Dave Smith Instruments PROPHET 12 DESKTOP - Manual (Page 33)

21 Prophet 12 Module Operation Manual High-Pass Filter
High-Pass Filter
After each voice’s low-pass filter, the signal passes through a 2-pole, resonant
analog high-pass filter. There is also a control for modulating the filter cutoff with
the keyboard.
Frequency: 0...127 —Sets the high-pass filter’s cutoff frequency. Frequencies
below the cutoff are attenuated at a slope of 12 dB per octave. Frequencies above
the cutoff pass through the filter unaffected, hence the name “high-pass.”
Resonance: 0...127 —Emphasizes a narrow band of frequencies around the
cutoff frequency. Normally, the high-pass filter does not self oscillate at the
maximum resonance setting. However, it may be driven into self-oscillation by
routing DC modulation to resonance to push it beyond what can be achieved
by the Resonance control alone. Be aware, though, that the signal level of the
self-oscillation is significantly higher than normal, and will likely cause severe
clipping, especially as more voices are played.
That can be mitigated by turning
down the voltage controlled amplifier envelope amount and, if used, the VCA
Velocity
’
Amount.
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.
Note: The high-pass filter does not have a dedicated envelope like the low-
pass does. However, auxiliary envelopes 3 and 4 can be routed directly to
the high-pass filter, and any of the envelopes can be used to modulate the
high-pass using the modulation matrix. See Modulation on page 32 for
more information.