Guitar Week: Build Your Own Firefly Tube Guitar Amp
By James Grahame
It's all fine and good owning a classic Strat, but don't forget that vintage instruments deserve to spend at least part of their life being played through real vacuum tube gear. The Firefly is one of the smallest guitar amp kits created by the AX84.com cooperative. It's a three tube design built around a pair of 12AX7 tubes and a single 12AU7.
This tiny device puts out around 1W - perfect for use as a warm practice amp or for oddball recording sessions. There are no tone controls, but there's a quite promising variable "boost" circuit to muck things up a bit. A double sided & silkscreened Firefly Revision 5 PCB costs $19, although the rest of parts will set you back another $150 or so.
By far the coolest thing about this circuit is that it has been released as "open hardware," so you can tweak the design or produce your own PC boards if you wish. John Calhoun has done a great job with his "Firefly PCB Guide," which includes lots of photos of the build process, along with a pattern to help you cut and bend an aluminum enclosure.
Order a Firefly PCB
Take a look at the Firefly PCB Guide [pdf]
Explore AX84, the Cooperative Tube Guitar Amp Project
