MAKE:TNT Tools 'n' Tips started as a Yahoo group for people interested in a rare Marshall guitar amp made in the 1960s. People shared details of the circuit and design.

There are now companies offering kits and complete amplifiers based on's research. (Marshall reissued the amp, bringing the whole deal full circle.)

At, folks with a little electrical know-how can make, for about $500, an amp that could otherwise cost $7,000 for an original.