PROEL DSO480 - Low;High Pass Variable ‘Q’ Filter; Elliptical filters

38
Low/High Pass Variable ‘Q’ Filter (Low Pass shown)

InA Input A LPF:1~~\
1k00Hz Q=3.0 LPF VarQ

Remember–tochangefiltertypes,pressBYPASSto
bypassthefilter,andthenuseENTERtoselectthefilter
type.

Thelowandhighpassvariable‘Q’filtershaveadjustable
frequencyand‘Q’(orBandwidth)controls.The‘Q’
controladjustthedampingofthefilter,sothatlow‘Q
’
settingsshowlessovershootattheturnoverfrequency,
butalsoslowerroll‐off.

Rememberthat‘Q’is1/Bandwidth,sothehigherthe
‘Q’,thelowertheBandwidth,andthesmallertherange
offrequenciesaffected.Thefilterisprimarily12
dB/Octave,butinachievingthissortofroll‐offwitha
high‘Q
’valuewillresultinquitealargeovershootin
levelattheturnoverfrequency.Thistypeoffilterisoftenalsocalledaresonantfilter.
Elliptical filters

InA Input A HPF:1/~~
1k00Hz HP Ellip

Remember–tochangefiltertypes,pressBYPASSto
bypassthefilter,andthenuseENTERtoselectthefilter
type.

Theellipticalfilterhasadjustablefrequencyonly .This
setsthe3dBpointofthefilterwhichfeaturesasteep
roll‐off(ofapprox36dB/OctavedowntooneOctave
above(o
rbelowinthecaseofaHPF)theturnover
frequency.

However,thegaindoesincreaseagainabovethis
frequencytosettleat12dBdownfrom0dBr.Thisfilter
canbeusedinconjunctionwiththestandardcrossover
filterstoproducesharperroll‐offsthanwouldbe
otherwiseachievable.

Theuseofthisfilterisexpl
ainedinthefollowingexample.