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DOEPFER System A-100 Quad LFO A-143-3
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1. Introduction
Module A-143-3 Quad LFO is a low-cost four-fold
modulation oscillator and includes four independent low
frequency oscillators (LFO's), which produce cyclical
control voltages in a wide frequency range.
Three waveforms are available for each LFO: triangle,
square and sawtooth. The frequency of the sawtooth
output is twice the frequency of the other outputs.
The LFO's can be used as modulation sources for any
control voltage input of other modules - for instance
modulating the pulse width or frequency of a VCO,
modulating the cut-off frequency of a VCF or the phase-shift
of a VCP, amplitude modulation with a VCA, delay time of a
BBD module, parameters of a voltage controlled wave
shaper/multiplier, or any other control voltage input.
A three-way switch let’s you select three frequency ranges,
spanning from about two cycles per minute at the lowest, to
moderate audio frequency at the highest.
The module includes four identical units.
Fig. 1: A-143-3 Controls and Outputs
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Quad LFO A-143-3 System A-100 DOEPFER
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2. Overview
3
1
2
!
§
"
Controls:
1 Frequ. : frequency control
2 Range: frequency range switch
3 :LED control
Outputs:
! : triangle output
: rectangle output
"
: sawtooth output
§
The controls and outputs are the same for all four sub-units.
Module width: 14 HP / 70.8 mm
Module current: 70 mA
Fig. 2: A-143-3 front panel
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DOEPFER
DOEPFER System A-100 Quad LFO A-143-3
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3. Controls and Outputs
1 Frequency
This control adjusts the frequency of the LFO within the
frequency range set by the range switch 2.
2 Range
Use switch 2 to select a suitable frequency range:
• L (low): minimum about 2 cycles per minute
• M (medium): normal LFO range
• H (high): moderate audio range
Pay attention that the high range is in the middle position
due to technical reasons.
LED
3
LED 3 displays the triangle signal that appears at socket !.
If the LFO frequency goes above about 25 Hz, our
persistence of vision means that the LEDs look permanently
on.
!
This is the output for the triangle wave, whose frequency is
displayed by LED 3. The output is symmetrical around 0V,
the level is about ± 7 V.
"
This is the output for the square wave. The output is
symmetrical around 0V, the level is about ± 6 V.
§
This is the output for the sawtooth wave. The output is
symmetrical around 0V, the level is about ± 7 V. To obtain
an inverted sawtooth the voltage inverter module A-175 may
be used.
Fig. 3: A-143-3 waveforms and levels
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Quad LFO A-143-3 System A-100 DOEPFER
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4. User Examples
An LFO can be used for all sorts of different modulations:
• VCO Pitch/Frequency Modulation
Pitch/frequency modulation of a VCO produces vibrato.
• VCO Pulse Width Modulation
Pulse width modulation of a VCO produces cyclical
variation in tone colour (sounds similar to phasing)
• VCA Loudness Modulation
Modulation of the gain of a VCA produces Tremolo
• VCF Frequency or Resonance Modulation
Modulation of the cut-off frequency of a VCF produces
cyclical variation in tone colour. For some filters even the
resonance can be modulated.
• VCP Phase Shift Modulation
Phase shift modulation of a phaser (e.g. A-101-3 or A-
125) produces cyclic phasings or phase vibrato
Please refer to the user’s manual of other LFOs or
modulation sources for detail (A-145, A-146, A-147, A-1491, A-118 random output).
By means of the universal vactrol module A-101-9 the
frequency can be voltage controlled. Please refer to the A101-9 manual for details.
In principle any control voltage input can be controlled by an
LFO to modulate the parameter in question.
A special application of the quad LFO is the simultaneous
modulation of several parameters of the same module.
Example #1: Wave Multiplier A-137
• LFO 1 controls Multiplication
• LFO 2 controls Folding Level
• LFO 3 controls Folding Symmetry
• LFO 4 controls Harmonics
Example #2: VC Mixer A-135
• LFO 1 controls VCA1
• LFO 2 controls VCA2
• LFO 3 controls VCA3
• LFO 4 controls VCA4
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