JBL SG520 - Page 3

1.1.7 LOUDNESS CONTROL.—This switch controls the way in which the volume control operates. With
loudness switched off, the VOLUME control adjusts only sound intensity. With the loudness
switched
ON
there
is
emphasis
placed
on
the
very
low
and
very
high
frequencies
as
the
vol-
ume
is
decreased.
This
compensates
for
the
tendency
of
the
human
ear
to
lose
these
frequen-
cies
at
low
listening
levels.
When
it
is
desired
to
accomplish
all
compensation
with
the
individual
bass and treble controls, then the LOUDNESS control can be switched off.
1.2 CONCEALED SECONDARY FRONT PANEL SWITCHES AND JACKS
The
lower
portion
of
the
face
panel
of
the
Graphic
Controller
is
covered
by
a
bottom-hinged
panel
which
conceals
infrequently-used
controls,
and
input
and
output
connectors.
This
puts
them
in
a
readily
accessible
location
but
out
of
sight
when
not
in
use.
1.2.1
FUSE.
—
At
the
far
left
is
a
Slo-Blo
fuse.
A
3/10
AMP.
fuse
is
required
for
110-120
volt
operation,
15/100
AMP.
for
220-240
volt
operation.
This
acts
as
protection
for
the
Graphic
Controller’s
internal
circuitry.
The
AC
outlets
located
on
the
back
of
the
Graphic
Controller
are
not fused.
1.2.2
MICROPHONE
JACK.—Directly
to
the
right
of
the
fuse
is
a
microphone
jack
for
Channel
A.
The
signal
from
the
microphone
jack
is
fed
to
the
amplifier
when
the
MIC
pushbutton
is
pressed.
1.2.3
RUMBLE
FILTER.—The
purpose
of
rumble
filter
is
to
diminish
low-frequency
noise
which
may
be
generated
by
some
record
changers,
or
some
of
the
noises
coming
from
older
records.
This
slide
switch
is
normally
kept
in
the
down
or
OFF
position.
1.2.4
AUXILIARY
FRONT
INPUTS.—These
are
high-level
input
jacks,
one
for
Channel
A
and
one
for
Channel
B.
They
are
controlled
by
the
SOURCE
button
marked
AUX
FRNT.
These
jacks
allow
connection
of
temporary
inputs
without
having
to
disrupt
the
permanent
connections
made
on
the
back
panel.
1.2.5
SCRATCH
FILTER.—This
serves
to
get
rid
of
objectionable
high-frequency
noises
in
poor
or
old
'
records,
a
noisy
tape
recording,
or
excessive
noise
in
a
FM
stereo
broadcast.
1.2.6 TEST TONE SWITCH.—This switch will usually be in the up or ON position when you use the
TEST
button
in
the
MODE
bank.
A
more
detailed
description
of
the
use
of
this
feature
is
given
in paragraphs 3.3 and 3.5.
1.2.7 TAPE MONITOR.—This switch allows connection of a 3-head tape recorder for recording directly
from any program set up on the Graphic Controller, and at the same time allows listening to
the actual recording as picked up by the playback head. Most high-quality tape recorders have
separate recording and playback preamplifiers and will enable use of this feature. When the
hinged panel is closed, the. TAPE MONITOR switch automatically goes back to its OFF position.
1.2.8 OUT TO RECORDER.—A pair of jacks marked CHANNEL A and CHANNEL B allow making record-
ings directly from the Graphic Controller. The signal which appears at the OUT TO RECORDER
jacks is not affected by the VOLUME or TONE controls. A second set of jacks are located on
the rear panel. Generally, the front panel connections will be used only for temporary connec-
tions for portable machines.
1.2.9 HEADPHONES JACK.—The next item, to the extreme right, is the HEADPHONES jack used for
monitoring. When headphones are plugged in, signals to the power amplifier are disconnected
and speakers are muted. The signal level at the headphone jack is sufficient to give satisfactory
results with most 8-16 ohm phones (although better performance will be realized with 500-600
ohm or high impedence units).
1.3 FRONT PANEL SCREWDRIVER ADJUSTMENTS
1.3.1 PH LEVEL.—A separate control is provided to adjust the loudness of each phonograph input.
This allows trimming these sources so that when switching from one input to another there
will not be a sudden change in the loudness level.
1.3.2 PH 1 STEREO BALANCE.—A balance control is also provided for the phono-1 input. This makes
it possible to compensate for any minor unbalance in the signals supplied from the two chan-
nels of the phono-1 pickup cartridge. Once this auxiliary balance is set, it matches the SG520
to a particular pickup, and it need not be re-adjusted unless the pickup cartridge is changed.
ein pai OE Snape te
ii Sane
peer iccoin ae!