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

Model 215, 220 with code 810 

On vehicles as of 1.9.03 all audio signals and video signals of the audio/TV components are transmitted by the Media Oriented Systems Transport (MOST).

Sound amplifier, function 

Data exchange of the sound amplifier (A2/13) takes place via the D2B (Digital Data Bus) with the following signal sources:

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

In the process both the control information and the signals of the audio sources (Radio, AUX connection for external audio sources, CD, navigation voice output) are transmitted via the Digital Data Bus (D2B).

Signal processing 

In order to make possible the diverse adjustments to the sound, the sound amplifier (A2/13) has a digital signal processor which carries out the complete signal filtering.

Compared with conventional analog filters, digital filters have the following basic advantages:

• The filter parameters (sound adjustments) do not change in the course of time; this means exact reproducibility of all adjustments.
• Lower noise.
• The cost of components is reduced considerably as the filter parameters are adjusted by the software and not by varying component values (resistances, capacitances or inductivities). This also increases the number of possible filter adjustments

Sound optimization 

Each of the 6 amplifier channels is provided with individual compensation which corrects the vehicle-specific acoustics if necessary. In addition further sound optimizations and effects such as e.g. "voice-emphasized" or "Room sound" can be called up.

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

Noise suppression 

The output level of the 6 output stages is monitored constantly.

Regulation is such that distortions are minimized.

Automatic Vehicle Noise Compensation (VNC) 

The noise level inside the vehicle is measured using the sound amplifier microphone (B25/6) which is connected directly to the sound amplifier (A2/13). The volume of the music output signal is continuously adapted to this noise level.

For this purpose the sound amplifier (A2/13) must detect which signals of the measured level are driving noise and which are audio signals. This takes place through a comparison of output signals from the sound amplifier (A2/13) with the measured signal, i.e., the difference between the two signals is 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 transmitted via Digital Data Bus (D2B) to the COMAND operating, display and control unit (A40/3) or radio (A2) and can be read out there via the diagnostic line (K-line).