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

The sound amplifier's (A2/13)  data exchange with possible signal sources such as, e.g.:

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

is performed over the digital data bus (D2B  ). In doing so both the control information and the signals from the audio sources (radio, CD, navigation system voice output) are transmitted via the digital data bus (D2B  ).

Signal processing 

In order to make possible the diverse tone settings the sound amplifier (A2/13)  is equipped with a d  igital s  ignal p  rocessor (DSP  ), which carries out the complete signal filtering process. In comparison to conventional analog filters digital filters exhibit several distinct advantages:

• the filter parameters (the tone settings) do not change in the course of time which means that it is possible to reproduce the settings exactly
• low noise level
• the outlay in terms of components is greatly reduced because the filter parameters are set by the software and not by varying component values (resistance, capacity or inductivity), which in turn means that the number of possible filter settings increases

Sound optimization 

Each of the six amplifier signals is provided with its own individual equalization, which where necessary can be used to balance the vehicle-specific acoustics. In addition, it is possible to retrieve other tone optimizations and effects such as 'voice-acentuated' or 'surround sound'.

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

Noise suppression 

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

Automatic Vehicle Noise Compensation (VNC) 

The sound amplifier microphone (B25/6)  , which is connected to the sound amplifier (A2/13)  is used to measure the noise level within the vehicle. The volume of the music output signal is constantly matched 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 done through comparing the sound amplifier (A2/13)  output signal with the measured signal.

A simple way of looking at it is to regard the difference in both signals as being the driving noise level.

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 via the digital data bus (D2B  ) to the COMAND operating, display and control module (A40/3)  where they can be read out via the diagnosis line (K line  ).