ECF-42 Envelope Controlled Filter

The ECF-42 is a multimode filter with a built in envelope generator. It is mainly designed to be used together with pattern devices to create pattern controlled filter and envelope effects, but it can also be triggered via MIDI, or used as a “static” filter for shaping the sound of an instrument device or a whole mix.

Usage

The Envelope Controlled Filter is best connected as an insert effect. However, unlike the other effects it is not a pure “stand-alone” device. To make the most of the ECF-42, you need either CV/Gate from an external device or MIDI notes from a sequencer track.

•	If you connect a device to the ECF-42 using audio inputs/outputs only, it will simply act as a filter with no velocity or envelope modulation.

Hence, all filter parameters are “static”, unless you manually turn the knobs or automate them in the sequencer.

•	Connecting a gate signal to the Env Gate input on the back panel of the device allows you to trigger the envelope generator for the filter.

Note that the ECF-42 envelope generator is not triggered by the audio itself - the envelope parameters won’t do anything unless the device receives gate signals.

•	By creating a sequencer track connected to the ECF-42, you can have the envelope triggered by MIDI notes on the track.

The envelope is affected by the position, length and velocity of the MIDI notes (but not by their pitch).

If you are unfamiliar with basic filter and envelope parameters, please refer to “Envelopes - General” in the Subtractor chapter for a description of these.

The Filter Parameters

The ECF-42 filter section has the following parameters:

| Parameter	| Description
Mode	This button sets the desired filter mode. Three modes are available: 24dB/octave lowpass, 12dB/octave lowpass and 12dB/octave bandpass.
Freq	This is the filter cutoff frequency. When using the ECF-42 in “static” mode (without triggering the envelope), this parameter adjusts the frequency content of the sound. When using the envelope, the Freq parameter serves as the start and end frequency for the filter sweep.
Res	This is the filter resonance. Raising this produces a more extreme, “synthy” effect.
Env Amt	Determines how much the filter frequency should be affected when the envelope is triggered. The higher the value, the more drastic the effect. Note though, that if the Freq parameter is set high, raising the Envelope Amount will not make any difference over a certain value! This is because the filter is already fully opened - try lowering the Freq parameter in that case.
Velocity	This parameter determines how much the gate velocity value should affect the envelope amount.

The Envelope Parameters

This is a standard envelope generator with Attack, Decay, Sustain and Release parameters. It is triggered by a gate signal connected to the Env Gate input on the back panel, or by MIDI notes on a sequencer track connected to the ECF-42. The parameters have the following functionality:

| Parameter	| Description
A (Attack)	When the envelope is triggered, this is the time it takes before the envelope signal reaches its max value.
D (Decay)	After reaching its max value, this is the time it takes for the envelope signal to reach the sustain level.
S (Sustain)	If the gate remains open (or the MIDI note is held), the envelope signal will remain on this level.
R (Release)	When the gate is closed (gate CV goes back to 0) or the MIDI note ends, this is the time it takes for the envelope signal to drop from its current value to the start value (set by the Freq parameter).

•	The Gate indicator lights up when the device receives a signal to the Env. Gate input on the back panel or a MIDI note from a sequencer track.

CV/Gate Inputs

On the back panel of the ECF-42, you can find the following CV/Gate inputs:

•

Freq CV.

Use this for controlling the filter frequency from another device. For smooth filter modulation, try connecting an LFO to this input.

•

Decay CV.

For controlling the envelope decay parameter from another device.

•

Res CV.

Allows you to control the filter resonance from another device. Can be very effective in combination with filter frequency sweeps.

•	Env. Gate.

This is where you connect a gate signal (e.g. from a Matrix or Redrum device) for triggering the envelope.

Pattern Controlled Filter - An Example

This example shows how to use the ECF-42 and the Matrix to create pattern controlled filter effects. Proceed as follows:

1.	Start with an empty Song.

2.	Create a Mixer.

3.	Create a Subtractor Synthesizer.

An Init Patch will work fine for these examples.

4.	Create an ECF-42.

5.	Create a Matrix Pattern Sequencer.

If you flip the rack around, you can see that the audio out from the Subtractor is passed through the ECF-42 and then on to the Mixer. The Matrix Curve CV is connected to the ECF-42 Frequency CV parameter, and the Matrix Gate CV is connected to the ECF-42 Env Gate input.

6.	Select the Track connected to the Subtractor (given that you are handling MIDI input via the sequencer) so that you can play it from your keyboard.

If you play a few notes and turn the ECF-42 filter freq knob, you should hear the sound being filtered.

7.	Draw a Gate pattern in the Matrix, using mixed velocity values.

Draw only a Gate pattern, not a Curve pattern.

8.	Set both the Env.Amt and Vel knobs on the ECF-42 to about “40”.

9.	Click the Run button on the Matrix panel.

10.	While in Run mode, hold a chord down on your keyboard.

Now you should hear the envelope (controlling the filter) being triggered with every gate step.

By increasing the Env.Amount, you determine how much the envelope parameters should affect the filter frequency.

By increasing the Vel. parameter, you determine how much the gate velocity should affect the filter frequency.

If the filter effect isn’t very noticeable, try lowering the filter frequency, and raising the Res value.

11.	Set both the Env.Amt and Vel knobs on the ECF-42 to “0”.

12.	With the Matrix still playing, draw a Curve pattern in the Matrix pattern window.

Now, you should hear the filter frequency being modulated by the curve pattern. By combining the various parameters you can create many new filter effects.

You can also control the ECF-42 from other devices with CV and/or Gate outputs.

Triggering the ECF-42 via MIDI

To trigger the envelope in the ECF-42, proceed as follows:

1.	Create a sequencer track for the ECF-42.

This is easiest done by bringing up the context menu for the device and selecting “Create Track for XX” (where “XX” is the name of this particular filter device).

2.	Record or draw some notes on the sequencer track.

Remember that the envelope takes the note length and velocity into account. The note pitches doesn’t matter.

3.	Play back the track.

The actual notes will not be heard (since the track is connected to the ECF-42, which produces no sound in itself) but the envelope will be triggered according to the notes.

You can even control the envelope “live” via MIDI: just set Master Keyboard input to the sequencer track for the ECF-42 and play your MIDI instrument!

To route MIDI input to a track, click on the device icon in the track list, so that the Master Keyboard Input frame appears around it.