Manual

ManualsBrandsDoepfer ManualsAudioA-110 Standard VCO

doepfer

System A - 100

VCO

A-110

1. Introduction

Module A-110 (VCO) is a voltage-controlled oscilla-

tor.

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.

Because of the analog nature of the design,

the VCO may need about 20 minutes’ warm-

up time for the tuning to become completely

stable.

SYNC

CV 2

PW CV 1

PW CV 2

CV 1

Range

A-110

VCO

Tune

Summary of content (12 pages)

PAGE 1
VCO A-110 System A - 100 doepfer 1. Introduction SYNC A-110 VCO CV 1 Range CV 2 CV 2 PW CV 1 Tune PW Module A-110 (VCO) is a voltage-controlled oscillator. 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.
PAGE 2
A-110 VCO System A - 100 Controls: 2.
PAGE 3
VCO A-110 System A - 100 doepfer 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 §. 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. Sawtooth The VCO’s sawtooth waveform is present at output &.
PAGE 4
A-110 VCO System A - 100 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% doepfer 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.
PAGE 5
System A - 100 doepfer VCO A-110 Sine Wave Frequency Modulation (FM) Sine waves are pure waves: they just contain the fundamental, without any harmonics (see Fig. 5). They are thus not suitable for subtractive synthesis (shaping sound with a filter). Because the frequency of the VCO is controlled by the voltages at inputs " and §, Frequency Modulation is possible: frequency (pitch) is continuously varied by the voltages at the CV input/s.
PAGE 6
A-110 VCO System A - 100 4. Controls 1 Range Footage (the octave of the fundamental) is controlled with this knob. Five settings are available, giving a wide frequency range. doepfer 3 CV 2 The pitch of the VCO is controlled by the voltages present at inputs " and §. The amount the control voltage at input § affects VCO pitch can be controlled with Attenuator 3 (see also §). 4 PW 2 Tune The TUNE control enables Fine Tuning of the oscillator frequency in a range of roughly ± ½ Octave.
PAGE 7
doepfer VCO A-110 System A - 100 5. In / Outputs ! SYNC Socket ! is the Sync Input for the VCO. What sync means in this context is that the waveform of one VCO ("Slave") is locked to the waveform of another VCO ("Master"), by connecting the audio out of the master VCO to the Sync input of the slave VCO. Master f >f M S Slave Slave with Hard Sync Master In the A-110, this is designed as "Hard Sync". Check out the following example (see Fig.
PAGE 8
A-110 VCO System A - 100 Input " is normally connected to a control voltage governing pitch (for instance from a MIDI-CV interface, or a master keyboard with a 1V / octave output). H Socket CV 1 " is designed as a normalled socket, connected to whatever CV is present on the internal System Bus. This CV (for instance from a master keyboard) governs the VCO’s pitch, unless a plug is inserted in socket " .
PAGE 9
System A - 100 doepfer When you try this out (see Fig. 8), start off with sine waves, and slowly raise the modulation frequency from the sub-audio into the audio range. 6. User examples FM in the audio range Using audio range oscillators for FM can produce interesting sounds.
PAGE 10
A-110 VCO System A - 100 doepfer Tone colour changes using VCO SYNC +1 0 -1 Fig. 9: exponential FM using the A-110 With FM in the audio range, the ear doesn’t resolve these octave transitions, but hears the whole sound as a very full and rather weird composite, with the middle frequency clearly at odds with the carrier frequency.
PAGE 11
VCO A-110 System A - 100 doepfer Pulse Width Modulation VCO and DIVIDER If you modulate the pulse width of a square wave with an LFO or ADSR (Pulse Width Modulation, or PWM), the harmonic spectrum constantly changes (see p.3, 4). Even with just one oscillator, you can create a dense timbre with internal movement, in some ways similar to vibrato, and otherwise only available by using two oscillators fractionally de-tuned from each other.
PAGE 12
A-110 VCO System A - 100 doepfer 7. Patch-Sheet 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. VCO VCO STANDARD VCO STANDARD VCO -2 -2 SYNC Range SYNC 0 0 +2 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.