DOEPFER A-191 Manuel utilisateur

doepfer System A - 100 MCV 16 A-191

H Connecting the A-191 to the system bus

requires an additional special power sup-

ply (+5 V / 50 mA).

1. Introduction

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 sa-

wtooth wave. Using a variety of modules, the Shepard

Generator can create some interesting psycho-

acoustic effects.

All A-191 settings can be saved into non-volatile

memory.

MIDI

Frequ. +

MCV16

S0/

LFO

S90/

LFO

Frequ. –

Mode

MIDI /

Reset/

Store

T0/

LFO

T315/

C16

A-191 MCV 16 System A - 100 doepfer

2. MCV16 - Overview Controls and indicators

1LEDs : Indicators for triangle and/or sawtooth

waveform frequency

2Freq. + : Button to increase LFO frequency

3Freq. – : Button to decrease LFO frequency

4Mode : Shepard function switch

5, 6LEDs : Shepard function indicators

7Mode : Switch to select either Shepard Gene-

rator or MIDI interface

8LED : Indicator to show which out of the

Shepard Generator or MIDI interface

is selected

9Reset/Store : 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

MCV16

MIDI

S0 /LFO

MIDI-CV / SHEPARD

➀



➁

Freq. +

➂

➃

➄

➅

➇



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

Freq. –

Control

Mode

MCV

Shepard

Fast

Slow

–

Learn

Reset/

Store

➈

➆

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 either as a MIDI-CV interface

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 7

8 LED

LED 8lights 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 8

flashes (see chapter. 4.2, "MIDI In).

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 relevant MIDI control-

ler messages on the channel you’ve selected, it con-

verts 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 de-

fault values.

H After switching your A-100 system on, pres-

sing the Store/Reset button 9sets the

voltages at the CV outputs to the default

values (see table 1).

If you’re running your A-100 from a MIDI

sequencer, you’ll need to save the appro-

priate MIDI controller messages at the begin-

ning of a Song, to initialise the A-191’s CV

outputs correctly.

A-191 MCV 16 System A - 100 doepfer

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 2and/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).

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

doepfer System A - 100 MCV 16 A-191

Fig. 1: The sawtooth (1/2 note cycle) generated by

a MIDI controller value of 8.

Table 2: Typical values for controller #92 and the

resultant length of the LFO cycle.

H Because the A-191’s LFO is purely a soft-

ware device, the following considerations

apply, which it’s well worth remembering.

The A-191 uses an 8-bit D/A converter, whose maxi-

mum resolution is 256 steps per 0.02 V. Conse-

quently, 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.

Controller value LFO cycle

0LFOoff

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

A-191 MCV 16 System A - 100 doepfer

4.2 Indicators and controls

1 LEDs

The LEDs 1indicate 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. + • 3Freq. –

Buttons 2and 3have a double function in the MIDI-

CV interface:

• Setting LFO frequency

Pressing buttons 2or 3increases and/or de-

creases the frequency of the internal LFOs.

While buttons 2or 3are pressed, LEDs 5and 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.

HIt’s easier and definitely more precise to

alter the LFO frequency by MIDI controller

#92.

Setting the MIDI input channel

If you simultaneously hold down buttons 2and 3,

"learning mode" is activated. This is signalled by

LEDs 5, 6and 8 all flashing at once.

You can now set the MIDI channel you want the

MCV16 to respond to. To do this, send a valid MIDI

controller (see table 1) to the A-191. This automati-

cally ends learning mode, the LEDs go out, and the

MIDI channel of whatever controller was used beco-

mes the input channel for all the MIDI data sent after

this.

LFO frequency and MIDI- input channel are only tem-

porarily stored, unless you save them by pressing

button 9(see below).

H The labels on LEDs 5and 6("Fast", "Slow",

"--") don’t have a function yet in MIDI-CV

mode, but are hoped to have in a future

update.

9 Reset / Store

To save the settings for MIDI input channel and LFO

frequency press button 9.

LEDs 5, 6and 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).

doepfer System A - 100 MCV 16 A-191

4.3 In- / Outputs

! CV outputs

Sockets !are the MIDI-CV interface’s CV outputs:

LFO • LFO • LFO

These sockets are the outputs for the sawtooth,

triangle and rectangle waves produced by the inter-

nal LFO. LEDs 1and 2give an indication of the

voltages at the sawtooth and triangle wave outputs.

H Don’t forget that the LFO will only work if a

MIDI clock is being received on the selected

MIDI channel (see chapter 4.1, Basics).

AT • ... • C16

These 13 sockets output the control voltages conver-

ted from their respective MIDI controllers (see table

1). Their voltage range is from 0 V to +5 V.

" MIDI In

This MIDI input socket should be connected to the

MIDI keyboard or sequencer, etc., that you want to

control the System A-100, with a standard MIDI lead.

As well as converting MIDI controllers After Touch,

Pitch Wheel, #01, #02, #04 to #08, #10, #11, #12 and

#16, and turning them into voltages available at the

corresponding CV outputs (see table 1), the A-191

also responds to MIDI clock - and to MIDI controller

#92 ("Tremolo Depth") for controlling the internal

LFOs.

A-191 MCV 16 System A - 100 doepfer

4.4 User examples

Modulation-rich synthesizer patch

The example in Fig. 2 shows a ‘classic’ synthesizer

patch: 2 VCOs, VCF (A-122) and VCA (A-130). Modu-

les A-190 and A-191 act as the link to a MIDI key-

board, and are set to the same MIDI channel. The

THRU from the A-190 is connected to the MIDI IN of

the A-191.

This patch gives a vast range of modulation possi-

bilities accessible from velocity, mod wheel, pedals,

and aftertouch:

• VCO 2 level

VCO 2’s amplitude level (ie. volume) can be con-

trolled with a pedal. In this example, the A-190’s

second CV output (CV 2) has been previously

programmed to respond to MIDI controller #04, but

CV output C4 on the A-191 could have equally

well been used.

• Modulation of VCF resonance

Filter resonance is modulated by a random vol-

tage source (the A-118’s random output). The

intensity of this modulation is controlled by the

modulation wheel (output C1 on the A-191).

• Amplitude modulation

The intensity of the amplitude modulation created

by the LFO patched into the VCA (A-130) is control-

led by aftertouch (output AT on the A-191).

• Overall volume

The overall volume of the output signal sent to the

monitoring system is controlled by MIDI controller #7

(Volume) (output C7 on the A-191). This controller can

be assigned to a pedal, pitch ribbon, etc. on your

master keyboard.

H If you want to use a MIDI controller which the

A-191 doesn’t support - for instance a

sustain pedal - then you can always set the

A-190 to respond to it, and output it from its

CV2 socket.

MIDI-synchronised LFO

The internal LFO on the A-191 is synchronised to MIDI

clock. This is particularly useful when you’re using a

MIDI sequencer or arpeggiator with the A-100.

An example is shown in Fig. 3. In this patch, the

internal LFO modulates the VCF’s cut-off frequency.

doepfer System A - 100 MCV 16 A-191

Fig. 2: Classic synthesizer patch with multiple modula-

tion possibilities.

VCO 1

A-132

VCO 2

A-138a

CV 1

MIDI In

MIDI

Out

A-190

CV 2

A-122

A-130

ADSR 1

A-131

ADSR 2

A-118

A-132

Gate

MIDI Thru

A-191

LFO

MIDI In

A-132

QCV FCV

C 1

C 7

Foot

Mod. Wheel

After Toucn

Volume

A-191 MCV 16 System A - 100 doepfer

Fig. 3: VCF cutoff control with a MIDI-synced LFO.

Set the LFO frequency so that it completes one cycle

every whole note.

During the first four 1/8th notes of the sequence, the

filter is opening; and in the last four 1/8th notes, it’s

closing.

Another example of MIDI-synchronised use of the

internal LFO is shown in Fig. 5. Two A-125 phasers

set to opposite phase are sent to two audio outputs

(OutL and OutR) to produce MIDI-synchronised spa-

tial effects.

CV 1

MIDI In

MIDI

Out

A-190

VCF

VCA

ADSR

Gate

MIDI Thru

A-191

MIDI In

LFO

MIDI -

Sequencer

VCO

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