Conrad Electronic XCA 1000 Manuel D'utilisation page 37

or
Minimum loudspeaker impedance of 4 ohms
Mono-bridge mode XCA 1000 and XCA 1002 model
Minimum loudspeaker impedance of 4 ohms
Connecting the cinch outputs
Additionally to the loudspeaker outputs, the amplifier is provided with cinch outputs
by means of which the input signal can be fed to other components of the car hi-fi
system without using adapters.
For connecting the cinch outputs, use only shielded cinch cables
suitable for this purpose. The use of any other cable may cause
interference.
Keep the length of the connection cables as short as possible.
Do not install the cables in the proximity of other cables. Thus, you
avoid interface at the input of the subsequent component.
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