"The BB Preamp offers awide variety of sounds. It's capable of a 30dB+ clean boost with an adjustable ±15dB two band active EQ which adds a wide range of harmonic content to your ideal sound.
The BB also utilizes a pre-gain stage which allows the Pedal to go from a very pristine clean to a very smooth,compressed, overdriven sound.
True bypass for eliminating any signal interference when switched off.
Can be used with AC adaptor (optional) or 9V Battery.
"The BB Preamp is a great sounding soft Distortion and Sustain pedal. It really produces a great fat singing lead tone! The BB gives you a more sustained focused lead tone than the AC. Between the RC, AC, and BB, you can cover all your boost, overdrive, and gain needs!
Here's th ProGuitarShop demo video of the Xotic BB Preamp in action:
Here's the great MadBeanPedals Project file with a schematic, PCB Layout and wiring diagram: http://madbeanpedals.com/projects/Glitterrattii/docs/Glitterrattii.pdf
As you can see from the schematic it's an op amp based clipping stage into a tone and boost section. Nothing revolutionary but it works well
Here's a vero layout from Hewie:
Here's the freestompboxes.org forum topic for reference: http://freestompboxes.org/viewtopic.php?f=7&t=11