Mr. Ageous, you piqued my curiosity and I just monitored both mics through some 7506 headphones. At first listen, the built in mics are sensative, detailed and well...useable. Then I plugged in the 957, the D50 menu automatically prompts you to choose plug 'n power, yes or no. I chose no as the 957 has a battery. What I hear is no more noise than the built in mics which in comparison to the handheld come off rather strident and etched, detailed to a fault, like they're jumping up and down saying "HEY YOU, LISTEN TO ME!" The 957 on the other hand, to my ear, is quite detailed yet warm sounding, like a nice large diaphragm condenser. Quite a shock to me as I had no luck whatsoever getting it to work well with the R-09, the internal mics always bettered it. Go figure.
Just my view.
Bruce