User Manual

User's Guide Fireface UFX II © 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 Fireface refreshes and cleans up any clock signal, and provides it

as reference clock at the BNC output (see chapter 39.8).

Input

The Fireface's word clock input is active when Clock Source in the Settings dialog has been

switched to Word, and a valid word clock signal is present. The signal at the BNC input can be

Single, Double or Quad Speed, the Fireface UFX II automatically adapts to it. As soon as a valid

signal is detected, the WC LED is lit, and the Settings dialog shows either Lock or Sync (see

chapter 39.1).

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 Fireface UFX II word clock input can be not terminated or internally terminated (75 Ohms).

The state is comfortably selected within the Settings dialog. To terminate the input check the

option Word Clock In Term. under Input Options.

Output

The word clock output of the Fireface 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. 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 Fireface UFX II 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 and 192 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 Fireface UFX II 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, short circuit proof output, the Fireface 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 output.