Oberheim Xpander Owner's Manual

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The number
of
"poles"
of
a
filter
affects
the
filter's
rolloff,
how
sharply the filter
cuts
off. in
technical
terms, each pole
of the
filter attenuates
(reduces the
volume of)
frequencies
beyond the
filter point by 6db
per octave
o
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7.
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FPEQrJErCV
More Poles
=
Sharper
Filter Cutoff
Comparative
filtering effects of
the
four low pass
fitters.
Adding
RESONANCE toasts tr>*
orr.pHti.iri-?
ot the
initial
cutoff point.
A
one
pole low pass
filter
will attenuate
frequencies by 6db
per octave
beyond the filter
point; 1?db
two
octaves beyond,
I8db
three octaves
beyond, etc. A
two pole
filter attenuates
at
12db
per octave,
a
three
pole
at 18db
per octave,
and a
four
pole filter
at 24db
per octave
In
musical terms,
fewer
filter poles
results
in a
brighter,
buzzter sound,
while more
poles
makes for
a
tatter
sound
VCAs
The VCF/VCA page
also
contains the two
output VCAs
that are used to
control the
volume
of
the
sound. VCAs act just
like the volume
control on your
stereo, you
turn
it up it gets
louder you
turn it down it gets
softer
VCAs
have
generally been
"invisible
'
on
programmable
synthesizers,
controlled only
by
the
volume
envelope generator The
X pander
has 15 VCAs
strategically
located
throughout each
voice because
they
are
useful tools. The two
VCAs
in the
VCF/VCA
page
are
the ones
through
which the
synthesizer's
sound passes,
and are
therefore most
important. It is
from
these
VCAs
that
enveloping of the
entire
sound occurs. In
working with these
VCAs remem-
ber that no
sound
will come out
of the
voice
unless both VCAs
are
turned up,
either
by
the gain
of the VCA itself or
by
modulating tfie VCA.
with an
envelope. LFO.
or some
other
source.
Velocity
is
useful
as
a
modulator
for one of the VCAs.
because
the
harder
you
play
the
keyboard, the higher the
output
volume
will
be.
If
the
initial amplitude
of both VCAs are up.
the
sound
of the voice
will always
be
heard, even
when no
notes are
being
played.
n
""
«n
/
2/
Xpander Owners Manual
Creative
input/ The
Xpanoed
Voice

Oberheim Xpander Specifications

General

Type	Analog Synthesizer
Polyphony	6 voices
Oscillators	2 VCOs per voice
Control	MIDI
Synthesis Type	Analog Subtractive
VCA	1 per voice
Memory	100 patches
Modulation	Extensive modulation matrix
Year Released	1984
Filters	Multi-mode filter per voice
Envelopes	3 per voice
Keyboard	No keyboard
Inputs	CV/Gate
Outputs	Individual voice outputs