Oberheim 4-Voice User manual

Oberhetm
INSTRUCTION
MANUAL
FOR THE
4-VOCE
SYNTHESIZER
WITH
PROGRAMMER
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INTRODUCTION
The Oberheim 4-Voice Polyphonic Synthesizer is an
unique and powerful electronic musical instrument, per
mitting up to four notes on the keyboard to be sounded
simultaneously. Each of the four notes triggers a separate
Synthesizer Expander Module (SEM), which is a complete
set of tone generators and modulators required for a syn
thesizer "voice." Other electronic modules provide key
board logic and voice mixing controls. A programmable
memory module is available for storage of selected voice
settings, which can be instantly recalled at the touch of a
button.
This manual assumes the student has had only minimal
experience with synthesizers. This manual also assumes
students are eager to make some sounds as quickly as
possible on their new instrument. The following instruc
tions will lead the student directly through the basic
steps of generating a sound as well as briefly introducing
each of the electronic modules.
Photos and illustrations are on foldout pages at the back
of this manual for easy reference. After enough step-by-
step instructions have been given to set all electronic
modules properly to generate a sound, a more detailed
explanation of each module will follow, with suggestions
on how to use each control to modify the basic sound set
up initially.
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QUICK SETUP
PROCEDURE
While you're reading this manual, plug in and turn on the
machine. This will allow the electronic circuits to stabilize
(about 15 minutes). The photo in Figure 1 shows the
Oberheim 4-Voice with Programmer installed. Units sup
plied without Programmer are fitted with a blank panel in
the Programmer space. The initial instructions will not
deal with the Programmer except to assure it is switched
out of operation until the student is acquainted with the
operation of the other modules.
The electronic modules are numbered in order of impor
tance in setting up a preliminary sound:
1. PROGRAMMER (if installed). Set all switches and
controls as shown in Figure 2.
2. OUTPUT MODULE. Turn all controls to the settings in
dicated in Figure 3. The output from the synthesizer is at
line level and should be patched into the high level input
of an amplifier or mixing console. The PAN controls for
each voice can be used if a stereo amplifier is available. If
only a single amplifier is to be used, be sure the PAN
controls are all fully to one side or the other and the patch
cord to the amplifier is plugged into the corresponding
output. Each of the headphone jacks is for a pair of stereo
headphones. Note that the individual LEVEL controls are
turned almost all the way up. This is necessary if maxi
mum system signal-to-noise ratio is to be obtained.
3. POLYPHONIC KEYBOARD ELECTRONICS. Set all
controls and switches as shown in Figure 4.
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DETAILED MODULE
DESCRIPTION
4. SYNTHESIZER EXPANDER MODULES (SEMs). Set all
controls and switches on all SEMs as shown in Figure 5.
Press a key on the keyboard. The red LED indicator will
light on all SEMs. On SEM #1 (furthest to the left), turn
VCO 1 filter input (knob ®) fully clockwise, and press
note A below middle C on the keyboard. A low pitched
buzzy sound will be heard. Using VCO 1 Frequency con
trol (knob (§)), tune the pitch up to 4-440, using a tuning
fork or piano for reference, or, if not critical, just tune to a
medium frequency pitch. Then turn VCO 2 control (knob
©) fully clockwise. Keeping the A note depressed, tune
VCO 2 Frequency (knob (6)) until its pitch is in unison
with VCO 1. Then turn VCO 2 (knob ©) back to the ver
tical position (OFF).
On SEM #2 turn VC01 (knob ®) clockwise, and tune to
unison with the tone from SEM #1. Then turn off VCO 1
on SEM #2 and turn on VCO 2 and tune it to unison with
the tone from SEM #1. Then turn off VCO 2.
Repeat this procedure with SEMs #3 and #4, always using
the single tone from VC01, SEM #1, as a reference tone.
Now turn on all VCOs (all knobs ® and © fully clock
wise) and press a key on the keyboard. All voices will
sound in unison.
The synthesizer is now set as a single line instrument
with a very big bright sound. Care should be taken to not
disturb the VCO Frequency tuning knobs for the remain-
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der of these initial procedures. From this point the op
tions for experimentation are considerable.
POLYPHONIC KEYBOARD ELECTRONICS (See Figure 4.)
Mounted next to the keyboard itself is the Polyphonic
Keyboard Electronics module, comprised of 3 blocks of
controls adjusting the behavior of the keyboard; MODE,
PORTAMENTO, and TUNE. MODE — This set of controls
determines how the separate voices are selected by the
keyboard. In the preliminary setup above, the UNISON
switch was moved to the ON position, which causes all
SEMs to sound at the same time when only one key is
struck. Moving the UNISON switch to OFF allows several
possibilities of single voice combinations according to
the other switches in the MODE block. This also permits
polyphonic action from the keyboard. Try playing simple
chordal and harmony figures throughout the following
steps to determine the musical qualities of each control
mode. Actuate the switches in the following order:
1. ASSIGNMENT
a. CONT (Continuous) position — A single key actu
ates a single voice, but each successive striking of a key
will step to the SEM to the right. Strike one key
repeatedly and see how the note is sounded from each
SEM in sequence.
b. R/C (Reset/Continous) position — The first key
struck always actuates SEM #1. As long as that key is
held down, any more keys that are struck will actuate the
remaining SEMs in sequence, as in the CONT mode
above.
c. RESET (Reset) position—The first key struck always
actuates SEM #1. Subsequent keys that are struck and
held will actuate the lowest SEM that is not already
actuated.
2. REASSIGN
a. ON — Normal operating position
b. OFF — Normal assignment modes (CONT-R/C-
RST) are overridden. If a note being played was the most
recent note assigned to one or more voices, then that
note is directly assigned to those voices.
3. SPLIT
a. OFF — Normal operating position.
b. ON — Divides the keyboard into two separate
halves, with the division between middle B and C. Each
half controls selected groups of SEMs, with the groups
determined by the 3/1-2/2-1 /3 switch.
4. 3/1-2/2-1/3 SWITCH
a. 3/1 — Lower half of keyboard controls SEMs 1, 2,
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and 3; while the upper half operates on SEM 4 only.
b. 2/2 — Lower half controls SEMs 1 and 2 upper half
controls SEMs 3 and 4.
c. 1 /3 — Lower half controls only SEM 1, upper half
controls all others
5. FREEZE
a. OFF — Normal operating position.
b. ON — Stops the stepping and selecting action of
the ASSIGNMENT switch, locking the keyboard to one
single SEM. To freeze on a given desired SEM, the
FREEZE switch must be set to OFF, and the ASSIGN
MENT switch set to CONT. Press keys repeatedly until
the SEM just before the desired one is selected, then
slide the FREEZE switch to the ON position. All further
keys struck will activate the chosen SEM alone. Switching
FREEZE to OFF restores the synthesizer to normal op
eration.
Each combination of switch positions in the MODE block
causes a different response in keyboard-SEM selection.
The musical possibilities and keyboard fingering tech
niques for each switch position will become apparent to
the player with practice.
PORTAMENTO — Switching Portamento ON causes the
voices to glide from one note to another as successive
notes are played on the keyboard. The Portamento Pot
adjusts the glide time. The switch labeled UPPER-BOTH-
LOWER is effective only when the SPLIT switch in the
MODE block has been engaged, and selects which half of
the keyboard has Portamento.
TUNE — A master PITCH control (VCO) adjusts the pitch
of all SEMs simultaneously, over a continuously variable
range of ±1 octave, with a click-stop in the center posi
tion. In addition to this, a 3 position switch also changes
the pitch of all SEMs ±1 octave. The effects of the switch
and potentiometer are additive, so a pitch shift of ± 2
octaves is possible without touching the SEMs. This is
useful as a "pitch bender" or to tune the synthesizer as a
whole to an exterior reference pitch.
A master Filter control (VCF) adjusts the cutoff frequency
of the filters in all SEMs simultaneously. This can be
used to change the sound of all SEMs at once, or to
"swell" the sound of the entire instrument. This function
can also be controlled by an optional foot pedal.
SYNTHESIZER EXPANDER MODULES (SEMs) (See Fig
ure 6)
The SEMs are the sound generators, or voice modules, for
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the synthesizer. A separate manual is available for a com
plete description of the SEM, but a short discussion of
general synthesizer terms and principles as applied to the
SEMs and the 4-voice is appropriate at this time.
In the first section of this manual the controls on each
SEM were set for the simplest sound possible. Each was
tuned to the same pitch to best use the polyphonic
capabilities of the machine. For the remainder of this
manual it will be assumed that these initial pitch settings
for each SEM remain the same.
The other controls on the SEMs affect the quality of the
sound generated in terms of timbre, duration, percussive-
ness, vibrato, and volume. All of these sound qualities
are the results of the interactions between only two basic
sound quantities: frequency (pitch information) and level
(loudness information). The controls on the SEMs gener
ate and manipulate these quantities to produce a desired
quality.
An important concept to understand in using any synthe
sizer is the difference between audio (or sound) signals
and control signals.
The audio signals are generated and modulated by 3 basic
electronic elements which are controlled by either manual
adjustments or by electronic control signals from control
sources. The 3 electronic elements which directly manip
ulate frequency and level are:
1. The VOLTAGE CONTROLLED OSCILLATOR (VCO). A
tone generator whose fundamental frequency (or pitch) is
determined by an electrical signal (or voltage) from a
control source (keyboard, ribbon controller, potentiom
eter, etc.). The quality or timbre of this tone depends
upon the waveform generated (Sawtooth, Square, or
Pulse). Different waveforms are characterized by different
distributions of harmonic frequencies superimposed on
the fundamental frequency.
2. The VOLTAGE CONTROLLED FILTER (VCF). A filter is
an element that can change the relative strengths of the
different frequencies contained in any given waveform. A
LOW PASS filter pases low frequencies unaltered, but
above a certain frequency (called the CUTOFF FRE-
QENCY) the tones are reduced in strength. Adjusting the
cutoff frequency in effect adjusts the amount of filtering.
Filtering not only alters the frequency balance of a
waveform, but also alters the relative loudness or volume
of the signal. For example, a low pass filter set to a very
low cutoff frequency will not pass much signal at all.
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In a voltage controlled filter, the cutoff frequency is
controlled by an electrical signal from a control source,
as with the VCO.
3. The VOLTAGE CONTROLLED AMPLIFIER (VCA). A
loudness or volume control which is proportional to an
electrical signal from a control source, as with the VCO
and VCF. The VCA, in itself, has no frequency dependent
characteristics and affects all frequencies equally.
The dynamic qualities of sounds are created and adjusted
by modulating frequency and level with the above 3
voltage controlled devices. A fourth electronic element is
necessary to generate a time varying Control Signal, or
ENVELOPE which may be connected to the control inputs
of any of the above devices. This fourth element is known
as the ENVELOPE GENERATOR. When triggered by the
keyboard of the two basic quantities of frequency and
level are manipulated with respect to TIME, creating the
sound qualities of duration, stacatto, legato, vocalization,
etc.
Refer to Figure 6 for the location of the controls on the
SEM. In the diagram they are grouped by similar func
tions for easy understanding.
1a, 2a — FREQUENCY — These are the manual tuning
controls for VCO 1 and VCO 2 respectively. The lower
flanged portion of each knob is for coarse tuning, and the
upper part of the knob is a vernier fine tuner.
1b , 2b — MODULATION — The three position switch
selects one of three control signals, indicated on the
panel, to be routed through the rotary pot just above the
switch. If this knob is rotated to the right, the selected
control voltage will affect the VCO pulse width. If this
knob is rotated to the left, the selected control voltage
will affect the VCO frequency. If the knob is left in its
vertical position (as in the drawing), the selected control
voltage will have no effect on the VCO at all.
1c, 2c — PULSE WIDTH — These are manual pulse
width controls for the two oscillators. In the vertical posi
tion, as in the diagram, the pulse produced in each cycle
is exactly one-half as long as the cycle itself; such a
signal is called a Square Wave. As the knob is rotated in
either direction from vertical, the pulse becomes wider (to
the right) or narrower (left).
3 — SYNC — When this switch is moved to the right
VCO 2 is synchronized to the frequency of VC01. VC01
is not affected by this switch, but VCO 2, when it is
"sync'd" to VCO 1, can produce only harmonics of the
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frequency to which VCO 1 is set. When the switch is off
the two oscillators are completely independent.
4 — VCF — These are the three manual controls for the
filter. The smaller knob at the lower right determines
whether the filter will act as a bandpass filter (at the click-
stop position labelled "BP"), lowpass filter (immediately
clockwise from the click-stop, labelled "LP"), notch filter
(vertical, at the word "notch"), or highpass filter (extreme
clockwise, labelled "HP"). Do not try to turn the knob
clockwise past the highpass stop.
The FREQUENCY control at the upper left determines the
cutoff frequency of the filter.
The large single knob labelled RESONANCE determines
the filter resonance at its cutoff frequency. When this
knob is fully counterclockwise the filter resonance is at a
minimum; as it is rotated to the right the resonance in
creases. RESONANCE is a term for the gain of the filter at
or near its cutoff frequency. At maximum resonance, for
example, the filter amplifies strongly any components of
the input signal that lie within a semitone or so of the
cutoff frequency, but virtually ignores components that
are not near the cutoff frequency. In other words, a pro
nounced "peak" occurs in the filter frequency response as
the resonance is increased, which grows higher in ampli
tude as it grows narrower in width. When the center of
this peak is exactly at the frequency of an audio input to
the filter, a relatively weak signal can drive the filter to
produce a very strong output.
5 — MODULATION — The switch selects one of the
three sources for a control input to the filter. The left and
right positions are self-explanatory; the center position
allows control by the Programmer, if installed. The knob
is a "reversible attenuator" for the control signal selected;
in the diagram no signal will pass through to have any
effect on the VCF cutoff frequency. As the knob is rotated
to the right, the selected control signal affects the VCF
directly; as the knob is rotated to the left, the signal
affects the VCF inversely, that is, a positive voltage drives
the VCF frequency down rather than up.
6 — AUDIO INPUT SELECTOR/ATTENUATORS for the
VCF. In the illustrated positions, they are all OFF. Unless
at least one of these is "open," i.e., rotated either to the
left or to the right, the module will produce no sound
regardless of any of the other settings anywhere on the
module panel.
The first knob on the left, labelled VCO 1, selects either
the sawtooth or pulse signals from VCO 1 as an audio
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input to the VCF. The second knob does the same for
signals from VCO 2. The third knob is for adding signals
from external sources.
Signals from the two oscillators and exterior source may
be mixed in various proportions by opening all three of
the input attenuators at the same time.
7 — ENVELOPE GENERATOR 1 — The first two knobs
set two time constants: the attack time constant is the
amount of time required for the ENV 1 output voltage to
rise from 0 to maximum, and the decay time constant is
the amount of time required for the ENV 1 output to
fall ...
. . . from maximum to the sustain level set by the third
knob, and
. . . from this sustain level back to 0.
The third knob determines, not a time constant, but a
voltage constant. This constant is the level at which the
ENV 1 output will be sustained (hence the label) for as
long as a GATE signal is present at the gate input of the
envelope generator (as long as a key is held down).
8 — ENVELOPE GENERATOR 2 — This second gener
ator has the same controls as the first.
NOTE: As you can see by examining the MODULATION
switches for the two VCOs and the VCF, ENV 1 can be
used to control VC01, and ENV 2 can be used to control
VCO 2 and/or the VCF. In ordinary keyboard use, ENV 1
will be used only to control the VCA, and ENV 2 will be
used only to control the VCF.
9 — LFO — Low Frequency Oscillator. The output of
this oscillator is a sine wave and is available to control
the VCOs and/or the VCF through the voltage select
switches described in 1b, 2b, and 5 above. The frequency
of the LFO is set by the knob indicated here.
10 — LED indicator — This light indicates the presence
of a GATE signal at the input to two ENVELOPE
GENERATORS.
THE PROGRAMMER (See Figure 2.)
Some experimenting with the controls on the SEMs will
acquaint the student with the range of possibilities for
different kinds of sounds. At the same time it becomes
obvious that setting all the controls on all the SEMs is a
time consuming and sometimes confusing process. The
Programmer provides certain controls which can affect all
SEMs collectively (as well as individually), thereby sim
plifying setup procedures to achieve a desired sound. The
Programmer also is blessed with an electronic MEMORY,
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which can store up to 16 sets of these programmed
settings, which can be recalled by pressing a button.
To utilize the Programmer, set all SEM controls as shown
in Figure 7, except for the VCO frequency pots. This de
activates the interior control sources and connects the
SEMs to the appropriate control sources in the Program
mer.
Notice that the slide switches labelled "1-8" are all in the
MANUAL position. In this position, the Programmer
knobs affect the SEMs directly. When a given switch is
set to MEMORY, then data from the memory affects the
associated SEM.
Make sure that the Programmer controls are still set as in
Figure 2. Notice that the groups of control knobs in the
upper half of the module resemble similar groups in the
SEMs. In fact, the functions of these groups in the Pro
grammer either replace or are added to the corresponding
group functions in the SEMs. Let's take them one at a
time.
1. VCO 1 and VCO 2 FREQUENCY — These are master
VCO 1 and 2 PITCH controls and affect all SEMs simul
taneously. This is in addition to the master VCO Tune
control on the Keyboard Electronics module. Notice, how
ever, that the VCO 1 and 2 controls on the Programmer
change the pitch of their respective oscillators in half step
increments, rather than continuously. This QUANTIZING
effect makes relative tuning of the oscillators much
easier. For example, see how easy it is to tune all VC01 's
up on octave. Then tune all VCO 2's up one octave, then
up an additional 5th, then up to a second octave above
the original. Quantizing makes it easy. Take note, though,
that the frequency control knobs on each individual SEM
are still the primary tuning controls for each voice. They
should not be disturbed from their original unison setting
described earlier in this manual.
2. VCF FRECHJENCY — This is a master VCF frequency
control, and its effect is additive to the master VCF con
trol on the Keyboard Electronics module (which should be
set nominally at 12 O'clock) as well as the individual VCF
controls on the SEMs (set fully counterclockwise).
3. VCF MODULATION—This controls the amount of filter
modulation from the ENV 2 block on the Programmer.
Note that there is no master RESONANCE control on the
Programmer, nor is there a master BP/LP/Notch/HP con
trol. These adjustments must be made on each SEM
individually, and are not programmable functions.
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4. ENV 1 and 2. These voltage-controlled ENVELOPE
GENERATORS which replace the corresponding Envelope
Generators in the SEMs. ENV 1's controls the VCAs in the
SEMs directly, and ENV 2's control the VCFs.
5. VIBRATO FREQUENCY and AMOUNT — These con
trols are more convenient to use than the function of the
LFO in the SEMs. Frequency is simply the speed of
vibrato, and Amount controls how much modulation is
added to the pitch controls to each SEM.
The switches in the lower half of the module pertain to
entering into and recalling from MEMORY the settings of
the programmable controls. Before attempting to use
these switches, the student is advised to experiment
freely with the programming controls to become familiar
with their capabilities.
Eventually a group of program control settings will be
found which generate a sound the student will wish to
enter into the Programmer memory.
The bottom row of lighted pushbuttons, (PROGRAM
SELECT) designates a memory slot, or address. 16 mem
ory addresses are available, and they are selected by
means of the lighted pushbuttons and the MEMORY
SELECT slide switch to the left of the pushbuttons.
1. With MEMORY SELECT in the 1-8 position, press
PROGRAM SELECT switch #1.
2. With the left hand, pull down the first ("1") spring
loaded slide switch above the pushbuttons to the WRITE
position and hold it there against the spring tension,
while with the right hand the WRITE slide switch is also
actuated. This enters the program control settings for the
first voice into the memory.
Repeat the process with slide switches #2, 3, and 4. Both
hands are required to perform this as a safety feature, to
avoid accidental erasure of a programmed setting.
3. Move the 4 slide switches to the MEMORY position.
The Programmer is now controlling the SEMs according
to the control settings in the Memory. The control knobs
on the Programmer are no longer functional. In fact, the
manual controls are only effective with the slide switches
in the MANUAL Position, and in the WRITE position when
their settings are entered into the memory.
Each of the 8 MEMORY/MANUAL/WRITE switches per
tains to only one SEM, or voice. In the 4-Voice, only the
first 4 switches are active. Switches 5-8 are for additional
voices if they are installed.
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The programmed settings for all voices are the same in
the above example, that is, identical Programmer controls
were applied to all 4 voices when the settings were
entered into the memory. But it is possible (and often
desirable to have different programmed settings for each
voice entered into a single memory address. Here's how:
1. Move all Programmer slide switches to MANUAL.
Press PROGRAM SELECT Pushbutton #2.
2. Using the Keyboard Electronics module, freeze the
synthesizer on SEM #1.
3. Adjust the Programmer controls for an unique and
recognizable sound from SEM # 1.
4. Pull down MEMORY/MANUAL/WRITE switch #1 to
the WRITE position and hold while the other hand actu
ates the WRITE switch. Then move the first switch to
MEMORY.
5. Using the Keyboard Electronics again, step and freeze
the synthesizer onto SEM #2.
6. Readjust the Programmer controls to achieve a different
sound on SEM #2 from that set up previously on SEM #1.
7. Pull down MEMORY/MANUAL/WRITE switch #2 to
WRITE and enter into the memory.
8. Repeat steps 5, 6, and 7 for SEM #3, and again for
SEM
9. Using the Keyboard Electronics, unfreeze the synthe
sizer and play in a polyphonic mode. Each voice will be
heard to have its own distinctive preprogrammed sound.
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ILLUSTRATIONS
1. Photo — Oberhelm 4-Voice Synthesizer with
Programmer
2. Panel Facsimile — Programmer (Initial Setup)
3. Panel Facsimile — Output Module (Initial Setup)
4. Panel Facsimile — Polyphonic Keyboard Electronics
(Setup)
5. Panel Facsimile — SEM (Initial Setup)
6. Panel Facsimile — SEM (General Description)
7. Panel Facsimile — SEM ( For use with Programmer)
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FIGURE 2
POLYPHONIC SYNTHESIZER PROGRAMMER
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FREQUENCY
6
FREQUENCY
O
FREQUENCY
VCF
FREQUENCY
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MODUl ATION
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ENV
I ATTACK Dl.C AY SUSTAIN |
I VIBRATO
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ENV 2
ATTACK IJt. CAY SUSTAIN |
AMOUNT
8
MLMORY
MANUAl
WRITE
S § B § § § § B
MEMORY
MANUAL
WRITE
Ml MOKY I
SI I I C T
1 9 10
y.
PROGRAM SELECT
l|2|3|4|5|6|718
OBERHEIM ELECTRONICS. INC.
THE PROGRAMMER
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OUTPUT MODULE
r
L
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V
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s-—"v
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OBERHEIM ELECTRONICS, INC.
THE OUTPUT MODULE
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FIGURE 4
r
mode
REASSIGN UNISON ( SPLIT
ON ON ON
ASSIGNMENT
CONT. R/C RESET
FREEZE
ON 3-1 2-2 1-3
j
r~
PORTAMENTO
UPPER
ON
y o
BOTH
i "V^ ^*r LUWLK J
LOWER
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TUNE
VCF
UP OCT
VCO
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OBERHEIM ELECTRONICS. INC.
KEYBOARD ELECTRONICS MODULE
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FIGURE 5
r
VCO1
FREQUENCY
SYNTHESIZER EXPANDER MODULE
r
I MODULATION
SYNC
VCO2
FREQUENCY
MODULATION
FREQ PW
ENV EXT LFO
PULSE WIDTH
ON
FREQ PW
ENV EXT LFO
2
j PULSE WIDTH I
i 10% 90% j i 10% 90% I
SAW PUL SAW PUL*M ** 2
j ATTACK
ENVI(vca)
DECAY SUSTAIN
ENV 2
ATTACK DECAY SUSTAIN
OBERHEIM ELECTRONICS. INC
SYNTHESIZER EXPANDER MODULE (Initial Setup)
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FIGURE 6
r
SYNTHESIZER EXPANDER MODULE
r
VENV2
AT TACK A r% 1 DECAY SUSTAIN
ATTACK^ _\ DECAY SUSTAIN
OBERHEIM l|IOlRONlcs INC
SYNTHESIZER EXPANDER MODULE (General)
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FIGURE 7
SYNTHESIZER EXPANDER MODULE
r
saw mi saw pul ** i n i
r
ENVI(vca)
ATTACK DECAY SUSTAIN
ENV2
ATTACK DECAY SUSTAIN
VCA
J
on/I
OBERHEIM ELECTRONICS. INC.
SYNTHESIZER EXPANDER MODULE (For use with Programmer)
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