fuzzLab Jr.
A long time ago, I built a Fuzz Face that
replaced pretty much all the resistors with
pots. I called it the fuzzLab jr. It was
fun, but in the end, it really didn't sound
very good, nor was it terribly useful. I put
it away and promptly forgot about it. Over
the last few months, I've been working on
the Armageddon Processor, and it has been
exciting and frustrating all the same time.
Exciting because it can make sounds I've
never been able to obtain before.
Frustrating because it is so complex.
So I decided (as I often do because I'm
such a spazz) to start yet another new
project in the midst of all the other stuff.
This one is the fuzzLab Jr. as it should
have been originally.
The Prototype
Wat?
A lot of knobs on a fuzz face is hardly
new is it? In fact, between the ZVex Fuzz
Factory and the many-knob-fuzz-face that is
a rite of passage for DIY'ers, it has been
done to death. So why make another one?
Well, I think I've come up with some novel
things that are simultaneously strange and
musically useful. I've always been intrigued
by the fuzz factory but disappointed in its
lack of bass response and difficulty in
getting good fuzz tones along with the
stuttering/fart/glitch sounds.
My goal was to create a fuzz box with a
great deal of controllability, but not at
the expense of making yet another
stuttering/fart/glitch box. The solution in
the end was to start with a silicon tranny
fuzz face, change the circuit in key places,
and add tone stack of almost prehistoric
design. The result is ten knobs of fuzzy
goodness that I'm quite happy with.
The Schemo
Click
on the image for a bigger view
The preamp section around Q1 is taken
from the electro harmonix LPB-1 booster, an
old and trusted single-transistor boost. I
added this in the front to offer even more
drive. Next it goes into a two-transistor
fuzz face design. The key differences are
the addition of a Comp switch. This shunts a
47nf capacitor between the collector and
base which results is a bass-heavy
compressed sound. With Comp engaged, you
lose some volume so you'll want to turn the
volume pot a little higher, but the results
are pretty cool.
There is also a switch called feedback
that can switch between the collector of Q3
and the base of either Q2 or Q1. When you
switch in the feedback loop to Q2, it sounds
like a wildly oscillating fuzz, but a bit
more interesting because the VR4 pot is
not directly connected, rather it goes through
another 47nf cap which forms a filter. So
the same pot controls both amount of
feedback and acts as a filter control. When
you switch the feedback loop to the base of
Q1, something entirely different happens--it
shuttles negative feedback to the beginning
of the circuit which not only lowers gain,
but completely alters the frequency
response. There are also pots for
controlling the voltage to the Q2/Q3 pair, a
Bias pot to further tweak the voltage to Q3,
a Choke pot between the Q2 base and Q3
emitter, and the standard fuzz face 'Fuzz'
pot.
The whole thing ends up in a crude tone
stack that you would more commonly see in a
tube amp. From an electrical engineering
standpoint, this tone stack should 'suck
balls' because of the wild impedance
mismatch. But it is actually not only very
active, but very interactive with the
overall circuit. So instead of sucking
balls, it eats balls. You see the subtle
marketing difference?
Does the combination work? I sure think
so. I've been playing with this off and on
for about a month and am still discovering
new sounds.
The Enclosure
I wanted to come up with a design that
was simple and would belie the purpose of
the innards. The 1790NS enclosure is a bit
biggish, but gives me ample room for the 10
knobs and two switches. I thought a nice
touch would be to use an amp-type jewel
light instead of the traditional LED bezel.
It was wood sides. Heh.
Wood.
PCB rev 1
Layin' it out
More wires than an illegal NSA wiretap
More to Come....
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