The Crackler is a electronic based around a circuit similar to the Cracklebox. The Cracklebox uses an interesting design based around an ancient Opamp which was prone to oscillation.
This kit contains everything you need to build the Crackler, you only need supply some solder, a soldering iron, wirecutters and a little time. If you prefer, the kit is also available assembled.
Full assembly instructions and an assembly video are provided.