Audio amplifier

The sound reproduction is optimised by the 2 types of amplifier:

• Stereo/HiFi amplifier and
  
• Top HiFi amplifier.
  

They are fitted according to the desired type and number of speakers:

The active frequency gates transmit to the amplifier module concerned only that frequency range that can be effectively reproduced by the connected speaker system. The speakers (high, mid and low-range speakers/woofers) are connected to those audio output stages.

Brief description of components

The following components are described for the Top HiFi amplifier:

Top HiFi Amplifier

Top HiFi amplifiers are amplifiers with active frequency gates. Active frequency gates achieve better acoustic results than passive frequency gates.

The Top HiFi amplifier is a control unit on the MOST network which has following functions:

• High and mid-range output stages, 4 x 40 Watt
  
• Subwoofer output stages, 2 x 70 Watt (2-channel subwoofer amplifier)
  
• Vehicle-specific equalizing
  
• Speed-dependent equalizing
  
• Volume-dependent equalizing
  

Audio System Controller (radio/M-ASK/CCC)

The Audio System Controller (ASK) is integrated in the radio/M-ASK/CCC control unit. The ASK manages all audio signals.

Central Information Display (CID) with controller

The space simulation and user-programmable equaliser functions are operated with the aid of the Central Control Display. The desired function is selected by means of the Controller on the front of the centre arm rest.

System functions

The following system functions are described for the Top HiFi amplifier:

• Electronic power-up
  
• Electronic power-down
  
• Undervoltage cutout
  
• Speed-dependent equalizing
  
• Space (room) simulation
  

Electronic power-up

The amplifier is connected to continuous positive and ground as the power supply. The amplifier is woken up via the MOST bus. The amplifier becomes active when

• it detects a voltage above 9 Volts at the control input and
  
• a voltage at the constant positive input that is greater than the voltage at the control input.
  

Electronic power-down

The amplifier is connected to continuous positive and ground as the power supply. It operates within an operating voltage range of 9-16 Volts at the control input.

At voltages < 9 Volt at the control input, the amplifier is automatically switched off. This ensures that the amplifier is not left on when the vehicle is parked, for example.

Undervoltage cutout

The amplifier is automatically switched off on engine start-up because the voltage falls below the lower operating voltage limit of 9 Volts for a brief period.

Once the conditions for switching on are satisfied, the amplifier is automatically switched on again.

Speed-dependent equalizing

In conjunction with the Top HiFi amplifier optional extra, the ASK (Audio System Controller) provides the 7-band equalising function.

This increases the volume of a set sound frequency range in order to counteract vehicle noise when the vehicle exceeds definable speed thresholds. The volume of the individual frequency bands, and particularly the lower frequencies, is individually adjusted in response to the speedometer A signal.

Space (room) simulation

The Top HiFi amplifier features a spatial sound function which enables improved space acoustics. The spatial sound effect is particularly effective in conjunction with ”pure” sound sources (CD mode).

The spatial sound function is switched on when terminal ”R” is switched on (identification lock in position 1). It is switched off by means of the Controller.

Note: The spatial sound function is not recommended for predominantly voice reproduction or poor radio reception.