ATI Audio DDA208-BNC - Manual (Page 3)

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DESCRIPTION
INPUTS
Incoming AES/EBU formatted digital audio data is selected by the internal
jumpers and applied to the input transformer. Both XLR and BNC inputs are
balanced and DC isolated from ground. Input termination resistors at
75 ohms for BNC inputs or 110 ohms for XLR inputs can be switched in or out of
the circuit with the internal jumpers. Inputs should always be terminated unless
they are looped thru to another device or DDA input. The last device or input
should always terminate the line.
RECEIVERS
When input re-clocking is enabled, the equalized AES/EBU data stream is
applied to the receiver circuit, which recovers the clock and synchronization
signals and separates the audio and digital data. The audio data may be 16 to 24
bits at sample rates from 27 to 192 kHz.
Frame sync (FSYNC), Serial Clock (SCK), Serial audio data (SDATA), Channel
status (C), User channel data (U), and data validity information (VERF) are
passed directly to the transmitter section for reformatting into the output data
stream. VERF is an OR’ing of the validity information from the incoming data (V)
with an internal error flag (ERF) that detects serious transmission errors such as
parity errors, bi-phase coding violations and an out-of-lock PLL receiver. VERF
then becomes the transmitted validity bit (V) and can be used by downstream
error correction devices to interpolate through errors.
TRANSMITTERS
The Frame sync (FSYNC), Serial Clock (SCK), Serial audio data (SDATA), Channel
status (C), User channel data (U), and data Validity information (VERF) are passed
directly to the transmitters for reformatting into the AES/EBU output data stream. The
transmitters are capable of operation from 27 to 192 kHz equivalent sample rates. The
transmitters operate in a transparent mode, which allows the transmitter block
structure (Channel Status, User and Validity bits) to be slaved to the block structure of
the receiver. In the transparent mode the propagation delay of data are less than 25
nanoseconds even at the lowest sample rate.
OUTPUT DRIVERS
DDA208-XLR units are equipped with balanced, 110-ohm, transformer coupled
outputs and XLR type connectors. DDA208-BNC units use the alternative 75-
ohm unbalanced outputs to BNC coax connectors. The XLR outputs are in full
compliance with specification AES3-1992 and the BNC outputs are in
accordance with the recommendations of AES-3id-1995. XLR outputs are
transformer coupled for ground isolation.