Dave Smith Instruments PROPHET 12 KEYBOARD - Manual (Page 31)

21 Prophet 12 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 oscil-
late 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
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.
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.