Taken from David Rolo website:
"The Bipolar Bear is a dual overdrive with on one side (South Pole) an overdrive derived from an OD820 with Mosfets in the clipping section and a mids control inspired by a modification Mark Hammer posted about the Shin-Ei FY-2. The South Pole side runs on +9V/-9V using a charge pump and its drive knob can go from full overdrive to clean boost (using a dual pot).
On the other side (North Pole), a distortion derived from all kinds of Mu-Amp circuits, mainly BSIABII but with bits from the OKKO Diablo, Dirty little secret and probably others. It also has a mids control (that I snatched from GrindCustoms’ Ultrastoner because I thought it worked particularly well) alongside the usual BMP tone control."
LINK w/ schematic and info:
http://www.davidrolo.com/effects/bipolar-bear-dual-overdrive/