Dave Smith Instruments PROPHET 12 DESKTOP - Manual (Page 30)

18 Low-Pass Filter Dave Smith Instruments
Low-Pass Filter
The Prophet 12 features one analog resonant low-pass filter per voice. The filter
is switchable between 2- and 4-pole modes and has a dedicated five-stage (delay/
attack/decay/sustain/release) envelope generator, capable of looping the delay,
attack, and decay segments. There are also controls for modulating the filter
cutoff with the keyboard and envelope amount with keyboard velocity.
4-Pole —Selects the filter configuration. When lighted, the filter is in 4-pole
mode. A 4-pole, low-pass filter rolls off frequencies above the cutoff frequency
at a slope of 24dB per octave. When the button is off, the filter is in 2-pole mode
and has a slope of 12dB per octave and a more gradual roll-off of the higher
frequencies. Frequencies below the cutoff pass through unaffected, hence the
name “low-pass.”
Frequency: 0...164 —Sets the low-pass filter’s cutoff frequency over a range
of more than 13 octaves, stepping in semitones. The cutoff transitions smoothly
across the values when the frequency is swept.
Resonance: 0...127 —Emphasizes a narrow band of frequencies around the
cutoff frequency. In 4-pole mode, high levels of resonance can cause the filter to
self oscillate. In 2-pole mode, resonance is much more subtle and self-oscillation
does not occur.
Key Amount: 0...127 —Sets the amount of modulation from the note data
received via MIDI to F
requency
(the filter’s cutoff frequency). A setting of 64
will step the filter in semitone increments for each note, 32 would be quarter-
tones, and so on.
Velocity’Envelope Amount: 0...127 —Enables keyboard velocity to modu-
late the filter e
nveloPe
a
mount
.
Envelope Amount: -127...127 —Sets the amount of modulation from the
low-pass filter envelope to the low-pass filter frequency. The modulation amount
can be positive or negative, allowing for inverted envelope control.
Note: The low-pass frequency setting may limit the effect of the envelope
on the filter. For example, if F
requency
is all the way up, a positive enve-
lope amount will have no effect on the filter.
Delay: 0...127 —Sets a delay between the time the envelope is gated on and