Doepfer Dark Energy II - Manual (Page 29)

29
Dark EnerGy II DOEPFER Nuts and Bolts of Sound Generation
instead of the VCO for special applications.
You guessed it - Dark Energy II’s filter is also capable of self-oscil-
lating and thus creating a whole lot of typical synthesizer sounds.
There are several ways to control the filter’s cutoff frequency.
First, it can be adjusted manually by the “Freq.” pot. ADSR as well
as LFO 2 can influence the cutoff frequency at varying degrees of
intensity, too.
The intensity is set by the XFM control. Additionally, the filter is
controllable via MIDI, i.e. its cutoff frequency can be controlled by
any MIDI controller and / or by the velocity data of the incoming
MIDI notes. Finally, by using a switch, you can determine whether
the VCF cutoff frequency follows the VCO frequency (keyboard
tracking, keyboard follow). Filter resonance can be adjusted until
self-oscillation of the filter occurs. The same applies to the VCO-
LFO (LFO 1) with regard to the LFO for the filter (LFO 2). LFO 2
can also produce frequencies up to audio range. The timbral results of VCF frequency modulation by audio
frequencies are similar to those of the VCO. You can create metallic sounds typical of FM synthesis, espe-
cially at high frequency settings, no matter whether you use tonal material (VCO / external audio signal) or
not. You can even create vowely sounds when setting the VCF to the appropriate value, using slowly evolv-
ing ADSR envelopes. The sound will become really extreme if you use frequency modulation at audio rate
for both VCF and VCO. The tonal results are nearly unpredictable. There is only one way to tell: Go ahead,
and watch your eardrums! More often than once the results will be totally surprising.
Amplifiers
The voltage-controlled amplifier (VCA) amplifies – would you have guessed – the sound by a factor be-
tween 0 and 1, governed by a control voltage, usually from the envelope generator and/or the LFO. The
VCA controls the loudness contour of the sound or its articulation, if you want to use a musical term.
The text above explained how the components VCO, VCF, and VCA generate or process the audio signal
itself.
We have already mentioned components that do not generate any audible signals, but generate control
voltages to modulate the parameters of the sound-processing modules with. These are the envelope gen-
erator (or ADSR) and the Low Frequency Oscillator (LFO).
Envelope Generators
Envelope generators, usually of the ADSR species (attack - decay
- sustain - release), produce a sequence of four voltages which
can be used for controlling VCO frequency, VCF cutoff frequency,
and VCA amplitude. The ADSR produces a “one shot” contour in
contrast to an LFO which generates a continuous modulation. The
envelope is made up of 4 parameters: attack time, decay time,
sustain level, and release time.
When depressing a key on a keyboard (note-on command / gate
= on), the envelope will rise within a period of time which can be
set by the “attack” control. After reaching its maximum, the enve-
lope will decay to the sustain level within a period of time, adjust-
able by the “decay” control. The envelope will sustain this level
until the key is released again (note-off command / gate = off).
Then it will return to zero within a period of time adjustable with
the “release” control.
Resonance changes the filter characteristics
f
c
Resonance
Frequency
0 db
Attenuation
ADSR Envelope and its Parameters
Sustain
Level
Attack
Time
Decay
Time
Release
Time
+3 ... +12 V
0 V
On Off
Time
ca. +8 V
CV Output Level
Gate