The best way to describe a fuzz tone is to see one.
I attached the Discovery’s first oscilloscope input to the
input jack of the Big Muff Pi. The second oscilloscope input
performed guard duty at the Big Muff Pi’s output jack. The
input signal is a 500 Hz sine wave courtesy of the Analog
Discovery’s first arbitrary waveform generator. As you can
see in Screenshot 1, the input sine wave amplitude is
50 mV. Note that the original sine wave is presented at the
output of the Big Muff Pi slightly distorted and out of phase.
The Big Muff Pi controls at this point are at their minimum
I chose to add some measurements in the upper right
of the oscilloscope view you see in Screenshot 1. You can
also see the oscilloscope’s time base, channel 1, and
channel 2 settings in this area of Screenshot 1.
Let’s turn the Big Muff Pi’s control potentiometers to
their maximum positions. What you see in Screenshot 2 is
fuzz. Not only did the Big Muff Pi distort the input sine
wave, it also amplified it. I activated the Discovery’s
oscilloscope persistence feature to enhance the trace view.
Virtual Switches and Such
Everyone has that one thing they really just don’t enjoy
doing unless it is absolutely necessary. For me, it’s mounting
switches and LEDs on solderless breadboards. It seems that
the switch terminations are always just a wee bit too short
or too large for the breadboard holes. That’s why one of my
favorite features of the Discovery is the virtual pushbutton/
switch/LED options that can be applied to its GPIO.
In Screenshot 3, I’ve electrically connected GPIO 0 to
GPIO 8, and GPIO 1 to GPIO 9 using the fly-wires and a
male header. Obviously, the GPIO 0 position is configured
as a pushbutton. GPIO is a simple on/off slide switch. GPIO
2 is configured as a logic source that includes a logical high,
logical low, and high impedance state. The remaining GPIOs
are breakouts of the GPIO 2 logic switch. I left GPIOs 8
through 15 in their default LED configurations. We will use
LEDs 8 through 15 as indicators.
The logic levels of all the switches are displayed on their
personal LED indicators. This is done to eliminate the need
of wasting a GPIO just to indicate a logic level. To
demonstrate the logic level output of the switches at GPIO
positions 0 and 1, I tied their outputs to the LEDs at GPIO
positions 8 and 9, respectively. As you can see, I’ve clicked
on the pushbutton and set the output at GPIO 1 to logically
high. The GPIO 8 and GPIO 9 LEDs and the switch 0 and
switch 1 personal LEDs reflect those actions.
When I first started speaking binary in my pre-microcontroller days, I found that if I needed a manually
controlled counter, I had to wire up a counter IC and
provide an input clock. After I discovered microcontrollers,
the other option — which became the preferred option —
was to write a counter program that ran on the target
The Analog Discovery allows you to simply configure a
slider that counts up or down with the click of a mouse
button. The Discovery’s low byte of GPIO is configured as a
slider in Screenshot 4. Moving the slider or clicking on the
up/down buttons places the resultant binary value on the
November 2013 73
■ Screenshot 1. With all of the fuzz control
potentiometers at minimum, the Big Muff Pi is still
affecting the input signal.
■ Screenshot 2. This is what fuzz looks like. I activated the
persistence option to emphasize the traces.
■ Photo 5. There are two
models of the Big Muff
Pi. This one is made in
Ne w York City. You can
also get a version that is
made in Sovtek, Russia.
Big Muff Pi