4. FUNCTIONAL DESCRIPTION
synchronised with another AES/EBU digital audio signal or with
a Word Clock signal, the input selector must be set to ANALOG
extern.
The AES/EBU signal or Word Clock signal which the unit is
required to synchronise the sampling frequency of its
AES/EBU output with can be applied to the AES/EBU input
connector or to the EXT SYNC word clock input connector
respectively. The sampling frequency of the external
AES/EBU or Word Clock signal (and hence the operating
sampling frequency of the d02) will be indicated by the lighting
of a yellow LED in the d02's front panel sampling frequency
display.
All three LED's in the d02's front panel sampling frequency
display will flash red if the d02 can not synchronise to an
external sampling frequency signal because no signal is
connected or because the connected signal is outside the
admissable working sampling frequency range of the unit
(30KHz to 50KHz).
The digital audio signal (either an AES/EBU digital input signal
or an analog input converted by the A/D converter) is processed
in a Texas Instruments Floating Point Signal processor with a
data width of 32 bits. The use of 32 bit digital audio sample
length in calculation ensures that there is no deterioration in
signal quality, even if AES/EBU digital audio data with the
maximum word length of 24 bits is input into the unit.
The DSP carries out the functions of the dynamics processing,
the linear gain and the emphasis filtering. It measures the input
and output levels and generates data for GAIN CHANGE display.
Reading of the front panel buttons and operation of the front
panel display is performed via a special interface (see also
chapter 3.).
One main task of the digital
transmission
processor
d 02 is the
compression
of low signal levels. The compression- RATIO
expresses the effects of a change of the input signal in dB on the
change of the output signal in dB.
E.g. a ratio of 2:1 means that a change in input signal of 20 dB
causes a change in output signal of 10 dB. With the choice of a
compression ratio, the intensity of the compression is determined
and with it also a certain compression characteristic (see also
fig.2 and fig. 3). The RATIO parameter is adjusted on the front
panel in four steps, from 1.1:1 to 2.0:1. The transition to another
characteristic can be carried out during the running programme.
It does not cause any clicking noises.
External
synchronization
Digital signal processor
compression
20
