Doepfer A-110 User Manual
doepfer
SYNC
A-110
System A - 100
1. Introduction
Module A-110 (VCO) is a voltage-controlled oscillator.
VCO
A-110
CV 2
PW CV 2
CV 1
CV 2
PW CV 1
PW CV 2
VCO
Range
Tune
PW
This VCO’s frequency range is about ten octaves. It
can produce four waveforms simultaneously: square,
sawtooth, triangle, and sine wave.
The Frequency or pitch of the VCO is determined by
the position of the octave (Range) switch and tuning
(Tune) knob, and by the voltage present at the CV
inputs. Frequency modulation (FM) of the VCO is
therefore a possibility. Footage (the octave of the
fundamental) is set by the Range control, and Fine
tuning controlled by the Tune knob.
You can control the pulse width of the square wave
either by hand, or by voltage control - Pulse Width
Modulation or PWM.
H
Because of the analog nature of the design,
the VCO may need about 20 minutes’ warmup time for the tuning to become completely
stable.
1
A-110
VCO
System A - 100
doepfer
2. VCO Overview
SYNC
CV 1
CV 2
PW CV 1
PW CV 2
VCO
STANDARD VCO
-2
Range
0
+2
Tune
10
0
10
0
10
0
PW CV 2
10
0
CV 2
PW
➀
➁
➂
➃
➄
Controls:
1 Range: 5-position Octave or Footage switch
2 Tune: Fine tuning control
3 CV 2: Attenuator for voltage at CV 2 ()
4 PW: Manual control for Pulse Width
5 PW CV 2: Attenuator for PWM voltage at PW
CV 2 ()
In / outputs:
! SYNC: Sync input
" CV 1: Voltage control input 1
§ CV 2: Voltage control input 2, level ad-
justable with ➂
$ PW CV 1: PWM input 1
% PW CV 2: PW M input 2, level adjustable with ➄
& : Sawtooth output
/ : Square wave output
( : Triangle wave output
) : Sine wave output
2
doepfer
System A - 100
3. Basics
Module A-110 puts out four waveforms simultaneously.
All these signals have the same pitch, since all are
controlled by the same voltages present at inputs "
and §.
Sawtooth
The VCO’s sawtooth waveform is present at output &.
It has a ‘cutting’ sound, rich in overtones. All the
harmonics of the fundamental are present, with a linear
reduction in intensity as the harmonic series progresses - so that the second harmonic is half as
100%
A-110
VCO
strong, the third is one third, the fourth a quarter, and
so on (see Fig. 1).
Sawtooth waves are ideal for synthesizing sounds
which are rich in harmonics, such as percussion, brass
or vocal timbres.
Square wave
The VCO produces a square / rectangle wave at output
/. You can alter its pulse width manually, or by voltage
control (Pulse Width Modulation).
c
a
b
0%
f1f
f3f4f
2
f
6
5
Harmonics
f7f8ff
Fig. 1: Harmonic spectrum of a sawtooth
1/f 1/f
9
➨
Fig 2: Square waves with different pulse widths
3
A-110
VCO
System A - 100
doepfer
A symmetrical Pulse wave (i.e. an exact square
wave, with a pulse width of 50 %), has only odd
harmonics of its fundamental (see Fig. 3) and produces a typically hollow sound.
100%
0%
f1f
f3f4f
2
f
6
5
Harmonics
f7f8ff
9
➨
Fig. 3: Harmonic spectrum of a true square wave
The further the pulse width deviates from 50% (see
Fig. 2, b and c), the weaker the lower harmonics
become, and the more the sound gets thin and nasal.
Square waves are often used as a sound source in
subtractive (filtered) synthesis, because of their rich
overtones, and are good at producing woodwind-like
timbres.
Triangle wave
A triangle wave (VCO Output () is poor in upper
harmonics, and sounds softer and more mellow. It only
contains odd harmonics, whose strength decreases
exponentially - the third harmonic is a ninth as strong,
the fifth 1/25, and so on.
100%
0%
f1f
2
f3f4f
Fig. 4: Harmonic spectrum of a triangle wave
Because of their soft, rounded timbre, triangle waves
are ideal for synthesizing timbres like flute, organ and
vibes.
f
6
5
Harmonics
f7f8ff
9
➨
4
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