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.