Doepfer A-191 User Manual
doepfer
System A - 100
1. Introduction
MCV 16
A-191
H
S0/
LFO
T0/
LFO
S90/
LFO
T315/
C16
MIDI
In
Frequ. +
Frequ. –
Mode
MIDI /
SG
MCV16
Reset/
Store
Connecting the A-191 to the system bus
requires an additional special power sup-
ply (+5 V / 50 mA).
Module A-191 is a combination of a MIDI-CV inter-
face
and a
Shepard Generator
. Most of the controls,
indicators and in/outputs have a double function; there
is a switch which toggles between the two sets of
functions.
In use as a MIDI-CV interface, 13 of the 16 control
voltage outputs are dedicated to sending voltages
converted
from a particular MIDI controller
(such as
Mod Wheel, Volume, Pitch Wheel, Aftertouch, etc.).
Controller messages on your
chosen MIDI channel
are converted into voltages in a range from 0 to 5 V.
The other three sockets output an internal LFO gene-
rated in sync with MIDI clock, in three waveforms:
sawtooth, triangle and rectangle.
In use as a Shepard Generator, the sockets output
eight different phases each of a triangle and sawtooth
wave. Using a variety of modules, the Shepard
Generator can create some interesting psychoacoustic effects.
All A-191 settings can be saved into non-volatile
memory
.
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A-191
MCV 16
System A - 100
doepfer
2. MCV16 - Overview
MCV16
MIDI-CV / SHEPARD
S0 /LFO
T0 /LFO
S90 /LFO
T90 /AT
S180 /Pit
T180 /C1
S270 /C2
T270 /C4
S45 /C5
T45 /C6
S135 /C7
T135 / C8
S225 / C10
T225 / C11
S315 /C12
T315 / C16
Control
Control
Freq. +
Freq. –
Reset/
Store
Learn
Mode
Fast
Slow
–
MCV
Shepard
MIDI
In
➀
➁
➂
➄
➅
➇
➆
➈
Controls and indicators
LEDs : Indicators for triangle and/or sawtooth
1
waveform frequency
Freq. + : Button to increase LFO frequency
2
3 Freq. – : Button to decrease LFO frequency
4
5, 6
: Shepard function switch
Mode
LEDs : Shepard function indicators
7 Mode : Switch to select either Shepard Gene-
rator or MIDI interface
LED : Indicator to show which out of the
8
Shepard Generator or MIDI interface
is selected
Reset/Store
9
: Button for saving set-ups or resetting
Shepard Function Generator
In- / Outputs
! sockets : CV outputs from the Shepard Genera-
tor and MIDI-CV interface (see text)
" MIDI In : MIDI input socket
➃
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doepfer
System A - 100
MCV 16
A-191
3. Switching between the functions
Because the A-191 has two separate functions in it,
which share some of the controls and outputs, at any
one time it can be used
or as a Shepard Generator. To switch between the two
you simply press a button (see below).
H
The A-191’s controls and in / outputs for
each function are explained in their
respective sections of this manual.
7 Mode button
To switch between functions, press the lowest mode
button 7777
.
8 LED
LED 8 lights when the Shepard Generator is active;
otherwise it’s the MIDI-CV interface which is active.
H If the A-191 receives MIDI clock, LED
flashes (see chapter. 4.2, " MIDI In).
as a MIDI-CV interface
either
4. MIDI-CV interface
4.1 Basics
In its MIDI-CV mode, the A-191 provides a MIDI-CV
converter, and a MIDI-synchronized LFO.
Whenever the A-191 receives
ler messages on the channel you’ve selected, it converts them into control voltages (in a 0 V to +5 V
range), and sends these out on the corresponding CV
outputs. Table 1 on page 4 lists the MIDI controllers,
their corresponding CV output sockets, and their default values.
H After switching your A-100 system on, pres-
sing the Store/Reset button 9 sets the
voltages at the
values (see table 1).
If you’re running your A-100 from a MIDI
8
sequencer, you’ll need to save the appropriate MIDI controller messages at the beginning of a Song, to initialise the A-191’s CV
outputs correctly.
relevant MIDI control-
CV outputs
to the
default
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A-191
MCV 16
System A - 100
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Output corresponding MIDI controller default [V]
AT After Touch 0
Pit Pitch Wheel 2.5
C1 CTRL. #01 - Modulation Wheel 0
C2 CTRL. #02 - Breath Controller 0
C4 CTRL. #04 - Foot Controller 0
C5 CTRL. #05 - Portamento 0
C6 CTRL. #06 - Data Slider 0
C7 CTRL. #07 - Volume 5
C8 CTRL. #08 - Balance 2.5
C10 CTRL. #10 - Pan 2.5
C11 CTRL. #11 - Expression 0
C12 CTRL. #12 0
C16 CTRL. #16 0
Table 1: Valid MIDI controllers, their corresponding CV
outputs, and default values.
The A-191’s internal MIDI-synchronised LFO has three
waveforms - sawtooth, triangle, and rectangle.
This LFO is only active when a MIDI clock is being
sent to the MIDI IN, from a START or CONTINUE
message until a STOP message. LED 8 indicates
that it’s active.
At a STOP message, the voltage at the CV output is
held; at a CONTINUE message, the LFO starts from
this value; and at a START message, the waveform
begins again, starting from 0 V.
The LFO rate can be slowed down by dividing the
clock rate. You set the
divisor
either with
MIDI
controller #92 (Tremolo Depth) or manually, with
buttons 2 and/or 3.
The note length N of a full cycle of the waveform
generated by the LFO follows this formula :
Nth Note = 1/16 x controller value (see Table 2)
So, for instance, in 4/4 time, with a controller value of
8, the note length of a full LFO cycle would be half of a
whole note: that is, the LFO would cycle twice for each
beat in the bar (see Fig. 1).
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4
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System A - 100
Fig. 1: The sawtooth (1/2 note cycle) generated by
a MIDI controller value of 8.
Controller value LFO cycle
0LFO off
11/16
2 2/16 = 1/8
33/16
4 4/16 = 1/4
8 8/16 = 1/2
16 16/16 = 1 whole note
32 32/16 = 2 whole notes
64 64/16 = 4 whole notes
Table 2: Typical values for controller #92 and the
resultant length of the LFO cycle.
MCV 16
H Because the A-191’s LFO is purely a
A-191
soft-
ware device, the following considerations
apply, which it’s well worth remembering.
The A-191 uses an 8-bit D/A converter, whose maximum resolution is 256 steps per 0.02 V. Consequently, the
sawtooth
and
triangle
waves can’t be as
smooth as, for instance, those of the A-145 LFO. The
waveforms on the A-191 LFO are
digital
("stepped").
If you use it to control, eg, a VCO, the result is less of
a smooth continuous pitch sweep, and much more
akin to a glissando. How audible these steps are
depends on the MIDI-Clock tempo, and the divisor
you’ve chosen.
P If the steps are audible (and unwanted), you
can use a Slew Limiter (A-171) to smooth
out the waveforms.
Erratic or sudden changes of tempo or the divisor
will take a whole note to register, before the LFO
changes to this new frequency.
5
A-191
MCV 16
System A - 100
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4.2 Indicators and controls
1 LEDs
The LEDs 1 indicate the frequency of the internal
LFOs. They indicate the state of the sawtooth signal
at output S0 and/or the triangle wave at output T0 .
2 Freq. + • 3 Freq. –
Buttons 2 and 3 have a double function in the MIDICV interface:
Setting LFO frequency
•
Pressing buttons 2 or 3 increases and/or de-
creases the frequency of the internal LFOs.
While buttons 2 or 3 are pressed, LEDs 5 and 6
blink to show the increase or decrease in the LFO
frequency. If you reach the upper or lower limit of
the frequency, the LED stops blinking.
It’s easier and definitely more precise to
H
alter the LFO frequency
#92.
Setting the MIDI input channel
If you simultaneously hold down buttons 2 and 3,
"
learning mode
LEDs 5, 6 and 8 all flashing at once.
" is activated. This is signalled by
by MIDI controller
You can now set the MIDI channel you want the
MCV16 to respond to. To do this, send a valid
controller (see table 1) to the A-191. This automatically ends learning mode, the LEDs go out, and the
MIDI channel of whatever controller was used becomes the input channel for all the MIDI data sent after
this.
LFO frequency and MIDI- input channel are only temporarily stored, unless you save them by pressing
button 9 (see below).
H The labels on LEDs
"--") don’t have a function yet in MIDI-CV
mode, but are hoped to have in a future
update.
and 6 ("Fast", "Slow",
5
MIDI
9 Reset / Store
To
frequency press button 9.
LEDs 5, 6 and 8 light for about a second to confirm
the save procedure has succeeded. At the same time,
all CV outputs are set to their default settings (see
table 1).
the settings for
save
MIDI input channel
and
LFO
6
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