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The
VCF
is
perhaps the
single
most
expressive
module
in
the Trident Mk.II.
Its
basic
function
is
to
modify
the tonal
quality
(timbre) of
the
waveforms
pro-
duced by
the
VCOs
by
eliminating
certain
harmonics
(overtones)
and
emphasizing
other
ones.
Understanding
how
to
use
it
is
a key
part of getting the
most from
your
instrument.
There
are
|
VCFs
in
the
Synthe
Section,
one
per
voice.
Each
VCF
is
a
4
pole,
24
dB/octave low
pass
filter
with
voltage controlled cutoff
frequency,
vari-
able resonance,
positive
and
negative
EG
modulation
("enveloping"),
and
variable
keyboard
tracking.
Each
of these
terms
will
be explained
in
detail
below.
How
does
a
filter
modify
timbre?
There
are
two
basic
functions;
cutoff
frequency
and
resonance.
O
CUTOFF FREQ
The
cutoff
frequency
is
the point
in
the
audio spectrum
where
the
filter
starts
to affect
sounds
passing
through
it.
The
Trident
Mk.II
filters
are
termed
Low
Pass,
which
means
that
they
pass frequencies
which
are
lower
than
the cutoff point.
Any
frequencies
above
the cutoff
fre-
quency
of
the
filter
are
progressively
rolled
off.
or
reduced
in level.
The
higher
a
frequency
is
above
the cutoff point, the
more
it
gets rolled
off.
This
rolloff
can
occur
at
different
rates.
The
Trident
Mk.II
filters
have
a
24
dB/octave
rolloff.
This
means
that a
harmonic
an octave
above
the cutoff point
would
be about
16
times
softer
coming
out
of the
filter
than
going
in.
At
two
octaves
above
the cutoff
point, a
harmonic would
be about
250
times
softer!
This very sharp
rolloff
helps
to
produce
realistic
imitations of
most
instruments,
a
wide
variety
of
punchy
synth
voicings,
and
many
special effects.
Since
the cutoff
point
can
be
varied
throughout
the
audio spectrum,
you
can
choose
to
remove no
harmonics, upper
harmonics
only,
everything
but
the
fundamental,
or
anything
in
between.
It
can
also
remove
everything,
silencing
the
instrument,
if
the cutoff point goes
much
below
the
fundamental
pitch.
There
are
five
ways
to
vary the cutoff
frequency
of
the
|
VCFs;
manually,
via
the
VCF CUTOFF
control; or
auto-
matically
via
each
voice's
Envelope Gen-
erator, the
Keyboard
Tracking
function,
or
via
any
external device
plugged
into
the
rear
panel
VCF
fcM
IN
jack.
The
actual
cutoff
frequency
of the
VCF
will
be proportional
to the
sum
of the voltages
(control
signals)
from
these
five
sources
at
any
given
moment.
O
CUTOFF FREQ
Diese Funktion ermbglicht
das
Regulie-
ren
der Einsatzlrequenzen
des
Tiefpafl-
Filters.
(Siehe "Synthesizer
Basics").
Bei einer Einstellung aul Position
10
blei-
ben
die
Wellenlormen
der
VCO
unbeein-
flusst.
Je
weiter
dieser Regler
nach
links
(in
Richlung
gestellt
wird,
umso
hbhere
Fre-
quenzen
(obere,
Harmonische)
werden
ausgesiebt.
Genngere Harmonische
fiihren
zu
einem runden und weichen
Klang.
RESONANCE
Mil
diesem Knopf
wird
die
Starke der
an
der Einsatzfrequenz
des
VCF
erzeugten
Resonanzen
eingestellt.
Doch
sei
auch
hier
vor
Ubersteuerung
gewarnt.
KBD TRACK
Bestimmt den Grad,
in
welchem
die
Grenzfrequenz
sich
im
Verhaltnis
zur
Hohe
der gespielten
Note
verandert.
Da-
durch
lassen sich
unnatiirliche
Verande-
rungen
der
Klangfarbe an verschiedenen
Siellen
der Tastatur
vermeiden.
Die
VCF
-Grenzfrequenz
steigt
und
fall
t
im
Verhaltnis zur
Tonhbhe
um
die folgen-
den
Betrage:
0%
bei
OFF,
25%
bei
QUARTER.
50%
bei
HALF.
100%
bei
FULL
und 150%
bei
OVER.
Um
diese
Funktion zu
veranschaulichen,
stellen
Sie
die
Grenzfrequenz
auf
5.
Resonanz
auf
10.
EG-lntensitat
auf
und
KBD
TRACK
auf
FULL.
Beachten
Sie,
wie
die
Reso-
nanz-Eigenschwingzahl
sich
mit
der
Hohe
der
gespielten
Noten
verandert.
O
EG
INTENSITY
Dient
zur
automatischen Modulation
der
Grenzfrequenz mit
VCF
EG.
Stellungen
von
der
Mine
nach
rechts
liefern
eine
im
Vergleich zur
VCF
EG-
Hiillkurve
hellere
Klangfarbe.
Bei
Ein-
stellungen
von
der
Mitte nach
links
erzielt
man
ungewohnliche
Effekte.weil
sich
die
Klangfarbe
im umgekehrten
Verhaltnis
zur
Hiillkurve
andert.
O
CUTOFF FREQ
Permel
d'ajuster
la
frequence
de
cou-
pure
du
filtre
passe-bas
(Se
reporter
au
paragraphe
intitule
"Principes
de base
du
synthetiseur").
En
position
10,
la
forme d'onde
de
loscil-
lateur
VCO
passe sans
subir
de change-
menl.
Au
fur
el
a
mesure que
le
bouton
est
tourne vers
le
bas,
de
plus
en
plus d'har-
momques
supeneure
sonl
filtrees
et
ceci
permel
d'obtenir
un
son
plus
moelleux.
RESONANCE
Ajusie
le
degre
de
resonance
produil
autour
de
la
frequence
de
coupure.
II
faut
(aire
attention
car
des
oscillations
se
pro-
duisent
si
le
bouton
est
tourne
au
maximum.
O
KBD TRACK
Selectionne
le
degre auquel
la
fre-
quence
de
coupure
varie
en proportion de
la
hauteur
du
son
de
la
note
jouee. Ceci
evite
que
des
sonorites
peu
naturelles
changent de timbre
a differents
points
du
clavier.
La frequence de
coupure du
filtre
VCF
augmente
et
chute en proportion
a
la
hauteur
du
son
dans
les
proportions
suivantes:
0%
sur
OFF,
25%
sur
QUAR-
TER,
50%
sur
HALF, 100%
sur
FULLet
150%
sur
OVER.
Pour
que
cette
fonction
soit
pleinement
revelee, faire
un
reglage
de
la
frequence de
coupure
sur
5,
de
resonance
sur 10, d'intensite
de
EG
sur
et
de
KBD TRACK
sur
FULL.
Verifier
la
facon
dont
la
frequence
a auto-oscillation
de
resonance change avec
la
hauteur
du
son des notes
jouees.
O
EG
INTENSITY
Commande
une modulation automa-
tique
de
la
frequence
de coupure
par
le
generateur
VCF
EG. Avec
les
reglages vers
la
droite a
partir
de
la
position
centrale,
le
timbre
devient plus
brillant
en proportion
de
I'enveloppe
du
VCF
EG. Avec
les
reglages
vers
la
gauche
a
partir
de
la
position
centrale,
des
effets
inhabituels
sont
obtenus
parce
que
le
timbre change
en
proportion
inverse a I'enveloppe.
VCF CUT
OFF
control
This
determines the
initial
cutoff
fre-
quency
of the
filter.
At
0,the
cutoff
is
so
low
that
no sound
will
be
passed.
As you
turn
the
control
clockwise
(towards
higher
numbers),
the cutoff
frequency
increases
and
the
note
will
begin
to
sound,
first
with
a
dark,
muted
timbre
and
then with
a brighter
one.
At
10, the
cutoff
point
is
above any
audible
har-
monic
and
the
sound
will
be
very
bright.
RESONANCE
The
second
way
that a
filter
modifies
timbre
is
by
adding
resonance,
(also
known
as
"Q", "Peak"
or
"Emphasis")
at
the cutoff point.
Resonance
is
useful for
a
wide
variety of
sounds, such
as
organ,
french horn,
classic
synth
bass
and
lead
sounds,
and
many
special
effects.
The
RESONANCE
control allows
you
io vary
the
amount
of
resonance
from
to
self-oscillation.
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