ARP 2600 - Voltage Controlled Filter (VCF) Adjustments; Output Offset Adjustment for VCF

Ill
6.12 ADJUSTING
THE
VOLTAGE-CONTROLLED
FILTER.
Here
the
"offset" adjustment minimizes any DC
in
the Filter
output,
and
the "gain"
adjustment sets
the
Filter
gain to
exactly unity.
The
fre-
quency
calibration and tracking adjustments
are
the same as
for
the
VCO's but
are
somewhat
less
critical.
6.121 OUTPUT OFFSET ADJUSTMENT.
1
.
Begin
with
allcontroisat minimum (down
or
left).
2.
With
a
patch
cord, connect the
VCO-2 SINE
output
to the
Mixer
VCA
input. Raise
the
attenuator
over
this input
to
maximum and
raise
the
Speaker
Volume controls until
the
sine
tone
is
comfortably audible.
3.
With
another
patch
cord,
connect
the
VCF
output to
the
first attenuator-governed FM
input to
VCO-2,
interrupting
the
S/H
connection to
that
input.
Raise
the
attenuator
over
that
input to maximum.
You should
hear
a
change in
the
pitch
of the sine
tone.
4.
ADJUST
THE "OUTPUT
OFFSET" TRIMMER
FOR
MIN-
IMUM PITCH CHANGE
WHEN THE PATCH
CORD
CON-
NECTING THE
FILTER
TO
VCO-2
IS
ALTERNATELY
REMOVED AND INSERTED
AGAIN.
5.
Remove
all
patch
cords.
6.122
GAIN ADJUSTMENT.
1
.
Set all
controls to
minimum.
2.
Make
the
following
patch
connections with
patch
cords:
VCO-3 SAWTOOTH
to
VOLTAGE PROCESSOR
INPUT
No.
1
,
Fl
RST
PROCESSOR
OUTPUT to second
MIXER
fNPUT (interrupting
the
VCA
connection
to
that
input).
3.
Raise
to.maximum the
VCO-3
input
to
the
Filter, the Filter
INITIAL
FREQUENCY control,
and
the
two
Mixer
input
attenuators. Raise the Speaker Volume controls to
a
high
listening
level.
4.
ADJUST
THE "GAIN"
TRIMMER
FOR
MINIMUM
VOL-
UME
THROUGH THE SPEAKERS.
If necessary
raise
the
Speaker Volume controls to
maximum.
5. Remove all
patch cords
and
return all
controls
to minimum.
6.123
FREQUENCY CALIBRATION.
1
.
Begin
with
all control
sliders
at minimum, i.e.
down
or
left.
2.
With
a
patch cord, connect
the VCO-2
SINE
output to
the
Mixer,
interrupting the VCA
connection.