The project described in this page utilizes POTENTIALLY LETHAL VOLTAGES. If you are in any way unfamiliar with high voltage circuits or are uncomfortable working around high voltages, PLEASE DO NOT RISK YOUR LIFE BY BUILDING IT.

For my third tube amplifier I decided to make my own design. It uses one tube for each of the three stages:

Preamp: Inspired by famous American made amps, it uses two halves of a 12AX7 and a tone stack with controls for Bass and Trebble.

Reverb: I think this is my best achievement in this amp. I manage to drive a reverb tank with only one tube and no transformer. The tube is a 12WD7 (i.e. half 12AX7 and half 12AU7), the 12AU7 drives the tank in constant current generator scheme and the 12AX7 amplifies the signal from the output of the tank.

Power Stage: it’s a self-split push-pull copied from the famous Firefly. Not very powerful but as cheap and compact as it gets.

Schematics

Layout

Cabinet

The cabinet was designed around a Jensen speaker CH 8/35. The goal was to make it as small as possible.

(Clik on the picture to download SketchUp file)

Gallery