Using the A-100 for Sound Processing

A-119 External Input /
Envelope Follower

The A-119 External Input / Envelope Follower module allows you to integrate any audio signal (electric guitar, microphone, midi sound module, computer sound card, CD player, tape-recorder ...) into your A-100 system.

Audio inputs of audio-processing A-100 modules (e.g. filter, VCA, phaser, flanger, waveform processor, distortion, wave multiplier, ring modulator, frequency shifter, spring reverb, panning ...) all require line level signals of around 1Vss. , and if the signal source does not have the required level an external pre-amplifier like the A-119 is recommended. 

This module consists of a (pre-)amplifier, an envelope follower and a comparator.

The pre-amp has 2 inputs, one unbalanced (Asymmetric) for line level signals, and a balanced (6.3mm jack /Symmetric) input for inserting low level signals, like microphones or electric guitars.
The module provides two simultaneous audio outputs of the amplified signal.

The envelope follower 'reads' an incoming audio-signal and sends out a proportional voltage as an envelope to its own output.
The brightness of the LED indicates the envelope output level, which is very useful...

The voltage at the output signal can be used to control the filter frequency, loudness or any other voltage controlled parameters such as filter resonance, LFO speed, clipping level, wave multiples, frequency shift, phase shift, delay time and more...

The comparator generates Gate signals out of the incoming signal.

Whenever the audio input exceeds a certain (adjustable) level, a Gate-signal is produced.

This signal can again be used to trigger various other external modules like envelope generators or even voltage controlled switching.

Again, this is a very useful module that i cannot do without anymore because i often use external audio inputs. Most of the times i have a microphone plugged in for vocoder use or for filtering pleasures, but i have used it with my guitar and other audio too.
I do find it a bit strange that it is not included in one of Doepfer's pre-configured basic systems, for me it was a must-have.