If you run line in, with no battery box or preamp, you won't get a signal, because the mics need some power. The Mic-in jack can provide some power (probably 3V). Some mics are able to record louder music without distorting when they use a 9V battery box instead of that 3V from the R09. I'm not sure if the DPA's are in that category or not.
I run the standard CSB's, with their battery box, line in to my R09.