CESYG DUALFO User manual

CESYG
DuaLFO
Installation and User Manual
Document CE-101-0002A
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DUALFO Installation and User Manual
Copyright © 2012 Neil Johnson
First edition, May 2012
Revised, October 2012
All rights reserved No part of this publication may be reproduced, stored in a retrieval
system, or transmitted, in any form or by any means, electronic, mechanical, photo-
copying, recording, or otherwise, without the prior written permission of the author
CESYG
Web: http://www cesyg com
Email: info@cesyg com
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Make beautiful sound
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Contents
32Service History
318. WARRANTY AND SER ICE
277. NOTES
23Applications
21Controls
21Output waveforms
216. USING THE AUXILIARY LFO
18Applications
17Controls
17Output waveforms
175. USING THE MAIN LFO
15Sine Shape Trim (VR2)
15Shape Maximum Bias Trim (VR1)
154. ADJUSTMENTS
14Power-on Test
13Installing the DUALFO
13Main LFO Normalising Options
11Installing the Power Cable
11Unpacking
113. INSTALLATION
92. SPECIFICATION
8Special Features
71. INTRODUCTION
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1. INTRODUCTION
This manual describes the installation and operation of the CESYG DUALFO
two-channel low-frequency oscillator (LFO) for the Eurorack modular synthesizer
system
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Main 0° Out
Main 120° Out
Main 240° Out
Aux Tri Out
Aux Sine Out
Main LFO CV In
Aux LFO Sync In
Aux LFO CV In
Aux LFO Shape In

Special Features
The DUALFO has been designed and constructed with care and attention to detail:
- The SYNC edge switch is a high-quality ALPS SPUN push switch, the same type as
commonly found in many mid-range British audio mixing consoles (maybe not Neve or
SSL, but definitely Allen+Heath, SoundCraft, and SoundTracs)
- A Dual Earth system, similar to that employed by MOTM and Oakley, is used to
separate the internal power and signal ground from the front panel and jack ground
This helps keep the noisy external ground away from the internal ground while
remaining completely compatible with existing Euro modular power systems
- Robust power input protection Series Schottky diodes only permit current flow in
the normal safe direction If the power cable is fitted backwards, no current flows
This is in contrast to some Euro modules that use reverse diodes and series resistors,
where during a fault the diodes conduct the full power supply current through the
low-values resistors until you notice a burning smell and/or smoke before turning the
power off! Or other Euro modules that have no protection whatsoever
- Designed for maintenance Signal jacks suffer a lot of mechanical stresses In the
DUALFO all jacks are mounted on easily removable jack boards All pots are standard
16mm commercial types (e.g , Alpha, Alps, BI Technologies, etc) so when they eventually
fail spares should be widely available wherever you are
- All inputs are nominally 51kOhm to minimise loading of signal sources, with special
input circuitry designed to minimise changes of input impedance over the full input
control range
- High quality double-sided FR4 fibre-glass PCB, through-hole plated with solder mask
and silk screen legend, tin-plated, and assembled using lead-free components and lead-
free solder throughout to comply with the European RoHS directive
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2. SPECIFICATION
Main Oscillator
Frequency range: Approx 200uHz (approx 90 minutes) to 45Hz
Outputs
Waveforms: Three phase-related sinewaves at 0°, 120°, 240°
Level: 10Vp-p output centered about 0V (typ +/-5V)
Impedance: 1kOhm
Indication: Red/green bi-colour LED showing 120° sinewave
Inputs: CV (impedance: 51kOhm)
Controls: Manual frequency control, log scale
External CV control of frequency with unipolar attenuator, link-
selectable normalised to either auxiliary sine wave output or bus
CV
Auxiliary Oscillator
Frequency range: Approx 200uHz (approx 90 minutes) to 45Hz
Output
Waveforms: Triangle, sine, both variable shape (see below)
Level: 10Vp-p output centered about 0V (typ +/-5V)
Impedance: 1kOhm
Indication: Red/green bi-colour LED showing triangle wave
Inputs: CV (impedance: 51kOhm)
Sync (impedance: 51kOhm)
Shape (impedance: 51kOhm)
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Controls: Manual frequency control, log scale
External CV control of frequency, with unipolar attenuator
External sync input, with switchable positive or negative edge
sensitivity
Shape: Manual control over 10% to 90% range, centre 50%
External shape modulation over the range -5V to +5V, manual
control operates as bipolar attenuator (left = negative, right =
positive)
Power
Input: +/-12V to +/-15V, 40-50mA per rail
Connector: Eurorack standard 16-pin power/bus connector
Protection: Reverse voltage protected, missing rail protected
Ground: Dual Earth grounding system, compatible with all Euro power systems
Mechanical
Panel size: 18HP Euro format, 128 40mm x 91 10mm
Panel material: 2mm Anodised Aluminium
Depth behind panel: 100mm
Note: As this is an analogue device specifications are subject to minor variations
between devices
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3. INSTALLATION
Fitting the DUALFO into your modular synthesizer is a straightforward task This
section describes the basic steps in unpacking and installing your DUALFO and a first
initial power-on test
Unpackin
The DUALFO comes packed in anti-static packaging Do not open the packaging until
you are ready to install the module in your modular synthesizer As well as the
DUALFO you should find this manual, a 16-way power cable, and a bag of M3x6mm
screws
Make sure you have a space of at least 18HP (91mm) in your rack unit, and one spare
power connection
Installin the Power Cable
The DUALFO is fitted with a standard 16-pin power header and supplied with a power
cable If your power distributor is 10-way then will need a special 10/16-way adaptor
cable These are available from many sources online
Disconnect power from your synthesizer It is recommended to remove the AC power
cable from the wall socket Fit one end of the module power cable to the DC distribu-
tion board in your synthesizer Leave the other end trailing out of the case
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Hold the DUALFO in one hand and insert the other end of the power cable into the
power socket on the DUALFO, located at the bottom edge of the rear of the PCB Both
the header and the connector are polarised to ensure that they can only mate one
way As a guide, note that the RED stripe of the cable aligns with the marks on the
PCB:
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Main LFO Normalisin Options
Before fitting the DUALFO into your synthesizer there is an on-board link option This
sets the source of the normalised CV input of the main oscillator The default position
sets the source to the sine wave output of the auxiliary oscillator You can change the
link to select the CV line on the power bus The link is located just above the power
connector:
Installin the DUALFO
Now fit the DUALFO into your synthesizer Carefully slide the module into the case,
making sure the power cable is not caught on anything Offer up the DUALFO panel to
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the frame and fit the four M3 screws supplied to hold the DUALFO in place Tighten
the screws, but do not over tighten them The recommended torque is 1 0Nm
Note: if your rack rails are made to accept M2 5 screws you must either supply them
yourself, or they were provided with your DUALFO as a special option, or you can
purchase them either from CESYG or elsewhere
Power-on Test
Refit the AC power cable to your synthesizer Set the DUALFO Freq controls to
maximum, set the CV controls to minimum, and the Shape control to midway; the
Sync button can be in or out
Turn on power
Both oscillator LEDs should be flashing red/green - they should be visibly flickering
This concludes the installation
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4. ADJUSTMENTS
There are two adjustments on the DUALFO, both related to the Auxiliary LFO
Shape Maximum Bias Trim (VR1)
The maximum range of the effect of the Shape control can be adjusted During assem-
bly this is set to approximately 10% to 90%
Sine Shape Trim (VR2)
The Auxiliary sine wave output is derived from the triangle waveform using a diode
shaper VR2 can be used to fine-tune the shape of the sine wave to minimise
distortion
Normally this is done during assembly, but if the unit is subject to excessive mechani-
cal shock or to a repair to the auxiliary LFO then it may be necessary to re-adjust VR2
to achieve the optimum sine wave shape While it can be done with only an oscillo-
scope, it is recommended that an audio distortion analyzer is used if available The
auxiliary LFO should comfortably achieve sine wave THD of around 1 5%
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5. USING THE MAIN LFO
The Main LFO provides three sine wave signals, ideal for providing spatial modulation
or pseudo-stereo effects Or, together with a 2-channel mixer, you can generate two
sine waves with any phase offset you require in the range 0 to 360 degrees
Output waveforms
Each of the three outputs of the Main LFO is a low-distortion sinewave The three
outputs are at fixed phase offsets of 0, 120 and 240 degrees
Controls
The Main LFO has two controls and one external control input
FREQ
The FREQ control provides manual control of the frequency of the Main LFO With the
control turned fully anti-clockwise the frequency is at its minimum; turned fully clock-
wise the frequency is at maximum
CV
The CV control determines how much of the signal fed to the CV jack is used to
modulate the Main LFO frequency The control provides a linear scale, from 0% (fully
anti-clockwise) to 100% (fully clockwise)
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The CV jack is normalised to one of two internal signals: the internal bus CV or the
Auxiliary LFO sine wave When no jack is inserted into the CV socket then the normal-
ised signal is fed into the CV input and treated in exactly the same way
Applications
The three outputs of the Main LFO can be used separately - for example, to generate
pseudo-stereo rotation - or combined to generate a sine wave of any desired phase
offset
3D Pannin
Connect each output to a VCA, with all three VCAs fed from the same audio source
Now send each VCA’s output to a separate amplifier and speaker, arranged at equidis-
tant points around a circle Place yourself in the middle of the circuit, and the result
will be a sound that rotates around you! Swap over two of the sine outputs to change
the direction of rotation
Arbitrary Phase Sine Wave
A sine wave of any arbitrary phase offset can be generated from some combination of
three equally-spaced sine waves This is easy to achieve with the DuaLFO and a
two-input mixer For your convenience a phase diagram is given at the end of this
manual
For example, suppose you want two sine waves with a 90 degree phase offset between
them (this is often called quadrature) Let the first sine wave be the topmost output
jack of the Main LFO - the 0 degree output
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Now take a look at the phase diagram (end of manual) An arrow at the 90 degree
position lies between the 0 degree and 120 degree arrows, so we need some mix of
these two sine waves to produce the required 90 degree one
As the 90 degree arrow is closest to the 120 degree arrow we start with 100% of the
120 degree sine wave Then, note that the 90 degree arrow crosses the dashed horizon-
tal line - this corresponds to the 0 degree sine wave As it crosses the middle this
shows that we need half, or 50%, mix of the 0 degree sine wave Finally, also see that
the length of the arrow from the centre to where it crosses the dashed line is about
87% of the full length This tells you the amplitude of the result: about 87% of the full
scale signal (about +/- 4 3V)
If all this sounds complicated, it really isn’t! Try it for yourself with a pencil and ruler
After a couple of minutes you will soon master this technique! And then you will be
able to synthesize two sine waves with any phase offset you want You could also use
three VCAs (e.g., three-channel VCA mixer) so that the synthesized sine wave is under
full voltage control
Video Synthesis
With three phase-locked outputs the main LFO is ideal for modulating the red, green
and blue components in video synthesis The auxiliary LFO can then be used to
modulate the main LFO to introduce further colourful modulations, perhaps synchro-
nised to some visual trigger or some multiple of the frame period
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