The Nine Volt Nirvana BrontoBoost is a two stage booster/fuzz/OD/Distortion unit, described by its designer Joe as having "a ton of different tones in it, all good!" It sits in the overlap between boost pedals and fuzz pedals: the same circuit covers treble boost, full range boost, overdrive, fuzz and amp-style saturation, depending on how it is set.1
What it does
The BrontoBoost does four things, and does them well in the words of the Guitar FX Layouts writeup: a cleanish boost that can be a treble boost or full range, an overdrive like a TS, a fuzz, and a tube amp simulator. Its range is described as going "from awesome treble boost like a British top booster, to fullrange boost, to very fat fuzz and everything in between."1
A feature the writeup singles out is how the pedal responds to the guitar: "at all settings, it retains an incredible 'gain' control - your guitar's volume knob!"1
The gain stage switch
The pedal's central control is a switch that selects the number of gain stages, one or two. With one stage engaged the circuit behaves as a booster; with both, it becomes the two stage fuzz and overdrive unit the design is built around. The schematic calls for a 3PDT footswitch, which is what the layout author recommends using.1
Power and the negative ground question
The BrontoBoost runs at -9V and is a negative ground effect, which the writeup notes is generally the case with PNP circuits. That means it needs a voltage converter, such as an Lt1054 or a 7660, to run from a conventional positive supply.1
Because the circuit is negative ground, it cannot be powered the way most modern pedals are without a converter. Plan the power arrangement before building or integrating it into a board.
Circuit notes for builders
The layout was published on Guitar FX Layouts in September 2017, and errors found in the original posting were corrected the following day, after which the author said "it should be good to go now."1
Two circuit points matter to anyone building it:
- Q2 base connection: the schematic the layout was taken from has an error. Connecting the Q2 base directly to -9V does not work; replacing that connection with a 470k resistor results in a clean boost, though the author could not be sure that was the original designer's intent.1
- Q3 transistor: Q3 is a 2SB54 PNP germanium, and the author assumed it can be substituted with any other PNP germanium transistor.1
One builder who completed the project in 2019 reported that it worked well but that the output volume was lower than the bypass volume even at the highest level setting.1
Related Nine Volt Nirvana pedals
Guitar FX Layouts has published layouts for other pedals in the Nine Volt Nirvana range, including the Nine Volt Nirvana Tone Dog and the Nine Volt Nirvana Dino Drive, as well as the Nitroburner Fuzz.
Videos
Joe Gagan
stekks
Questions
Does the BrontoBoost need a negative ground power supply?
Yes. The BrontoBoost runs at -9V and is a negative ground effect, which is typical of PNP circuits. That means it needs a voltage converter such as an Lt1054 or 7660 to run from a standard 9V supply, and it cannot simply share a normal center negative daisy chain with your other pedals without one.
What is the Q2 base error in the BrontoBoost schematic?
The schematic the layout was taken from contains an error: connecting the Q2 base directly to -9V does not work. Replacing that connection with a 470k resistor results in a clean boost, though the person correcting it could not be certain that was the original designer's intent.
Can I use a different germanium transistor for Q3 in the BrontoBoost?
Q3 is a 2SB54 PNP germanium transistor. The layout's author assumed the 2SB54 can be substituted with any other PNP germanium transistor, so builders have that latitude if they cannot source the original part.
Can the BrontoBoost sound like a Tube Screamer?
Among its four described modes is an overdrive sound described as being like a TS, alongside a cleanish boost (treble boost or full range), a fuzz mode, and a tube amp simulator mode.
Why is my BrontoBoost quieter than bypass?
One builder reported a working unit whose output volume was lower than the bypass volume even with the level at its highest setting. If your build shows the same symptom, that reported behavior is the known reference point.
Sources (1)
- Guitar FX Layouts: Nine Volt Nirvana BrontoBoost, Guitar FX Layouts (tagboardeffects.blogspot.com), 2017-09-27
