CONTOUR 1
SLEW LIMITER/FUNCTION GENERATOR
INTRODUCTION
For decades, the voltage controlled slew limiter
has been a staple of modular synthesisers. With
its extreme versatility, it can be used to slew
control voltages (CVs), create envelopes, as a lowfrequency or audio oscillator and much more.
Today, Contour 1 brings a fresh approach to this
classic circuit. It delivers much improved
performance and control by incorporating
modern design techniques.
At its most basic, a slew limiter slows down the
rate of voltage change in a signal. On Contour 1,
the rising and falling rates can be individually set
using sliders and CV modulation.
The gate and trigger inputs allow the module to
be used as a function generator: create snappy
attack-release (AR) and attack-decay (AD)
envelopes, with slope times ranging from 500 µs
to 30 seconds. The dedicated gate input makes
it easy to generate +10 V envelopes from any
signal source. Using the large tactile push button,
AD envelopes can be manually triggered. A
trigger will also reset the output voltage.
CONTENTS
In the Contour 1 box, you’ll find:
Product card, stating serial number and
production batch.
16-to-10-pin Eurorack power cable.
Mounting hardware: two black M3 x 6 mm
hex screws, two black nylon washers and a
hex key.
The Contour 1 module itself, in a protective
cotton bag.
If any of these items are missing, please contact
your dealer or support@joranalogue.com.
When set to loop mode, Contour 1 will
continually re-trigger itself. In this mode, it fulfils
the role of a variable-shape low-frequency
oscillator (LFO) or temperature-stable voltage
controlled oscillator (VCO) in the audio range.
Both the rising and falling slopes can be
individually bent, from concave through linear to
convex. While doing so, the deviation in slope
time, and thus oscillation frequency, is kept to a
minimum. Since the bend parameters are
separately voltage controllable, boundless
modulation possibilities present themselves.
Explore anything from shape-shifting envelopes
to rich VCO timbres: Contour 1 will make you rethink what a slew limiter can do.
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CONTOUR 1
SLEW LIMITER/FUNCTION GENERATOR
CONTROLS & CONNECTIONS
1 SLEW RATE SLIDERS
Use these sliders to set the rising and falling slew
rates, from fast on the bottom to slow on top. In
the full mode, the 0 to +10 V slew time range is
500 µs to 30 seconds (1 kHz to 8.3 mHz loop). In
the audio mode, it is 500 µs to 30 ms (1 kHz to
16 Hz loop).
The LEDs on the levers, show the module’s status
in real time. When the slew core is rising or falling,
only the corresponding LED will light up. When it
is holding, both LEDs will be illuminated. The
brightness is at all times correlated with the
positive output voltage.
2 TRIGGER BUTTON AND INPUT
Pressing the trigger button or applying a rising
edge to the trigger input has two effects: firstly, it
resets the output voltage to 0 V. Secondly, while
in slew mode, it starts a single-shot: the voltage
will rise to +10 V, and then fall again until it
reaches the voltage on the analogue input. This
feature can be used to create attack-decay (AD)
envelopes.
Contour 1’s trigger, gate and hold inputs are
uniquely designed to be driven reliably even
from weak, slow, bipolar signals. They feature
Schmitt action, with a +2 V low and +3 V high
logic threshold.
3 SLEW/LOOP SWITCH
With this switch to the left, Contour 1 will
function as a standard slew limiter or envelope
generator. Set it to the right, and the circuit will
continually re-trigger itself for sustained
oscillation.
In this mode, the output voltage will rise to +10 V,
and subsequently fall to the voltage at the
analogue input. Once this point is reached, a new
cycle will start. Adjust the rise and fall slew rates
to change both the frequency and waveshape of
the output signal.
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CONTOUR 1
SLEW LIMITER/FUNCTION GENERATOR
4 FREQUENCY RANGE SWITCH
This switch determines over which time range
Contour 1 will operate: full (slew limiter, VCLFO,
envelope generator, envelope follower…) or audio
frequency (VCO, VCF, waveshaper…).
5 BEND KNOBS
Using these knobs, the rising and falling slopes
can be individually bent: from concave through
linear to convex. While in loop mode, changing
the shape will inevitably affect slope time as well.
However, Contour 1 has been designed to
minimise this effect as much as possible.
9 GATE INPUT
The gate input has a different function
depending on Contour 1’s mode of operation.
In slew mode, a high gate switches the source
between the analogue input socket and a
precision +10 V reference. This allows accurate
attack-release (AR) envelopes to be created from
any gate signal.
In loop mode, it allows for gated oscillation: once
a cable is inserted in the socket, Contour 1 will
only loop while the incoming gate is high.
6 SLEW RATE CV INPUTS
An increase in voltage at one of these CV inputs
will increase the corresponding slew rate, and
thus decrease the slew time.
The rise CV socket is normalised to the fall CV,
allowing both to be modulated by the same
source simultaneously. In this case, the module
will respond at a standard 1 volt per octave. For
the best possible pitch tracking performance, set
both rise and fall slew rates equal and the slope
shapes linear (bend knobs centred).
7 BEND CV INPUTS
These inputs are used to modulate the slope
shapes. With the corresponding bend knob
centred, the CV range is −5 V to +5 V. Both slopes
can be modulated separately or together thanks
to the normalisation from rise to fall.
10 HOLD INPUT
A hold gate signal ‘freezes’ the slew core, slowing
it down to near-standstill until the hold is
released. This is useful for halting modulations, or
as a sync-like effect at audio frequencies.
11 ANALOGUE OUTPUTS
The slew limited output signal is available from
the main output socket. It is highly accurate and
impedance-compensated, allowing portamento
effects to be applied on pitch-accurate CV
sequences. An inverted output is included as
well.
12 SLOPE GATE OUTPUTS
These gate outputs go high (+5 V) whenever the
slew core is rising or falling. At any other time,
they are low (0 V).
8 ANALOGUE INPUT
Apply the signal to be slew limited to this input
socket. When the gate, trigger or loop features
are used, this sets the minimum voltage for each
cycle (0 V by default).
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CONTOUR 1
SLEW LIMITER/FUNCTION GENERATOR
13 VOLT PER OCTAVE TRIMMER
This trim potentiometer is used to calibrate the
module’s pitch tracking. Since it is accessible
from the front panel, calibration can be easily
performed without removing the module from
the system. Each module is individually
calibrated during production; do not adjust this
trimmer if not needed.
Should you find your Contour 1 to be out of tune,
set it to loop mode, range switch to audio, both
slew rate sliders to about 30 % down from the
top positions, and both bend knobs centred.
Make sure Contour 1 has been powered for at
least 20 minutes at a stable ambient
temperature. Now connect any output to a
calibrated digital tuner. The rise slew rate CV
input should be switched between 0 V and a
precision +4 V source, toggled automatically or
by hand. Leave all other inputs unpatched.
Using a dedicated trimming tool or standard
2.5 mm flat screwdriver, adjust the trimmer until
the interval between both states is exactly 4
octaves.
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CONTOUR 1
SLEW LIMITER/FUNCTION GENERATOR
PATCH IDEAS
IMPROVED SAW WAVE OSCILLATOR
Approximate saw/ramp waves can be created by
engaging loop mode, setting one of the slew
directions to a rather slow rate and the other to
the maximum rate. However, it is possible to
speed up the saw ‘step’ immensely by taking
advantage of the resetting trigger feature.
ENVELOPE FOLLOWER
To extract an envelope from a signal applied to
the analogue input, set the rise slew rate to the
fastest and the fall to a moderate setting, in the
full rate range and slew mode. Varying the fall
rate results in different decay settings. The
output signal can be used to modulate any
aspect elsewhere in the patch, for example a
lowpass filter.
Simply patch the fall gate output to the trigger
input. Now, as the module enters the fall period,
rather than slewing down at the selected fall
slew rate, the output voltage will instantly reset
to 0 V, resulting in a brighter saw sound.
COMBINED FM/AM VCO
The lower voltage bound in loop mode is
determined by the analogue input, a unique
feature creating deep modulation possibilities.
With Contour 1 patched as a VCO, apply an
external oscillator’s output to the signal input.
This causes a combination of frequency and
amplitude modulation, as the module will
oscillate ‘on top of’ the modulator signal.
Vary the input amplitude to adjust the
modulation depth. This technique can of course
be combined with rate and bend modulation,
manual, external or via feedback, resulting in an
extreme range of possible waveforms.
You can also increase the rise rate to reject
transients. A concave fall bend will create the
most ‘natural’ sounding decay.
VOLTAGE CONTROLLED FILTER
Fast signal edges represent high frequency
harmonic content. Slewing a signal attenuates
these harmonics. In other words, a slew limiter
can function as a type of lowpass filter. The (by
default) linear slopes and separate rise/fall
slewing differentiate the sound from a standard
lowpass filter.
Set both slew rates to the maximum speed, in
audio range slew mode, and apply an audio
signal to the analogue input. Use a signal
containing fast edges, such as a square wave, for
best effect.
Lowering both the slew rates results in a filtering
effect on the analogue output. The rise/fall gate
outputs deliver bonus pulse signals.
SUBHARMONIC GENERATOR
To create this classic patch using Contour 1,
process the signal source through a normally
closed gated switch, the output of which is sent
to the trigger input. The rise gate output drives
the switch, disabling triggering during the rise
stage.
The resulting waveforms at Contour 1’s outputs
will be at a subharmonic frequency of the
original source. Vary the rise time to select
different subharmonics.
PULSE WIDTH MODIFIER/ DELAY
Shrinking, stretching and delaying pulses has a
multitude of uses within a modular system.
These pulses can be gates, triggers or audio
frequency signals.
With the module set in slew mode, patch the
pulse source to the trigger input. Two pulses are
generated on a trigger: one on the rise output,
and another on the fall. The width of each pulse
is controlled by the corresponding slew rate. The
fall pulse is delayed, with the delay time set by
the rise rate.
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CONTOUR 1
SLEW LIMITER/FUNCTION GENERATOR
SPECIFICATIONS
Module format
Doepfer A-100 ‘Eurorack’ compatible module
3 U, 8 HP, 30 mm deep (inc. power cable)
Milled 2 mm aluminium front panel with nonerasable graphics
Maximum current draw
+12 V: 90 mA
−12 V: 85 mA
Power protection
Reverse polarity (MOSFET)
I/O impedance
All inputs: 100 kΩ
Analogue outputs: 0 Ω (impedance comp.)
Gate outputs: 1 kΩ
Outer dimensions (H x W x D)
128.5 x 40.3 x 43 mm
Mass
Module: 110 g
Including packaging and accessories: 195 g
SUPPORT
As all Joranalogue Audio Design products,
Contour 1 is designed, manufactured and tested
with the highest standards, to provide the
performance and reliability music professionals
expect.
In case your module isn’t functioning as it should,
make sure to check your Eurorack power supply
and all connections first.
If the problem persists, contact your dealer or
send an email to support@joranalogue.com.
Please mention your serial number, which can be
found on the product card or on the module’s
rear side.
REVISION HISTORY
Revision D: no functional changes.
Revision C: initial release.
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With compliments to the following fine people,
who helped to make Contour 1 a reality!
Ben ‘DivKid’ Wilson
Boris Uytterhaegen
Jan D’Hooghe
Jérémy Bocquet
Sebastiaan Tulkens
Everyone at Wired Electronics
Björn Jauss
Gregory Delabelle
Jens Van Daele
Lieven Stockx
Contour 1 User Manual
version 2019-09-18
21st Century Analogue Synthesis—Made in Belgium
© 2019
info@joranalogue.com
https://joranalogue.com/
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