Sequential PROPHET-600 - 7-6 ENVELOPE GENERATORS

KEYBOARD switch:
When FULL,
the KEYBOARD control
voltage (CV) is applied to
the filter's cutoff frequency just as it is normally applied to OSC
A and
OSC
B.
With
the filter thus "tracking"
the keyboard,
cutoff
frequency is maintained at a constant
point
relative
to the notes being played. This results
in a consistency of timbre over
the whole keyboard
range.
When
FILTER KEYBOARD is switched OFF, notes played
higher on the keyboard will have
more of their overtones
suppressed than notes played
lower.
As a result, the higher notes will have a duller timbre. Obviously, the 1/2
setting selects the midrange between
these two effects.
If FILTER RESONANCE
is set for self-oscillation (that is,
above
7),
then switching
FILTER KEYBOARD on FULL will allow
the
filter to be played from the keyboard.
(Unless
a complex effect is desired, the FILTER
ENVELOPE
AMOUNT
knob will in this
case normally be set to
0,
to maintain
a steady
response from voice to
voice).
If the KEYBOARD switch is toggled while holding keys down, the effect will not be
heard
until the key is restruck.
7-6
ENVELOPE GENERATORS
Each voice contains two independent ADSR envelope generators: one controls filter
cutoff frequency (through the ENVELOPE
AMOUNT knob), the other controls the
amplifier
gain. An "envelope" is a specific dc voltage which changes value over time at
a rate adjusted by the ATTACK,
DECAY, and RELEASE knobs. As the envelopes are
generated with
each keystroke, they "contour"
the
voice timbre and dynamics,
animating the otherwise raw
waveshapes which come from the mixer.
LEVEL
ENVELOPE
AMOUNT
(FILTER ONLY*
SUSTAIN
LEVEL
Figure
7-6
ENVELOPE
4
ATTACK
TIME
M
DECAY
TIME
h
RELEASE TIME
*
LENGTH
OF TIME
KEY
IS HELD DOWN
The
contour pattern
is initiated when a key is struck, producing
a gate. The initial
appearance of the gate "triggers" the envelope
generator(s) to proceed through their
attack and decay
periods. These periods can each range
from
zero
to about 9 seconds,
during which time the
envelope voltage rises to its full value, then
falls (decays) to the
level set by the SUSTAIN
knob, where it remains until the key
is
released.
When the
key is released, the gate goes
off
and the envelope voltage
drops to zero at a rate set
by
the
RELEASE
knob.
7-6
CM600A I2/S2