PRESONUS AudioBox Stereo Quick Start Manual page 321

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Internal Sidechain. Click to activate internal filter sidechain (for
frequency-dependent compression). Uses 48 dB filters.
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13.6.2 Expander
Expander is a fully variable downward expander with range control. It features sidechain
capability, including an internal sidechain filter with variable low-cut and high-cut. Expanders
increase the dynamic range of a signal such that low-level signals are attenuated while the
louder portions are neither attenuated nor amplified. This is effectively the opposite of
compression. Use Expander to decrease the levels of unwanted noise or bleed from other
sources in the desired signal or to restore dynamic range to a compressed signal.
The following parameters are available for the Expander:
• Threshold. Adjusts the maximum amplitude at which processing will occur. Variable
from -60 dB to 0 dB.
• Range. Adjust the maximum amount of attenuation applied to the signal. Variable
from -72 dB to 0 dB.
• Ratio. Adjust the ratio of the Expander. Variable from 1:1 to 1:20.
• Look Ahead. Click to engage/disengage 2 ms Look Ahead function.
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Listen Filter. Click to listen to the filtered control signal of the internal
sidechain. Helps find specific target frequency for control signal when
de-essing, transient damping, etc.
LC/HC Freq. Frequency selection for internal-sidechain filters. LC is
variable from Off to 20 Hz to 16 kHz; HC is variable from 20 Hz to 16
kHz to Off.
Filter Type Display. Shows notch or bandpass characteristic of filter.
Swap. Click to swap the frequencies used for LC and HC.