I You will find the the DB engines used a setup very similar to a Torque Converter/hydraulic linkage for the compressor linkage, thus giving an Infinite number of solutions to the speed ratio ?
if you look on the German Cockpit Instruments page, you can find a very nice technical manual for the DB601, it may even be on this site also ? it has good schematics and cross section drawings, but of course is in German :O