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Doug Hammond's FireFly is a low wattage tube guitar amp with a push-pull output stage. It uses both halves of a 12au7 dual triode to produce less than .5 W of clean output power. 12au7 tubes are typically used in preamps but because of their ability to drive current, may be employed in a low-wattage power stage as well.

The output stage used here is in ?self-split? configuration. It does not require a phase splitter stage to drive each side of the push-pull power stage. This is not as efficient as traditional push-pull stages, but in this case the emphasis is on tone, not power. Besides, since this is intended as a low power practice/recording amp, the lower the output volume, the better! This produces the ?cranked-up? vintage tone without the eardrum-shattering volume.


  • Very low volume- less than 1 watt of output power
  • Switchable gain boost
  • Single gain/volume control

  • Skill Level: intermediate --- Status: ready to build
    Primary Documents:
    •IMAGE: Revision 3 of the FireFly amp. : [download]

    •IMAGE: Doug's rev 3 FireFly interior : [download]
    •IMAGE: Doug's rev 3 FireFly top of chassis : [download]
    •IMAGE: Doug's rev 3 FireFly, front view : [download]
    •MPEG AUDIO: Doug's rev 3 FireFly played through a closed back G12H30 1x12 cabinet : [download]

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