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page 23
A.2 A/D level
Except for the Pure Audio inputs, all other analogue inputs will be converted to digital
samples (A/D conversion) by the built-in 24 bit 96kHz high quality A/D converter. The
digital audio samples are then used in the DSP circuit e.g. for further processing,
e.g. Dolby ProLogic II.
However, a fundamental problem by A/D conversion is that the peak analogue input
level should be as close as possible to the maximum input range of the A/D
converter, otherwise the important dynamic range will degraded.
On the other hand, the peak analogue level must in no circumstances exceed the
maximum analogue limit for the A/D converter or very hard clipping will occur.
In the PR350 B is included an autogain feature, which operates in the following way:
when an input is selected, initially the high sensitivity position is selected for best
dynamic range. If clipping occur the sensitivity is automatically reduced. During
changes in sensitivity a small click can be heard.
A.3 Electrical (coaxial) versus optical digital input.
Normally the coaxial connection between e.g. DVD and Processor has been
preferred by hifi-enthusiasts due to larger bandwidth and consequently less jitter on
the receiver side.
However, with the increasing complication of a surround system with integrated
analog, digital and video signals it is easy to create disturbances and ground
problems in the system.
To avoid such problems the digital coaxial inputs of PR350B has been designed with
a special “floating ground” system.
On the other hand the optical transmitters and receivers in PR350B is a new type
with much increased bandwidth of 13MHz compared to the normal 7MHz type. This
eliminates most problems with the optical connection, and the advantage with full
galvanic isolation is clear.
If any problems in the system with ground loops or disturbances appear, please
change to optical digital connection.
A.4 Automatic failure correction system
A special “watch dog” will monitor the operation of the DSP (Digital Signal
Processor). If any external disturbances, like lightning or burst transients on the
Mains connection or static discharge causes the DSP to crash , the DSP will
automatically be reset for correct operation. This is done in a fraction of a second,
and only a short dropout in the sound can be heard.
During standby, the entire system in PR350 B is reset. If any problem occurs with
the operation of PR350 B, set the unit into standby shortly.
If standby do not cure the problem, please turn off and turn on the Mains switch on
the rear side.
With the many possible settings in PR350 B it is possible to select a setting, which
do not match the installed system and cause misoperation. If misoperation is
observed and standby/operate command does not help, then run the factory default
in the config menu followed by standby/operate command.