Sound amplifier, function - GF82.62-P-3100-04GH

The data interchange between the sound amplifier (A2/13)  and the possible signal sources, e.g.:

• Radio (A2)  or
• COMAND operating, display and control module (A40/3) 

is performed via the digital databus (D2B  ). Here, both the control information and the signals from the audio sources (radio, CD, navigation voice command) are sent via the digital databus (D2B  ).

Signal processing 

In order to make the diverse sound settings possible, the sound amplifier (A2/13)  is equipped with a D  igital S  ignal P  rocessor (DSP  ), which performs the entire signal filtering process. In comparison to conventional analog filters, digital filters contain the following significant advantages:

• the filter parameters (sound settings) do not alter throughout the period, this thus means that all the settings can be repeated exactly
• low noise level
• the component outlay is significantly reduced, as the filter parameters are set by the software and not by varying component values (resistances, capacitances or inductance values), thus the number of possible filter settings is increased

Sound optimizations 

Each of the six amplifier channels is equipped with an individual compensation, which can, when requested, rectify the vehicle's acoustics. In addition further sound optimization settings can be made and effects such as, e.g. 'voice emphasizing' or 'stereoscopic sound' invoked.

Bass, treble, volume, balance, fader and the dynamic loudness function can be individually set.

Noise suppression 

The output level of the six 6 output stages is constantly monitored and regulated such that distortion is kept to a minimum.

Automatic Vehicle Noise Compensation (VNC)) 

With the aid of the sound amplifier microphone (B25/6)  , which is connected directly to the sound amplifier (A2/13)  , the noise level in the vehicle is measured. The volume of the music output signal is constantly adapted to this noise level. To this end the sound amplifier (A2/13)  must be able to detect which of the measured signals are noise emissions from the moving vehicle and which are audio signals. This is conducted by comparing the output signal of the sound amplifier (A2/13)  with the measured signal.

Put simply, the vehicle noise level is the difference between the two signals.

Diagnosis 

The sound amplifier (A2/13)  can set up the following messages which are relevant for the diagnosis:

• Operating status
• Undervoltage
• Internal fault in the sound amplifier (A2/13) 

The messages are sent over the digital databus ( D2B  ) to the COMAND operating, display and control module (A40/3)  or the radio (A2)  , and can be read out there over the ( K-wire  ) diagnostics line.