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Doepfer A-123 24dB High Pass (no longer available) User Manual

System a - 100, A-123, Introduction

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doepfer

System A - 100

VCF 4

A-123

1

1. Introduction

Module A-123 (VCF 4) is a voltage-controlled high-
pass filter
, which filters out the lower parts of the
sound spectrum, and lets higher 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). Two CV inputs are available.

The cut-off slope is -24 dB/octave. The circuitry uses
a Curtis CEM 3320 chip.

Voltage controlled resonance: on the VCF 4, reso-
nance can be controlled not just manually, but by
voltages as well, right up to self-oscillation. In this
case, the filter behaves like a sine wave oscillator.

FCV 1

Resonance

FCV 2

QCV

Audio

In

Level

Audio
Out

QCV

Frequency

A-123

VCF 4

FCV 2