DOEPFER Dark Energy - Page 29

29
Basics of Soundgeneration
Dark EnerGy
DOEPFER
Thereareseveralwaystocontrol the lter’s cutoff frequency.First,itcanbeadjustedmanuallywiththe
Freq.knob.FurthermoretheADSRaswellasLFO2caninuencethecutofffrequencywithanyintensity.
TheintensityissetbytheXMknob.Additionally,thelter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,
usingaswitch,youcandeterminewhethertheVCFcutofffrequencytrackstheVCOfrequencyfully,half
ornotatall(keyboardtracking,keyboardfollow).Filterresonancecanbeadjusteduntilselfoscillationof
thelteroccurs.SimilarappliestotheVCO-LFO(LFO1)withregardtotheLFOforthelter(LFO2).LFO
2canalsoproducefrequenciesuptotheaudiorange.ThetonalresultsofVCFfrequencymodulationwith
audiofrequenciesaresimilartothoseoftheVCO.YoucancreatetypicalFMmetallicsoundsespecially
withhighfrequencieswhetheryouusetonalbasematerial(VCO/externalaudiosignal)ornot.Youcan
evencreatevoice-similarsoundswhensettingtheVCFtotheappropriatesettingandusingslowlypro-
gressingADSRenvelopes.Thesoundwillbecomerealyextreme,ifyouusefrequencymodulationwithau-
diofrequenciesforbothVCFandVCO.Thetonalresultsarenearlyunpredictable.Thereisonlyoneway:
tryitout;veryoftentheresultsaretotallysurprising.
Veryunusualinanaloguesynthesizersbutmusicallyusefulisthelinearfrequencymodulation,featuredby
DarkEnergy.HeretheVCFscutofffrequencyismodulatedinalinearmatterbythetrianglewaveofthe
VCO.IntensityissetbytheLMknob.ThisfeatureisveryusefulforFMsoundswiththelterworkingas
asinewaveoscillator(selfoscillating)thatkeeptheirharmoniccontentwhilethesoundise.g.playedbya
sequencer,keyboardorUSB/MIDIinterface.
Ampliers
Thevoltagecontroplledamplier(VCA)emphasesthesoundbetweenthefactor0and1,dependingona
controlvoltage,usuallyprovidedbytheenvelopegeneratorand/ortheLFO.TheVCAcontrolstheloudness
contourofthesound,resp.theirarticulation,touseamusicalterm.
TheabovedescribedcomponentsVCO,VCFandVCAgenerateresp.processtheaudiosignalitself.Next
tothis,wealreadymentionedcomponentsthatdonotgenerateanyaudiblesignals,butprovidecontrol
voltages to modulate the parameters of the soundprocessing modules. These are the envelope generator
(orADSR)andtheLowFrequencyGenerator(LFO).
Envelope Generators
Envelopegenerators,typicallyoftheADSRtype(attack-decay-
sustain-release),produceasequenceoffourvoltageswhichcan
beusedforcontrollingtheVCOpitch,VCFcutofffrequencyand
theVCAamplication.TheADSRproducesa“oneshot”contour
inoppositetoanLFO,whichgeneratesafrequentmodulation.
Theenvelopeconsistsof4parameters:attacktime,decaytime,
sustain level and release time. When pressing a key on a key-
board(note-oncommand/gate=on),theenveloperiseswithin
aperiodoftimewhichcanbesetbytheattackcontrol.After
reachingitsmaximumtheenvelopedecaysdowntothesustain
levelwithinaperiodoftimeadjustablebythedecaycontrol.The
envelopestaysonthisleveluntilthekeyisreleased(note-off
command/gate=off).Thenitdecreasestozerowithinaperiod
oftimeadjustablewiththereleasecontrol.
: ADSR-Hüllkurve und ihre Parameter
Sustain
Level
Attack
Time
Decay
Time
Release
Time
+3 ... +12
V
0
V
On
O
Zeit
ca. +8 V