Doepfer A-126 VC User Manual

doepfer

System A - 100

1. Introduction

Module A-126 (VCFS) is a voltage-controlled fre­quency shifter.

VC Frequency Shifter

A-126

A-126

VC Frequ. Shifter

Audio

In

Audio

Out

CV

Up

Mix

Down

Over­load

Level

Shift

CV

Mix

The amount of frequency shift can be varied from
about 50 Hz up to 4 kHz, either manually, or by voltage
control (via an attenuator).

The amount of input signal gain can be controlled
with the

The

upward- (Up)

signals are available at separate outputs, and also at
the Mix output, where a mix of the two frequency-
shifted signals is available, with the balance controlled
by a Mix knob.

The Audio Out socket provides an amplified but not
frequency-shifted version of the original input signal.

Level

knob.

and

downward- (Down)

shifted

1

A-126

VC Frequency Shifter

System A - 100

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2. VCFS - Overview

A-126

VC Frequency Shifter

Audio In



0

Over load



Audio Out

CV



Mix

Output



Down

Output



0

0

0

VCFS

Up

Output

Level

10

Shift

10

CV

10

10

Mix

➀

➁

➂

➃

➄



Controls:

1

Overload : LED overload warning light for the

2

Shift : control for manual frequency-shifting

3
4

5

: gain control for the signal connected

Level

to input

input signal

: attenuator for the frequency-shifting

CV

control voltage at input

: control to balance the relative

Mix

amounts of Up and Down frequency­shifted signals at output

!

§

$

In / Outputs:

Audio In : audio input (line level)

!

Audio Out

"

: control voltage input for pitch-shifting

CV

§

Mix Output

$

Down Output

%

Up Output

&

: audio output (the original signal

amplified but not frequency-shifted)

: mix output for Up and Down signals

: output for just the downward-shifted

audio signal (Down)

: output for just the upward-shifted

audio signal (Up)

2

doepfer

System A - 100

VC Frequency Shifter

A-126

3. Basic principles

Frequency shifting can slide an audio signal upwards
("UP Shift") or downwards ("DOWN Shift").

This is
the components of an audio signal are raised or lowe­red by an equal interval).

With frequency shifting, all the component harmo-
nics of a sound are shifted not by an equal musical
interval, but by the same frequency.

As a rule, the resulting output signal is very likely to
be

dissonant

altered not by a proportional amount, but by exactly
the same number of Hz. Think of a sawtooth with a
500 Hz fundamental, a first harmonic at 1 kHz, second
at 1.5 kHz, and so on. If the signal is shifted upwards
by 100 Hz the new fundamental will be 600 Hz, and
the overtones 1.1 kHz, 1.6 kHz, etc.. These overtones
are no longer perfect harmonics of the fundamental.

As with ring modulation, very complex, spectrally rich
sounds often result.

the same as

not

, because the overtone frequencies are

transposition

(in which all of

4. Controls

1 Level

Control 1 is used to set the amount of
of the input signal at socket !.

2 Overload

LED 2 lights up when the input signal

3 Shift

The amount of frequency shifting is set manuallywith
this control in a range from c. 50 Hz to 4 kHz.

4 CV

In addition to the manual control, the amount of fre­quency shifting can also be altered by a control voltage
patched into input §; the level of voltage control can
be set with attenuator 4.

amplification

overloads.

3

A-126

VC Frequency Shifter

System A - 100

doepfer

5 Mix

Use control 5 to set the relative amounts of upward­and downward- shifted signals present at the mix
output $. If the knob is turned fully clockwise or
anti-clockwise, only one of the signals is audible:

Mix = 0

Mix = 10 : just the upward-shifted signal is heard

: just the downward-shifted signal is heard

5. In / Outputs

! Audio In

Socket ! is the frequency shifter’s audio input. Use it
to patch in the audio signal you want frequency­shifted.

" Audio Out

§ CV 1

Patch a control voltage for modulating the amount
of frequency-shift into socket §. The level of voltage

control is set with attenuator 4.

As a rule, a slowly-changing voltage (e.g. LFO, ADSR,
Random, etc.) or the CV output from a MIDI-CV­Interface (e.g. A-190, A-191) is used for this.

$ Mix Output

Depending on the position of control 5,
contains a mix of the downward and upward
frequency-shifted signals.

output $

% Down Output

Output % contains just the downward frequency-
shifted signal.

& Up Output

Output &
shifted signal.

contains just the

upward frequency-

Output "

4

relays the

original signal

, amplified.

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R

System A - 100

6. User examples

A typical use for a frequency shifter is to transform the
human voice - for instance, in a simple example, to
produce ‘robot voices’.

Audio­Signal

VC Frequency Shifter

VCFS

Up

CV In

A-138

A-126

A kind of vibrato effect can be produced by modula-

Colored

ting the frequency-shift with a slow sine-wave from an
LFO (frequency about 5 - 7 Hz).

A-118

More drastic effects can be produced by replacing the

: "roughening up” an audio signal

sine wave with a sawtooth (frequency about 1 - 2 Hz)

fig. 1

to produce a repeated rising modulation.

With the patch in fig. 1 you can ‘roughen up’ audio
signals (e.g. voices) by modulating the frequency-shift
with colored noise, and sending the original and the
frequency-shifted signals to a mixer, to control the
amount of

‘harshness’ or ‘edge’

.

With the patch in fig. 2, you can create a new type of

Audio­Signal

VCFS

CV In

Up

Down

VCA

VCA

L

percussive stereo effect, using the square wave from
an LFO (frequency c. 5 - 6 Hz) to modulate the
frequency-shift and continuously alter the side-bands.

LFO

The Up and Down outputs are sent to left and right
stereo channels respectively.

fig. 2: percussive stereo effect

5

A-126

VC Frequency Shifter

System A - 100

doepfer

If you increase the LFO frequency into the audio range
(above about 20 Hz), other effects are produced.

Particularly if the LFO frequency is harmonically rela­ted to the fundamental of the audio signal, this can be
a very pleasing effect.

One popular effect in the past was to

frequency-shift

an octave band of sound, produced by band-pass

filtering the output from a noise module (see fig. 3).

VCF

VCFSA-118

CV In

LFO

fig. 3: frequency-shifting an octave band

Interesting and unusual

percussion sounds

can be

produced with the patch in fig. 4.

In this patch, a percussive sound (e.g. kick drum,
snare) is fed into the frequency shifter. Using the shift
control, you can then alter the apparent size of the
instrument.

By deriving a trigger or gate signal from the drum, and
controlling the frequency shifting with a short enve­lope, some effective and exciting percussion sounds
emerge.

VCFS

Up

Drum­Signal

A-119 ADSR

Audio

In

Gate

Out

fig. 4: using the A-126 for new percussion sounds

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doepfer

System A - 100

VC Frequency Shifter

A-126

Very interesting sound textures can result from a

combination of frequency shifting and frequency
modulation (see. fig. 5).

Just combining the two VCOs with frequency-shifting
and FM can produce a wide range of massive sounds,
and adding dynamic control of the frequency-shifting
by using an ADSR can make them even more inter­esting. A whole new category of sounds is waiting to
be explored.

VCO 1

VCO 2

CV

Gate

: combining frequency-shifting and FM

fig. 5

VCA

ADSR

VCFS

Up

By using a mixer module A-138b, and altering the
relative levels of the Up, Down and original signals, the
tonal possibilities of the frequency shifter can be ex­panded still further.

Audio Out

A-126

Up

Down

A-138 b

fig. 6: mixing the Up, Down and original signals to

produce your chosen blend of sound

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A-126

VC Frequency Shifter

System A - 100

7. 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.

P • Draw in patchleads with colored

pens.

• Draw or write control settings in the
little white circles.

A-126

VC Frequency Shifter

Audio In

Overload

Audio Out

CV

Mix

Output

Down

Output

0

0

0

0

Up

Output

VCFS

Level

10

Shift

10

CV

10

Mix

10

A-126

VC Frequency Shifter

Audio In

Overload

Audio Out

CV

Mix

Output

Down

Output

0

0

0

0

Output

VCFS

Up

Level

10

10

10

10

Shift

CV

Mix

doepfer

A-126

VC Frequency Shifter

Audio In

0

Overload

Audio Out

CV

Mix

Output

Down

Output

0

0

0

Output

VCFS

Up

Level

10

Shift

10

CV

10

Mix

10

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