
4
THA 1250 PnP
Loudspeaker connections
As with every audio component, the correct polarisation
of amplifier and loudspeakers is of essentially importance
for a good bass response. For this reason, ensure that
the positive (+) connection of the amplifier is connected
with the positive connection (+) of the loudspeaker; the
same applies to the negative (-) connections. In addition,
the left amplifier channel must be connected with the
left loudspeaker and the right amplifier channel with
the right loudspeaker.
Note:
The amplifier can add the right and left signal information
only if the right as well as the left RCA connection were
carried out.
Adjusting the type and range of the frequency
crossovers
With the THA 1250 PnP, the type of frequency crossover
(i.e. "Low Pass" or "Hi-Pass") and the desired crossover
frequency can be adjusted. For example, if a pair of
subwoofers is to be connected, low-pass settings are
required. The crossover frequency is dependent upon the
frequency range of the loudspeakers (see recommended
frequency range of the loudspeakers).
High-Pass
At a setting of 250 Hz, the amplifier has a frequency
range of 250 Hz to 30,000 Hz.
Low-pass frequency control
This control is active if the switch is in the position
"Low-Pass", and allows for setting the desired crossover
frequency.
Example:
At a setting of 150 Hz, the amplifier has a frequency
range of 10 Hz to 150 Hz.
Bass boost
The bass boost control on the remote control is used to adjust
the bass response of the amplifier. The adjustment range is
from 0 dB to +12 dB (see Fig. 7).
The control is active only if "LOW Pass, ON" is switched on.
Radio detection - Auto Remote
With a connection via a PnP INPUT cable, the amplifier
is automatically switched on (Auto Remote function).
A remote connecting cable is not needed!
Power-on indicator (POWER / PROTECTION)
Green LED:
Output stage on, regular operating status.
Red LED:
Output stage is electronically switched off due to an
error.
- Route a commercially available positive cable to the
battery and connect it via fuse holder 30 cm from
the battery.
- Use cable glands for holes with sharp edges.
- Securely fasten commercially available minus cables to
a noise-free earth point (chassis screw, chassis metal)
(not to the minus pole of the battery).
- Scrap the contact surfaces of the earth point until
they are bright and grease with graphite grease.
Integrated fuses (Fuse)
The fuses integrated in the amplifier protect the power
amplifier and the entire electrical system in case of an
error. If a replacement fuse is used, never bridge fuses
or replace them with a type with higher current.
Connection examples
Connection of the voltage supply.................. Fig. 2, 2a
Connection to car sound system
with cinch output ..........................................Fig. 3
Loudspeaker connections ............................Fig. 4, 4a
+12V
Remote connection of the amplifier with
switchable +12 V voltage source.
This allows the amplifier to be switched on and off using
the on/off-switch of the radio device.
Note:
If the connection is made using a PnP-INPUT cable,
the switch-on is performed automatically.
!As a special feature, +12 V/200 mA are now available
as output switching voltage at the remote input/out-
put after automatic switch-on.
High-level connections (via PnP High-Inputcable
only)
The amplifier features high-level connections (High Input)
to be able to connect to radio devices without pre-stage
outputs (Fig. 2a). This allows for a direct connection at
the loudspeaker output of the radio device.
Level control
The Level control is used to adjust the input sensitivity
of the power amplifier to the output voltage of your car
sound system.
The adjustment range is from 0.3 V to 8 V.
A few important explanations in this context:
By turning the control clockwise, the input sensitivity of
the amplifier and, therefore, also the volume increases.
However, this is not a volume control; no further amplifier
output can be achieved in the end position, even if it
may sound like that at the beginning. The system merely
increases the volume faster if the volume control of the
car sound system is turned up.
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