User Manual

34
User’s Guide OctaMic XTC © RME
14. Word Clock
14.1 Word Clock Input and Output
SteadyClock guarantees an excellent performance in all clock modes. Its highly efficient jitter
suppression refreshes and cleans up any clock signal, and provides it as reference clock at the
BNC output (see section 18.10).
Input
The OctaMic XTC word clock input is active when WCK is chosen in the clock section. The
signal at the BNC input can be Single, Double or Quad Speed, the OctaMic XTC automatically
adapts to it. As soon as a valid signal is detected, the WCK LED is constantly lit, otherwise it is
flashing.
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 menu Clock -
WCK Term. has an option to activate internal termination with 75 Ohms.
Output
The OctaMic XTC's word clock output is constantly active, providing the current sample fre-
quency as word clock signal. In master mode, the word clock will be fixed to 44.1 kHz or 48 kHz
(DS x 2, QS x 4). In any other case the sample rate is identical to the one present at the cur-
rently chosen clock input. When the current word clock source fails, the last valid sample rate
will be held automatically.
Selecting the option WCK Alw. Singl in the menu Clock causes the word clock output to always
stay within the range of 32 kHz to 48 kHz. So at 96 kHz and 192 kHz sample rate, the output
word clock is 48 kHz.
The word clock signal received by the OctaMic XTC can be distributed to other devices by using
the word clock output. With this the usual T-adapter can be avoided, and the OctaMic XTC op-
erates 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 also with most critical word
clock signals.
Thanks to a low impedance, but short circuit proof output, the OctaMic XTC delivers 4 Vpp to 75
Ohms. For wrong termination with 2 x 75 Ohms (37.5 Ohms), there are still 3.3 Vpp at the out-
put.