Module A-155 (Analog / Trigger Sequencer) is a combined
8-step analog and trigger sequencer
simultaneously produce sequences of analog voltages
and trigger and/or gate signals.
Module A-155 works very much like the Clock Sequencer module, A-161, but includes many extra (and
expensive to implement!) functions.
The control section includes switches for Start, Stop,
Step and Reset - which can be operated by pushbutton
eight LEDs show the progress of the sequence, with
each step’s LED lighting in turn.
The A-155 has two analog rows, each with eight
knobs
step. The upper row is particularly designed for pitch
control of a VCO, with a
to set pitches precisely.
as well as
, with which to set the control voltage for each
digital signals
range switch
. Above the top row,
giving the ability
: it can
The lower row of eight knobs has the ability to accept
an external signal for each step, in which case the
knobs act as attenuators for this voltage.
The variable voltages from the analog rows can either
be output direct, or can go through a sample-and-
section and a
hold
S&H and glide control inputs, it’s possible to select
‘hold’ (S&H) or portamento (glide) for whichever step
or steps you want.
Three rows of triggers and one row of gates are
available. For each step, a three-way mini-switch lets
you decide whether one or the other (or neither) of the
two triggers works. Each row has an LED which lights
whenever a trigger or gate is active at any particular
step.
slew limiter (‘glide’).
Using the
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A-155
Analog / Trigger Sequencer
2. Overview
System A - 100
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➂➊➋ ➈
Analog / Trigger Sequencer
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External CV / Audio Inputs
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➍
Trig.
Control
1 V
2 V
4 V
10
Range
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ScaleGlide
➅➆ ➇
Trigger OutputsControl
Trig 1
Trig 2
Trig 3
Gate
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Glide
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Pre
Out
S&H
Ctrl.
Pre
Out
S&H
Ctrl.
Start
Stop
Step
Reset
Post
Out
Glide
Ctrl.
Post
Out
Glide
Ctrl.
➌
➁
➀
➃
➄
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A-155
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System A - 100
Analog / Trigger Sequencer
A-155
Controls
1Switches :these select triggers and/or gates for
each step
LEDs :indicators to show the step reached
2
Trig. Control: indicators for trigger and gate rows
3
CV knob
4
5
6 Range :switch to select the voltage range of
Scale :range control for the lower CV row
7
8 Glide :control for the glide time (amount of
Control :manual controls
9
:these set the control voltage output
for each step of the upper CV row
CV knob
:these set the control voltage output
for each step of the lower CV row,
and/or act as attenuators for the external CV / audio inputs
the CVs put out by the upper CV row
slew) on either upper or lower CV row
:start button
Start
Stop :stop button
Step :button for manually stepping through a
sequence
Reset :reset button
In / Outputs
Trigger Out :outputs for the three triggers and
!
one gate
Control
"
Start :input for start signal
Stop
Step :input for clock signal
Reset :input for reset signal
§ CV outputs, control inputs :
Pre Out
Post Out :as above, but after the sample-and-
S&H Ctrl. :control input for sample-and-hold
Glide Ctrl. :control input for the glide section
$ External CV/
Audio Inputs :inputs for controlling the voltage of
:digital control input sockets
:input for stop signal
:output for the upper or lower analo-
gue CV row
hold and/or glide circuitry
section
each step of the lower analog CV
row by a CV or audio signal
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A-155
Analog / Trigger Sequencer
System A - 100
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3. Controls
1 Switches
The three-position toggle switches 1 are used to
select whether a particular step outputs a trigger signal
on its respective row.
Position of the upper switches:
• up: trigger output on row 1 (Trig 1 output)
• centre:no trigger output
• down:trigger output on row 2 (Trig 2 output)
Position of the lower switches:
• up: trigger output on row 3 (Trig 3 output)
• centre:no trigger output
• down:gate output on row 4 (Gate output)
The three upper rows produce triggers - each step that
is switched to a row will produce a short pulse like a
clock signal. The lowest row produces gates - the
signal remains "high" for the duration of the step (see
fig. 1 on the next page).
2 LEDs
The eight LEDs 2 show the sequence’s progress;
each LED lights when its respective step is active.
Trig. 1
12
Trig. 2
Trig. 3
Gate
Clock
Trig. 1
Gate
fig. 1: timing diagram for trigger and gate rows
4
3
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3 Trig. Control
The four LEDs 3 are status indicators for the trigger
and gate rows. Each lights when a step is reached
which is switched to its own row.
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System A - 100
Analog / Trigger Sequencer
A-155
4 CV knobs (upper row)
You use the CV knobs 4 (upper row) to set the
voltage output for each step
row. The control voltage set for each step is output at
the upper
The range of voltage output can be controlled with
the range switch 6. Three very accurate voltage ranges are provided (see below) so that the upper analog
CV row is ideally suited for precise VCO pitch control.
Pre Out
§ socket.
in the upper analog CV
5 CV knobs (lower row)
You use the CV knobs 5 (lower row) to set the voltage
output for each step
control voltage set for each step is output at the lower
Pre Out
You use the Scale control 7 to adjust the range of
the voltages controlled by the CV knobs.
§ socket.
in the lower analog CV row. The
H If for any step you patch in an external CV /
audio input
knob in the lower row doesn’t put out its own
voltage.
Instead, it acts as an
external CV / audio signal, before sending it
to the lower
(socket $), the corresponding-
for the
Pre Out
attenuator
output §.
6 Range
The position of the Range switch (a three-way toggle
switch) 6 selects the precise voltage control range,
within which the upper row of CV knobs 4 will operate.
There are three ranges to choose from:
• up :1 V(i.e. one octave)
centre : 2 V(i.e. two octaves)
•
• down
The maximum voltage is obtained by turning the knobs
fully clockwise.
:4 V(i.e. four octaves).
7 Scale
Control 7 sets the
which the lower row of CV knobs 5 will operate. If an
external CV / audio signal is patched into any of the
sockets $, the scale control affects the amount of
attenuation
the CV knob will produce on that voltage
range of control voltages
, within
8 Glide
The internal slew limiter's rate is set with control 8.
If for the current step in a sequence (e.g. step three)
the slew limiter is switched in (by a "low" control
signal at the Glide Ctrl. § socket), the control voltage
sent to output
the voltage at the previous step (in this example, step
two). Instead, it glides gradually to the new voltage, at
Post Out
§ doesn’t jump instantly from
.
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A-155
Analog / Trigger Sequencer
System A - 100
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a speed determined by the Glide control knob (fig. 2).
If you patch the output from the Gate row into the
Glide Ctrl. input §, you can switch the glide function on
off
for
each step
, like on the Roland TB-
or
303 (see fig. 2). If you patch the gate output through
an A-165 trigger modifier, every gate activates ‘glide’.
12
Trig. 3
Gate
Clock
Gate
Pre Out
Post Out
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9 Control
The control section 9 includes four push-buttons for
manual sequencer control. Alternatively, digital control
signals can be sent to four corresponding sockets.
• Start
• Stop
• Step
• Reset
:Used to start the sequence - i.e. to set it
running.
:Used to stop the sequence.
:Used to step through the sequence one
step at a time. Each button-press corresponds to a clock pulse.
:Used to ‘reset’ the sequence - i.e. to send
it back to begin again at step one.
: glide function
fig. 2
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Analog / Trigger Sequencer
A-155
4. In / Outputs
! Trigger Outputs
Sockets ! are the outputs from the three trigger rows
and the gate row.
Control
"
Alongside the four buttons for sequencer control, there
are four corresponding digital control input sockets ".
• Start
• Stop
• Clock
• Reset
H
:A signal here starts the sequence.
:A signal here stops the sequence.
:A clock signal here steps through the
sequence. Also called ‘step’ input.
:A signal here sends the sequence back to
step one.
and
Start
As soon as they sense the rising edge of a
pulse, they produce a momentary signal.
The length of the pulse makes no difference
- a pulse of long duration still just produces a
momentary trigger.
Stop inputs
work in
trigger
mode.
Clock (step)
hand, work by sensing level: so, for instance,
Reset will always be active (keeping the
sequence at step one) as long as the reset
signal is "high".
and
Reset inputs
, on the other
§ CV outputs, control inputs
The two groups of sockets § contain the analog CV
outputs
for the sample-and-hold and slew limiter sections.
The upper group of sockets relates to analog CV row
1, and the lower to analog CV row 2.
• Pre Out
• Post Out
for each row, and the
:The
:The control voltages set on the
control voltages
respective analog CV row are output
here, before (pre) passing through the
slew limiter and sample-and-hold sections.
respective analog CV row are output
here,
after
slew limiter and sample-and-hold sections.
digital control inputs
set on the
(post) passing through the
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A-155
Analog / Trigger Sequencer
System A - 100
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• Glide Ctrl.
• S&H Ctrl.
P
The purpose of this ‘hold’ function becomes
clear if you e.g. want to hold the pitch of a
VCO over 2 or more steps. In this case the
S&H function takes care that the CV is held
over the regarding steps provided that the
S&H control input is connected to one of the
trigger outputs and the trigger switches are
set suitable. Without the use of the S&H you
would have to adjust the potentiometers of
the regarding steps very careful to obtain
exactly the same voltage for the successive
steps.
: The glide function is active whenever
the control signal input here is “low”.
: If nothing’s connected to the
H
socket, glide function is active!
: This is the socket for the digital
Sample & Hold control input.
Whenever a "high" control signal is
sensed, the analog CV output is held
at the same level until the control signal goes low. Usually one of the trigger rows would be patched in to this
socket.
$ External CV / Audio Inputs
The inputs $ for the lower analog CV row can be
used to patch in any control voltage or audio signal.
For any step used in this way, the CV knob 5 then acts
as an attenuator for the signal input.
5. User examples
Module A-155 has limitless potential. All sorts of very
complex sequences, modulation and audio manipulation are possible. In the following examples of typical
patches, there’s only room to mention a few of the
most common uses.
Fig. 3 shows a standard patch - a six-step sequence
with pitch, filter and glide control, to give an example of
some of the typical control possibilities the A-155
provides.
The
upper analog CV row
the VCO. In this example, output "Post Out 1" has
been chosen, because the glide function is being
used.
is controlling the
pitch
of
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System A - 100
Analog / Trigger Sequencer
A-155
Trigger row 1
the accented notes, by triggering an ADSR, which
controls the VCA.
Trigger row 2
quence, by triggering the reset function. In this
example, step seven is switched to this row, which is
patched to the reset input, making the sequence six
notes long.
The gate row is used for controlling the glide func-tion. In this example, step two is switched to this row,
so that portamento (at a rate set by the Glide control)
occurs between the voltages at step one and step two.
The lower analog CV row is controlling the VCFcut-off frequency.
Trigger row 3 is available for any other control job you
choose. Variations on the patch in fig. 3 might include
controlling the VCF with either the same or a different
ADSR, or using the lower analog CV row to control the
decay time of a VC-ADSR (see also fig. 4).
Interesting effects can be obtained by patching exter-nal control voltages (e.g. from an LFO or Random
CV) or
lower analog CV row. The latter can sound particularly interesting, because of the effects of short bursts
of audio-range frequency modulation.
(steps 1, 2, 3 and 5 selected) picks out
determines the
audio signals
(e.g. VCO or Noise) into the
length of the se-
Interesting effects can be obtained by patching
nal control voltages (e.g. from an LFO or Random
CV) or audio signals (e.g. VCO or Noise) into the
lower analog CV row. The latter can sound particularly interesting, because of the effects of short bursts
of audio-range frequency modulation.
exter-
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A-155
A-155
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Analog / Trigger Sequencer
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S&H Cr tl. 1
Post Out 1
System A - 100
Clock
Reset
Trig. 1
Trig. 2
Trig. 3
Gate
Glide Ctrl.
Pre Out 2
fig. 3: standard patch with VCO, VCF and glide control
VCO
ADSR
VCF
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:
VCA
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A-155
12345678
System A - 100
Clock
Trig. 1
Analog / Trigger Sequencer
A-155
Post Out 1
Pre O ut 2
fig. 4: controlling decay time in a VC-ADSR
In fig. 4 the lower analog CV row controls the decay
time of a VC-ADSR. This in turn controls the cut-off
frequency of a VCF, and so produces filter accents of
different lengths.
VCO
VC-ADSR
Decay
VCF
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A-155
Analog / Trigger Sequencer
Clock
System A - 100
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A-155
12345678
controlling accents / dynamics
fig. 5:
Trig. 1
Trig. 3
Post Out 1
Pre Out 2
With the patch in fig. 5 you can create
variable dyna-
ADSR
VCO
mics or accents within the sequence. The gain con-
trol of VCA 2 needs to be set to greater than zero (a
setting of 5 is a good starting point).
VCF
VCA 1
VCA 2
ADSR
The patch in fig. 6 shows how to use the A-155 as a
16-step sequencer with one single analog CV row.
What’s needed are the Clock Divider
A-160 (output /8) and the two voltage-controlled switches in the A-150 VCS module.
With every eight clock pulses, the A-150 switches
between the two trigger and analog CV rows, so that
there’s now a 16-step trigger and CV sequence available at the outputs of the A-150.
:
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Clock
Trig. In
System A - 100
A-160
Analog / Trigger Sequencer
A-155
A-155
12345678
Trig. 1
Trig. 3
Post Out 1
Post Out 2
fig. 6: 16-step sequence with single analog CVs
/ 8
A-150
CV
I/O 1
I/O 2
O/I
Trig. Out
A-150
CV
I/O 1
I/O 2
O/I
Trig. 1Trig. 3
CV Out
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Analog / Trigger Sequencer
System A - 100
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The following are some short notes with suggestions
for further exploration, to act as inspiration for your
own patching ideas.
• Gate patched to glide control
Glide / portamento can be switched on or off for
each step (a la TB-303, see. p. 6).
• Trigger (Gate) patched to Reset
Shortening a sequence to, e.g., six notes.
• Trigger (Gate) patched to Stop
"One shot": the sequence runs just once, and only
repeats when a Start signal is received.
• Chopping up audio signals
Using the lower analog CV row, audio signals
patched into the inputs will be output ‘chopped up’
from the Pre Out socket.
• MIDI control
The A-155 can be controlled by MIDI-Clock with the
help of an A-190 module; the Clock and Reset
outputs of the A-190 are simply connected to the
Clock and Reset inputs on the A-155.
• Random Clock
The Random Clock output from the A-117 can give
a sequence random timing.
• VC-LFO as Clock
Using one of the analog CV rows to control a
VC-LFO (A-147), the timing of each step of the
sequence can be completely variable.
• Variable decay time for each step
Using one analog CV row to control the decay time
on a VC-ADSR (A-141 or A-142 - and on the A-141
attack and release times could also be controlled)
the envelope output can then control, e.g., a VCF
or VCA.
• Variable audio pulse width for each step
Using one analog CV row to control the pulse width
of a VCO square wave.
Variable control pulse width for each step
Using one analog CV row to control decay on an
A-142 (and taking the gate output from the A-142).
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System A - 100
6. Patch-Sheet
The following diagram of the module can help you
recall your own Patches. It’s designed so that a complete 19” rack of modules will fit onto an A4 sheet of
paper.
Photocopy this page, and cut out the pictures of this
and your other modules. You can then stick them onto
another piece of paper, and create a diagram of your
own system.
Make multiple copies of your composite diagram, and
use them for remembering good patches and set-ups.
Analog / Trigger Sequencer
A-155
P
•Draw in patchleads with colored pens.
•Draw or write control settings in the little
white circles.
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Analog / Trigger Sequencer
System A - 100
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A-155
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External C V / Audio Inputs
Trigger OutputsControl
Trig 1
Trig 2
Trig 3
Gate
10
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Glide
10
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Pre
Out
S&H
Ctrl.
Pre
Out
S&H
Ctrl.
Start
Stop
Step
Reset
Post
Out
Glide
Ctrl.
Post
Out
Glide
Ctrl.
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Control
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Trig.
1 V
2 V
4 V
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