I built an active one a while ago with LED's - instructions are here: http://www.generalguitargadgets.com/...ab-switch-box/. That said, Dr - your one looks like a whole lot less moving parts and straightforward. May give it a crack in a small enclosure.

Build diary (ish) here: http://www.buildyourownguitar.com.au...ead.php?t=2481