Allen&Heath XONE 42 - Manual (Page 23)

Allen & Heath 23 XONE:42 User Guide
FILTER REFERENCE
The VCF Filters
A voltage controlled filter is an audio filter where the cut-off frequency is altered by a DC
control voltage rather than a variable resistor. This produces a much wider operating
range and more control over the filter response to create unlimited combinations of
tonal effect.
Filter Type Select
The filters are ‘state variable’. This means that they provide three simultaneous filter
types: high-pass, band-pass and low-pass. Three large illuminated switches select which
type is active. You can press any combination together to create different response types
such as ‘notch’ and an interesting ‘all-pass’ effect. The switches are ‘soft switched’ for live
performance, meaning that the audio signal is ramped between filter states to prevent
audible clicks.
Note that the last selected type is lost when power is removed from the console. The
LPF is always selected when power is applied.
The graphs below show the effect on the audio frequency response for the three filter
types. The range of sweep from low to high frequency is shown together with the effect
of adjusting RESONANCE (one frequency with several resonance settings shown).
The vertical scale shows the amount of cut or boost around the normal 0dB operating
level. The horizontal scale shows the change in frequency from low (bass) to high
(treble).
10k 20 1kHz 100 20k
0dB
+5
+10
+15
+20
-5
-10
-15
-20
HI-PASS FILTER
LO HI
BAND-PASS FILTER
LO HI
10k 20 1kHz 100 20k
0dB
+5
+10
+15
+20
-5
-10
-15
-20
10k 20 1kHz 100 20k
0dB
+5
+10
+15
+20
-5
-10
-15
-20
LO-PASS FILTER
LO HI