Roland SH-1 - VCF Resonance and Width Adjustments

VCF
-
VOLTAGE
CONTROLLED
FILTER
VCF
(VOLTAGE
CONTROLLED FILTER}
The VCF
is a
low pass filter whose
cutoff
frequency (or
filtering characteristics) can
be
controiied
by
means of a
control
voltage. The VCF, being
a
low pass
filter,
acts in a way opposite to
that
of
the
HPF,
It
passes low frequencies
and blocks
high
frequencies.
The VCF
is
used to alter tone colors by
cutting
or boosting harmonics in the
signals
sent from the VCO or noise
generator.
1.
CUTOFF
FREQ CONTROL
This
control determines the
frequencies
which will be removed by the
VCF. At its
highest position, all sound
passes through
the
VCF without change, thus this may
be
considered its
normal position.
If
the
control is slowly lowered, it
will begin to
shave
off the upper
harmonics
of
the
sound
passing through the
VCF.
In its
lowest
position, the
VCF CUTOFF FREQ
control
will remove ail frequencies so
that the
VCF blocks all sound.
NOTE: If the synthesizer
produces no-
sound, this is one
of the first things
you
should check.
Tone
color is
determined by the
waveform,
or
the
harmonic content,
of
the
sound;
the
more
harmonics
there are, the
sharper
the
waveform and
the
brighter the
tone
color. The
fewer the
harmonics
there
are,
the
more
rounded the
waveform
will be
and the
softer the
tone color.
The
polarity
of
the
envelope control
voltage
which
reaches the
VCF is
determined
by
the
ENVELOPE
POLARITY switch (7).
In
the
normal
{/S.)
position, the
VCF
cutoff
frequency
point
will
rise,
following
the
shape
of the
envelope,
each time
the
envelope
generator
is triggered.
Since
the
cutoff
point
rises, the
CUTOFF
FREQ
control
should be kept
away from
its
HIGH
position,
otherwise the
envelope
will have
no
effect.
With the
ENVELOPE
POLARITY
switch
in
the
invertedd^"}
position,
the
cutoff
point
of the
VCF will fall,
following the
envelope
pattern, thus,
for this
position,
the
CUTOFF FREQ
control
should be
kept
away from
its LOW
position
for
the
envelope to
affect the
VCF.
The
cutoff frequency
is also
affected by
the
KYBD slider.
Compensate
for this by
adjusting the
CUTOFF FREQ
slider.
o
© ©
I
VCF
FREQUENCY
RESPONSE
t
dB
FREQUENCY
^fe^s
tr^^mrs^
r
^r^r\
/
15