ARP 2600 - VCO-1 Square Wave Symmetry Adjustment

110
10. Holding down
the
C
three
octaves
above
the lowest
note
on
the keyboard,
ADJUST
THE
VCO-3
TRIMMER LABELLED
"1
V/OCT" UNTIL VCO-3 ZERO-BEATS WITH VCO-2.
1
1
.
Insert a dummy
plug
into the
KBD
CV
input
to VCO-3,
and set
the
VCO-3 INITIAL FREQUENCY
control
at
1 KHz,
1
2.
Holding
down
the
lowest
note on the keyboard,
tune
VCO-2
to unison with
VCO-3 by zero-beating
the
two
oscillators.
13.
Holding
down the
C
two
octaves above the lowest note on
the
keyboard,
ADJUST THE VCO-2
TRIMMER
LABELLED
"Hl-FREQ
TRACK"
UNTIL
VCO-2
EXACTLY
ZERO-
BEATS WITH
VCO-3's FOURTH
(two
octaves
above the
fundamental)
HARMONIC.
1
4.
Repeat steps 1
2 and
1
3,
substituting VCO-1
for
VCO-2.
15.
Remove
the dummy
plug from
VCO-3's KBD CV
input.
16.
Holding down
the
lowest note on the keyboard,
tune
VCO-3
and
VCO-2 to unison
by
zero-beating
them.
17.
Holding
down the
C
two octaves above the lowest note
on
the
keyboard,
ADJUST
THE VCO-3
TRIMMER LABELLED
"HI-FREQ TRACK" UNTIL VCO-3 EXACTLY ZERO-
BEATS
WITH VCO-2.
6.113
VCO-1
SQUARE WAVE
SYMMETRY ADJUSTMENT.
1
.
Begin with
all sliders at
minimum (down or left).
2.
With a patch cord, connect the
VCO-1
SAWTOOTH output to
the VCO-1 input jack on
the
Filter.
Raise the
attenuator
for
this
input to
maximum.
3. Raise
the VCF Mixer input
to
maximum
and the Speaker
Volume controls
to
maximum.
4.
Set
the
VCO-1
INITIAL
OSCILLATOR FREQUENCY
con-
trol
to
a little under 1 KHz.
5.
Set
the
INITIAL FILTER
FREQUENCY control to 1KHz
and
the
Filter RESONANCE control
to
just
below oscillation.
6. Tune
the Filter
to the
2nd harmonic
of
the VCO-1
sawtooth.
(If you
have any
difficulty,
tune
first to the fundamental
and
then find
its
octave. The Filter
will peak sharply at each
harmonic.)
7.
REMOVE
THE
PATCHCORD
CONNECTION AND
ADJUST
THE "SYMMETRY"
TRIMMER UNTIL THE
2ND
HAR-
MONIC
DISAPPEARS
COMPLETELY.