Doepfer Dark Energy II - Manual (Page 15)

15
Dark EnerGy II DOEPFER Functions
setting of the „Freq.“ pot influences the modulation depth: The higher its set value, the less the effect of the
XFM knob on the sound. The XFM function uses exponential frequency modulation.
In some cases, FM has to be controlled and used in a very subtle way, especially when the filter is self-
oscillating (that is, working as a sinewave oscillator) and modulated by LFO2 at audio rate. In order to
optimize parameter scaling, the XFM control works in an exponential way. Thus, audible modulation might
require higher settings, especially when using the ADSR as a modulation source.
• XFM Source switch
This switch selects which source is to modulate the cutoff frequency exponentially. The switch toggles bet-
ween LFO2, envelope (ADSR) and no source (off). Controlling the cutoff frequency by the ADSR is one of
the most common applications as it imitates the typical timbral characteristics of most acoustic instruments
from bright- to dull-sounding. Of course, Dark Energy II‘s envelope generator allows many more ways of
shaping timbre.
LFO2 produces a periodic and continuous modulation signal. Low frequencies will create sweeps similar
to a „wah-wah“ pedal as used by guitarists. Using the LFO´s „high“ range setting, XFM will generate very
noisy sounds that cannot really be played tonally. This way of modulation is great for unique and interesting
„outer space type“ sound effects. Feel free to experiment with the settings of cutoff frequency, LFO2 speed
and XFM pot, and keep watching the skies while you are at it.
• Mode control
This knob crossfades continously between the different filter types. Turned fully counterclockwise, a 12 dB
lowpass is generated. By turning clockwise, the characteristics change to notch, further on to a 12 dB high-
pass (approx. at center position) and finally to a bandpass (close to fully clockwise position).
• Resonance control (Res)
This pot determines the intensity of the filter resonance. This effect depends a lot on the cutoff and mode
settings. At high resonance settings, the filter will start resonating and will generate a waveform close to a
sine wave. It can be used as an additional signal source to produce popular sound effects, e.g. typical syn-
thesizer percussion sounds when the cutoff is modulated by a suitable ADSR setting. Think disco hits ca.
1975 and you will get an idea.
When the filter is self-oscillating (high resonance) and the VCO is disabled (waveform switch at center po-
sition and PW pot turned fully clockwise or counter-clockwise), the filter will work as a sinewave oscillator. It
can be modulated by LFO2 (exponential FM).
• Tracking switch
The tracking switch has the positions „half / off / full“. It determines whether or how much the filter cutoff
frequency will depend on the pitch of the played key (resp. VCO pitch). When set to „full“, higher notes will
sound increasingly brighter, lower notes the duller the deeper you go on the keyboard. This corresponds
to the typical character of acoustic instruments. When set to „half“, this effect is less intense. If the filter is
self-oscillating and is to be played tonally as an oscillator from a MIDI keyboard, this switch has to be set to
„full“. This way it recieves the same control voltage as the VCO.
• VCF F Input
Please use this socket if you want to modulate the filter cutoff frequency by an external control voltage or
an external audio signal. This input also uses an (exponential) 1V/Oct scaling. This way the self-oscillating
VCF can be played (almost) chromatically (the scaling is not as precise as the VCO scaling due to technical
reasons but much better than found on many other analog synthesizers.) The control voltage fed into this
input will be added to the internal CVs (Freq. knob, tracking switch, XFM knob.) Please bear in mind that
the sum of these CVs cannot exceed the maximum value of the modulation depth range.
• Ext. Audio Input
It can be very interesting and musically useful to process external audio signals, such as acoustic instru-
ments, drum loops or even complete tracks, with the components of a synthesizer. You guessed it – Dark
Energy II offers an input socket for external audio signals which can be used as a sound source in addition