ALLEN & HEATH XONE:DB4 Guide de l'utilisateur télécharger pdf (Page 42)

Allen & Heath 42 XONE:4D 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.

Two stereo VCFs are provided, one either side of

the crossfader. Each can be switched in or out

and has its own frequency sweep control. A Low

Frequency Oscillator (LFO) provides filter

modulation.

LFO modulation

The LFO automatically sweeps the cut-off

frequency up and down according to the beat

entered by tapping the tap tempo button or

locking to the analysed BPM. The LFO can be

applied to Filter 1, Filter 2, or both filters together

for additional cyclic filter modulation effects.

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).

10k20 1kHz100 20k

0dB

+ 10

+ 15

+ 20

-5

-10

-15

-20

LO-PASS FILTER

BAND-PASS FILTER

10k20 1kHz100 20k

0dB

+ 10

+ 15

+ 20

-5

-10

-15

-20

10k20 1kHz100 20k

0dB

+ 10

+ 15

+ 20

-5

-10

-15

-20

HI-PASS FILTER

1 2 ... 37 38 39 40 41 42 43 44 45 46 47 48

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ALLEN & HEATH XONE:DB4 Guide de l'utilisateur Page 42

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