly to the motors, but would love to have the sounds also thanks for any help Brian

Well THis has been posted for a while n ow, unfortuantly noone has a clue as to how to doo the above, great pity would like some sound when running never mind and thanks to all for reading this posting will leave it on line for a while maybe just maybe someone may have an idea Thanks all Brian