GTA 475
8
tion system) via a 3.5 mm jack plug optionally
to the FRONT and/or REAR Direct Aux Input.
All signal sources will then be heard simulta-
neously and their volume must be adjusted
on the respective source device.
Note:
All AF sources must be set to Off during
installation and connection!
Installing the jack-plug cable
Please use our 5 m jack-plug cable (Order No.
7 607 001 525) to make the connection.
A special feature is that it has its own On/Off
switch.
Switch position is OFF:
During installation and de-installation and
when no AF source is connected.
Switch position is ON:
Only after an AF source has been con-
nected.
Caution:
When making the connection, always set the
volume control to minimum and switch off
the amplifier.
If you want to listen to an audio source over
the front and rear loudspeakers, you must
connect the Direct Aux Inputs using our jack-
plug Y cable (7 607 001 524) (see Fig. 6).
Level control
The Level control enables the input sensitivity
of the final stage to be matched to the output
voltage of your car radio preamp output.
The range of adjustment extends from 0.1 V to
8 V.
Adjust the input sensitivity in accordance with
the manufacturer’s specifications when connec-
ting the amplifier to other radios.
Important:
Turning the Level control clockwise increases
the input sensitivity of the amplifier, and there-
by also the volume. The Level control is however
not a volume control; an increase in volume is
not achieved in the maximum position, even if
this subjectively appears to be the case. The sy-
stem merely increases the volume more quickly
when the volume is turned up on the radio.
Loudspeaker connections
(If the amplifier is to be connected in a bridged
mode, proceed with the section “Bridged lou-
dspeaker connections”.)
As with any audio component, connection of the
amplifier and speakers with the correct polarity
is essential for good bass reproduction. Ensure
therefore when connecting that the positive (+)
amplifier terminal is connected to the positive
(+) loudspeaker terminal. The same applies to
the negative (-) terminals. The left-hand ampli-
fier channel must also be connected to the left-
hand loudspeaker and the right-hand amplifier
channel to the right-hand loudspeaker.
Bridged loudspeaker connections
The GTA can also be bridged in a mono configu-
ration. This enables you to use the amplifier for
one or more subwoofer(s) or a mid-range spea-
ker. In this configuration the amplifier sums the
right-hand and left-hand channels, delivering a
single channel (mono) output.
Note:
The amplifier can sum the right- and left-hand si-
gnal information only if both the right- and left-
hand RCA connections have been made.
CAUTION:
The amplifier must be presented with a load of
4 Ohms or higher in bridged mode. A lower load
will cause the amplifier to overheat or switch off.
This can lead to permanent damage of the unit.
Adjustment of the type and range of the
cross-over frequencies
The type of crossover (i.e. “low-pass” or “hi-
pass”) and the desired crossover frequency can
be selected on the GTA 475. If, for example, you
wish to drive a pair of subwoofers, connect in
accordance with the low-pass diagram (fig. 3).
The crossover frequency is dependent upon
the loud-speaker frequency range (consult the
loudspeaker manufacturer’s data for the recom-
mended frequency range).
“High- Pass”
At a of 250 Hz , the loudspeaker has a frequency
range of 250 Hz to 35.000 Hz.
“Low-pass” frequency control
This control is active when the switch is set to
“Low-pass” and permits selection of the desired
crossover frequency.
