ARP 2600 - Ring Modulator (RM) Functionality; Ring Modulator: AC vs. DC Coupling Effects

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The
PORTAMENTO
control
introduces,
when
it is
switched
on, a
variable
slide into
the
control
voltage
output.
Electrically
its action
is
very
similar to that
of
the Lag
Voltage
Processor.
Its
effect
is to
prevent
the
control
voltage
output
from
responding
instantly as
different
keys
are
depressed;
it
moves^more
slowly
from
one
value
to
another.
This
in
turn
means that
a
VCO
being
controlled
from
the
keyboard will
not
move
sharply and
quickly
from
one
pitch to
another
but
will
"slide"
from
one
to
another
of
the
pitches
dictated
to it by the
keyboard.
4.341
WIRING
OF THE
KEYBOARD SOCKETS is
given in the
marginal diagrams.
The socket
on
the right
side of
the
2600
is the
POWER
connection
to the
keyboard
and
the
socket
on
the
left side
of
the 2600 is the INPUT
from the keyboard. If for
any
reason
it
is
desired
to
extend
the short
keyboard connecting cables,
great
care
should
be
taken to wire
the
added connectors
properly,
and not
to
interchange
them
in
use.
Both the
2600
and the
3604 could possibly
be
damaged by incorrect
wiring of
the
connectors.
4.4
The
RING MODULATOR
is essentially
a voltage
multiplier;
ft
two
inputs A and
B
it produces the
output
function
A
x
B/5.
The
kind
of
transformation
this
effects on input signals depends
to a
large
ex-
tent on what they
are and
on
whether
the
modulator
is AC
or
DC
coupled
to
them.
The coupling is selected
by
the
AUDIO-DC
switch
at
+
the
bottom
of
the modulator.
When the
inputs
are
AC
coupled
(AUDIO
position
of
the
switch),
any DC
component
present
in
them
is cancelled
before
they
are
fed
to
the modulator.
Thus a
sawtooth
that starts
from
zero
and
goes
to
+10V
will
instead
start at
—
5V and
move
to +5V so
that its
overall positive and
negative deviation cancels to zero. Under
these
conditions
the
modulator will
generate from
any
two periodic signals
an
output signal consisting
of
the
sum and
difference frequencies that"
can
be
generated from
the
frequencies
of the two inputs. The
input
frequencies themselves
will
be
suppressed.
If
both
signals are
audio-frequency, a large
variety
of
harmonic
and
inharmonic
timbres can
be
produced from the modulator,
depend-
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Keyboard
Input
Connection
Power Connection