Joranalogue audio design Contour 1 User Manual

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 [e-mail].

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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