In general, the following can be stated about the Top HIFI DSP amplifier, as with all other amplifiers:
If the TOP HIFI DSP amplifier is installed freely in the car and has not been installed with another device, it is responsible for all sound outputs in this vehicle.
Top HiFi DSP Amplifier have been installed in BMW vehicles since 2003. The amplifier receives the signal from the CIC or NBT module and distributes it to all speakers in your vehicle.

