RME Fireface UCX II 40-Channel USB-B Audio/MIDI Interface - Manual (Page 24)

24 User's Guide Fireface UCX II © RME
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8.7 Clock Modes - Synchronization
In the digital world, all devices must be either Master (clock source) or Slave (clock receiver).
Whenever several devices are linked within a system, there must always be a single master
clock.
A digital system can only have one master! If the Fireface’s clock mode is set to 'Master', all
other devices must be set to ‘Slave’.
The Fireface UCX II utilizes a very user-friendly, intelligent clock control, called AutoSync . In
AutoSync mode, the system constantly scans the digital input for a valid signal. If any valid signal
is found, the Fireface switches from the internal quartz (
Clock Source – Current Internal) to a
clock extracted from the input signal ( Clock Source – Current ADAT, SPDIF, AES or Word). The
difference to a usual slave mode is that whenever the clock reference fails, the system will au-
tomatically use its internal clock and operate in clock mode Master.
AutoSync guarantees that record and record-while-play will always work correctly. In certain
cases however, AutoSync may cause feedback in the digital carrier, so synchronization breaks
down. To remedy this, switch the Fireface clock mode to
‘Internal’.
RME’s exclusive
SyncCheck technology enables an easy to use check and display of the cur-
rent clock status. SyncCheck indicates whether there is a valid signal (Lock, No Lock) for each
input (Word Clock, SPDIF, ADAT, AES), or if there is a valid and synchronous signal (Sync).
See chapter 40.1.
Via
Clock Source a preferred input can be defined. As long as the Fireface sees a valid signal
there, this input will be designated as the sync source, otherwise the other inputs will be scanned
in turn. If none of the inputs are receiving a valid signal, the Fireface automatically switches
clock mode to ‘Internal’.
Under WDM the Fireface will (has to) set the
sample rate. Therefore the error shown to the
right can occur. An AES, SPDIF or ADAT
signal with a sample rate of 48 kHz is used as sync source, but Windows audio had been set to
44100 Hz before. The red color of the text label signals the error condition, and prompts the user
to set 48000 Hz manually as sample rate.
Under ASIO the audio software sets the sample rate, so that such an error will usually not hap-
pen
– but it can too. In slave mode the external sample rate has priority. Feeding 44.1 kHz will
prevent the ASIO software to set 48 kHz – obviously, as the only way to do so would be to enter
a different clock mode (Master/Internal).
In practice, SyncCheck provides the user with an easy way of checking whether all digital devic-
es connected to the system are properly configured. With SyncCheck, finally anyone can master
this common source of error, previously one of the most complex issues in the digital studio
world.