Manual

DOEPFER System A-100 Synthesizer Voice A-111-5
11
4. Controls
1 VCO Tune
2 VCO Range Switch (Octave Switch)
3a VCO FM Source Switch
3b VCO FM Level
This group of elements is responsible for the frequency of
the Voltage Controlled Oscillator (VCO).
Tune control 1 enables the tuning of the oscillator
frequency in a range of roughly one octave (or ± ½ octave).
By means of an internal jumper (JP4) the range can be
extended to roughly six octaves. For details please refer to
the appendix. The factory setting is one octave.
Switch 2 can be used to increase (upper position "+1") or
decrease (lower position "-1") the basic frequency of the
VCO by one octave.
Switch 3a and control 3b are responsible for the
frequency modulation (FM) of the VCO. Switch 3a is used
to select the FM source:
upper position: LFO1 = FM source
center position: no internal FM
lower position: ADSR = FM source
Control 3b is used to adjust the intensity of the internal
frequency modulation. A potentiometer with an exponential
scale is used to enable a finer resolution in the lower range.
In addition to the internal FM controlled by 3a and 3b the
control voltages applied to the A-100 bus CV line and to the
"VCO F" socket 1 modulate the frequency of the VCO as
described in chapter 3.
With Tune control and Range switch 2 at center position,
no frequency modulation (i.e. 3a = center or 3b = CCW)
and no external control voltages (socket "VCO F" and A-100
bus CV line) the VCO frequency is about 65 Hz ("C").
4 VCO Waveshape Switch
This switch is used to select the "first" waveform:
upper position: triangle
center position: no wave
lower position: sawtooth
To this "first" waveform the rectangle can be added (see
below).
A detailed description of the sound and overtone content
(spectrum) of different waveforms can be found in the user
manuals of the modules A-110 and A-111.