Level: Sets the volume of the overdriven signal.
Drive: Sets the amount of saturation in the overdriven signal.
Blend: Mixes the clean input signal with the overdriven signal. The clean signal remains at unity gain while the volume of the overdriven signal is set by the Level knob, allowing for fine control of the blend ratio.
Grunt Switch: Sets the amount of low frequency content to saturate by selecting between three different bass boost levels before the clipping stage.
Attack Switch: Sets the amount of treble content to saturate: The œBoost setting emphasizes the treble content extra clarity and presence. The œFlat position leaves this register untouched while the œCut position will reduce the amount of high frequencies being saturated. This new addition helps to keep the treble portion of the signal under control, specially useful when playing with new strings and/or cabinets with tweeters."
You can find the original FSB thread and schematic here.
The layout (like the Friedman BE-OD) has been verified as "working" in the forum section but the original has been built using SMD components and there's been some "guessing" in some of the values.
I don't know how close it is to the B3K (it may be 100%) but this is the best schematic we can get at the moment.