SequentialSystems PRO-ONE 100 User manual

PRO-ONE SYNTHESIZER
OPERATION MANUAL
by Stanley Jungleib
MODEL 100
S/N 1 and up
Sequential Circuits, Inc.
3051 North 1st Street
San Jose, CA 95134
[phone]

About the Pro-One
The Pro-One is a monophonic (one-voice) keyboard synthesizer. Its principal sound
sources are two voltage-controlled oscillators (VCOs), referred to as OSC A and
OSC B. OSC A, OSC B, and a white noise source can be mixed into the resonant
low-pass filter (VCF). The filter modifies the voice timbre under control of its
four-stage envelope generator. The filter may also serve as a sound source. This
stage is followed by a voltage-controlled amplifier (VCA), which shapes the voice
amplitude also under control of a four-stage envelope generator. The ,keyboard
provides frequency control voltage (K YBD CV) for the oscillators and filter, and
generates a GATE which controls the envelope generators.
In addition to this basic voice, the Pro-One has extensive modulation prov1s10ns.
Three modulation sources are available: the filter envelope generator (FILT ENV),
OSC B,
and a separate low-frequency oscillator (LFO). Each can be mixed and
routed for either DIRECT or WHEEL-controlled modulation of five destinations:
OSC A frequency (FREQ), OSC A pulse-width (PW), OSC B FREQ, OSC B PW, and
filter frequency (FILTER).
This
complement of analog synthesizer modules and the routings provided for their
interconnection have been well-proven in the Pro-One's ancestors, the Prophet-5
and Prophet-10 polyphonic synthesizers. Besides allowing the synthesist to play up
to five or ten notes at one time, these two instruments contain microcomputers
which program all the control settings comprising a sound. The Pro-One is neither
preset nor programmable: you always "patch" the precise sound you want with the
knobs and switches on the control panel. But the Pro-One voice itself is identical to
a single Prophet voice, so it is capable of as much range and expression.
Possessing the Prophet's sound and all standard monophonic synthesizer features,
the Pro-One's own microcomputer makes possible innovations unheard of on a low-
cost synthesizer; a 40-note sequencer, an arpeggiator, keyboard modes such as -
single- or multiple- triggering, and the unique automatic glide feature. Arr audio
input with preamplifier and automatic GATE generator allows synthesizer process-
ing of low-level inputs such as a microphone or electric guitar. The audio output
can drive a monophonic or stereo amplifier, or stereo headphones. Of special
interest to computer enthusiasts, the Pro-One readily interfaces for control by an
external microcomputer.
This manual contains all the information you'll need to fully enjoy this outstanding
instrument.
CMlOO 2/81 3

Table of Contents
About the Pro-One 3
SECTION 1 BASIC OPERATION
1-0
INTRODUCTION 6
1-1 CONNECTIONS
6
1-2
PLAYING 8
1-3
KEYBOARD CONTROLS 9
1-4
MODE 10
1-5
ARPEGGIATE 10
1-6
SEQUENCER 11
1-7
IN CASE OF DIFFICULTY 12
SECTION 2 FRONT PANEL
2-0
INTRODUCTION
13
2-1
THE VOICE
13
2-2
OSCILLATOR A
15
2-3
OSCILLATOR B
16
2-4
GLIDE
17
2-5 MIXER 17
2-6
FILTER
18
2-7
AMPLIFIER 20
2-8
MODULATION
20
SECTION 3 BACK PANEL
3-0
INTRODUCTION
23
3-1
AUDIO IN
23
3-2
FILTER CV IN
23
3-3
GATE OUT
24
3-4
CV OUT
24
3-5
GATE/CLK IN
24
3-6
CVIN 24
4
CMlOO 2/81

1
SECTION 4 ROUTINE MAINTENANCE
4-0
INTRODUCTION
25
4-1
CLEANING
25
4-2 USER TRIM
25
4-3 OPENING
28
4-4
FUSE
28
SECTION 5 SERVICE
5-0
INTRODUCTION
29
5-1
REMOVING PCB
29
5-2
DAC SCALE
29
5-3 TUNING 30
5-4
AMPLIFIER BALANCE
33
5-5 KEY
CONTACTS
33
5-6 DIGITAL
INTERFACE
34
5-7
AUTHORIZED SERVICE CENTERS
35
SECTION 6 SELECTED BIBLIOGRAPHY
SECTION 7 FACTORY PATCHES
SECTION 8 PANEL BLANKS
y'
CMlOO 2/81 5

l
l
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SECTION 1
BASIC OPERATION
1-0 INTRODUCTION
This section contains instructions for Pro-One set-up and basic operation. After
unpacking, read paragraph 1-1 and connect the instrument as described. To quickly
learn how to use the Pro-One, read also paragraph 1-2. This explains use of the
factory-provided patch diagrams (Section 7). Additional performance information
on the keyboard modes, triggering, the arpeggiator, and the sequencer follows
(paragraphs 1-3 through 1-6).
The Pro-One synthesizer offers extraordinary capabilities for spontaneous control
of pitch, timbre, and loudness. To exploit these capabilities fully, learn as much as
you can about it with this manual and the books listed in Section 6. Additional
references can be obtained from the more extensive bibliographies contained in the
sources listed. Thus prepared, you will no doubt create many interesting sounds. Be
advised that the best patches tend to disappear if not documented. Panel blanks for
this purpose are provided at the back of this manual.
Remember the Pro-One is a sophisticated instrument. It should be handled with as
much care as you would give a violin. Shock or vibration can damage the keyboard,
wheels, knobs, and can loosen socketed integrated circuits (ICs). If you expect to
transport the Pro-One regularly, we recommend that you invest in a professional
"flight" case for it. These are made.by several manufacturers and should be carried
by your music dealer. If you can't find a case, please contact our Sales Department.
1-1 CONNECTIONS
The Pro-One has a switch on its back panel for selecting between a 115- or 230-Vac
power source. Pro-Ones shipped in the U.S. and to Japan are usually switched to
115V, and those destined for Europe are usually switched to 230V. WARNING:
Check this switch and set to match your line voltage before plugging the
instrument in. Don't change this switch when the line cord is connected. If you do
switch the line voltage selector, you will have to change the fuse also. For
directions, see paragraph 4-4.
As with most electronic equipment, the Pro-One comes with a three-prong power
plug to insure safe grounding with other equipment. The ground prong is connected
directly to the metal chassis. It is up to you to check the power and ground
interconnections of the Pro-One and all other instruments and equipment you use
to prevent potentially lethal shocks. As you probably know, many older buildings
and clubs are notorious for their poor quality AC wiring. We therefore urge you to
use one of the several "ground-checking" devices available on the market to verify
AC connections.
6 CM 100
2/81

Because of the AC ground, a "ground loop" will of ten be created when the audio
cable is connected between the Pro-One and its amplifier. As a result, low-level
hum may occur. Defeating the AC ground with a two-prong adapter will usually
defeat the hum but this practice can set up a shock hazard between the units. The
hum level will depend on how the two units are connected to the AC. For minimal
hum, use
the same AC outlet for the Pro-One and its amplifier. This should reduce
the hum to an acceptable level.
In short, we recommend the following steps when connecting the Pro-One:
1. Plug the Pro-One into a three-prong outlet. Don't defeat the AC ground.
2.
Plug all other equipment such as amplifiers, volume pedals, and effects
devices into the same outlet. Don't overload. When in doubt, consult an
electrician.
3. Verify all equipment grounding with a ground tester.
Sequential Circuits, Inc. is not responsible for any equipment failure due to
incorrect AC power connections, and is not liable for any personal injury due to
electrical shocks as a result of poor grounding.
This is
an excellent time to think about your amplifier and speaker system. By
converting the synthesizer's electrical output to the potent vibrations you hear,
your sound system becomes part of the instrument. Of course you can use anything
you like. But if your speakers are muddy and weak, so will be your sound. Using
your home stereo will generally give you good high-frequency range, but if you go
this route be careful. The Pro-One has much more dynamic range than the typical
stereo source. It can generate powerful transients which can damage component
speakers if the volume is set too high. Therefore, you might consider using
amplifiers and speakers specifically designed for electronic instruments.
The AUDIO OUT is a standard stereo phone jack, but it accepts a stereo or mono
plug.
For single-channel use with instrument amplifiers, a mono cable with mono
plugs
at both ends should suffice. For playing through both channels of a stereo
amplifier, you will probably need a stereo cable with a stereo phone plug at one end~
and two phono plugs at the other. These will connect to the amplifier AUX, or
TAPE inputs. (To protect speakers, it is customary to switch off the amplifier when
making
these connections.)
Stereo headphones can be plugged directly into the AUDIO OUT jack. The
headphones should
have a minimum impedance of 600 Ohms.
When power and audio output connections have been made, first switch Pro-One
power on with back panel switch, then switch amplifier power on. If you think the
Pro-One may not be operating, see paragraph 1-7.
For other back panel connections, see Section 3.
CMlOO 2/81 7

1-2 PLAYING
At this point (after unpacking) the Pro-One is probably not ready to play. As a
synthesizer, the knobs and switches on the control panel have to be set purposeful-
ly. Certain minimum conditions such as mixer volumes, filter cutoff frequency and
envelope sustain level need to be established. You can learn about the controls by
reading Section 2. But if you are like most people, you'll want to play the Pro-One
before studying it. To do this, simply turn to Section 8 and select a factory patch.
Set the Pro-One's controls as closely as possible to the diagram while playing on
the keyboard. Patching is a fine art: be patient. Note that there is inherent error in
the diagrams and some degree of subjective preference as to exactly where the
knobs should be set. For completeness, all control positions are diagrammed even
though some may have no effect (for example, PULSE WIDTH when the pulse wave
shape is switched off.) When oscillator intervals are harmonically related, the
FREQUENCY knob(s) will have to be tuned by ear, usually for a minimum of
"beating."
PITCH
WHEEL
MOD CO
WHEEL
Figure 1-0
WHEELS and KEYBOARD
8
BO Cl
Bl
C2 B2
C3
CMlOO 2/81

The MOD and PITCH wheels are at the left of the keyboard, as shown in Figure 1-
0. The MOD wheel sets the modulation level. When not in use the wheel is left
"down" and no modulation will occur. When the wheel is advanced fully "up,"
modulation is maximum. The PITCH wheel is normally left in its center-detent
position, from which it is possible to simultaneously "bend" OSC A and OSC B pitch
up or down by about a fifth. An integral part of playing is using the wheels and the
module controls (e.g. GLIDE and FILTER ENVELOPE AMOUNT) for expression
through dynamic and timbral variations.
The diagrams don't indicate VOLUME and MASTER TUNE knob settings because
these are set as required. VOLUME, of course, sets the audio output level to the
amplifier or headphones. For optimum signal-to-noise ratio, the Pro-One's
VOLUME knob should be set as high as possible (without overdriving your amplifier
or speakers, of course). MASTER TUNE simultaneously adjusts OSC A and OSC B
pitch over a four-semitone range. It is used to easily tune the Pro-One to another
instrument, such as a piano. Once set, MASTER TUNE is not usually adjusted
during performance. If no other instrument is in use, the MASTER TUNE knob
should
be centered.
Other methods of controlling the Pro-One are possible via the back panel. For more
information, see Section 3.
1-3 KEYBOARD CONTROLS
You can't play chords on a Pro-One for the same reason you can't play chords on a
clarinet or trumpet: they are all monophonic instruments. So you will most often be
playing solo lines on the keyboard. But you have some options as to how the keys
are played, and when you can play more than one key. These are the keyboard
controls, with which you can experiment on almost any patch. The keyboard
controls include the arpeggiator and sequencer, which are keyboard "memory"
devices of great utility in performance. And by freeing both hands from the
keyboard, these tools aid your learning how to patch.
r
LFO/CLOCK
SEQUENCER
ARPEGGIATE
MODE
·~·
A
/\
rL
SEQ 1 RECORD
UP
RE TRIG
REPEAT/EXT
ORONE
2 -8
B B B
§OFF
a
§OFF
B B BGATE
1
\'9
0
10
-SHAPE--
SEQ 2
PLAY
UP/DOWN
NORMAL NORMAL
OFF
FREQUENCY
Figure 1-1
KEYBOARD CONTROLS
CMlOO 2/81 9

To understand the keyboard controls you first need to know that inside the Pro-One
a GA TE signal is produced when a key is played, which controls the envelope
generators. The initial appearance of the GATE "triggers" the envelope generators
to proceed through their ATTACK and DECAY periods. After the ATTACK and
DECAY periods set for each envelope generator have elapsed, it will produce a
steady control voltage (CV) at the level set by the SUSTAIN knob for as long as the
GATE is present. When the GATE goes off, indicating the key has been released,
the envelope generator output voltage decays to zero at a rate set by the
RELEASE knob. (For more information, see paragraph 2-6.)
1-4 MODE
The MODE module contains a GATE indicator light-emitting diode (LED) to clarify
operation in the various keyboard modes. And it eases adjustment of the external
audio input GATE generator. (For more information, see paragraph 3-1.)
The NORMAL-RETRIG switch selects the envelope generator triggering mode.
NORMAL means low-note priority with single triggering. That is, if you play more
than one note at a time, the lowest note on the keyboard will be the one you will
hear. Furthermore, all keys must be completely released before a new GATE
(initiating new envelopes) will be produced. When switched to RETRIG (retriggering
mode) a GATE will be produced whenever a' new key is hit, regardless of its
position on the keyboard or of the number of keys simultaneously held. In other
words, the last key played will be the one you hear.
When switched up, the NORMAL-REPEAT /EXT switch repeatedly gates the enve-
lope generators at a rate set by the LFO/CLOCK FREQUENCY knob. Activating
this switch also enables the back-panel GATE/CLK IN input. When an external
GATE is plugged into this jack, the LFO/CLOCK is overridden and the envelopes
will be gated by the external GATE/CLK IN input. This signal will also clock
(advance) the arpeggiator or sequencer (see below).
The DRONE switch simply forces the GATE on, holding the envelope generators at
their SUSTAIN level. DRONE overrides REPEAT. With REPEAT or DRONE on,
hitting keys will not retrigger the envelope generators, but it will change the
frequency of both oscillators (providing OSC B KYBD is switched up), and of the
FILTER, (providing the KEYBOARD AMOUNT knob is advanced).
1-5 ARPEGGIATE
The arpeggiator automatically sequences between any depressed keys either UP
(ascending only), or UP/DOWN (ascending and descending) the keyboard. ARPEG-
GIATE speed is set by the LFO/CLOCK FREQUENCY knob. To arpeggiate, select
UP/DOWN or UP and hold the desired keys. There is no limit to the number of keys
which can be arpeggiated. Set LFO/CLOCK FREQUENCY as you wish. To stop the
arpeggiator, return the direction switch to OFF.
10
CM 100 2/81

The arpeggiator can be "latched," which means it continues to play keys even when
you remove your hand(s) from the keyboard. To latch the arpeggiator, first turn it
on, hold the desired keys, then switch SEQUENCER PLAY-RECORD to RECORD.
After all held keys have sounded at least once, you can remove your hand--the Pro-
One will continue to arpeggiate. To "unlatch" the arpeggiator, switch from
RECORD to PLAY.
You can't change directions in the middle of an arpeggiate sequence. If you do
switch from UP to UP/DOWN or vice versa, the Pro-One will wait until all held or
latched notes have been arpeggiated in one direction before it recognizes the
change of direction.
While the arpeggiator is latched, you can hold additional keys which will sound as
part of the arpeggiate sequence only as long as they are held. These additional
notes remain "unlatched." Note: even though the SEQUENCER RECORD switch is
used
to latch the arpeggiator, the SEQUENCER memory banks are not affected
(see also paragraph 1-6).
1-6 SEQUENCER
The Pro-One's 40-note sequencer allows you to record themes, riffs, walking bass
lines or the like. All sequenced notes and rests are single-step recorded with the
same duration. (Unlike "real-time" sequencers like our Model 800 and Model 1015,
the Pro-One sequencer does not record notes of varying duration.) No matter how
unevenly you record a Pro-One sequence, it will always play-back with all notes
and rests evenly timed. The playback speed is controlled by the LFO/CLOCK
FREQUENCY knob. The 40-note memory capacity is divisible in any proportion
between two "banks," referred to as SEQ 1 and SEQ 2.
When
the Pro-One is switched on, its sequencer is preprogrammed with a 20-note
ascending scale in SEQ 1 and a 20-note descending scale in SEQ 2. Provided the
PLAY-RECORD switch is down, you can now hear these two sequences by just
switching the bank selector to SEQ 1 or SEQ 2.
To
record, first switch PLAY-RECORD up, then select SEQ 1 or SEQ 2~ Simply
play the notes on the keyboard, inserting rests by switching from RECORD to
PLAY, then back to RECORD. Rhythmic variations can only be arranged by
inserting rests. All notes must be played detached, as you would in NORMAL--as
opposed to RETRIG--mode (see paragraph 1-4). A sequence cannot begin with a
rest.
Be sure to not exceed the 40-note capacity, or the sequence will be destroyed.
When the 4lst note or rest is entered, the first 40 notes are cleared. The bank then
contains one note.
When finished recording, first switch the bank selector OFF, then switch from
RECORD to PLAY.
When switched to PLAY, the Pro-One will sequence the notes and rests you
recorded in the selected bank at a rate set by the LFO/CLOCK FREQUENCY knob.
(Or, the sequencer can be advanced by pulses at the GA TE/CLK IN jack. See
Section 3.) The sequence will play continuously ("loop") until the bank selector is
switched OFF.
CM 100 2/81
11

When both memory banks are being used, care must also be taken to not exceed the
l/.0-note limit. The Pro-One assigns memory priority to the bank which is currently
being recorded, and will "steal" notes from the other bank once the 4-0 total note
limit is reached. For example, if SEQ l already has a 25-note sequence recorded in
it, you will erase SEQ l if you attempt to record more than 15 notes in SEQ 2. (SEQ
2
then retains the additional notes.)
As shown in Figure 1-0, the Pro-One's keys are named CO, CllO, DO ... through C3.
In playback, the entire sequence can be transposed over a two-octave range by just
hitting a key between CO and C2. The transposition is equal to the interval between
Cl and the key played. For example, to transpose down a fifth, hit FO. To transpose
up a major seventh from the original key, hit Bl. To transpose back to the original
key, hit Cl.
The sequencer memory banks will retain their contents until power is switched off
(or interrupted). Any transposition is cleared as well.
1-7 IN CASE OF DIFFICULTY
To check that the Pro-One is receiving power, switch DRONE on. The GA TE LED
should
light. If it doesn't, either power is not reaching the unit or the internal fuse
has blown. First check the power source by plugging in other equipment. Examine
the Pro-One's power cable for damage. To chec;::k fuse, see Section l/..
If the GATE LED lights but no sound can be obtained, check the front panel
controls--including VOLUME--carefully against a factory patch in Section 7.
If still no sound can be heard, try substituting the audio output cable with one
known to be good.
Check your amplifier by trying a high-level audio input such as another synthesizer
or an FM tuner.
Check headphones by trying them with a standard headphone output from a stere0
amplifier.
If the SEQUENCER won't record, check that you didn't leave ARPEGGIATE on.
If you are having trouble recording or playing sequences or arpeggiating, it may
help to reset the internal microcomputer by switching power off then back on after
a moment. Note this will erase any sequences which you have recorded.
Other problems may be rectified by "user trim" procedures given under Section 4-,
Routine Maintenance.
Authorized U.S. and Canadian Service Centers are listed in Section 5. If these
locations are too inconvenient, please contact the factory Service Department.
12 CM100 2/81

SECTION 2
FRONT PANEL
2-0 INTRODUCTION
This section explains the "modules" outlined on the front panel. The front panel is
divided
into "voice" and "modulation" sections. The basic voice is discussed first,
then modulation. Signal flow, the alternatives of each switch, and ranges of each
knob are described.
2-1 THE VOICE
As an analog voltage-controlled synthesizer voice, the Pro-One can be understood
at its most general level in terms of three functions: audio waveshape generation,
modification, and control.
Figure 2-0 diagrams voice signal flow. As mentioned above (About the Pro-One),
OSC A and OSC B are the principal sound generators. They are supplemented by
the NOISE source (for unpitched sounds such as "surf") or an external audio input
which bypasses the NOISE source. (To learn how to use the external audio input,
see paragraph 3-1.)
The MIXER is a modifier. It sets OSC A, OSC B, and NOISE (or EXT audio) levels
and combines them into one signal which enters the FILTER. The FILTER also
functions normally as a modifier, by cutting off the high-frequency components of
input audio signals.
However, by feeding a sufficient amount of FILTER output
back to its input with the RESONANCE control, the FILTER will become a pitch
generator at its CUTOFF frequency.
The AMPLIFIER stage is also a modifier because it raises or lowers the signa.llevel
from the FILTER to the external power amplifier and speaker. The AMPLIFIER is
controlled by its own envelope generator and the VOLUME control, which attenu-
ates the generator's control voltage output, reducing the overall output level.
OSC A, OSC B, the FILTER, AMPLIFIER, and envelope generators are all voltage-
controlled. Mechanical devices such as the keyboard, switches, knobs and wheels
form one group of controllers. The other group is electronic, consisting of the
LFO, OSC B, and FILT ENV modulation sources. The term "modulation" refers to a
periodic or consistent (as opposed to random) aural change which is interesting or
musically useful. Modulation is created with electronic controllers when it is not
possible to adjust a mechanical controller with the required speed or precision.
Electronic controllers free the hands for other uses.
The keyboard is the most conspicuous controller. It issues a CV which increases as
you play upwards
from CO to C3. This keyboard control voltage (KYBD CV) always
CM 100 2/81 13

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controls OSC A's frequency, and controls OSC B frequency if the OSC B KYBD
switch is on. The KYBD CV also controls the FILTER CUTOFF frequency to the
extent the FILTER KEYBOARD AMOUNT knob is advanced. The TRIGGER/GATE
produced by the keyboard controls the envelope generators, which in turn control
the FILTER cutoff frequency and AMPLIFIER gain.
A few
controllers also produce GA TEs or TRIGGERs which control the envelope
generators. For example, when the MODE is switched to REPEAT, the LFO gates
the envelopes.
The oscillator FREQUENCY and filter CUTOFF knobs are controllers which set
inital frequency over a continuous range. The oscillator OCT AVE switches are
controllers which transpose by exact octaves. The envelope ADSR knobs are also,
in actuality, control voltage sources.
2-2 OSCILLATOR A
OSCILLA 0
,.
T RA
"
.~,
1 2 A
rL
.~,
•••
SYNC
E3
E3
E3
2 -8
1 \ 9
21 I \" ,8
0
10
-SHAPE-
OCTAVE
0 10
OFF
FREQUENCY PULSE WIDTH
....
~
Figure 2-1
OSC A is an audio frequency source always under control of the keyboard.
FREQUENCY knob: Adjusts initial frequency continuously over a one-octave"tange.
OCTAVE rotary switch: Transposes initial frequency over a four-octave range.
SAWTOOTH SHAPE switch: Enables full-level waveshape containing all harmonics.
This unmodified shape is often described as "brassy."
PULSE SHAPE switch: Enables full-level waveshape whose harmonic content
depends on setting of PULSE WIDTH knob.
If neither waveshape switch is on, OSC A will have no output to the MIXER. If both
waveshape switches are on, the sawtooth and pulse are mixed at full level and
supplied as OSC A's output to the MIXER.
PULSE WIDTH knob: Adjusts the harmonic content of the pulse wave by setting
pulse wave duty cycle from 0 to 100%. A 50% duty-cycle pulse, also called a square
wave, can be obtained by setting the knob to 5, then carefully adjusting for the
dropout of the second harmonic (the first octave overtone). At the extreme knob
settings the pulses may "thin out" until they degenerate to de, resulting in nd
output signal. This knob has no effect on the saw;ooth wave.
CMlOO 2/81
15

SYNC switch: Forces OSC A to follow OSC B in hard synchronization. Intermediate
FREQUENCY settings will produce unusual timbres at the next lower harmonic of
OSC B. When a wide-width pulse is selected for OSC A in sync with OSC B, and
OSC B's frequency is set much higher than OSC A, the signal from OSC A may
degenerate to de since the pulse is not given a chance to discharge before being re-
synced.
2-3 OSCILLATOR B
OSCILLATOR B
·~'
1 2 A
/\ rL
.~,
•••
LO FREQ KYBD
B B B B B
2 -8
21 I \.........._ s8
1 \ ............ 9
0
10
-SHAPE-
0 10
NORMAL OFF
OCTAVE
FREQUENCY
PULSE WIDTH
Figure 2-2
OSC B is similar to OSC A, except that in addition to being a keyboard-controlled
audio frequency source, it can also be a low-frequency, modulation source with or
without keyboard control. The identically named controls function as described
under OSC A. In addition:
TRIANGLE SHAPE switch: Enables waveshape which is centered at ground so as
not to offset modulation destination. When used in the audio range, this shape
provides little harmonic energy.
NORMAL-LO FREQ switch: Extends OSC B range to sub-audio frequencies.
OFF-KYBD switch: Allows keyboard control or independent operation.
When OSC B is used as an audio source, usually LO FREQ is switched to NORMAL
and KYBD is switched on.
16 CMlOO 2/81

2-4 GLIDE
r GLIDE
~
3~7
AUTO
2 -8
B
1 \"9
0
10
NORMAL
RATE
"'"
~
Figure 2-3
The GLIDE module is a "lag processor." It sets the rate of change for the KYBD
CV. When
set to zero, the KYBD CV instantly steps between notes. As the GLIDE
knob is advanced, the KYBD CV does not step quickly between the notes, but
begins instead to "slew" between them.
RA TE knob: Determines the rate of glide (portamento) between notes.
NORMAL-AUTO switch: In NORMAL, Glide operates in the traditional manner. In
AUTO, the keyboard will glide only when a new key is hit with the previous key
still held. This enables complex, "tuned" pitch bending with one hand.
2-5 MIXER
,..
MIXER
.,
3~7
21 I \" 98
3·~7
.,:/ \-98
3~7
21 I \" 98
0
10
0 10
0 10
OSC A
OSC B
NOISE/EXT
"'"
....
Figure 2-4
OSC A and OSC B/ knobs: Set the level of oscillator input to the FILTER.
NOISE/EXT knob:
Sets the white noise level input to the FILTER. Noise is an
unpitched source useful for effects such as surf, wind or cymbals. When the back-
panel external audio input is used, noise is bypassed and this knob sets the level of
external signal input to the FILTER.
To
get any sound out of the Pro-One, at least one of these three knobs must be
turned up (unless the filter is being used as a pitch source).
CM 100 2/81
17

2-6 FILTER
3~7
21 // \" 98
0 10
CUTOFF
3~7
21 I \" 98
0 10
ATTACK
Figure 2-5
FILTER
3~7
21 I \" 98
0
10
RESONANCE
3~7
.. ~ \":
0 10
DECAY
3~7
21 I \" 98
0
10
ENVELOPE
AMOUNT
3~7
21 I \" 98
0 10
SUSTAIN
3~7
2 -8
1// \"9
0
10
KEYBOARD
AMOUNT
4 5 6
... 7•
1 ; \ 9
0 10
RELEASE
The FILTER module contains controls for tl;le filter itself and for its envelope
generator.
CUTOFF knob: Sets cutoff frequency for the 24 db/octave (4-pole) low-pass filter.
It is rather like a tone control. Cutoff is the frequency below which all elements of
a signal are let through. The higher-frequency components of the signal (i.e. all
those above the cutoff frequency) are suppressed. The higher the knob is set, the
higher the frequencies that are allowed through the filter.
RESONANCE knob: Determines the amount of filter resonance. As the setting is
increased from 0 to approximately 7 the amount of resonance ("emphasis,'J
"regeneration," or "Q") applied to those signal components at the cutoff frequency
will increase. The components far below the cutoff frequency will be less audible
relative to the frequencies being resonated. As the setting is increased beyond 7,
the filter breaks into oscillation and will act as a sine-wave audio source whose
pitch is determined by the cutoff frequency.
ENVELOPE AMOUNT knob: Sets amount (not the shape) of ADSR filter envelope
CV controlling the filter cutoff frequency. The filter envelope generator is
discussed below.
KEYBOARD AMOUNT knob: Determines the amount of KYBD CV controlling the
filter cutoff frequency. When set between 7 and 8, the filter cutoff frequency is
maintained at a constant point relative to the notes played on the keyboard,
creating consistent tone. When set to 10, notes played higher on the keyboard will
have less of their overtones suppressed than those played on the lower end of the
keyboard. As a result, the higher notes will have a brighter timbre. When reduced
or off, notes played higher on the keyboard will have more of their overtones
suppressed than noted played lower. As a result the higher notes will have a duller
timbre. --
'y'
18
CM 100 2/81

FILTER
ENVELCJ>E
AMOUNT
OR
Mf>LIFIER
Wll . .M:
LEVEL
I
: TIME
SUSTAIN 1
LEVEL
··-··-··-··"f---~----------+-----------------!-----------------+- .............
Figure 2-6
ENVELOPE
ATTACK TIME
DECAY TIME
LENGTH C-:TIME llfAT THE KEY IS HELD~.
RELE.AR
TIME
The filter envelope generator contours timbre by controlling the filter cutoff
frequency. The entire contour pattern is initiated when a key is struck, producing a
GATE.
The initial appearance of the GATE "triggers" the envelope generators to
proceed through their ATTACK and DECAY periods. After the ATTACK and
DECAY periods set for each envelope generator have elapsed, it will produce a
steady control voltage (CV) at the level set by the SUSTAIN knob for as long as the
GATE is present. When the key is released, the GATE goes off and the envelope
generator output voltage drops to zero at a rate set by the RELEASE knob.
ATTACK knob:
Varies time for envelope to increase from zero to maximum, from
2 milliseconds to more than 6 seconds.
DECAY knob: Varies time for envelope to decrease from maximum to SUSTAIN
level, from 2 milliseconds to more than 6 seconds. .~.~
SUSTAIN knob: Varies level from zero to maximum. Remember, this is a level
control, not a time control. (SUSTAIN time is the period between the end of tl:le
DECAY and when the key is released.)
If SUSTAIN is set at maximum then the DECAY knob setting is irrelevant.
RELEASE knob: Varies time for envelope to decrease from sustain level to zero,
from 2 milliseconds to more than 6 seconds. If the key is released before either the
ATTACK or DECAY periods have elapsed, this knob controls the time taken for the
output to drop to zero from its level when the key was released.
If the ATTACK and DECAY periods have elapsed and SUSTAIN is set to O, the
RELEASE knob setting is irrelevant.
CMlOO 2/81 19

2-7 AMPLIFIER
r
AMPLIFIER
~
.~,
.~,
.~, .~,
2 -8
·, ~ \"':
21 I \.........._ 98
·,~/ \"':
1 \ ........... 9
0
10
0 10 0
10
0
10
ATTACK DECAY
SUSTAIN
RELEASE
I.
,..ii
Figure 2-7
The ATTACK, DECAY, SUSTAIN, and RELEASE knobs in this module shape the
envelope applied to the final VCA in the same manner as the corresponding
controls in the FILTER module.
Unless the SUSTAIN knob is somewhat advanced, nothing wilf be heard after the
ATTACK and DECAY periods have elapsed.
2-8 MODULATION
A synthesizer's expressiveness stands on its modulation facilities. The Pro-One has
three modulation sources which are fully mixable and routable over simultaneous
WHEEL-controlled or DIRECT paths to five destinations in the voice itself.
Two of the three modulation sources (filter envelope generator and OSC B) were
described above. The third source is the LFO.
r~---------LFO/CLOCK-------- ....... ~
A A fl
BBB
-SHAPE-
FREQUENCY
Figure 2-8
FREQUENCY knob: Varies LFO range from approximately .1 to 30 Hz.
Waveshape switches: Function identically to OSC B.
"
20
CM 100 2/81