Earthquaker Devices Erupter User Manual

The Erupter fuzz started as something I wanted just for
myself - the ultimate classic fuzz tone. One with a simple,
yet effective control interface and that work anywhere in the
signal chain. A fuzz with a big low end, but not too mushy, a
biting top end without being too harsh, and just enough output
to politely send a tube amp over the top. It must also have
excellent wide-range clean up with the guitar’s volume control
without losing too much low end. It took a long time and a lot

of experimenting to get there but I think I nally nailed it.

A lot of people think this classic circuit is a no-brainer due
to its low parts count, but I beg to differ. Since there are so
few parts in the circuit, everything makes a difference. That’s
why you see so many variations on the market today. You
can use the topology, but the sound always varies. I’ve made
plenty of designs based on this circuit in the past, but none

of them gave me the perfect, overloaded-yet-rened full-force

fuzz tone with crushing lows, smooth top end and an input
that is responsive through the full range of the guitars volume
control without losing too much low end in the process. Until
now!

I spent almost two years swapping transistors, measuring
resistors, adding controls, removing controls, trying all types
and values of capacitors, and basically using every trick I ever
learned. What I landed on is exactly the sound I had in my
head - the perfect crushing fuzz tone. I managed to whittle
down the controls to the most important one of all, Bias.
Why leave out the volume and fuzz controls? Most people
leave the volume and fuzz all the way up, at least that’s the
way I always do it. This yields the thickest fuzz and the level
is slightly above unity to push the full frequency range of
the guitar out front when you kick it on. By setting these at
maximum and allowing control over the bias, you can freely
adjust the character of the fuzz for more tonal variations.

We had a custom center-detent pot made to t the required

resistance for the Erupter. When the Bias control is set at noon
you will feel a little click. That means the pedal is perfectly
biased to give the best possible fuzz tone. As you turn the
Bias counterclockwise (colder) the fuzz lowers in level and
becomes more gated. As you turn the Bias clockwise (hotter),

the fuzz becomes cleaner and more rened and the output

level increases.

The Erupter also has a buffered front end to give the best
possible input signal with stronger highs, tighter lows, and
allows it to be used before or after any other effects (even a
wah pedal) without the usual problems associated with this
circuit. What!? How’s it do that? By using transformer based
pickup simulation, of course. It’s a cool little trick I learned
from an article written by Jack Orman almost 15 years ago.
These two features allow greater use of the guitar’s volume
control to clean up the fuzz. Try it, you’ll be amazed at the
amount of tones you can get all the way across the dial!

But what about the parts? What kind of magic is in there? The
Erupter uses new production 5% ½ watt carbon composition

resistors, metallized polyester lm capacitors, Sprague and

BC electrolytic capacitors and NOS, hand-matched, low gain
silicon transistors for temperature stability and predictable
operation under all extremes. I tried a lot of parts in this circuit
during the development. Everything from our usual production

1% metal lm resistors and caps to expensive NOS paper in

oil capacitors. I tried every rare germanium transistor I had
and countless different silicon transistors. What I landed on

gave me the well-rounded and dened fuzz tone with just

enough pummeling intensity that I’ve been wishing for.

Each and every Erupter is built by the hands of real-life dream
warriors in the foothills of Mt. Akron, Ohio.

Controls

Bias: This control has a center detent for the “perfect” fuzz
setting. When in the center position, the tone will be big
and round with a slight volume boost and great sustain. As
you turn this counter clockwise it becomes more gated with
lower output. As you turn this clockwise it becomes louder

and more rened.

Power

The Erupter can be powered by a 9v battery or a standard
9-volt DC power supply with a 2.1mm negative center

barrel. We always recommend pedal-specic, transformer-

isolated wall-wart power supplies or multiple isolated­output supplies. Pedals will make extra noise if there is
ripple or unclean power. Switching-type power supplies,

daisy chains and non-pedal specic power supplies do not
lter dirty power as well and let through unwanted noise. Do

not run at higher voltages!

Current Draw: 15ma

Input impedance: 500K

Output impedance: >1K

Switching

This device is true bypass and uses electronic relay based
switching. Audio will not pass without power.

Questions? Comments? Concerns?

Send an email to [e-mail] and we’ll
help you out.

This device is guaranteed for life (or at least the life of
EarthQuaker Devices).

© 2017 EarthQuaker Devices LLC. | www.earthquakerdevices.com | [e-mail]