Dave Smith Instruments PROPHET 12 KEYBOARD - Manual (Page 28)

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 dedi-
cated 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
transistions 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
keyboard 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
modulate 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 modula-
tion 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 envelope amount will have no effect on the filter.