Access Virus Rack User Manual
©2000, 2001 Access Music GmbH, Germany . Virus™ is a trademark of Access Music GmbH.
All other trademarks contained herein are the property of their respective owners. All
features and specifications subject to change without notice.
Written by Christoph Kemper, Uwe G. Hönig, Wiland Samolak
Guido Kirsch and Marc Schlaile.
Translation by Thomas Green. Graphic design and DTP by Babylonwaves Media.
http://www.access-music.de
The Virus - Resistance is futile.
|
info@access-music.de
Table Of Contents
2
Important Safety Remarks
- Set-up 6
- Connections 7
- Operation 7
- Memory battery change 8
- Care 8
- Fitness for Purpose 8
Prologue
Introduction
The Virus 14
- Cable Connections 15
- Power Up the Virus 15
- Listening to the Factory Sounds 16
- Listening to the Multi Programs 17
- Your First Sound Program 17
The Amplifier Envelope 19
The First Filter 22
Filter Modulation 25
The Saturation Stage 27
The Second Filter 28
Filter Routing 32
The First Oscillator 34
The Second Oscillator 37
The MIXER Section 39
The LFOs 41
- LFO 1 42
- The modulation targets 42
- LFO 2 45
Volume and panorama 46
- Volume and Panorama Position 46
Velocity 47
Unison Mode 48
The Chorus/Flanger Effect 49
The Delay Effect 50
More to Come 51
Concept and Operation
Operating Modes 54
The Multi-Single Mode 55
the Edit Buffers 57
Operation
Parameter Selection and Data Entry 60
Display of values 64
All About The Memory
Store 66
Compare 67
Modmatrix And Definables
Creating Modulations via Assign 70
The Definable Knobs 72
Master Clock And Midi-Clock
Master Clock and MIDI-Clock 74
The Effects Section
The Effect Section 76
Audio Inputs
Audio Inputs 78
- OSC Volume / Input 79
- Input global Settings 80
- Input Level Indicator 80
Audio Routing
The Audio Outputs 82
Categories
Sound Categories 84
Random Patch Generator
Random Patches 86
Additional Functions
Additional Functions 90
- Panic Function 90
- Audition function 90
- Reset Function 91
The Parameters
OSC Section (Encoder) 94
- Oscillator 1 95
- Oscillator 2 95
OSC Sektion (Menu) 96
- Oscillator 1 96
- Oscillator 2 97
- Oscillators 98
- Sub Oscillator 99
- Ringmodulator 100
- Noise 100
Filter Section (Encoder) 101
Filter Section/Menu 102
- Filter 1 102
ACCESS VIRUS RACK
3
- Filter 2 103
- Filters 104
Envelope Section (Encoder) 107
- Filter Envelope 107
- Amplifier Envelope 108
LFO Section (Encoder) 109
- LFO 1 109
- LFO 2 110
- LFO 3 110
LFO Section (Menu) 111
- LFO 2 112
- LFO 3 113
EFX Section 115
EFX Section/Encoder 116
- Chorus 116
- Reverb 117
- Delay 119
- Input 120
- Vocoder 123
- Analog Boost 123
EFX Section/Menu 124
- Chorus 124
- Delay/Reverb 125
Edit Section/Encoder 129
Edit Section/Menu 131
- Common 131
- Unison 134
- Punch 135
- Assign 136
- Velocity 138
Arpeggiator&Ctrl Section (Encoder) 141
Arpg&Ctrl Section (menu) 143
- Arpeggiator 144
- Random Patch Generator 145
- Definable 1+2 146
MIDI 149
- Midi Dump TX 149
- Midi Dump RX 150
System 154
Multimode parameters 156
The Vocoder
Vocoder 162
- The Modulator Bank 163
- The Envelope Follower 163
- The Carrier Bank 163
The parameters of the Virus vocoder 164
Notes about the vocoder 166
The Virus and Sequencers
Parameter Control via MIDI 168
Organizational Information 169
Handling MIDI Parameter Control 172
Notes on Adaptive Parameter Smoothing 173
Problems Related to Parameter Control 175
Dump - The Sound in the Song 176
Tips, Tricks& Words Of Wisdom
Tips and Tricks 180
- Multi Single Mode 180
- Value Buttons 180
All abouts Inputs 182
- Audio Inputs and Audio Routing 182
- OSC Vol / Input 182
- Input Level Indicator 183
About Effects 184
- Delay/Reverb Effect Send 184
- The Virus as an Effect Device 184
Oscillators 185
- Pulse Width Modulation 185
- Oscillator Sync/FM 186
Filters 187
- 24-dB Filter Variations 187
- Filter Balance 187
- Filter Routing: Split 188
Saturation for Added Grit and Dirt 189
- Saturation and OSC Vol 189
- Saturation Curve: Shaper 189
LFOs 190
- LFO Env Mode 190
- LFO Mode 191
- LFO Trig Phase 191
- External LFO Trigger 192
- Filter Gain 192
Volume Control 193
- Patch Volume 193
- Part Volume 193
- Channel Volume 193
Assign and the Definable Knobs 194
Arpeggiator 195
MIDI 196
- MIDI Dump RX 196
- Expression Controller 197
- Bank/Program Change via SysEx 197
- Priority 198
The Operating System (OS) 200
- Installing an operating system update 200
- Loading the OS from One Virus to Another 201
- Software Updates 201
4
Appendix
System Exclusive Data 204
- System Exclusive Implementation 204
- Control Change message (only Page A) 205
- Polyphonic Pressure message (only Page B) 206
- System-Exclusive-Message 206
- SysEx Parameterchange 206
- Single Dump 207
- Multi Dump 207
- Single Request 208
- Multi Request 208
- Single Bank Request 208
- Multi Bank Request 209
- Arrangement Request 209
- Global Request 209
- Total Request 209
- Controller Dump Request 209
MIDI Implementation Chart 210
FCC Information (U.S.A) 212
FCC Information (CANADA) 214
Other Standards (Rest of World) 216
Declaration of Conformity 218
Garantie Bestimmung 220
Warranty 222
ACCESS VIRUS RACK
5
6
CHAPTER 2
Important Safety Remarks
s
Please read and heed the follow-
ing safety guidelines!
Set-up
A few fundamental rules on handling
electrical devices follow.
Please read all notes carefully before you
power the device up.
Operate and store the device in
enclosed rooms only.
Never expose the device to a damp
environment.
Never operate or store the device in
extremely dusty or dirty environments.
Assure that air can circulate freely on
all sides of the device, especially when
you mount it to a rack.
Don’t set the device in the immedi-
ate vicinity of heat sources such as
radiators.
Don’t expose the device to direct
sunlight.
Don’t expose the device to strong
vibrations and mechanical shocks.
ACCESS VIRUS RACK
7
Connections
Be sure to use exclusively the
included mains power supply adapter.
Plug the device only into mains sock-
ets that are properly grounded in compliance with statutory regulations.
Never modify the included power
cord. If its plug does not fit the sockets
you have available, take it to a qualified electrician.
Always pull the power plug out of
the mains socket when you won’t be
using the device for prolonged periods.
Never touch the mains plug with wet
hands.
Always pull the actual plug, never
the cord, when you’re unplugging the
device.
Operation
Don’t set beverages or any other
receptacle containing liquids on the
device.
Make sure the device is placed on a
solid base. Set it on a stable tabletop
or mount it to a rack.
Make sure that no foreign objects
fall into or somehow end up inside the
device’s housing. In the event that this
should occur , switch the device of f and
pull the power plug. Then get in touch
with an authorized dealer.
Used on its own and in conjunction
with amps, loudspeakers or headphones, this device is able to generate
levels that can lead to irreversible
hearing damage. For this reason,
always operate it at a reasonable volume level.
8
CHAPTER 2
Memory battery change
The Virus stores its sound programs in a
battery-buffered RAM. This battery (general type designation: CR2032) should be
replaced every three to four years. The
housing has to be opened to change the
battery, so take the device to a qualified
service technician. Do your part in protecting our environment and take it to a
shop that disposes of batteries properly.
Before you have the battery changed,
save the entire memory content of the
RAM by loading it to a sequencer via
"Total Dump". Be advised that RAM content is lost when the battery is swapped
(see “Midi Dump TX” on page 149).
Care
Do not open the device, it is not
equipped with any user-serviceable
parts. Repair and maintenance may
only be carried out by qualified specialists.
Use only a dry, soft cloth or brush to
clean the device.
Do not use alcohol, solvents or simi-
lar chemicals. These can damage the
surface of the housing.
Fitness for Purpose
This device is designed exclusively to
generate low-frequency audio signals
for sound engineering-related purposes. Any other use is not permitted
and automatically invalidates the warranty extended by Access Music Elec-
tronics GmbH.
ACCESS VIRUS RACK
9
10
CHAPTER 3
Prologue
Dear Virus Owner,
Congratulations on your choice, the new
Virus. You have purchased a cuttingedge synthesizer that comes fully loaded
with several revolutionary features. Here
are just a few of the highlights:
The Virus delivers the sound characteristics and tone of traditional analog synthesizers - for instance the Prophet 5 or
Memorymoog to name just two popular
examples of the species - in a previously
unparalleled level of quality and handling ease. We’re not kidding, the Virus
actual delivers the authentic response of
an analog synth via a digital signal processor chip, although the sound shaping
and voicing options out-perform those
of it historical predecessors by a considerable margin.
The Virus comes with 512 slots for storing SINGLE sounds. These are organized
in four banks. The first two banks (A and
B) are located in the RAM, so you can
overwrite them with new sounds. The
other two banks are ”hard-wired”, i.e.
they’re programmed into the FLASH
ROM.
The Virus rack offers a maximum of 16
voices. In Multi Mode, these are allocated dynamically to 16 simultaneously
available sounds.
You have two audio oscillators plus one
suboscillator, a noise generator, a ring
modulator, two Multi Mode filters, two
envelopes, a stereo VCA, three LFOs and
a saturation stage (SATURATOR) for cascade filtering, tube and distortion
effects.
The Virus offers a veritable number of
effects. You have a powerful Chorus/
Flanger section at your disposal, as well
as the Analog Boost - a controllable bass
emphasis, with each effect available separately for every sound. You also get a
global reverb/delay unit that lets you
create high-quality reverb effects and
rhythmic delay taps. Delay time can be
synced up to MIDI clock.
With the benefit of two external audio
inputs, the Virus may also serve as an FX
device and signal processor that you can
use creatively to come up with all kinds
of effects. External signals can be processed with filter, gate and lo-fi effects,
routed to the Virus effects section and
serve as a modulation source for frequency and ring modulation.
Beyond that, you can use internal or
external signals as sources for the Virus’
on-board vocoder serve. The vocoder
works with up to 32 filter bands and
offers diverse manipulation and modulation options.
ACCESS VIRUS RACK
11
You'll find parallel external audio inputs
on the front and back panel. You can
determine the input sensitivity via a gain
selector switch. You're also free to activate a special Phono EQ that enables you
to connect a record player via a suitable
cord.
The two main oscillators produce 66
waveshapes, three of which are dynamically mixable so that spectral effects are
possible within the confines of a single
oscillator. In conventional synthesizers,
this type of effect requires several oscillators. Synchronization, frequency modulation and ring modulation between
the audio oscillators delivers additional
complex spectral effects that you can use
for all kinds of sound shaping purposes.
The filters can be switched in series or in
parallel within the voices via several
options. When you switch the filters in
series, the saturation stage is embedded
between the filters. Consequently, an
overdriven filter resonance can be re-filtered within the same voice! A maximum
of six filter poles (36 dB slope!) enables
radical tonal manipulations.
The LFOs feature 6 continuous variable
waveshapes each, including a triangle
with variable symmetry and infinitely
variable aperiodic oscillations for random variation of the controlled parameters. The LFOs are capable of polyphonic
as well as monophonic oscillation. In
other words, if several voices are active,
the LFOs can run independently or in
sync. A number of keyboard trigger
options enable you start LFO wave-
shapes with variable phase lengths at
the beginning of a note and/or to cycle
once only, like an envelope.
Next to the numerous ”hard-wired” or
fixed modulation configurations, you
can assign three modulation sources to
up to six different modulation destinations via the Modulation Matrix. For
your modulation sources, you have LFOs,
velocity, the pitch bender, aftertouch,
the modulation wheel, numerous MIDI
controllers and other sources to chose
from. For your modulation destinations,
you can select any sound parameter of
the Virus that is conducive to being
remote controlled.
Up to 16 arpeggiators are available in
MULTI mode. These give you countless
options for creating arpeggios, which
can also be synced up to MIDI clock.
Sounds and effects are patched out via
four audio outputs which of course can
also be used to route two stereo signals
out.
The Virus Rack comes with a powerful
software editor for PC and Macintosh. It
lets you edit and manage sounds on a
large-scale user interface. You can access
every sound parameter of the Virus Rack
directly via mouse click. When you edit a
parameter, the Virus will render the
changes immediately in real time.
Accordingly, every parameter change
that you make using the encoder knobs
(those knobs without left and right control range limits) on the Virus Rack
12
CHAPTER 3
appears immediately on the screen. Incidentally, this editor is based on Emagic's
popular SoundDiver.
In all modesty , we are especially proud of
a feature we developed called Adaptive
Parameter Smoothing. For the first time
in the history of synthesizers equipped
with memories, you can manipulate a
knob or control feature without an audible step or increment. In other words,
the sound does not change abruptly but
SEAMLESSL Y. No more zipper noises! The
Virus responds just as smoothly as analog
synthesizers did prior to the introduction
of digital sound storage.
And users of contemporary software
sequencers will appreciate the fact that
the Virus sends all sound shaping commands immediately in the form of MIDI
Controller or Poly Pressure data (and of
course accepts all of the corresponding
Controller and SysEx messages). This feature lets you dynamically control the
Virus and all its functions via computer.
Although far from complete, the features listed above give you some indication that you now own an exceptionally
versatile, high-quality musical instrument that will give you plenty of joy for
years to come. We certainly hope you
can fully exploit the enormous potential
of this fine instrument.
Have fun and enjoy!
Your Virus Development Team
Many thanks to:
Ben Crosland, Thomas Green, Axel Hartmann, Uwe G. Hönig, Jörg Hüttner, Timo
Kaluza, Frank Katzer, Shehryar Lasi,
Oliver Käser, Andrea Mason, Paul Nagel,
Kai Niggemann, Rob Papen, Wieland
Samolak, Howard Scarr, Jörg Schaaf,
Hans-Jörg Scheffler, Matt Skags, Joeri
Vankeirsbilck, Jay Vaughan and Jens
Wegerhoff.
Introduction
14
CHAPTER 4
Introduction
THE VIRUS
This section provides deliberate, step-bystep guidelines on operating and handling the Virus for those of you who are
new to the world of synthesizers and
MIDI. The following covers basics such as
how to connect the Virus to an AC
power supply , your MIDI system and your
audio system. Then we will guide you
through a series of experiments
designed to demonstrate the different
functional groups, their control features
and the tasks they execute.
After you have finished reading this section, you will be able to handle virtually
all of the sound generating and sound
shaping functions of the Virus. All of
these are described in context. Even the
majority of less significant functions,
accessible via menus, are discussed here.
You will find a detailed, comprehensive
description of all functions of your new
synthesizer in the section following this
introduction.
Please keep in mind that within confines
of this introduction, we are unable to
impart all of the knowledge and skills in
acoustics, sound synthesis and MIDI control you might desire or need to acquire.
If you are keen to learn more about
these subjects, you should consider
becoming a regular reader of one or several of the leading trade publications in
your country. Your local musical instruments dealer or more experienced musicians will be able to recommend the best
magazines to you. And of course there is
a wide range of books available on these
subjects.
If you decide to read this section, we recommend you read it in its entirety from
the start - rather than begin with a subsection that is of particular interest to
you. A fitting metaphor for the basics
discussed in this section might be a
house where each bit of information in a
subsection is a brick that builds on a preceding brick and interlocks with those
next to it. You want your knowledge
base to be a sound structure so you
won’t run into problems when you find
one of the “bricks” is missing.
ACCESS VIRUS RACK
The Virus
15
Cable Connections
Before you connect the Virus to an AC
outlet and the rest of your equipment,
ensure that all of the devices are
switched OFF. If your Virus does not have
a build-in keyboard, then connect the
MIDI OUT of the desired MIDI send
device (keyboard, computer, hardware
sequencer, etc.) with the MIDI IN of the
Virus.
Connect the audio outputs of the Virus
with the signal inputs of your audio system. In order to receive a signal, as a
minimum you must connect the output
OUT 1 R/MONO. However, we recommend you also connect the output OUT 1
L so you are able to enjoy the stereo
sounds of the Virus.
Once you have established the desired
cable connections, make sure the main
volume controls of all the connected
devices are dialed to the lowest possible
setting. Switch the devices on in the following sequence: the MIDI send device
(computer, master keyboard, etc.) first,
then the sound generators (Virus and
the other signal sources), followed by
the mixing console and finally the amplifier.
Power Up the Virus
Power up the Virus Rack by pressing the
POWER button. T o shut the device down,
press and hold this button for approx.
two seconds.
Now while you are sending notes on
MIDI Channel 1 of the Virus, turn the
master volumes of the connected devices
up in the same order that you switched
the devices on. Be sure to keep on eye
on the signal level indicators of your mixing console.
16
CHAPTER 4
Introduction
Listening to the Factory
Sounds
The program memory of the Virus was
loaded with sound programs (SINGLE
PROGRAMs) and sound combinations
(MULTI PROGRAMs) before it left the
factory. To hear the SINGLE PROGRAMs
(and gain an initial impression of the
possibilities your new instrument has to
offer in terms of sounds), first make sure
your MIDI source is sending on MIDI
Channel 1.
Press the SINGLE button. A number, a letter, number and name appear in the display. These indicate the the MIDI
Channel, the current Program Bank (A to
D) as well as the number and name of
the current sound program.
You’ll find that some sound programs
are labeled with the abbreviations ”INP”
or ”VOC”. These use the external audio
input as a signal source for the filter section (INP) or vocoder (VOC). This means
that you won’t hear anything until you
route an audio signal into the external
audio inputs.
Now if you play notes you should be able
to hear this sound and a quarter note
(the round dot at the end of the note
staff is solid black) should appear in the
display every time you press a key and
release a key. If you do not hear a sound
but you see a half note (blank note
head) check to see if you are sending on
the wrong MIDI Channel.
Press the VALUE button to call up the
128 single programs of Bank A in
sequence. (The VALUE encoder is inactive in this operating mode.) In order to
hear the sound programs in banks B, C
and D, simply use the PARAMETER/BANK
buttons to step from one program bank
to another.
Listening to the Multi
Programs
The Virus not only has the capability of
playing SINGLE PROGAMs, but also combinations consisting of more than one
sound simultaneously (MIDI Multi
Mode). T o call up the MULTI PROGRAMs,
press the MULTI button and select these
combination programs via the VALUE
button. The Virus features “only” 128
MULTI PROGRAMs, so you don’t have to
switch back and forth between banks
they way you just did while activating
single programs.
The majority of available MULTI PROGRAMs contain sound combinations that
are controlled via a single MIDI channel.
In these MULTI PROGRAMs, the sounds
involved are allocated side-by-side (split)
or on top of one another (layered) on
the keyboard. In other MULTI PROGRAMs, the sounds are divided up over
several MIDI channels to make it easier
to work with a sequencer. If you activate
a MULTI PROGRAM and hear a single
sound only, then you can control this
MULTI PROGRAM via several channels.
ACCESS VIRUS RACK
The Virus
Your First Sound Pro-
gram
If you have never created or changed a
sound on a synthesizer , we now have the
pleasure of introducing you to this fascinating process.
Press the button
single program “A127 - START -” by
using the
on the connected keyboard. You should
hear a sound that, for lack of better
description, is a bit harsh or biting, but
above all completely static. It should
start immediately after you press a key
and sustain indefinitely for as long as
you hold the key down. As soon as you
release the key, the sound should end
VALUE
SINGLE
buttons. Press any key
and select the
17
18
CHAPTER 4
Introduction
abruptly. This sound is not designed to
be especially pleasant; it is intended to
be as neutral as possible to give you a
basis from which you can begin creating
or shaping your own sound.
THE AMPLIFIER ENVELOPE
ACCESS VIRUS RACK
The Amplifier Envelope
19
Long-term exposure to this sound will
definitely grate on your nerves, so let’s
get started with changing it into a signal
you might enjoy hearing, beginning with
the volume characteristics.
Locate the two vertically arrayed buttons
next to the seven LEDs. Use these UP and
DOWN buttons to select from among the
seven parameter groups and/or sections.
The appropriate LED lights up to indicate
that the given section has been selected.
Select the
five encoder knobs for this section read
ATTACK
RELEASE
These controls will help you to dial in
volume characteristics called an amplifier
envelope and put an end to the nerveracking drone that may remind you of
one of those cheesy organs that you
hear in ‘60s B-movie sound tracks.
ENV
section. The labels on the
,
DECAY, SUSTAIN, SUS TIME
.
and
The section labeled
envelope. On a synthesizer, an envelope
is used to modulate sound over time.
The Virus has two envelopes, one for volume (AMP ENV) and one for the filters
(FILT ENV), which we will learn more
about later . The five encoder knobs serve
to shape either the amplifier envelope or
the filter envelope. Make sure that you
can see AMP ENV in the display, and not
FILT ENV. If this is not the case, use the
PARAMETER buttons to set the section to
the amplifier envelope.
ENV
addresses the
20
CHAPTER 4
Introduction
Rotate the
ATTACK
encoder while you
repeatedly engage a key to hear the
note. The further you turn the encoder
up, the longer it takes for the sound to
achieve maximum volume after the start
of the note. So you can say
ATTACK
controls the initial volume swell of the
sound.
T ake a look at the display of the Virus to
gain an impression of the difference
between these two values. It shows two
numeric values when you dial a encoder:
at the left you can see the value stored
in the sound program and at the right,
the numeric equivalent to the value
determined by the current position of
the encoder.
Now fiddle with the DECAY encoder
while you repeatedly press a key to activate a note. Hold the key down for good
while. You will notice that the volume,
once it reaches maximum level at the
end of the
reaches a minimum level. The
ATTACK
phase, drops until it
DECAY
encoder determines the speed, or in synthesizer jargon, the rate at which the
volume decreases.
However, the
DECAY level does not
always drop to the minimum level; you
can determine a random value between
the maximum and minimum levels at
which the volume remains constant. This
level in turn is controlled via the SUS-
TAIN encoder.
Whenever the SUSTAIN level is set to
maximum, the volume cannot drop during the DECAY phase; in other words, in
this situation the DECAY encoder is inef-
fective.
. The individual functions of a synthe-
sizer are designed to interact; many
functions are dependent on other functions. In a number of cases this means
that some functions are subordinate to
others, i.e. the effectiveness of a control
feature is altered, modified or even
negated completely by other related
functions.
The final encoder, RELEASE, determines
the speed or rate at which the volume
decreases when you release the key: At
low values the sound ends relatively
abruptly , at high values, the sound fades
out more gradually and softly. The
length of the RELEASE phase also
depends on which level the amplifier
curve is at when you release the key: The
lower the level, the shorter the RELEASE
phase. If you dialed in a brief DECAY or
SUSTAIN-TIME phase and it ended while
you held the key down then of course
there will not be an audible RELEASE
phase.
The next phase of the amplifier envelope
is determined by the SUSTAIN-TIME
encoder: If the encoder is set to the center position, then the SUSTAIN level
remains constant through to the end of
the note.
If you turn it counter-clockwise to the
left, then the level drops off at an
increasing rate towards the minimum
level much in the manner you just experienced with the DECAY encoder; If you
turn the encoder clockwise to the right,
the level rises at an increasing rate to
maximum and remains there until you
release the key.
T he amplifier envelope can be described
as a variable curve which, depending on
the type and duration of attack, hold
and release data, automatically influences an imaginary volume encoder
(turns it up or down). At the beginning
of the note, ATTACK controls the rise or
rate of increase to the maximum level.
Once the maximum level is achieved,
DECAY determines the fall or rate of
decrease to the SUSTAIN value, which is
infinitely variable between the minimum
and maximum levels. The amplifier envelope may remain at this value until the
end of the note, fall towards the minimum level as determined by the variable
TIME value, or even rise again towards
the maximum level. After the end of the
note, RELEASE controls the fall or rate of
decrease to the minimum level. Consequently, the control encoders labeled
ATTACK, DECAY, TIME and RELEASE con-
trol a speed or rate, where as SUSTAIN
actually controls a level.
ACCESS VIRUS RACK 21
The Amplifier Envelope
22 CHAPTER 4
Introduction
THE FIRST FILTER
Now we will take a look at a component
of a synthesizer that is generally
regarded as the most important functional unit as it enables drastic sound
shaping measures: the filter - or in the
case of the Virus, the two filters.
But first we will concentrate on just one
of the two filters.
Use the UP or DOWN buttons to activate
the filter section FILT. The second enco-
der knob in this row is labeled CUTOFF
(not to be confused with CUTOFF 2!).
Rotate the encoder to the left and right
and note how the sound becomes muddier and clearer in response to the direction in which you turn the encoder. (To
ensure this effect and the following
aural experiments are most pronounced, adjust the amplifier envelope
so that the Virus generates a constant
level while you hold a key down).
This is how a low pass filter works: it suppresses, or in technical jargon, attenuates the higher frequencies in a signal
and allows the lower frequencies
through. Think of the CUTOFF encoder
as a bouncer and the Virus as your pub.
Y ou can tell it which frequencies to let in
and which frequencies to keep out. The
frequencies above the so-called cutoff or
filter frequency are suppressed, those
below it remain unaffected.
ACCESS VIRUS RACK 23
The First Filter
Now we'll look at a parameter that is not
assigned a dedicated knob of its own,
but can be dialed up in the display. This
type of parameter may be selected via
the PARAMETER buttons and then
adjusted with the VALUE knob or the
VALUE buttons.
Select the FILTER 1 Mode parameter via
the PARAMETER buttons. To do this,
make sure that the display is still in the
filter section FILT. This parameter enables
you to select a filter operating mode
from the four available options:
LP the low pass filter we have just
discussed.
HP the high pass filter which works in
the opposite manner of the low pass
filter: It suppresses the lower frequencies in a signal and lets the higher frequencies pass.
BP the band pass filter which sup-
presses both ends of the tonal spectrum and allows only a narrowly
defined bandwidth of the original
sound to pass.
BS The band stop filter, band reject
filter or notch filter which works in the
opposite manner of the bandpass filter. It allows all of the frequencies of a
signal except for a narrow frequency
band around the cutoff to pass. The
term “notch” is fairly descriptive; you
might say this filter chops a notch out
of the sound spectrum.
01111111111111111112
1 FILTER1
Mode Lowpass≤
61111111111111111154
Now activate the different operating
modes and rotate the CUTOFF encoder
to get a feel for the way each filtering
option works.
Along with the CUTOFF encoder, the
RESONANCE encoder is the most important control feature of a filter. The filter
resonance increases the volume of the
frequencies located near the cutoff frequencies and suppresses the more
remote frequencies. This sound shaping
feature has a striking effect - especially
when used in conjunction with the low
pass filter: it produces a nasal or honking
type of tone which increases as you turn
the resonance up. Experiment by varying
the RESONANCE setting in the different
operating modes in conjunction with different CUTOFF settings. You will find the
effect that the RESONANCE encoder
achieves is markedly different for the
band stop filter in comparison to the
effect it has on the other filter types: as
the resonance increases, the bandwidth
24 CHAPTER 4
Introduction
of the notch decreases; in other words
more frequencies on both sides of the filter frequency are allowed to pass.
FILTER MODULATION
ACCESS VIRUS RACK 25
Filter Modulation
Of course we don’t want to require you
to execute every sound modification
manually by twiddling encoders. All
kinds of sound modifications in the Virus
can be executed automatically much in
the way of your previous experiments
with the volume controls: The amplifier
envelope can be described as a variable
curve which, depending on the type and
duration of attack, hold and release
data, automatically influences (turns it
up or down) an imaginary volume pot.
Similar procedures are applicable to the
filter frequencies. The FILTERS section
features its own envelope, the structure
of which is identical to the amplifier
envelope.
Like the aforementioned amplifier envelope, the filter envelope is located in the
ENV section. In that section use the
PARAMETER buttons to select FILT ENV.
Much like the amplifier envelope, the filter envelope automatically “rotates” the
CUTOFF encoder. However there is one
significant difference between the two
envelopes. With the amplifier envelope,
you are always dealing with an initial
volume level of 0 because of course you
want absolute silence prior to the beginning of a note. After the RELEASE phase,
it is again highly desirable that your box
is silent. With the filter envelope, the situation is somewhat different: It always
starts at the CUTOFF value that you
determined manually. And it is definitely not always desirable that the filter
frequency is brought to the maximum
level.
Consequently , you need a tool that limits
the effective range of the filter. This is
why we equipped the Virus with a control labeled ENV AMOUNT (short for
Envelope Amount). This encoder is positoned in the Filter section. When the
encoder is turned counter-clockwise to
the far left, the filter has no effect on
the cutoff frequency; the further you
turn the encoder to the right, the
greater the effect the filter envelope has
on the filter frequency. The maximum
level of the envelope may lie outside the
audible range when the filter has
already been partially opened via the
CUTOFF encoder or was manipulated via
other control options. In extreme cases
where the filter is already completely
open, the filter frequency cannot be
increased regardless of how high you set
the ENV AMOUNT.
Go ahead and spend some experimenting with different ENV AMOUNT, CUT-
OFF and RESONANCE settings for the
diverse filter operating modes. Also try
varying the settings for the amplifier
envelope. You will find that with just
these few parameters you are able to
come up with a vast amount of sound
settings. If you are among the many
musicians who are associative listeners,
26 CHAPTER 4
Introduction
you might say many of the settings produce sounds reminiscent of stringedinstruments; some sound picked, plucked
or snapped, others sound bowed.
For your next experiment set the amplifier envelope so that you hear a constant
level when you press and hold a note.
Now deactivate the filter envelope by
setting the ENV AMOUNT to 0. Set Filter1Filter-1 to low pass mode and decrease
the filter frequency until you just barely
hear a muddy signal when you play
notes in the mid-range.
Now play a few higher and lower notes.
Y ou will find that the lower notes have a
greater overtone content, whereas the
higher notes sound muddier and their
volume decreases until the notes are
completely inaudible. You might already
suspect what this is all about: As the
notes are transposed ever lower, more
portions of the signal fall below the cutoff frequency, whereas with the notes
that are transposed ever higher, more
portions of the signal rise above the cutoff frequency and subsequently are suppressed until the root note and the last
audible portion of the signal is silenced.
To avoid this effect - or if desirable, to
amplify it - you have the option of influencing the cutoff frequency via the pitch
of the note, i.e. the note number. The
degree of influence is determined by the
KEY FOLLOW parameter. You'll find this
parameter in the filter section using the
PARAMETER buttons just like you did in
FILTER 1 mode earlier on.
Please note that KEY FOLLOW is a socalled bipolar parameter: Its control
range is not limited to the positive end
of the spectrum (0 to a maximum of
127). Bipolar controls effect negative values as well, in this case from the negative maximum of -64 through 0 an on to
the positive maximum of +63. Consequently, if this value is set to the center
position (0) the pitch of the notes corresponding to the keys on your keyboard
has no effect on the cutoff frequency. If
on the other hand you turn the KEY FOLLOW parameter clockwise towards the
positive control range, you will find that
the filter opens up increasingly as the
pitch increases with higher notes. At
lower notes, the filter closes down again.
If you turn the encoder counter-clockwise towards the negative control range,
the KEY FOLLOW effect is reversed.
With the Virus, you will encounter this
feature - intensity control via a bipolar
parameter - again in conjunction with
other modulation sources and targets.
Now experiment as much as you like
with different KEY FOLLOW settings and
tune the settings via the CUTOFF
encoder. And remember to bring all of
the other parameters you have encountered thus far into play.
THE SATURATION STAGE
ACCESS VIRUS RACK 27
The Saturation Stage
In the signal chain of the Virus, Filter-1 is
followed by a saturation stage. It
enables you to add overtones to the filtered signal via distortion. Locate the
parameter SATURATION in the FILTERS
section.
01111111111111111112
1 SATURATION
Curve Off≤
61111111111111111154
The display will read ”SATURATION
CURVE OFF”, which means exactly what
it says. With the VALUE buttons or the
VALUE encoder, you can now select from
a number of saturation/distortion curves.
Feel free to experiment with the diverse
saturation curves and be sure to vary the
OSC VOL settings. Note how the differ-
ent CUTOFF and RESONANCE settings
influence the saturation curve.
At this point we would like to mention
the OSC VOL parameter, which is next to
the SATURATION parameter. The portion
of the control range from the far left to
the center position (0) determines the
volume of the filter section’s input signal. The portion of the control range
located to the right of the center position does not achieve any increase in volume; it simply intensifies the degree of
saturation or distortion. This effect is
only achieved when you have activated a
saturation curve.
28 CHAPTER 4
Introduction
THE SECOND FILTER
You probably noticed that by a adding a
bit of saturation to the signal you can
come up with a pretty heavy, aggressive
sound - especially with a low filter frequency level and high resonance. You’re
probably thinking these types of sounds
could do with some more filtering. We
had the same idea, which is one of the
reasons why we equipped the Virus with
another filter per voice.
The technical design of this second filter
is identical to the first, so we won’t discuss it in as much detail as we did the
first filter. However, there are few differences in how you handle the second filter:
Only two parameters of the Virus are
allocated exclusively to Filter-2: CUTOFF
2 and FILT 2 MODE.
The RESONANCE, ENV AMOUNT and
KEY FOLLOW parameters can be allocated to either of the two filters or both
simultaneously. Use the FILTER SELECT
menu in the FILTERS section to select the
desired operating mode. For instance, if
you choose FILT2, then the values you set
with RESONANCE, ENV AMOUNT and
KEY FOLLOW apply exclusively to Filter-
2. The corresponding parameters of Filter 1 remain unaffected. On the other
hand, if you choose FILT1+2, the values
that you dial in apply by the same measure to Filters 1 and 2.
In the sound program we are using for
our experiments, both filters are
selected, so that all adjustments to the
given parameters affect both filters.
However, you have yet to actually hear
the effect of Filter-2 on the signal
because it is mixed out of the audible
signal path of the Virus.
Before we get started with our next
experiment, deactivate SATURATION, set
the ENV AMOUNT of the filter envelope
to zero and set CUTOFF 2 to the center
position so that Filter-2 always has the
same cutoff frequency as Filter-1 (we’ll
explain CUTOFF 2 a bit later). Set CUT-
OFF to a medium or middle value and
turn the RESONANCE encoder counterclockwise to the far left to achieve a relatively muddy sound.
Now locate the FILTER BALANCE param-
eter in the FILT menu and rotate it from
the left to the right. You will note the
sound becomes muddier as you turn the
encoder towards the center position and
that the sound is somewhat brighter at
the far right of the control range then at
the far left.
The reason for this effect is that when
you turn the FILTER BALANCE to the far
left, only Filter-1 is audible. When you
rotate the parameter to the right, Filter2 is blended in so that it follows Filter-1
in the signal chain. When you turn the
FILTER BALANCE clockwise, Filter-1 is
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