Word Clock; Word Clock Input And Output - RME Audio HDSPe MADI FX User Manual

24. Word Clock

24.1 Word Clock Input and Output

SteadyClock guarantees an excellent performance in all clock modes. Based on the highly effi-
cient jitter suppression, the HDSPe MADI FX refreshes and cleans up any clock signal, and
provides it as reference clock at the BNC output (see chapter 30.6).
Input
The HDSPe MADI FX 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 HDSPe MADI FX 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 Termina-
tion.
Output
The word clock output of the HDSPe MADI FX 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 HDSPe MADI FX 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 HDSPe MADI FX 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 HDSPe MADI FX 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!
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User's Guide HDSPe MADI FX © RME