Kurzweil PC3K8 - Filters; Envelope Filter; Triggered Filter; Resonant Filter

9-18
Effects
Filters
Spacingdeterminesthestartingpitchofthedescendingbuzzandhowfastitdescends,by
settingtheinitialseparationofimpulsesandthesubsequentrateofincreasingimpul se
separation.Thespacingbetweenimpulsesisgiveninsamples(20.8μs).Atlowvalues,thebuzz
startsathighfrequenciesanddropsslowly,
whileathighvaluesthebuzzstartsatalowerpitch
anddropsrapidly.Rangeis0.0to40.0samples,witharesolutionof0.2sample.
Contourcontrolstheoverallshapeofthereverb.Whensettoahighvalue,soundspassed
throughthereverbstartatahighlevel,and
itslowlydecays.Asthecontrolvalueisreduced,it
takesmoretimefortheeffecttobuildupbeforedecaying.Atavalueofaround34%,thereverb
behaveslikeareversereverb,buildinguptoahit. Whenitissettozero,thealgorithmactslikea
simpledelay.Rangeis0to100%.
Filters
TherearefourtypesofResonantFilteralgorith msinthePC3K.Allofthemhavethese
parametersincommon:
FilterType(orFiltType)canbeLowpass,Highpass,Bandpass,orNotch(band‐cut).
Resonanceistheresonanceofthefilter,adjustablefrom0to50dB.
Resonant Filter
Frequency(orFreq)isthefixedresonantfrequencyofthefilter.Itsrangeis16to8372Hz.
Envelope Filter
EnvelopeFilterisaresonantfilterwhosecenterfrequencycanbemadetovaryaccordingtothe
leveloftheincomingsignal.
FilterTypecanbeLowpass,Highpass,Bandpass,orNotch(band‐cut).
MinFreqistheminimumresonantfrequencyofthefilter,thatis,thefilterfrequencywhenthe
inputgain
isbelowthetriggeringthreshold.Itsrangeis16to8372Hz.
Sweepdetermineshowfartheresonantfrequencymoveswhentheinputlevelincreases.At
positivelevelsitmovesupinpitch,andatnegativelevelsitmovesdown.Thehighestpossible
resonantfrequencyis8372Hz,thelowestis
0Hz.Thisparameter’srangeis‐100%to+100%.
Resonanceistheresonanceofthefilter,adjustablefrom0to50dB.
AtkRateadjuststheupwardslewoftheatta ckportionoftheenvelopedetector.Rangeis0to
300.0dB/sec.
RelRateadjuststhedownwardslewofthereleaseportion.
Rangeis0to300.0dB/sec.
SmoothRateslowsdowntheenvelopefollower.IfitissettoalowerratethanAtkRateorRel
Rate,itcandominatethoseparameters.Rangeis0to300.0dB/sec.
Triggered Filter
TheTriggeredFilterisasweepingresonantfilterthattriggerswhenacertaininputthresholdis
reached,andthenfollowsitsownenvelope,consistingofaninstantaneousattackandan
exponentialrelease,ratherthantheenvelopeoftheinputsignal.
MaxFreqistheresonantfrequencyofthefilteratthe
peakoftheinternalenvelope.Itcanbeset
lowerthanMinFreq(above),inwhichcasethefilterwillsweepdownwards,thenbackup.
Rangeis16to8372Hz.