Type Rocker Switch - Alesis ModFX Reference Manual

3
Using the Philtre

TYPE Rocker Switch

The up/down rocker switch on the left side of the unit selects the
type of filter. The LEDs next to the switch light up to indicate the
current type. There are four types available, explained below.
Low Pass
Perhaps the most-popular type of filter effect, the Low Pass filter
has a 2-pole, 12 dB per octave slope that cuts the high frequencies
above the corner frequency set by the [PHREEQ] knob. Most
synthesizer filters are low pass filters, as are wah-wah pedals.
When [STEEP] is on, the Low Pass filter slope increases to 8-pole,
rolling off the high frequencies at a rate of 48 dB per octave.
High Pass
The High Pass filter has a 2-pole, 12 dB per octave slope that cuts
the low frequencies below the corner frequency set by the
[PHREEQ] knob. The most common use of high pass filters is to
cut rumble out of microphones; as an effect they can create an
intentionally-thin "transistor radio" sound by cutting out the low
frequencies.
When [STEEP] is on, the High Pass filter slope increases to 8-
pole, rolling off low frequencies at 48 dB per octave.
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