pigtronix Resotron User manual

RESOTRON
RESONANT TRACKING FILTER
User’s Guide
All contents c Absara Audio LLC 2018

Contents
Contents 1
1 Welcome to The Resotron 2
1.1 Features:......................... 3
1.2 Safety Precautions . . . . . . . . . . . . . . . . . . . . 4
ThankYou........................ 4
2 Anatomy and Functions 5
2.1 The Interface . . . . . . . . . . . . . . . . . . . . . . 5
Jacks........................... 5
Knobs and Switches . . . . . . . . . . . . . . . . . . . 8
3 Getting Started 11
3.1 Basic Hook Up . . . . . . . . . . . . . . . . . . . . . . 11
3.2 GuidedTour....................... 12
4 Resotron Back Story: 14
5 Pigtronix Limited Warranty 15
1

1. Welcome to The Resotron
The Pigtronix Resotron is an all-analog stompbox that brings pitch-
tracking capabilities to the world of envelope filter pedals for guitar,
bass and beyond. The revolutionary PITCH mode in the Resotron
allows the filter to follow the notes you play rather than how hard you
hit the strings! This function causes the cutoff frequency of the filter
to move around based on what notes the musician plays in real time.
Traditional, UP and DOWN (velocity-controlled) envelope modes are
also included in the Resotron along with an EXPRESSION input for
foot-controlled filter sweeps and CV modulation.
The multi-mode filter at the heart of the Resotron can be set to Low
Pass (LPF), Band Pass (BPF) or High Pass (HPF) modes. Each of
these voices has a distinctive character which can be manipulated by
adjusting the PEAK knob to emphasize frequencies below, at or above
the position of the CUTOFF knob. As the PEAK is increased, the res-
onance or ”Q” of the filter becomes more extreme, up to the point
of self-oscillation. A SENSITIVITY control sets how dramatically the
pedal will respond to playing dynamics in the UP and DOWN envelope
modes, while a GLIDE control allows you to set how long it takes for
the filter to move between notes in the PITCH mode.
A push-button OSCILLATE function turns the Resotron into an analog
synthesizer pedal. This mode shorts out the PEAK knob, effectively
setting it to 100% while simultaneously activating a voltage-controlled
amplifier (VCA) in the output stage. With the OSCILLATE function
turned on, the CUTOFF knob sets the tuning of the synth effect while
the VCA instantly follows the volume of your input signal. The syn-
thesizer sounds created by the Resotron can also be radically altered
by switching between the LPF, BPF and HPF modes, each of which
2

CHAPTER 1. WELCOME TO THE RESOTRON 3
has its own distinctive waveform and modulation characteristics when
overdriven by the on-board compressor.
Before the signal from the input of the pedal hits the filter inside the
Resotron, it passes through an optical compression stage derived from
our Philosophers Tone pedal. The increased volume and punch from
the compressor can then be mixed into the audio signal using the
BLEND control without affecting the SENSITIVITY of the envelope.
The Resotron also has a TRIGGER (aka Sidechain) feature which
enables the musician to use an external audio source to modulate the
filter.
1.1 Features:
•24db/oct Filter based on the SSM2040 chip
•Low Pass, Band Pass & High Pass Filter options
•Velocity controlled UP & DOWN envelope modes
•Pitch Following envelope function with variable GLIDE
•BLEND control mixes in Philosophers Tone compression
•Expression pedal / 0-5V CV input modulates CUTOFF
•OSCILLATE mode for monophonic synth sounds
•Sidechain TRIGGER input for external audio
•Hardwired True Bypass Switching
•18VDC Power Supply Included
•100% Analog Design
•Circuit Design by Nick Cote
•Sound Design by David Koltai

1.2 Safety Precautions
The safety precautions listed below are intended to ensure your safety when-
ever you use the Resotron.
NEVER OPEN THE CASE - Never try to separate the two pieces of the
chassis from one another and/or modify the equipment. Opening this de-
vice will effectively void the warranty.
STOP USE IN CASE OF PROBLEM - Stop using the equipment if ever you
should notice smoke or a strange odor coming from it. Contact [email protected]
for service.
AVOID HIGH TEMPERATURES & HEAT BUILD UP - Never cover the
power supply with cloth or other objects. Built up heat creates a danger
of equipment deformation and fire. Do not expose the Resotron to direct
sunlight, heating devices, or other extreme temperatures.
USE SPECIFIED POWER ADAPTER ONLY - Be sure to use only the 18-
Volt DC 300mA Adapter that came with your Pigtronix Resotron.
DO NOT EXPOSE TO WATER/BEER - To reduce the risk of fire or electric
shock, do not expose your Resotron to rain or moisture. If water gets inside
the unit, turn off the power.
Thank You
The Resotron represents a decade of continuous R&D involving some of
the top minds in the audio industry. Pigtronix would like to formally thank
the following individuals for their help in creating the Resotron: Nick Cote,
Thomas Elliott, Cyril Lance, Howard Davis, Ben Artes, Ray Heasman, Steve
Turnidge, David Buchter, Fischer Mao, Vernon Reid, Doug Wimbish, Fredrick
Thordendal and Teddy Kumpel.
−Pigtronix
4

CHAPTER 2. ANATOMY AND FUNCTIONS 5
2. Anatomy and Functions
2.1 The Interface
Jacks

CHAPTER 2. ANATOMY AND FUNCTIONS 6
1. DC 18V - Use only the 18-Volt, 300mA, negative tip power
supply that came with your Pigtronix Resotron. Using the wrong
power supply is likely to result in a damaged pedal.
2. INPUT - Effect input. Plug in your instrument here.
3. OUT - Effect output. Plug in your amp, mixer, or DI box here.
4. EXPRESSION - The expression pedal input allows remote con-
trol of the filter cutoff. A passive foot-controller or active (0-5V)
CV signal can be used with the EXPRESSION jack to modulate
the cutoff frequency of the filter in parallel with the on-board en-
velope and pitch tracking systems. When a passive expression
pedal is used, the onboard CUTOFF knob sets the maximum
sweep range. Since the envelope and pitch following signals are
wired in parallel with the expression input, you can effectively
use an expression pedal as a wah, with an envelope riding on
top of it!
Note: Use a TRS (Stereo) cable to connect a standard, low-
impedance (20K) foot controller to the EXPRESSION jack.
Note: Use a TS (Mono) cable to send control voltage (0-5V)
signals into the EXPRESSION jack.
5. TRIGGER - The trigger input is an auxiliary source for the en-
velope follower and pitch tracking system. When the TRIGGER
jack is in use, the audio signal at the INPUT jack is disconnected
from the envelope follower and pitch tracking system that modu-
lates the filter in the Resotron. When using the TRIGGER input,
it is recommended that the BLEND knob be set fully counter-
clockwise. This allows the signal feeding into the TRIGGER
jack to control the filtering of the signal from the INPUT jack.
Turning up the BLEND knob when using the TRIGGER input
will feed the audio from the TRIGGER jack directly through the
compressor and into the main audio path, in parallel with the
signal from the INPUT jack.

CHAPTER 2. ANATOMY AND FUNCTIONS 7
Note: If identical audio signals are sent to both the INPUT
and TRIGGER jacks, a ducking effect will occur when feeding
when the BLEND control is set to 12-o-clock. To eliminate this
ducking phenomenon, flip the phase of the TRIGGER signal.

CHAPTER 2. ANATOMY AND FUNCTIONS 8
Knobs and Switches

CHAPTER 2. ANATOMY AND FUNCTIONS 9
6. ENGAGE - This footswitch turns the entire Resotron on and
off. When the engage light is turned off, the Resotron is true
bypassed.
7. CUTOFF - This knob sets the resonant frequency of the lter.
Depending on the FILTER MODE setting, this position of the
CUTOFF knob will produce dramatically different sounds.
8. PEAK - This knob sets the amount of resonance in the fil-
ter. When the PEAK knob is fully clockwise the VCF will self-
oscillate. This creates a sine wave drone that will continue to
play regardless of a signal at the INPUT jack. When the OS-
CILLATE switch is pressed in, the PEAK knob is shorted to
maximum.
9. SENSITIVITY - This knob sets the responsiveness of the en-
velope follower in the ENV UP and ENV DOWN modes only.
When the SENSITIVITY knob is fully counterclockwise the en-
velope follower is turned off.
10. GLIDE - This knob determines the rate of portamento for the
PITCH mode only. This is heard as the time it takes for the
filter cutoff to move between the notes you play. Lower GLIDE
settings provide a fast, snappy filter motion that jumps quickly
between pitches. Higher GLIDE settings cause a more legato
filter motion. When the OSCILLATE switch is pressed in, the
GLIDE function sets the time it takes for the sine wave voice
to move from one note to another. This is heard as a glissando
effect.
Note: Turning the GLIDE control fully counter-clockwise
will disable the portamento function, providing the fastest, most
accurate pitch-tracking.
11. BLEND - This knob mixes in Pigtronix signature Philosophers
Tone compression before the filter. This powerful optical com-
pression stage adds considerable volume and clean punch to the
audio signal, without changing the response of the envelope fol-
lower! The compression BLEND knob allows the Resotron to

CHAPTER 2. ANATOMY AND FUNCTIONS 10
create robust and loud filter effects without the need to switch
on additional boosters or other pedals which can adversely af-
fect the performance of the envelope follower and pitch tracking
systems.
12. FILTER MODE (LPF/BPF/HPF) - This toggle sets the filter
mode for the Resotron. The Resotron has three filter modes,
high pass filter, band pass filter, and low pass filter.
In the LPF (low pass) mode, the Resotron will filter out all
frequencies ABOVE the CUTOFF.
In the BPF (band pass) mode, the Resotron will filter out all
frequencies AT the CUTOFF.
In the HPF (high pass) mode, the Resotron will filter out all
frequencies BELOW the CUTOFF.
Note: It is recommended that you begin exploring the Resotron
using the LPF mode.
13. ENVELOPE MODE (ENV⇑/PITCH/ENV⇓)- This toggle de-
termines whether the envelope follower or the pitch tracker con-
trols the movement of the cutoff frequency. The Resotron has
three different cutoff controls, upward envelope, pitch tracking
mode, and downward envelope.
In the ENV ⇑mode, the cutoff will move higher as you play
harder.
In the PITCH mode the cutoff will move around based on the
notes you play.
In the ENV ⇓mode, the cutoff will move lower as you play
harder.
Note: As you switch between the envelope and pitch modes, it
may be necessary to adjust the position of the CUTOFF knob
to achieve the optimal effect.
14. OSCILLATE - When the OSCILLATE switch is pressed in, the
PEAK knob is automatically set to maximum, causing the voltage-

controlled filter (VCF) in the Resotron to create a sine-wave
synthesizer voice. In this mode, the CUTOFF knob acts as a
tune knob for the sine wave voice, providing a wide range of
tuning control. It is recommended that the toggle switch on
the right be moved to the PITCH setting when using the OS-
CILLATE function so that the sine wave will follow the notes
you play. In this setting, the GLIDE knob causes a portamento
effect, allowing the sine wave to glissando as you move between
notes. When OSCILLATE is activated, a voltage-controlled am-
plifier (VCA) that follows the loudness of your playing is turned
on at the output to prevent the Resotron from screeching out
of control. If the ENV UP or ENV DOWN modes are selected
when using the OSCILLATE function, the pitch of the sine wave
synthesizer voice will move around based on how hard you play.
3. Getting Started
3.1 Basic Hook Up
1. Unpack your Resotron and place it on a flat, stable surface.
2. Make sure you are using the 18-Volt DC (negative center)
power supply that came with your Pigtronix Resotron.
3. Plug the power cord into the 18VDC jack on the back of the Re-
sotron and then plug the power adapter into an electrical socket.
The Resotron is now powered up. To turn the device off, un-
plug it from the wall or turn off the power going to the 18VDC
supply.
We recommend that you do not leave your Resotron pow-
ered up for long periods of time when it is not in use.
4. Plug your instrument into the INPUT jack and plug your ampli-
fier into the OUTPUT jack.
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CHAPTER 3. GETTING STARTED 12
3.2 Guided Tour
The following steps will guide you through the sonic palette of the
Resotron and show you how to access the range of tones that it has
to offer.
1. Set all of the controls fully counter-clockwise, and set each tog-
gle in the up position. Make sure the LED is off. The Resotron
is in bypass mode. Play your instrument and make sure a clean
sound is passing through the pedal.
2. Turn the CUTOFF knob to 3:00, and the PEAK, and SENSI-
TIVITY knobs to 12:00. Put the FILTER MODE toggle to LPF
mode. Click the Engage footswitch to turn the Resotron on.
The LED will come on.
3. Play your instrument to hear the low pass filter sweep based on
the volume of your instrument.
4. Explore the range of the CUTOFF knob. Adjusting the CUTOFF
will change the the frequency content of your effected output as
well as the range of filter sweeps.
5. Explore the range of the SENSITIVITY knob. Adjusting the
SENSITIVITY knob will change how the filter responds to the
volume of your instrument.
6. Explore the range of the BLEND knob. Adjusting the BLEND
knob will change the blended amount of your instrument and
compressed signal into the filter. This allows for additional dy-
namic control over the headroom of the filter.
7. Toggle the CUTOFF CONTROL from the upwards envelope to
the downward envelope to change the direction the filter sweeps.
8. Toggle the CUTOFF CONTROL to the PITCH mode to cause
the filter to track to the pitch of your instrument. Explore the
range of the CUTOFF knob. In PITCH mode, the filter will

CHAPTER 3. GETTING STARTED 13
keep the tone consistent as you play in different registers of
your instrument.
9. Explore the range of the GLIDE knob. Adjusting the GLIDE
knob will change the amount of time it takes for the filter to
sweep from frequency to another.
10. Explore the range of the PEAK knob. Adjusting the PEAK
knob will change the amount of resonance of the filter, based
on where the filter cutoff frequency is, different harmonics of
your instrument signal will be emphasized.
Note: Be careful when turning the PEAK knob fully clock-
wise as this will cause the Resotron to oscillate at a loud volume
without VCA gating.
11. Toggle the FILTER MODE between the different the three types
of filters to see how the effect changes.
12. Push the OSCILLATE button inward to put the Resotron in
synth mode. Start with the FILTER MODE toggle in the LPF
mode and the CUTOFF CONTROL toggle in the PITCH mode.
13. Play the highest string on your instrument and adjust the CUT-
OFF knob so that the pitch of the sine wave voice is in tune with
your instrument signal. Once it is in tune, play your instrument
in all registers.
14. Toggle the FILTER MODE between the different the three types
of filters to see how the effect changes. LPF and BPF mode pro-
duce a clean sine wave with the BPF containing some additional
harmonics, where as the HPF mode produces a voice with high
frequency harmonics seen in a square wave.

4. Resotron Back Story:
The voice of the Resotron is inspired by the Octave CAT synthesizer.
In 2012, I scored a vintage Octave CAT in mint condition on Craigslist
and was completely blown away by the bass tones I could get out of this
synth’s self-oscillating filter. Made in Long Island City, NY in the late
1970’s and powered by SSM2040 filter chips, the CAT’s low-pass filter
was capable of creating ultra-smooth sub bass tones when pushed into
self-oscillation. The CAT’s key-follow function allowed this powerful,
self-oscillating filter to be played in tune with the keyboard. It would
literally shake the entire Pigtronix factory, rivaling the sonic impact of
any instrument in my vast and evolving collection of vintage and new
synthesizers.
In 2017, when I began working with design engineer, Nick Cote we set
out to create the Resotron by utilizing the pitch-tracking technology
from our Mothership 2 pedal to control a network of currently avail-
able components arranged in a fashion that would effectively mimic
the sound and behavior of SSM2040 chip. We then added the Philoso-
pher’s Tone compressor in front of this 24db/octave multi-mode filter
engine to create a massive sounding pedal capable of musical envelope
filter effects that can be made to accurately follow single-note lines
played on any instrument, in real-time. The thoroughly bombastic
and out of control self-oscillation that can be achieved by turning the
PEAK knob up all the way was then tamed by adding a switchable
VCA which watches your input signal to set the output volume of the
synth. Mutron III inspired UP and DOWN modes were also added to
augment the signature pitch-following abilities found in the Pigtronix
Resotron. I dreamed about making this pedal for years and I hope you
love it. David Koltai, 11/15/2018
14

5. Pigtronix Limited Warranty
Your Pigtronix effect pedal comes with a 1-year limited warranty on
parts and workmanship. During the warranty period we will repair
or replace, at our option, defective parts or pedals free of charge,
and return them to the owner. Warranty service does not include
damaged, modified, or misused pedals and such pedals will be subject
to a standard repair charge.
What you must do: First, contact us directly via email and describe
the problem to us. If the problem cannot be resolved we will have you
send the pedal directly to us for servicing.
How to contact us for warranty service:
Email: [email protected]
Phone: 631-331-PIGS (7447)
Warranty Limitations: This warranty does not cover defects resulting
from improper or unreasonable use, accident, unauthorized tampering
or modifications; and, warranty shall be considered void if Resotron
chassis has been opened. Please consult the instructions and warnings
in this manual for proper use. Warranty is only valid if your Resotron
has been properly registered within 30 days of original purchase date,
and upon warranty registration, will be valid for 12 months from orig-
inal purchase.
To validate your 1-year, limited warranty, please register
your Resotron, within 30 days of purchase, on the
web at:
www.pigtronix.com/warranty
15