Owner's manual

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doepfer

System A - 100

VCF 1 A-120

1. Introduction

Module A-120 (VCF 1) is a voltage controlled low-

pass filter, which filters out the higher parts of the

sound spectrum, and lets lower frequencies pass

through.

The Cut-Off Frequency determines the point at which

filtering takes effect. You can control this manually, or

by voltage control (filter modulation, for instance by

an LFO). Three CV inputs are available, and the sum

of the voltages from these affects the filter cut-off.

VCF1 is a co-called "transistor ladder" design, with a

cut-off slope of -24 dB/octave, as in various Moog

synthesizers. That’s what gives it its classic, legendary

Moog sound.

Resonance (or Emphasis) is adjustable all the way up

to self-oscillation - in which case the filter behaves like

a sine wave oscillator.

CV 1

Resonance

CV 3

CV 2

A udio In

Lev el

Audio

Out

CV 2

Frequency

A-120

VCF 1

CV 3

Summary of content (8 pages)

PAGE 1
System A - 100 doepfer VCF 1 A-120 1. Introduction CV 1 A-120 VCF 1 CV 2 CV 2 CV 3 CV 3 Frequency Lev el The Cut-Off Frequency determines the point at which filtering takes effect. You can control this manually, or by voltage control (filter modulation, for instance by an LFO). Three CV inputs are available, and the sum of the voltages from these affects the filter cut-off. VCF1 is a co-called "transistor ladder" design, with a cut-off slope of -24 dB/octave, as in various Moog synthesizers.
PAGE 2
A-120 VCF 1 System A - 100 Controls: 2. VCF 1 - Overview A-120 VCF 1 LOW PASS FILTER CV 1 Freq. 0 doepfer ➀ 1 Freq.: Cut-off frequency control 2 CV 2: Attenuator for CV at input " 3 CV 3: Attenuator for CV at input § 4 Lev.: Attenuator for audio input $ 5 Res.: Control for setting the filter’s resonance (emphasis) 10 CV 2 CV 2 0 ➁ 10 CV 3 CV 3 0 ➂ 10 Audio In Lev. 0 ➃ 10 Res.
PAGE 3
System A - 100 doepfer 2 CV 2 3. Controls 1 Freq. With this control you adjust the Cut-Off Frequency fc, above which the filter attenuates all frequencies. At 10, the filter is fully open. The more you turn down this control, the more the high frequencies are filtered. The sound becomes mellower and less bright (see Fig. 1) until at 0 the filter is completely shut, and there will be no output signal at all.
PAGE 4
A-120 VCF 1 System A - 100 doepfer modulated by its voltage: ie., the sound color changes according to the voltage put out by the modulator. Resonance 0 db If you use the VCF as a sine wave oscillator, connect the pitch CV into this socket. Do the same if you want the filter’s cut-off frequency to track exactly with the pitch of a note. " CV 2 fc Fig. 2: Frequency ➨ How resonance affects the response of a low pass filter 4.
PAGE 5
doepfer System A - 100 VCF 1 A-120 5. User examples Producing wind FX with A-120 and A-118 The filter’s cut-off frequency can be modulated in various ways: D Patch coloured noise into the audio input, and random voltage CV into CV2. Set the filter CV to 0, cut-off to a middle value, and the resonance just below self-oscillation. • VCF - LFO Modulation of the cut-off frequency produces cyclical changes of the sound spectrum. At low frequencies (c. 1 - 5 Hz), you get a "Wah-Wah"effect.
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A-120 VCF 1 6 System A - 100 doepfer
PAGE 7
doepfer System A - 100 VCF 1 A-120 6. 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. 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. A-120 VCF 1 A-120 VCF 1 CV 1 CV 1 10 CV 1 0 10 0 0 P • Draw in patchleads with colored pens.
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A-120 VCF 1 8 System A - 100 doepfer