doepfer
A-145
LFO
System A - 100
1. Introduction
Module A-145 (LFO) is a low frequency oscillator,
which produces cyclical control voltages in a very wide
range of frequencies.
Five waveforms are available: sawtooth, inverted
sawtooth, triangle, sine
and
square wave
LFO A-145
.
Reset In
Frequ.
Frequ.
Range
The LFO can be used as a
any number of modules - for instance modulating the
pulse width or frequency of a VCO, modulation of the
cut-off frequency of a VCF, or amplitude modulation
with a VCA.
A three-way switch lets you select three frequency
ranges, spanning from one cycle every several minutes at the lowest, to audio frequency at the highest.
The LFO signal can also be synchronised, via the
reset input.
modulation source
for
1
A-145
LFO
System A - 100
doepfer
2. Overview
➊
➋
➌
➍
➎
➏
A-145
Reset In
MHL
0
LFO
Frequ.
10
Frequ.
Range
➀
➁
➂
➃
Controls and indicators
LED: frequency indicator for the sawtooth
1
wave at output "
: frequency indicator for the sine and
LED
2
square waves at output § and/or
3 Frequ.: frequency control
4
Frequ. Range
:switch for selecting frequency range
In / Outputs
!
"
§ : output: sine wave
$ : output: triangle
% : output: square wave
& Reset In: synchronisation input
: output: inverted sawtooth
: output: sawtooth
$
2
doepfer
System A - 100
LFO A-145
3. Controls and indicators
1 LED ... 2 LED
LEDs 1 and 2 show the frequency of the voltage
output at sockets " to $.
H
3 Frequ.
This control adjusts the frequency of the LFO, within
the parameters of the frequency range set by switch
4.
4 Frequ. Range
Use switch 4 to select a suitable frequency range from
the three available:
• L (low):up to several minutes per cycle
•
• H
If the LFO frequency goes above about 15
Hz, our persistence of vision means that the
LEDs look permanently on.
M (medium): normal LFO range
(high): audio range
4. In / Outputs
!
This is the output for the
(Amplitude: ± 2.5 V).
inverted sawtooth
"
This is the output for the ordinary sawtooth, whose
frequency is displayed by LED 1.
(Amplitude: ± 2.5 V).
§
This is the output for the sine wave, whose frequency
is displayed by LED 2. (Amplitude: ± 2.5 V.)
$
This is the output for the triangle wave, whose frequency is displayed by LED 2. (Amplitude: ± 2.5 V.)
%
.
This is the output for the square wave
(Amplitude: ± 2.5 V.)
3
A-145
LFO
System A - 100
doepfer
& Reset In
LFO synchronisation is possible, by sending a trigger
signal (eg. a gate) to the
reset input
. Every time a
trigger voltage is sensed (for instance when a key is
pressed), the LFO’s waveform resets, and starts from
its zero point (see Fig. 2).
Without synchronisation, the LFO is free running, so
that wherever the waveform is when the trigger arrives, that’s where it starts from (see Fig. 1).
P Particularly with lower frequency modulati-
ons, you can use the reset / synchronisation
option to make sure that the LFO starts from
zero whenever a key is pressed (Keyboard
Gate Ö Reset LFO).
If you don’t want this effect, then leave the
reset input unconnected, for a random LFO
waveform response.
Trigger
Moment
Time
Off
On
Fig. 1: LFO without
Synchronisation Synchronisation
Trigger
Moment
➨
Off
Time
➨
On
Fig. 2: LFO with
4
doepfer
System A - 100
LFO A-145
5. User examples
An LFO can be used for all sorts of different modulations:
• LFO - VCA (A-130, A-131, A-132)
Modulation of the gain produces
• LFO - VCF (A-120, A-121, A-122, A-123)
Modulation of the cut-off frequency produces cyclical variation in tone colour - Wah-wah
• LFO - VCO (PWM A-110, A-111)
Pulse width modulation using the LFO produces
cyclical variation in tone colour (phasing type)
LFO - VCO (FM A-110, A-111)
•
Pitch modulation using LFO produces vibrato.
• LFO - VCP (A-125)
Phase shift modulation using LFO produces cyclic
phasings or phase vibrato
The above effects occur with LFO frequencies in the
sub-audio range. Once the LFO gets into the audio
range, timbral changes always occur. Examples and
further notes can be found in the manuals for the
respective modules.
Tremolo
Producing echo effects
As well as modulation effects, LFOs can also create
time-based
used to produce an echo effect. The frequency and
waveform of the LFO determine the delay-time and
character of the sound, and the ADSR parameters
determine the envelope and feedback amount of the
echoes.
VCO
Fig. 3
repeat effects
: Producing an echo effect
. In Fig. 3 the LFO is being
GA T E
VCA 1 VCA
LFO
ADSR
2
5
A-145
LFO
6. Patch-Sheet
System A - 100
doepfer
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-145
Reset In
MHL
0
LFO
Frequ.
Frequ.
Range
A-145
LFO
Frequ.
10
MHL
0
Frequ.
Range
10
Reset In
A-145
Reset In
MHL
0
LFO
Frequ.
10
Frequ.
Range
6
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