The Tone Dog is a fuzz from Nine Volt Nirvana, designed by Joe Gagan. It is built around germanium transistors, the old-style parts that give many classic fuzz designs their character. The circuit is documented publicly as a stripboard (vero) layout on the Guitar FX Layouts blog, which posted it on 16 October 2017, describing it simply as "Another Nine Volt Nirvana fuzz."1
What it does
As a germanium fuzz, the Tone Dog takes the guitar signal and clips it with germanium transistors, producing the thick, touch-sensitive distortion players associate with that family of circuits. The published layout includes a tone control and a volume control, and the clipping diodes can be swapped: builders on Guitar FX Layouts noted that "You can try different diodes to get different flavors of distortion." The layout as posted used 1N4002 diodes.1
Germanium transistors vary widely in gain (Hfe), but the Tone Dog tolerates that spread. Builders reported testing devices with Hfe from the high 30s to about 150 and found that all sounded good with the 68k resistor from Q2's base to ground in place.1
Building it from the layout
The Guitar FX Layouts thread is the main public documentation of the circuit, and builders there flagged two things worth knowing before soldering1.
- Missing resistor: the layout as first drawn leaves out a 68k resistor from Q2's base to ground. Builders found the right side of the board has room for it if the tone trimmer is changed to a smaller one or an off-board pot.1
- Tone control quirk: one builder found the tone pot, drawn as an off-board pot, had no effect on the sound until completely counter-clockwise, at which point the volume dropped and it sounded very muffled.1
- Layout correction: the jumper/resistor connects to the 4.7nF capacitor on the left, not to nothing on row G, as clarified in the thread on 19 October 2017.1
If you build the Tone Dog from the published stripboard layout, the 68k resistor from Q2's base to ground needs to be added, and the tone control wiring deserves a second look before you box it up.
Where it sits in the Nine Volt Nirvana range
The Tone Dog is one of Nine Volt Nirvana's fuzz designs, described on the site simply as "another Nine Volt Nirvana fuzz." It was designed by Joe Gagan, whose work the builder sums up with the remark "as usual if it's from Joe Gagan it's got to be good."1
Questions
What kind of transistors does the Tone Dog use?
The Tone Dog is built around germanium transistors. Builders on Guitar FX Layouts reported testing devices with Hfe (gain) ranging from the high 30s to about 150, and found that all of them sounded good with the 68k resistor from Q2's base to ground in place. That makes the circuit forgiving of the wide gain spread typical of germanium parts.
Can I swap the diodes in the Tone Dog?
Yes. The published layout used 1N4002 diodes, and builders noted that trying different diodes gives different flavors of distortion. Diode swapping is a common way to tailor a fuzz's clipping character without changing the rest of the circuit.
Sources (1)
- Guitar FX Layouts: Nine Volt Nirvana Tone Dog, Guitar FX Layouts (tagboardeffects.blogspot.com), 2022-11-28
