JBL Grand touring series User Manual page 14

14
Snternal Adiustments
Speaker-Level Input
Impedance Adiustments
The speaker-level inputs of the
GTSlEOx come factory-set at lOOk-
ohms input impedance. This will
provide the lowest distortion opera-
tion from the speaker outputs of
most modern head units by reduc-
ins the power that the source unit
amplifier must deliver to practicallv
nothing. The resulting signal will
practicallv be as free from noise
and distortion as a oreamp-level
connection. On some older or lower-
priced head units, this load will not
facilitate proper fader operation. To
allow for this, we have provided the
ability to change the input imwd-
ante of the speaker-level inputs to
15 ohms. This is accomplished bv
setting the jumpers as shown in the
diagram at right.
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If the head unit has four chon-
nels of built-in amplification
and/or an electronic fader con-
trol, YOU should leave the
jumpers in the factory set posi-
tioh (lOOk ohms).
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If the head unit has two chan-
nels of amplification, with a
speaker-level fader, the
jumpers should be set to the 15
ohm position. This will always
be a rotarv-type control, not one
controlled by electronic push-
buttons.
If YOU are not certain of the type
of fader control your unit has,
measure the resistance across
one set of speaker outputs with
an ohmmeter (with the head unit
off). Adiust the fader control
through its entire adiustment
range. If there is a change in the
resistance as the control is
adiusted, set the iumpers to the
15ohm position.
Crossover Frequency
Adiustments
The GTSlEOx includes built-in fre-
auencv selectable crossovers. One
crossover is connected in series
with the amplifier circuitry and
the other crossover is connected to
the preamp level output iocks.
These crossovers can be set in
either the "flat" (full bandwidth
operation) configurations, Low-
Pass (subwoofer operation), or
High-Pass (satellite operation)
configurations. More details on the
use of these crossovers are given
in the "Add-On and Upgrade
Steps" section.
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The crossover frequencies are set
by "chips" inside the amplifier
(see specification section for fac-
tory settings). These "chips" are
simplv a set of resistors, con-