ARP 2600 - Pulse Width

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4.1 12 The
second osciffator,
VCO-2, generates
SINE, SAWTOOTH,
TRIANGLE, and variable
width PULSE outputs at
four
independent
out-
puts. Amplitude
and
phase
relationships are
given In
the
diagram at
the
left.
Note that
the
SAWTOOTH and
PULSE
outputs are
positive-going
only, while the
TRI-
ANGLE and SINE
waveforms
are
balanced on
either
side
of OV.
When
these waveforms are
used
to control
the frequency of one
of the
other
VCO's,
for
example, the sawtooth and
pulse
out-
puts will only
be capable in genera!
of raising
the
VCO frequency, while
the triangle
and
sine
outputs will
alternately raise
and
lower
the
VCO frequency relative to its initial
frequency
setting.
.-
-
Note
too
that
the
triangle
and
sine
wave
outputs are
out
of
phase;
where
one
is
positive
the
other
is
negative.
Adding them directly to-
gether
would
simply cancel
the
fundamental
sine-wave component
in
the
triangle waveform
and
leave
a
waveform
representing
on/y
the
upper
harmonics.
Outputs from
the Sample and
Hold
circuit
(S/H OUT),
ADSR
Envelope
Generator,
and
VCO-1
SQUARE output
are
prewired to
the
three*
attenuator-governed frequency-control inputs. These connections
may be interrupted
by
insertion
of patch-cord plugs
or
dummy plugs
into
the input jacks. The
Keyboard
Control Voltage, normally
pre-
wired
to
the
unattenuated control input,
is
automatically disconnected
either
by
insertion
of a
patch
cord into
the
input
or by
use
of the
oscil-
lator
in
its
LF
range.
In
the
latter case,
if
for any
reason
the
keyboard
voltage
is
needed
it
may
be
patched in.
PULSE WIDTH is manually
controllable
by
a
slider (located
just
under the
two
sliders
for
manual
control of frequency) over
a
range
from
1 0% to
90% duty
cycle.
Pulse
width
is also subject
to
voltage
con-
trol;
the
sensitivity
is 1 0%
of
range/volt. There is
one
attenuator-gov-