RME ADI-648 [15/32] Word clock input and output
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RME ADI-648 [15/32] Word clock input and output

RME ADI-648 [15/32] Word clock input and output
User's Guide ADI-648 © RME
15
8.3 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 12.4).
Input
The ADI-648's transformer isolated word clock input is active when EXT is chosen in the clock
section. The signal at the BNC input can be single or double speed, the ADI-648 automatically
adapts to it. As soon as a valid signal is detected, the EXT 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 ADI-648's word clock input is shipped as
high impedance type (not terminated). A push
switch allows to activate internal termination
(75 Ohms). The switch is found on the back
between the BNC jacks. Use a small pencil or
similar and carefully push the blue switch so
that it snaps into its lock position. Another push
will release it again and de-activate the termi-
nation.
Output
The word clock output is constantly active, providing the current sample frequency as word
clock signal. In master mode (Int.), the word clock will be fixed to 44.1 kHz or 48 kHz. In any
other case the sample rate is identical to the one present at the currently chosen clock input.
When the current word clock source fails, the last valid sample rate will be held automatically.
The word clock signal received by the HDSP MADI can be distributed to other devices by using
the word clock output. With this the usual T-adapter can be avoided, and the HDSP MADI oper-
ates 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.
The word clock output usually operates in Single Speed mode, as do all ADAT and TDIF
ports.
In S/MUX or Double Speed mode, the word clock output will therefore be no higher than 48
kHz. In case a Double Speed word clock is needed (88.2 or 96 kHz), press the key 96K FRAME
several times, until the LED WCK is lit.
Thanks to a low impedance, but short circuit proof output, the ADI-648 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.

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