Elby Designs EURO-SERGE User manual

EURO-SERGE - SYSTEM MODULES
ELBY Designs - Laurie Biddulph
9 Follan Close, Kariong, NSW 2250, Australia
[email protected] http://www.elby-designs.com
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CONTENT
1. The Overall Design of the Euro-Serge System
2. Signal Sources
3. Control Voltage Sources
a. ES01 - Random Voltage Generator (i)
b. ES16 - Extended ADSR (i)
c. ES27 - Transient Generator (i)
d. ES05 - Noise Generator (i)
e. ES06 - 1973 Envelope Generator (i)
4. Audio Processors
a. ES33 – VCFQ (i)
b. ES22 - Resonant Equalizer (i)
c. ES10 - Triple WaveShaper (i)
d. ES04 - VC Multiplier 1 (i)
e. ES17 - VC Multiplier 2 (i)
f. ES18 - VC Multiplier 3 (i)
g. ES114 - Universal Slope Generator (i)
h. ES11 - Triple Comparator (i)
i. ES78 - VCA (i)
j. ES09 - Positive Slew Generator (i)
k. ES19 - Negative Slew Generator (i)
l. ES75 - Voltage Controlled Slope Generator (i)
m. ES07 - 1973 Voltage Controlled Filter (i)
5. Output Mixing
a. ES08 - Audio Mixer (i)
b. ES30 - Stereo Panner Module (i)
c. ES31 - Stereo Output Module (i)
6. Control Voltage Processors
a. ES114 - Universal Slope Generator (i)
b. ES12 - Triple Bi-Directional Router (i)
c. ES14 - Voltage Processor (i)
d. ES15 - Smooth & Stepped Generator (i)
e. ES09 - Positive Slew Generator (i)
f. ES19 - Negative Slew Generator (i)
g. ES75 - Voltage Controlled Slope Generator (i)
NB: Click on the (i)to go to our web-based datasheet

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ELBY Designs - Laurie Biddulph
9 Follan Close, Kariong, NSW 2250, Australia
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Fast-Forward and Rewind
The Introduction (Book 1)
Self-Teaching Patches #1 (Book 2)
The Theory of Electronic Music (Book 3)
Self-Teaching Patches #2 (Book 4)
So What Does It Sound Like? (Book 6)
Euro-Serge Catalogue (Book 7)
Appendices (Book 8)

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ELBY Designs - Laurie Biddulph
9 Follan Close, Kariong, NSW 2250, Australia
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THE OVERALL DESIGN OF THE EURO-SERGE SYSTEM
With this last STEP all three kinds of voltages and all four major types of
modules found on the Euro-Serge have been used, so to summarise:
The three kinds of voltage:
1. AC VOLTAGES: Black/White/Grey jacks. 20Hz to 20kHz. Output
voltage typically -2.5V to +2.5V. AC voltages produced by green jacks
typically 0V to +5V. However, any voltage range, so long as it oscillates
in the audio range can be used as an audio voltage. Black inputs are
typically AC coupled meaning that any slow or non-changing aspects of
the voltage are blocked.
2. DC VOLTAGES: Blue/Green/Violet jacks. Typically 0Hz to 500Hz but
can be higher particularly in the case of FM and AM. Usually either -5V
to 0V or 0V to +5V but can range over -10V to +10V. Blue inputs are
DC coupled meaning they respond to the full range including negative
voltages.
3. LOGIC VOLTAGES: Red/Yellow/Orange jacks. Either 0V or +5V with a
fast rising edge between 0V and +5V. Some yellow outputs can hold
high indefinitely, others fall back to 0V in a set time. Red inputs are
triggered by the rising edge and therefore other voltages, such as
inverted saw waves, can be used to trigger. Some red inputs control
certain functions of a module as long as the voltage remains HI. In
these cases any +5V level will sustain the function.
The four major kinds of module:
1. SIGNAL GENERATORS. These modules produce audio voltages as
their output. The oscillators are examples of this kind of module. The
ES05 Noise Generator is another
2. CONTROL VOLTAGE GENERATORS. These modules produce control
voltages as outputs. Envelope generators and sequencers are
examples of this type of module.
3. AUDIO PROCESSORS. These modules input audio voltages, operate
on these voltages and output a related audio voltage. Filters are
examples of audio processors. In general they operate on the timbre of
the sound. Another type of audio processor inputs two or more audio
signals and combines them in various fashions. Mixers and the ES79
Ring Modulator are examples of this type of module.
4. VOLTAGE PROCESSORS. These modules input a control voltage and
output a related control voltage. A processor is an example, in which

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ELBY Designs - Laurie Biddulph
9 Follan Close, Kariong, NSW 2250, Australia
[email protected] http://www.elby-designs.com
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case a control voltage is the input. The output might be the same
voltage inverted.
5. A fifth type of module that has not been dealt with yet is the Audio-to-
Control-Voltage converter. One example might be a module that inputs
an audio signal and outputs a control voltage representing the envelope
of that sound. The ES02 Preamp Detector is such a module and has
the function of an envelope follower.
Once the concept and basic principles of these five types of modules are
understood, an infinite array of new "instruments" can be made or "patched"
out of the modules available on the Euro-Serge. New modules, once their
basic type is determined and their internal workings understood can be easily
added to existing modules. In general, modules of the same type can be
substituted for each other.
Each of the next five chapters will cover one of these five types of module,
presenting modules and functions not yet covered. It is suggested that each
module be explored as it is presented by setting up patches using it modules
already understood.

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SIGNAL SOURCES
OSCILLATORS: All the Euro-Serge oscillators have the ability to generate
audio frequencies. They all also have an input labelled [SYNC]. This input
allows two VCOs to be locked together so that they will not drift apart in
frequency. Two VCOs that have drifted just a few Hertz apart can cause a
"beating" to occur at their difference frequency. Sometimes this is the desired
effect, producing a choral quality to the sound. When using the [SYNC], one
VCO is locked to the fundamental OR to a strong overtone of the second
VCO. Locking on to an overtone is useful in the setting up of chords.
Figure 5.2.1
In the above patch VCO #2 is locked to VCO #1. It cannot drift. An interesting
phenomenon occurs if VCO #1 is set very low and its [SAW] wave is used to
sync VCO #2. If VCO #2 is now swept upwards over its range, either using its
pot or a control voltage, you will hear it locking onto one overtone after
another, creating a "just-intoned" stepped scale.
WHITE and PINK NOISE. White noise is a complex wave in which ALL
frequencies appear mixed together. The sound is a sort of hissing sound.
Since it contains all frequencies it
can be filtered in various
fashions to produce bands of
sound in many different
frequencies. This is the ultimate
material for subtractive synthesis.
It is also useful for producing
sounds such as snare drums.
Figure 5.2.2

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Pink noise is like White noise except that it sounds lower, more like a
waterfall. The low frequencies have more amplitude.
Figure 5.2.3 - White noise (top) and Pink noise (bottom)
!!! CHECK YOUR SPEAKER VOLUME FIRST !!!
RINGING FILTER. The filter can be "rung" much like a gong, with a trigger
pulse to the [TRIG-IN].By adjusting the [FREQUENCY], different pitches can
be achieved. Adjusting the Q will alter the sound from percussive clicks to
bell-like sounds. The output is a damped sine wave:
Figure 5.2.4 - Damped Cymbal and Undamped Cymbal

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[email protected] http://www.elby-designs.com
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This technique can be used when other signals are applied to the [INPUT] of
the filter to produce a wide range of interesting sounds.
SLOPE GENERATOR. As already discussed, the ES114 can be patched to
trigger itself to produce a VCO. The frequency is set by adjusting the [RISE]
and [FALL] time either with the pots or with a control voltage.
Figure 5.2.5
The ES114 can have a voltage controlled wave shape if the switch on [VC IN]
is set to either [RISE] or [FALL].
AUDIO SEQUENCES. A sound source of a more unusual nature can be
found in the ES28. To use the ES28 as a sound source the [CLOCK] trigger
must be well in to the audio range. The output is taken from either the [A], [B],
[C] or [D] outputs and sent directly to the output or to an audio processor such
as a filter. Each pot on the chosen row defines the voltage of the wave at one
point, so the wave shape is composed of eight levels. The frequency is one-
eighth of the frequency of the clock. Interesting wave shape variations can be
produced by adjusting the position of the various pots.

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Figure 5.2.6

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CONTROL VOLTAGE SOURCES
ES01 RANDOM VOLTAGE GENERATOR. Very often you will want a
changing voltage. Either it won't much matter what voltage it is, or you may
want a surprise. Such situations come up when working with certain kinds of
modern music such as Stochastic or Aleatoric, as well as other music styles
such as symphony and rock and roll. In particular it sounds more "animated"
to have timbre of an electronic sound slightly changing in a random or non-
consistent manner.
The Euro-Serge provides three kinds of random control voltage: stepped,
smooth and pulse. These are diagrammed below:
Figure 5.3.1
The [RATE] pot determines the overall rate of change, a function which can
be voltage controlled.
Figure 5.3.2

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The rate of randomness can be controlled on the ES01, and a processor or
processing input can scale the random output to any desired level. The
following patch is useful for exploring the possibilities of the smooth and
stepped random output:
Figure 5.3.
If your Euro-Serge system has more than one random module it is possible to
use a random control voltage to control the rate of the second random voltage.
The pulse output can be explored using the following patch to provide a
random rhythm:
Figure 5.3.4

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ES16 Extended ADSR: The ES16 is an envelope generator that can produce
multi-segmented envelopes of a more complex variety than USG is able to
provide. In certain kinds of synthesis this is necessary, since few natural
envelopes are a simple rise and fall. The ES16 is able to provide a four-part
envelope labelled ATTACK, DECAY, SUSTAIN and RELEASE, as in Figure
5.3.5.
Figure 5.3.5
This envelope, in a general sort of way, represents the envelope of a trumpet
or any instrument which can sustain a note at a steady level. The sustain
section is settable to different SUSTAIN levels by means of a pot and a
control voltage. In addition to these functions the ES16 also provides a delay
that sets an amount of time between receiving a trigger and the onset of the
envelop itself. This is useful when triggering related envelopes with the same
TRIGGER or GATE.
The module is triggered by a pulse to its [GATE] input. Usually this trigger
comes from a keyboard device such as the ES28's output which is a trigger
that stays at a +5V level as long as a finger remains on the key:
Figure 5.3.6
The sustained high level will be used in the timing of the ES16's output.

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The ES16 has five pots, each with an associated control voltage input jack.
These control voltages affect the same segments as the corresponding pots.
The [DELAY (T1)] pot/control sets the length of the delay between receipt of
the trigger pulse and the onset of the envelope. The further left the pot is set
the longer the delay. The [ATTACK (T2)] pot controls the slope of the
ATTACK in much the same way as the [RISE] pot on the ES114. It too is
voltage controllable. The [DECAY (T3)] control/pot controls the slope of the
initial DECAY, which falls to the voltage level set by the [SUSTAIN]
control/pot. The ADSR will sustain the output voltage set by the control/pot for
as long as the [GATE] input remains high. In the case of the ES28 [GATE]
output, this is as long as one holds a finger down on the keypad. When the
[GATE] goes low, the [RELEASE (T4)] control/pot determines the slope of the
final DECAY.
Figure 5.3.7
The ES16 functions in a slightly different fashion if the trigger pulse is applied
to the [TRIGGER] input and not the [GATE] input. When there is no input to
the [GATE], the output of the ES16 remains at the voltage set by the
[SUSTAIN] control/pot. When the ES16 receives a trigger pulse the voltage
drops to 0V from this level at a rate set by the [RELEASE (T4)] control/pot.
The voltage then rises to the peak voltage at a rate set by the [ATTACK (T2)]
control/pot and finally drops back to the level set by the [SUSTAIN]
control/pot at a rate set by the [DECAY [T3)] control/pot.
Figure 5.3.8

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Using both inputs, more complex envelopes are possible. For example,
during the sustain time set up by a GATE pulse, a trigger received at the
[TRIGGER] will cause a new attack to start.
While in the sustain mode of an envelope, the ES16 will respond to changing
control voltages at it’s [SUSTAIN] input. This makes complicated sustains
possible.
Figure 5.3.9
ES34 TOUCH PAD KEYBOARD on the ES28. The ES28 can be thought of
as two separate but interconnected modules: the Sequencer and the
Keyboard. The sequencer can be used by itself by removing the ES34 and its
umbilical cord.
The ES28 provides the user with four voltage outputs [A], [B], [C] & [D], and
[VC TOUCH] which output a voltage depending on which keypad was last
pressed. Each keypad can be assigned a voltage such that keypad [1] has
the lowest voltage, keypad [2] the second lowest and so on up to keypad [8]
which has the highest voltage. Setting the voltage increase between any two
adjacent keys to an equal voltage, allows the ES34 to be used as an equal-
tempered scale keyboard. A processor or processing input can be used to
calibrate an oscillator to produce any desired equal-tempered scale including
the western 12 divisions to the octave.

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Figure 5.3.10
The [VC TOUCH] output is a voltage proportional to the amount of pressure
applied to the keyboard with the finger. When used to control a VCA, it can
act much like an expressive envelope generator simulating the ‘piano-forte’
(soft-loud).
Figure 5.3.11
ES27 TRANSIENT GENERATOR. The ES27 is a smaller version of the
ES114. The [RISE] and [FALL] are only voltage-controllable simultaneously
and can not be controlled separately. The ES27 has three outputs: a final

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pulse [END OUT] which can be used for recycling itself or triggering another
function, and two envelope outputs [DC] and [BI-POLAR].
In the patch in Figure 5.3.12, the outputs from two ES27 are mixed with the
ES14 Processor module to generate complex envelopes. Note that in this
patch diagram, the [END OUT] to [IN] connection is shown with a dotted line,
this is because the EURO-SERGE banana sockets have a unique feature
commonly known as ‘normalising’ in which a ‘default’ signal is internally
patched to the jacks ‘signal’ pin while there is no jack inserted. Inserting a
jack disables this ‘normalised’ connection allowing the external patched signal
to take control. This function is that same as fitting an ‘INTERNAL-
EXTERNAL’ switch alongside the jack.
Figure 5.3.12

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AUDIO PROCESSORS
There are four major paths to analogue electronic music synthesis:
1. ADDITIVE SYNTHESIS: Since any sound can be shown to be made of
sine waves, it is possible to construct any sound by adding the
appropriate sine waves together. While conceptually this seems to be
the most flexible method of synthesis, in reality it is a difficult and time-
consuming procedure except in some limited cases. Often it is more
practical to mix already complex sounds together
2. SUBTRACTIVE SYNTHESIS: The opposite of additive synthesis is
subtractive synthesis. In its ideal form, one can take white noise, which
contains ALL frequencies and subtract the ones not wanted, much like
the sculptor chipping away at a block of stone. More commonly, the
synthesist takes appropriate waveforms, such as sawtooth waves, or a
mix of waves, and "chips" away at these sounds.
3. MODULATION: There are a number of electronic processes that take
one simple waveform and modulate it, or alter is, with a second
waveform. This would include AM, FM and RING modulation. The
resultant waveforms are then often subjected to either additive or
subtractive synthesis.
4. WAVESHAPING: Wave shaping is a technique where a given wave is
input in to a device and a related but different wave is output. For
instance, a simple wave shaper is a "rectifier" which outputs the
absolute value of its input wave.
Figure 5.4.1
Modules that wave shape signals, add signals together, subtract parts of
signals, or that modulate signals are called Signal Processors. The Euro-
Serge system is a Signal Processor-rich synthesizer and includes many
processors that are not found on any other synthesizer. So far in this manual

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the processors dealt with have been mixers, voltage controlled amplifiers and
filters.
ES33 VCFQ. The VCFQ has all the functions of a regular VCF plus a few
unique features.
NOTCH OUTPUT. This output allows all of the frequencies for the input
signal to pass EXCEPT those in a band directly around the setting of
the [FREQUENCY] pot and control voltage. It is useful for removing a
certain sound from a complex one
VCQ or RESONANCE. ‘Q’ is the property of a filter where the cut-off
frequency is amplified and fed-back in to the original signal to produce a
bell-like or ringing sound. Different levels of [Q] produce different tonal
quantities. In the VCFQ this function is both adjustable by a pot and
voltage controlled by the [VCQ] input.
AUTOMATIC GAIN CONTROL. One of the problems with a Hi-Gain Q
filter is that the cut-off frequency hits an overtone that is higher in
amplitude than expected, it can overload the filter and/or the speaker

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system and cause distortion. The AGC keeps the output gain constant
at the cut-off frequency and is activated by inputting the signal in to the
[AGC] input. The regular input ([IN]) does not have an AGC, but does
have a [GAIN] pot associated with it to attenuate the signal to desired
levels.
ES22 RESONANT EQUALIZER. An Equalizer or Comb filter is a bank of
band pass filters that cover the entire spectrum and whose outputs are mixed
together such that amplitudes of each filter can be controlled. With this device
the sound as a whole can be adjusted and balanced to suit. The Resonant
Equalizer has ten bands with each band's output being controlled by a pot
that is labelled with the centre frequency of the band. When the pot is turned
right, the band it controls is amplified up to about the '8' position (this is 12dB
higher than the input signal). Past '8' the band is given more and more
resonance. If the pot is turned to the left the associated band is attenuated
further and further.
The ES22 has three outputs. The ES22 [ALL] output sums all ten bands
together while the remaining two outputs ([LOWER] & [UPPER]) each sum
together alternating outputs.
The bands are arranged in sevenths so that a false tonic does not develop. A
LEVEL pot adjusts the overall gain of the output and prevents overload when
resonance is set high. These fixed resonant bands are common in almost all
timbres produced by musical instruments, and it is the skill of the violin or
piano manufacturer in tailoring these resonances that partially determines the
quality of the instrument.
Figure 5.4.2

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ES10 TRIPLE WAVESHAPER. The ES10 module contains three identical
devices which can be used to convert sawtooth waves in to sine waves and
can provide a wide range of other forms of sound and timbre modification.
The timbre can be affected by a manual pot and two different VC inputs which
operate on the sound in two different ways. It is a useful module for producing
interesting and changing sound timbres, something difficult to achieve in
other synthesizers.
Figure 5.4.3
WAVE MULTIPLIERS (ES04,ES17,ES18). The Wave Multiplier modules are
a family of modules that operate on their inputs in a unique fashion,
transforming simple sounds into musically complex and interesting ones.
They should not be confused with such devices as Ring Modulators which
multiply their input signals in a linear fashion - the Wave Multipliers are highly
non-linear in their action. In many ways these modules represent a new node
in the typical synthesizer patch.
Figure 5.4.3

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ES04 VCM 1.ES04 is the simplest of the trio. It has a switch for two different
settings characteristics. In the [OVERDRIVE] position, ES04 acts to
moderately "square up” or soft clip the signal. The soft clipping is amplitude
dependent, producing changes in timbre as the loudness increases.
Figure 5.4.4
In the [LINEAR] setting it acts like a linear VCA. A device useful for producing
different types of AM sounds.
Figure 5.4.5
In both settings the module can be controlled either manually or with a control
voltage.
ES17 VCM 2.ES17 has two inputs, each producing a slightly different result
at the output. One input is DC coupled and has a Blue jack. The other input is
AC coupled and has a Black jack. A sine wave will sound the same when
connected to either input, but a triangle wave will produce different effects.
These inputs can be used together to provide unusual effects. The general
effect of the module is to produce new odd overtones from a sine wave input
when the manual pot is turned or when a voltage is applied to the [VC] input.
However, control voltages of complicated natures or inputs more complex
than sine or triangle waves can create shimmering bodies of sound
somewhat reminiscent of over-blown wind instruments. The [VC] input can
accept AC signals, allowing for more complex modulation.