Doepfer A-126 VC User Manual

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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

doepfer

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