Generally Sony's mic input design is quite good and mostly supplies ~2.5 volt mic power.
For what it's worth, I never liked what SBM did to sounds suggesting not using this if natural sound is important to you.
Some mod'd SBM-1 may have allowed 24 bit output not using SBM process.
Maybe better to upgrade to 24 bit recording depth featured on many newer flash recorders like Edirol R-09HR or Sony's D50.
More TS thread links to more recent PCM-D50 deck model (which has SBM optional mode!) technical posts/deck review info is at top of my tips page at
www.sonicstudios.com