GRP Synthesizer A8 User manual

Grp Synthesizer
A8 USER’S MANUAL
www.grpsynthesizer.it

Grp Synthesizer A8 User’s Manual V. 2.06 2

Grp Synthesizer A8 User’s Manual V. 2.06 3
CONTENTS
CONTENTS 3
FOREWORD 6
SOME WORDS OF WISDOM 6
Operating Conditions 6
Power Supply 6
Operation 6
Maintenance 6
Proper Use
SETUP AND CONNECTIONS 7
Contents 7
Connections 7
AC Connections 7
MIDI Connections 7
Audio Connections 7
Rear Panel Audio Connections 7
Front Panel Audio Connections 8
Analog CV/Gate Connections 8
OVERVIEW 9
WHAT IS INSIDE THE A8? 10
BASIC OPERATIONS 11
Powering the instrument 11
Tuning the instrument 11
Dealing with Modes and MIDI Interface 11
Note Priority 11
Mode Selection 12
Pitch Bend 12
MIDI Interface 12
CV Offset 13
FRONT PANEL CONNECTIONS 15
CV-Gate-Trigger 15
Sequencer 15
Filter 16
Main Out 16
REAR PANEL CONNECTIONS 17
Power 17
MIDI 17
Audio 17
Future Upgrades 17
A8 AUDIO AND MODULATION ROUTINGS 18
SOUND SOURCES AND SOUND MODIFIERS PATH 18
VOLTAGE CONTROLLED OSCILLATOR 1-6 19
Frequency Control 19

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Waveform Control 20
The waveform 20
Output 21
VOLTAGE CONTROLLED OSCILLATOR 1-6 REFERENCE 22
RING MODULATOR 23
NOISE GENERATOR 23
NOISE GENERATOR REFERENCE 23
VOLTAGE CONTROLLED FILTER 1-2 24
VOLTAGE CONTROLLED FILTER 1-2 REFERENCE 25
Controls in common for both Filters 25
Controls for 24 dB/Oct transistor-ladder Low Pass Filter 25
Controls for 12 dB/Oct state-variable Filter 26
FIXED FILTER BANK 26
FIXED FILTER REFERENCE 26
VOLTAGE CONTROLLED AMPLIFIER 27
VOLTAGE CONTR AMPLIFIER REFERENCE 27
MAIN MIX / AUTO PAN 28
MAIN MIX / AUTO PAN REFERENCE 28
Controls for the Upper Section 28
Controls for the Lower Section 28
Controls for the Auto Pan Section 29
STEREO MAIN 29
A8 MODULATION SOURCES AND CONTROL MODIFIERS 30
Modulation Sources 31
Modulation Destinations
VOLTAGE CONTROLLED LOW FREQUENCY OSCILLATOR 1-2 33
Frequency Control 33
Waveform Control 33
Hard Sync 34
Output Offset 34
Shaping 34
VOLTAGE CONTROLLED LOW FREQUENCY OSCILLATOR 1-2 REFERENCE 35
Frequency Controls 35
Waveform Controls 35
Sync Controls 35
Shaping Controls 36
LOW FREQUENCY OSCILLATOR 3 36
Frequency and Frequency Range 36
Waveshape 36
Output Control 37
Modulation Routings 37
LOW FREQUENCY OSCILLATOR 3 REFERENCE 37
Frequency 37
Waveshape Controls 37
Output Controls 37
Destination Controls 37
ENVELOPE GENERATORS 38
Common behaviours and controls - Trigger Mode 38

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Common behaviours and controls - Gate source select 39
Common behaviours - Envelope Structure 39
SIX STAGE ENVELOPE GENERATOR (ENV 1 / ENV 4) 39
SIX STAGE ENVELOPE GENERATOR (ENV 1 / ENV 4) REFERENCE 40
Envelope stages parameters 40
Gate (source) parameters 40
Trig switch parameters 40
Activity LED 41
SIX STAGE ENVELOPE GENERATOR (ENV 3 / ENV 6) 41
SIX STAGE ENVELOPE GENERATOR (ENV 3 / ENV 6) REFERENCE 41
FOUR STAGE ENVELOPE GENERATOR (ENV 2 / ENV 5) 42
FOUR STAGE ENVELOPE GENERATOR (ENV 2 / ENV 5) REFERENCE 42
Envelope stages parameters 42
Gate (source) parameters 42
Trig switch parameters 42
Activity LED 43
FOUR STAGE AUXILIARY ENVELOPE GENERATOR (ENV 7) 43
FOUR STAGE AUXILIARY ENVELOPE GENERATOR (ENV 7) REFERENCE 43
Envelope stage parameters 43
Gate (source) parameters 43
Trig switch parameters 44
Activity LED 44
Assign Switch 44
SAMPLE & HOLD / NOISE GENERATOR 44
Input Source Selection 45
Clock Source Selection 45
Glide 45
Clocked Envelope 45
SAMPLE & HOLD / NOISE GENERATOR REFERENCE 45
Sample & Hold Controls 45
Noise Generator Controls 46
STEP SEQUENCER 47
Clock and Divider/Multiplier Parameters 47
Advance and Repetitions Parameters 47
Sequencer Mode Parameters 47
Column Parameters 48
Step Parameters 48
Assign Parameters 48
STEP SEQUENCER REFERENCE 49
Integration, Quantization, Range and Assign Section 49
VCO Sequencer Enable 49
PW SEQ ENA(ble) 50
F(i)LT(er) SEQ ENA(ble) 50
Column A Section - Column B Section 51
Clock & Clock Divider 51
Step Repeat & Loop 52
Sequencer mode 52
Manual controls 53
Sequencer remote connections and controls on the front panel 53

Grp Synthesizer A8 User’s Manual V. 2.06 6
FOREWORD
Thank you for purchasing the Grp Synthesizer A8: this machine will rewards you with years of sonic
satisfactions and, to ensure your instrument will functions properly, please read this manual.
SOME WORDS OF WISDOM
Read the following safely tips carefully! You should always observe some basic precautions when
dealing with electronic equipment, for you safety and for safety of your own equipment.
Operating Conditions
•Never use the synthesizer under potentially damp/wet conditions such bathrooms, swimming
pools, etc.
•Do not use the instrument in extremely dusty and dirty environments.
•Do not place the instrument near heat sources like radiators.
•Do not expose the instrument to direct sunlight; the wooden cabinet is varnished with a
traditional and trusted procedure, but ultraviolet rays from sunlight can quickly fade the
original wooden colour.
•Do not expose the device to extreme vibrations.
•Save the original crate and boxing for future shipping of the instrument.
Power Supply
•Always check that the AC current in your area is correct for the instrument BEFORE turning it
on. The Grp Synthesizer A8 can be powered with 110-220 V 50-60 Hz, switchable in the rear
panel. Please, check and re-check.
•Unplug the device when you are not using it for longer periods.
•Never touch the plug with wet hands.
•When unplugging the instrument, always grab and pull the plug, never the cable.
Operation
•Although you are a rockstar, NEVER place cans of beer, coke, water (?) or other potentially
spilling liquids on or near the instrument.
•The Grp A8 Synthesizer is an heavy synthesizer: place it on a suitable solid surface or table.
•The Grp A8 Synthesizer can be very LOUD: please, be careful with the big volume knob on
the lower right of the front panel.
Maintenance
•Do not open the instrument; do not unscrew the front/rear panels. Inside the instrument,
there aren’t user’s serviciable parts.
Proper Use
•This synthesizer is designed exclusively to produce audio rate frequency signals for musical
purpose. Any other use is prohibited and voids the warranty extended by Grp Synthesizer.
Grp Synthesizer is non liable for damanges due to incorrect use.

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SETUP AND CONNECTIONS
Contents
Your Grp Synthesizer A8 comes completed with:
•The instrument (pretty big, eh?) itself.
•The suitable power supply cable.
•This manual.
Ensure that all the items above listed were included. If something is missing, contact your local dealer.
As said above, we recommend that you carefully save the original packing material for future
transport/shipping.
Connections
In order to get started with your Grp Synthesizer A8, you will need some connections:
•Suitable AC powering. Make sure (twice) that the power available in your country matches
the correct position in voltage switch 110-220V on the rear panel.
•A MIDI Keyboard/Controller with proper MIDI cable. Those can be unnecessary if you plan to
use the synthesizer only with analog CV/Gate or with the internal Step Sequencer.
•A analog CV/Gate source, with a bunch of !” TS unbalanced cables.
AC Connections
Without doubts, the only place to make
connection for AC cord is on the rear panel;
please. DO NOT detach the ground
connection.
MIDI Connections
Another easy issue:
the MIDI Port (with In and Thru) is located on the rear panel. While the Grp
Synthesizer A8 doesn’t emit any MIDI signal, it can receive MIDI messages
simoultaneously from up to two different sources connected to its MIDI Input.
The data received at Input connector are echoed back to MIDI Thru
connector.
Audio Connections
The things are more varied: you can choose
different connections, suited to different
needs, on both front and rear panel.
Rear Panel Audio Connections
If you’ll use the A8 in a fixed, studio
environment, is best to use the Rear panel
Audio Connections, otherwise, you’ll be free to use the more easy access to the front panel
connection (more on this, later). On the rear, you’ll find:

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•SECTION OUT UPPER LEFT-RIGHT: separate stereo out for Upper part after Pan/AutoPan
module, but before the Main Out Volume.
•SECTION OUT LOWER LEFT-RIGHT: separate stereo out for the Lower part after
Pan/AutoPan module, but before the Main Out Volume.
•MAIN OUT LEFT-RIGHT LOW LEVEL: doubles the front panel main stereo output (this
output is at a quiet low level).
•MAIN OUT LEFT-RIGHT HIGH LEVEL: doubles the front panel main stereo output (be
careful: this output is at a fairly high level).
•LEFT+RIGHT MONO OUT: the sum of Upper and Lower Sections; the connection doubles
the front panel mono output.
Front Panel Audio Connections
On the front panel, there are the following audio connections:
•MONO OUT: summed signal of Upper and Lower Sections (same
as Mono Out on the rear panel)
•PHONES: headphones stereo output.
•LEFT - RIGHT LOW LEVEL OUT: low impedance stereo output.
•LEFT - RIGHT HIGH LEVEL OUT: (fairly) high impedance stereo
output.
Analog CV/Gate Connections
If you dislike (or if you dont need) MIDI, you can rely on old school analog CV and Gate connections;
on the front panel you’ll find direct access to separate Upper and Lower Sections of the instrument
or, for a full scale control on a single couple of CV/Gate, the common Lower-Upper analog interface.
In details, there are connections for:
•LOWER SECTION Connections: Trig Input (0/+5V), Gate Input (0/+5V), CV Input (1V/Oct).
•UPPER SECTION Connections: as above.
•LOWER and UPPER Connections: as above, in common for both sections.

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OVERVIEW
The Grp Synthesizer A8 is a complex, but not-so complex analog machine dual structure/bitimbral,
with an integrated Step Sequencer.
Each part (Upper or Lower section) is a complete and independent analog synthesizer fitted with
three VCOs each with separate SubOsc, one Ring Modulator, one Audio Mixer, two dynamic VCFs,
one Fixed Filter Bank, one VCA, three EGs, one LFO.
The above picture shows the modules concerning the Upper and Lower sections. As you can see,
they are disposed in a pretty simmetrical way on the front panel.
In addition, there is a group of common modules who can be shared by the two section or can
controls both sections simoultaneously; they are: Tuning-Portamento, MIDI Interface, Sample &
Hold/Noise Generator, Auxiliary Envelope Generator 7, Main Mix/Auto Pan, LFO 3, Main Volume,
Step Sequencer and Front Panel Connections.
The above picture shows the modules in common for both Upper and Lower sections of the
instrument.

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WHAT’S INSIDE THE A8?
The whole instrument contains several different circuits:
•A MIDI INTERFACE who converts MIDI data in CV, Gate, Trigger, Key Velocity and Clock
data for Upper and Lower Sections.
•An ANALOG PORT who receives CV, Gate, Trigger, Clock for Upper and Lower Sections.
•A STEP SEQUENCER who drives VCO Freq & PWM, VCF Freq, EG Gate for Upper and
Lower Sections.
•A dual section ANALOG SYNTHESIZER able to create two entirely separate patches, or - at
request - work in cross audio rate modulation between VCOs on VCOs and VCOs on VCFs.
The above (simplified) picture shows the interactions between the different components of the A8.
Feel free to experiment with different sections of the synthesizer; first, with Upper/Lower synth parts,
then, with Step Sequencer.

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BASIC OPERATIONS
Powering the instrument
As you can easily imagine, this operation is done in the Power module on
left part of the front panel; the lamp goes red when the instrument is turned
on. Before turn on, please CHECK THE CORRECT AC RATING.
Tuning the instrument
The Grp A8 is an analog synthesizer but, despite this, the VCOs inside stays
in tune pretty well. For tuning the instrument to concert pitch, you should
work in the Tuning-Portamento module on the left part of the front panel.
With the Master Tune control, you can adjust the main tuning of the entire
instrument in a range of -7/+5 semitones; for a quick reference, you can
switch on the dedicated A-440 oscillator.
In the same module, there are the two Portamento Time Upper and Lower
(max time 2 seconds per octave) and Portamento On.
Dealing with Modes and MIDI Interface
In this module you’ll find all the settings related to
Note Priority, Voice Assign Modes, Pitch Bend
Amount and - obviously - MIDI Interface.
Note
As you can imagine, the external analog controls connected at the CV, Gate & Trigger
ports are not influenced by the settings of the Note Priority & Mode sections of the MIDI
Interface.
Note Priority
The Grp A8 offers three different Note Priority modes:
•In LOW Note, if the musician press more than a key, the instrument
will plays the lowest note .
•In LAST Note, the instrument will play the last note executed.
•In HIGH Note, the instrument will play the highest note.

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Mode Selection
With the MODE Selector, you can choose between three different
behaviours:
•MONO: Upper and Lower sections works on the same MIDI
Channel previously set from the user (see below); all six oscillators,
four filters, amplifiers and modules plays together forming a single big
instrument.
•DUAL: the synthesizer works as a two-voice single instrument on
the same MIDI Channel for Upper and Lower parts. When one key
is pressed, you’ll have both Upper and Lower sections playing the
same note. When you press two key simoultaneously, you’ll get high
note played from Upper synth section and low note played from
Lower synth section.
•POLY: the sinthesizer works on two separate and independent
user’s definable MIDI Channel, one for Upper and the other for
Lower part (see below).
Pitch Bend
The two PITCH BEND AMOUNT controls (UPPER and LOWER) allow
the exact setting of the frequency deviation from the nominal pitch; the
maximum range equals +/-12 semitones.
MIDI Interface
With this part of the module, you can set the MIDI
Channel(s) with the two Increase/Decrease
pushbuttons (see below). The MIDI Interface
manages the following messages:
•Note On/Off w. Key Velocity
•Pitch Bend
•Modulation Wheel
•Channel Aftertouch
•Expression & Volume Pedal
•Damper Pedal
•Clock
Note
You can choose between the standard MIDI Channels 1-16 and seventeenth position
corresponding to OFF; in the latter setting, you’ll disconnect the MIDI data from reach the
Upper or Lower synth section, leaving them at only disposal of the analog CV-Gate-Trig
Interface on the front panel.
As we’ll see later, the MIDI Interface reacts to Start, Stop and Continue RealTime Commands: those
will be routed to the internal Step Sequencer for normal transport functions.

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In the MIDI Interface, there are four LEDs:
•CH UPP LED: lighted in MONO and DUAL MODE, shows that the dual digit number
displayed is the MIDI Channel for the Upper synth section of the instrument.
•CH LOW LED: lighted in MONO and DUAL MODE, shows points that the dual number
displayed is the MIDI Channel for the Lower synth section of the instrument.
•PROG LED: turns on when you press the red PROG pushbutton in the MIDI Interface. When
lit, you are able to superimpose an octave(s) CV offset for the 3 Upper and 3 Lower VCOs.
More commands will be added in the future, with firmware updates (thru Host multiport on
rear panel).
•MIDI ACT(IVITY) LED: turns on if the synthesizer receive any MIDI message.
The available controls act as:
•MANUAL GATE UPPER: this button act as a Gate source for all the envelope generators
available (or assigned, as for the Aux EG 7) in the Upper synth section.
•MANUAL GATE LOWER: this button act as a Gate source for all the envelope generators
available (or assigned, as for the Aux EG 7) in the Lower synth section.
•INCREASE Button: will step forward the numeric value on the display.
•DECREASE Button: will step backward the numeric value on the display.
•PROGR BUTTON:
oIf the instrument is set in MONO MODE (see above), the button enters the
Programmable Mode for the MIDI Interface (for load firmware upgrades thru HOST
port on rear panel).
oIf the instrument is set in DUAL MODE, the button has the same function as above.
oIf the instrument is set in POLY MODE, each pression on the pushbutton will loop
cycle on the numeric display one of the following options:
•MIDI CH UPP [the corresponding LED will light],
•MIDI CH LOW [the corresponding LED will light],
•PROGR MODE [the corresponding LED will light].
oIn CH UPP and CH LOW MODE, you’ll set the desired MIDI Channel with the two
Increase/Decrease buttons. (Range 1-16, Off).
oIn MONO or DUAL Mode, pressing repeately the PROG button, will cycle thru one
of the following options:
•CV Offset (see below),
•Upper plus (see note below) Lower MIDI Channel select options (01-16, Off).
Note
The value you select will be applied simoultaneously for both Parts; as wrote before, if you choose “Of(f)”, the selected
Part of the instrument will be left under full control of the analog control connections.
oIn POLY Mode, you gain separate access to Upper and/or Lower MIDI Channel
adjust; the corresponding LED will turn on.
CV Offset
It is possible to add an octave offset on the CV received at the analog control inputs; in this way, you
can match the octave played by A8 with the range of your external analog controller.

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One more pressing on the PROG button will enter the synthesizer’s MIDI Interface in CV Offset
Mode; Upper and Lower Parts can be offset in 1 octave increment on a range of 5 available octaves.
In the numeric display, you’ll read:
•U1/U5 (the default value is U3).
•L1/L5 (the default value is L3).
Note
As a rule of thumb, with VCOs Octave on 8’, if you want to hear in the real octave of your external analog controller, you
should select an Offset value of 3 (remember that the parameter range is 1-5). So, if you want to hear A3 = 440 Hz, put
your VCOs on 8’ and impart a CV Offset with value U3 and/or L3. If you impart a CV Offset with value U2/L2, you’ll play
a lower octave (e.g.: like if you have selected 16’ on VCOs). If you impart value U4/L4, you’ll play a higher octave (like if
you have selected 4’ on VCOs).

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FRONT PANEL CONNECTIONS
On the front panel, the available connections are organized in four separate blocks related to: CV-
Gate-Trigger, Sequencer, Filter, Main Out.
CV-Gate-Trigger
This block of nine connectors is for the analog control of Lower section, Upper section, Lower &
Upper section; for control simoultaneously the two parts, you should connect external sources to the
central column of connections marked LOW-UPP. You can choose between:
•TRIG IN LOWER - LOW/UPP - UPPER: Analog Trig In 0/+5V
•GATE IN LOWER - LOW/UPP - UPPER: Analog Gate In 0/+5V)
•CV IN LOWER - LOW/UPP - UPPER: Analog CV In 1V/Oct.
Sequencer
Here are the connections for the Step Sequencer outputs and its external controls:
•GATE OUT COLUMN A - COLUMN A+B - COLUMN B: the Gate Output for the single
Column A or B and for the two Columns A+B combined in series (16x1 steps). Range:
0/+5V.
•CV OUT COLUMN A - COLUMN A+B - COLUMN B: the CV Out for the separate
Column A or B (8x2 steps) and for the two Columns combined in series. Range: 0/+8V.
•STEP ADVANCE: on each pulse (0/+5V) received at this port, the Step Sequencer advance
one step.
•RUN/STOP: each pulse (0/+5V) received will alternate between Run and Stop. This external
input will interact with the front panel control RUN/STOP. The Step Sequencer will restart
from step no. 1.
•CONTINUE: the pulse (0/+5V) received at this port will put the Sequencer in playback from
the last step played without resetting to step no. 1.
•EXT CLOCK: a train of pulse (0/+5V) received at this port will advance the Step Sequencer; it
will function only if the Step Sequencer is set to EXTERNAL CLOCK SELECT position.

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•LOOP: the switching closure received on this port will enable the LOOP ON MODE for Step
Sequencer. This external input is parallel with the hardware LOOP SWITCH on the front
panel. If you want to remotely control LOOP ON, don’t forget to turn off its hardware switch
on the front panel).
Filter
•24dB CV IN LOWER: external frequency control (0/+5v) for the Lower Low Pass Filter.
•24 dB CV IN UPPER: external frequency control (0/+5V) for the Upper Low Pass Filter.
•12 dB CV IN LOWER: external frequency control (0/+5V) for the Lower State-Variable Filter.
•12 dB CV IN UPPER: external freqyency control (0/+5V) for the Upper State-Variable Filter.
Main Out
•MONO OUT: summed signal of Upper and Lower Part.
•PHONES: headphones stereo output.
•LEFT - RIGHT LOW LEVEL OUT: low impedance stereo output.
•LEFT - RIGHT HIGH LEVEL OUT: high impedance stereo output.

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REAR PANEL CONNECTIONS
On the rear panel, you’ll find the connection related to:
Power
•AC RECEPTACLE
Midi
•MIDI IN
•MIDI THRU
Audio
•SECTION OUT UPPER LEFT-RIGHT: separate stereo out for Upper part after Pan/AutoPan
module, but before the Main Out Volume.
•SECTION OUT LOWER LEFT-RIGHT: separate stereo out for the Lower part after
Pan/AutoPan module, but before the Main Out Volume.
•MAIN OUT LEFT-RIGHT LOW LEVEL: doubles the front panel main stereo output (low
level).
•MAIN OUT LEFT-RIGHT HIGH LEVEL: doubles the front panel main stereo output (high
level).
•LEFT+RIGHT MONO OUT: doubles the front panel mono output.
Future upgrades
•HOST: this port is for future upgrades to the internal MIDI Interface firmware. At this very
moment, it is disabled.

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A8 AUDIO AND MODULATION ROUTINGS
We’ll start from audio signal path (sources and modifiers): from oscillators thru the filters, till the
amplifier. Then, we’ll follow the modulation sources and their applications on the audio circuit.
SOUND SOURCES AND SOUND MODIFIERS PATH
The above scheme is an over simplified view of the audio path for both Upper and Lower A8
Sections. As you can see, the signal produced from VCOs, SubOSCs, Noise Generator (in common
for both sections) and Ring Modulators is treated thru the dual VCF section and then equalized with
the Fixed Filter Bank; finally, the signal is amplified in the VCA and outputted thru the direct
connection on the rear panel. Both Upper and Lower signals goes into the Main Mix / Auto Pan and
the Stereo Main section.
Above, you can track the Upper and Lower audio signal path on the synthesizer’s front panel.
Below, the front panel with the highlighted positioning of the Sound Sources and the Sound Modifiers.
Following, we’ll give explanations of the single audio source/modifier sections.

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VOLTAGE CONTROLLED OSCILLATOR 1-6
The six VCOs comprised in A8 Synthesizer are, more or less, all equal; minor differencies are found in
the FM/PWM Sources and Hard Sync capability.
The VCO behaviours are organized in three main stages: Frequency Control and Frequency
Modulations, Waveform Selection and Pulse Width Modulation, Output Leveling and Suboscillation.
Frequency Control
The nominal Frequency of the VCO is defined with three dedicated controls on the front panel:
Octave Selector, Tune Pot and Fine Tune Pot. In addition, is possible to put the VCO under control
of any combinations of three external CV Sources: MIDI Interface, CV In (analog ports on the front
panel), Step Sequencer.
As we’ll see later, those three sources interact each other, for (e.g.) real-time transpose of the
sequencer or whatever. Is it possibile to detach the realtime Keyboard Control from the VCOs
Frequency; in this way, both the MIDI Note On conversion and the external CV In data are
disconnected from the selected oscillator; the Step Sequencer remains only external frequency
control available, free from unnecessary real-time transposition, but you’ll be forced to raise the
footage of VCOs for re-gain the correct playing range.

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Note
Once you’ll turn on the Oscillator Sequencer Enable switch (in Step Sequencer section), the Step Sequencer CV is always
connected to the oscillator nominal frequency; so, the only way for prepatch VCOs under Step Sequencer control and
not have undesired transposition is to put at zero the Step Value (zero means in full counterclockwise motion).
The VCO has two FM busses: FM 1 buss has a Linear/Exponential selector and a huge amount of
possible FM sources (low rate for cyclic modulation or audio rate for harmonic control). With audio-
rate modulation in Exponential mode, the perceived intonation drifts from nominal value; with audio-
rate modulation in Linear mode, the perceived intonation (for an ample modulation index) remains
stable. FM 2 buss works only in Exponential mode and can be connected with LFO 1 or 2; while this
kind of circuit can be found useful mainly for vibratos, don’t forget that in A8 Synthesizer, the LFOs
goes fairly high in the audio range.
As above, the Hard Sync capability can be useful not only for rock-steady tune, but for generating
more harmonic peaks in the slave oscillator.
Waveform Control
The waveform of the VCO can be selected with a dedicate multiposition switch; you can choose
between the typical analog waveshapes, plus the combination of Sawtooth and variable Pulse.
The Pulse Width Modulation can be controlled in nominal position, for the “starting point” in the
Symmetry value, and can be assigned as destination for a huge amount of possible modulation
sources. In addition, it is possibile to route straightly the output of the Step Sequencer CV (Row A or
Row B) to drive the PWM.
The waveforms
As you expect, the VCOs in A8 Synthesizer are full analog; so, the
waveforms available are pretty standardized in the analog heritage:
Sine Wave: full energy on the fundamental frequency, no higher
harmonics.
Triangle Wave: odd harmonics only, with energy decaying in exponential
shape.
Sawtooth Wave: even and odd harmonics, with energy decaying in linear
shape.
Triangle + Sawtooth: mix of the previous two waves.
Square/Pulse Wave: odd harmonics only, with linear decaying energy,
when the duty cycle (a.k.a. symmetry, a.k.a. pulse width) is at 50%.