Instruction Manual

ManualsBrandsDoepfer ManualsAudioA-191 Shepard Generator/16xMIDI-CV Interface (no longer available)

doepfer

System A - 100

MCV 16

A-191

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

Summary of content (18 pages)

PAGE 1
System A - 100 doepfer MCV 16 A-191 1. Introduction S0/ LFO Frequ. + T0/ LFO Frequ. – S90/ LFO Mode MIDI / SG T315/ C16 MIDI In MCV16 Reset/ Store Module A-191 is a combination of a MIDI-CV interface 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.
PAGE 2
A-191 MCV 16 System A - 100 Controls and indicators 2. MCV16 - Overview 1 LEDs : Indicators for triangle and/or sawtooth waveform frequency 2 Freq. + : Button to increase LFO frequency 3 Freq.
PAGE 3
doepfer System A - 100 MCV 16 A-191 3. Switching between the functions 4. MIDI-CV interface 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). 4.1 Basics In its MIDI-CV mode, the A-191 provides a MIDI-CV converter, and a MIDI-synchronized LFO.
PAGE 4
A-191 MCV 16 Output corresponding MIDI controller System A - 100 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.
PAGE 5
System A - 100 doepfer 4 4 Fig. 1: H The sawtooth (1/2 note cycle) generated by a MIDI controller value of 8. Controller value LFO cycle 0 LFO off 1 1/16 2 2/16 = 1/8 3 3/16 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 MCV 16 A-191 Because the A-191’s LFO is purely a software device, the following considerations apply, which it’s well worth remembering.
PAGE 6
A-191 MCV 16 System A - 100 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 decreases the frequency of the internal LFOs.
PAGE 7
System A - 100 doepfer 4.3 In- / Outputs ! CV outputs Sockets ! are the MIDI-CV interface’s CV outputs: LFO • LFO • LFO MCV 16 A-191 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.
PAGE 8
A-191 MCV 16 System A - 100 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). Modules A-190 and A-191 act as the link to a MIDI keyboard, 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 possibilities accessible from velocity, mod wheel, pedals, and aftertouch: • VCO 2 level VCO 2’s amplitude level (ie.
PAGE 9
System A - 100 doepfer MCV 16 A-191 MIDI Out CV 1 VCO 1 A-138a MIDI In A-122 QCV A-190 VCO 2 Foot A-131 FCV A-132 A-132 MIDI Thru CV 2 A-130 A-118 ADSR 1 ADSR 2 LFO A-132 Gate C1 Mod. Wheel MIDI In AT C7 After Toucn Volume A-191 Fig. 2: Classic synthesizer patch with multiple modulation possibilities.
PAGE 10
A-191 MCV 16 MIDI Sequencer System A - 100 VCO CV 1 doepfer VCF VCA MIDI In MIDI In MIDI Out A-190 LFO MIDI Thru A-191 ADSR Gate 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. 10 Another example of MIDI-synchronised use of the internal LFO is shown in Fig. 5.
PAGE 11
System A - 100 doepfer VCO VCF MCV 16 A-191 VCA ADSR MIDI Sequencer CV 1 MIDI In MIDI Out A-190 MIDI Thru VCP 1 MIDI In CV Gate Out L LFO A-191 A-175 CV VCP 2 Out R Fig. 4: MIDI-synchronised "stereo" phasing.
PAGE 12
A-191 MCV 16 System A - 100 5. Shepard generator doepfer S0 T0 S 90 T 90 S 180 T 180 S 270 T 270 5.1 Basics A Shepard generator is a modulation oscillator, which produces various phase inversions of triangle and sawtooth waveforms at its outputs.
PAGE 13
System A - 100 doepfer 5.2 Indicators and controls 1 LEDs The LEDs 1 give you a read-out of the frequency of the Shepard generators. They show the state of the sawtooth wave at output S0 and/or triangle wave at output T0. 2 Freq. + • 3 Freq. – Pressing buttons 2 or 3 raises and/or lowers the frequency of the Shepard generator. These settings are only temporary: if you want to save them, press button 9 (see below).
PAGE 14
A-191 MCV 16 System A - 100 doepfer 5.2 In- / Outputs 5.3 User examples ! CV outputs Generating "Shepard Tones" The CV output sockets ! send out sawtooth and triangle waveforms. The number on each output refers to the amount of phase displacement, in degrees: The Shepard Tone is a psycho-acoustic phenomenon, that gives the impression of a continuously rising or falling tone. S0 • S45 • S90 • S135 • S180 • S225 • S270 • S315 Sockets S0 to S315 output the sawtooth waveforms.
PAGE 15
System A - 100 doepfer S0 VCO 1 VCA 1 Out 1 VCO 2 VCA 2 Out 2 VCO 8 VCA 8 Out 8 T 45 A-191 S 315 gradually get quieter again, until the highest frequency is reached, and it’s inaudible again. Meanwhile, other harmonics have been replacing it, starting very quietly at the lowest frequency. T0 S 45 MCV 16 A-191 T 315 Fig. 7: Shepard tone patch To help understand this weird science, just picture the lowest harmonic of the tone (with the Shepard generator in its "Up" mode).
PAGE 16
A-191 MCV 16 System A - 100 Alright, we have to admit that to use the Shepard generator to maximum effect does take a huge number of modules. There aren’t going to be that many System A-100 owners (are there?) who have eight VCOs or VCFs or VCPs and eight VCAs to use to produce a perfect Shepard tone. What’s much more important is to use the modules you do have creatively. Try all sorts of unlikely combinations of modules and control voltages.
PAGE 17
System A - 100 doepfer MCV 16 A-191 Audio In A-191 VCA 1 T0 VCA 2 Quad Space T 90 VCA 3 T 180 VCA 4 T 270 Fig.
PAGE 18
A-191 MCV 16 System A - 100 doepfer 6. Patch-Sheet The following diagrams of the module can help you recall your own Patches. They’re 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.