User Manual

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User's Guide MADIface XT © RME
22. Word Clock
22.1 Word Clock Input and Output
SteadyClock guarantees an excellent performance in all clock modes. Based on the highly effi-
cient jitter suppression, the MADIface XT refreshes and cleans up any clock signal, and pro-
vides it as reference clock at the BNC output (see chapter 30.8).
Input
The MADIface XT word clock input is active when Clock Source in the Settings dialog has been
switched to Word Clock, and a valid word clock signal is present. The signal at the BNC input
can be Single, Double or Quad Speed, the MADIface XT automatically adapts to it. As soon as
a valid signal is detected the Settings dialog shows either Lock or Sync (see chapter 30.2).
Thanks to RME's Signal Adaptation Circuit, the word clock input still works correctly even with
heavily mis-shaped, dc-prone, too small or overshoot-prone signals. Thanks to automatic signal
centering, 300 mV (0.3V) input level is sufficient in principle. An additional hysteresis reduces
sensitivity to 1.0 V, so that over- and undershoots and high frequency disturbances don't cause
a wrong trigger.
The word clock input is shipped as high impedance type (not terminated). The Settings dialog
allows to activate internal termination (75 Ohms). Activate the option Word Clock Input Term.
Output
The word clock output of the MADIface XT is constantly active, providing the current sample
frequency as word clock signal. As a result, in master mode the provided word clock is defined
by the currently used software or the pitch setting. In slave mode the provided frequency is
identical to the one present at the currently chosen clock input. When the current clock signal
fails, the MADIface XT switches to master mode and adjusts itself to the next, best matching
frequency (44.1 kHz, 48 kHz etc.).
Selecting Single Speed in the Settings dialog causes the output signal to always stay within the
range of 32 kHz to 48 kHz. So at 96 kHz sample rate, the output word clock is 48 kHz.
The received word clock signal can be distributed to other devices by using the word clock out-
put. With this the usual T-adapter can be avoided, and the MADIface XT operates as Signal
Refresher. This kind of operation is highly recommended, because
• input and output are phase-locked and in phase (0°) to each other
• SteadyClock removes nearly all jitter from the input signal
• the exceptional input (1 Vpp sensitivity instead of the usual 2.5 Vpp, dc cut, Signal Adapta-
tion Circuit) plus SteadyClock guarantee a secure function even with highly critical word
clock signals
Thanks to a low impedance, but short circuit proof output, the MADIface XT delivers 4 Vpp to 75
Ohms. For wrong termination with 2 x 75 Ohms (37.5 Ohms), there are still 3.3 Vpp fed into the
network – per output!