Access VIRUS C SERIES User Manual

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ACCESS VIRUS OS5 19Filter ModulationNow locate the FILT 1 MODE switch, which isalso located in the FILTERS section. It enablesyou to select a filter operating mode from thefour available options:- LP the low pass filter we have just discussed.- HP the high pass filter which works in the op-posite manner of the low pass filter: It sup-presses the lower frequencies in a signal andlets the higher frequencies pass.- BP the band pass filter which suppressesboth ends of the tonal spectrum and allowsonly a narrowly defined bandwidth of theoriginal sound to pass.- BS The band stop filter, band reject filter ornotch filter which works in the opposite man-ner of the bandpass filter. It allows all of thefrequencies of a signal except for a narrowfrequency band around the cutoff to pass.The term “notch” is fairly descriptive; youmight say this filter chops a notch out of thesound spectrum.Now activate the different operating modes androtate the Cutoff pot to get a feel for the wayeach filtering option works.Along with the Cutoff pot, the RESONANCE potis the most important control feature of a filter.The filter resonance increases the volume of thefrequencies located near the cutoff frequenciesand suppresses the more remote frequencies.This sound shaping feature has a striking effect- especially when used in conjunction with thelow pass filter: it produces a nasal or honkingtype of tone which increases as you turn theresonance up. Experiment by varying the RES-ONANCE setting in the different operatingmodes in conjunction with different Cutoff set-tings. You will find the effect that the RESO-NANCE pot achieves is markedly different forthe band stop filter in comparison to the effect ithas on the other filter types: as the resonanceincreases, the bandwidth of the notch decreas-es; in other words more frequencies on bothsides of the filter frequency are allowed to pass. FILTER MODULATIONOf course we don’t want to require you to exe-cute every sound modification manually bytwiddling pots. All kinds of sound modificationsin the VIRUS can be executed automaticallymuch in the way of your previous experimentswith the volume controls: The amplifier enve-lope can be described as a variable curvewhich, depending on the type and duration ofattack, hold and release data, automatically in-fluences (turns it up or down) an imaginary vol-ume pot.Similar procedures are applicable to the filterfrequencies. The FILTERS section features itsown envelope, the structure of which is identi-cal to the amplifier envelope, located directlyabove the amplifier envelope on the control fea-ture panel. Much like the amplifier envelope, thefilter envelope automatically “rotates” the Cutoffpot.However there is one significant difference be-tween the two envelopes. With the amplifier en-velope, you are always dealing with an initialvolume level of 0 because of course you wantabsolute silence prior to the beginning of anote. After the RELEASE phase, it is againSELECTSELECTMODEMODEFILT 1FILT 1 FILT 2FILT 2EDITEDITBPBPBSBSHPHPLPLPFILT 2FILT 2FILT 1FILT 1