It depends on the amplifier and the vehicle. Many vehicles you can simply connect directly to speaker level inputs if the amp is equipped. The issue comes in that many amps take speaker level but do not accept a balanced speaker level input. This is where the issue comes in. All vehicles that need the LOC ship with the LOC.

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2009 E70 X5 - Third Row - Rear DVD
Past - 04 4.4i Sport Package