Sierra Video 507140 - Manual (Page 4)

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External Reference:
The converter can be set to a sample rate based on an external digital audio reference signal. The
external reference must be a valid digital audio signal. An internal AES receiver will lock to the
reference input signal and if present the sample rates of both channels of the converters can be
switched to the clock derived from this input reference. One position on JP1 is use select the used
of the external reference signal. Only the jumper closest to the JP1 silk screen markings is used.
If a suite case jumper is installed the external reference is used as the conversion clock. If no
jumper is installed the internal clock generator is used for the conversion clock.
The external reference can be set to be either 110 ohms input impedance or 75 ohm input
impedance using JP2 and JP3 as indicated below;
110 ohm Impedance 75 ohm Impedance
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Unused Jumpers:
At the present time, Jumpers JP11 and JP12 are un-used by the circuitry and are reserved for use
by possible future enhancements of the board.
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Factory default settings:
When the Analog to Digital converter is shipped from the factory, there board is set to use the
internal clock for the conversion running at a 48Khz sampling rate, 110 ohms output impedance in
differential mode (AES), and the maximum input signal is set to +24 dBu.