Luke Orsie at Luck Duck Pedals made this for me in February 2012. The circuit is a modified Fuzz Face with a few more controls than his Silly Duck Fuzz (a silicon fuzz face with a pregain control). This has a hybrid circuit (germanium and silicon transitors), external bias and voltage control (voltage sag runs down to about 3V), a tone knob (bass cut), and footswitchable boost. The boost is passive and lifts a resistor inside - it's actually cutting the volume when it's off. There's a pop that can't really be helped (it's just the way electronics work), but it's not too noticeable if I'm playing at the time I hit the switch. Luke did a really good job in getting the boost working much better than it did with the original plans I had. :)
Luck Duck Pedals is on Facebook. I'm not affiliated with them, I just like their stuff. :)
The guitar used for this demo has Reilander vintage Strat pickups (alnico III) in the middle and neck positions and a Benson Custom Alnico II in the neck. I have some demos up of them somewheres ...