ARP ODYSSEY - High Pass Filter

EXPERIMENT 3. THE
HIGH
PASS
FILTER
EXPERIMENT 4.
THE
VCF
The HIGH PASS FILTER
[HPF) Ib
another
signal
madifief. It attenuates
frequencies
helow the
Betting
of its
HPF
cutoff
frequency slider. It is
u^ful in eliminating
"Boominess"
froiti low bass notes, and
in
simulating
Certain instrumental sounds.
The HPF is not
voltage
controlled.
Try moving the HPF
control slowly over its
range v?hile holding
down
a low note on
the
keyboard.
The
Voltage
Controlled
Filter (VCF) is
the most
important
modifier on any
synthesizer.
Thfi
VCF
is
responsible
for taking the raw
signals
Pfom the VCO,
Ring
Modulator, and
the
Noise Generator and
shaping them
into
useful musical sounds.
The VCF in
your
ODYSSEY is
technically
called a "low
pass
ftlter." Low-pass
means that the
filter
wiU pass all
audio
frequencies below a
certain
point
(called
the "cut-
off
point")
aitd will filter out all
frequencies
above
this
point.
1.
Set the controls
on
your ODYSSEY
according
to
Figure O. In this set
ting
^
the sawtooth
wave from the
VCO
is entering the
VCF
through the
AUDfO
MIXER. Also, the VCA
GAIN
control is
raised so
that
any signa] passing
through
the VCF will be
heard.
2.
Play a note in
the
middle of the
keyboard.
You don't
have to hold it down.
Slowly
raise the VCF
FREQ
control
and listen to the
effect. Notice
how
the sound
gets
brighter
and louder as you
raise this
control.
It
does so
because
you are raiding the
cut-off
frequency
of the filter,
thereby letting more and
reiore high
frequencies pass
through.