I don't know about SOund Devices MP-2, but I'm going to be using a Aerco MP-2 into my R-09 and tha manufacturer of the MP-2 recommended using the RCA out to the 1/8". He said the 1/8" is pretty useless on the Aerco MP-2 and it was designed for headphone use. I'm having a 6 inch "Y" cable (2 RCA's > 1/8" miniplug) made to use with my setup. Maybe the SD MP-2 is different than the Aerco though.