Inside every VFD is a filament, grid ... this triode amplifies the electrical signal coming from a stereo or guitar. [Fernando] built his circuit on a breadboard, and with a little tweaking ...

This build from [mircemk] is of the latter variety, repurposing a VFD display to do the job. The project is built around a VFM202MDA vacuum fluorescent display, which provides that lovely green ...