Tristan Shone's "Big Knob" is exactly that: a giant knob for use as a controller in live music performance with a removable detent so it can "click" or turn smoothly. You can buy one in the Makers Market / Boing Boing Bazaar for $225.
This simple device is a heavy-duty CNC machined black anodized knob for use with your expression port on any midi/usb keyboard controller. Simply plug into your expression port and immediately have a 0-128 mappable control knob for use with Ableton Live, Reason, etc.Big Knob: $225
Currently there are 10 spring loaded detente positions and a hard stop for quantized physical snapping, however by removing the 1-inch chromed steel ball bearing and spring, you can create a smooth position knob controller. The detente disc is made from self-lubricating Delrin which both supports the potentiometer and creates a smooth snap in with the chrome spring loaded ball bearing.
The stainless steel frame is adjustable and clamps onto either your keyboard or table.
Mark Frauenfelder is the founder of Boing Boing and the editor-in-chief of MAKE and Cool Tools. Twitter: @frauenfelder. Come and hear Mark speak at the ALA conference in Chicago on July 1.