User Manual

32
User's Guide Fireface UC © RME
16.2 Clock Modes - Synchronization
In the digital world, all devices must be either Master (clock source) or Slave (clock receiver).
Whenever several devices are linked 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 'Internal', all
other devices must be set to ‘Slave’.
The Fireface UC utilizes a very user-friendly, intelligent clock control, called AutoSync. In Auto-
Sync mode, the system constantly scans all digital inputs for a valid signal. If any valid signal is
found, the Fireface switches from the internal quartz (Clock Mode – Current Internal) to a clock
extracted from the input signal (Clock Mode – Current ADAT etc). The difference to a usual
slave mode is that whenever the clock reference fails, the system will automatically use its in-
ternal clock and operate in Master mode.
AutoSync guarantees that record and record-while-play will always work correctly. In certain
cases however, e.g. when the inputs and outputs of a DAT machine are connected directly to
the Fireface UC, AutoSync may cause feedback in the digital carrier, so synchronization breaks
down. Remedy: switch the Fireface clock mode over to Master (Clock Source – Internal).
The Fireface UC's ADAT and SPDIF inputs operate simultaneously. Because there is no input
selector, the Fireface UC has to be told which one of the signals is the sync reference (a digital
device can only be clocked from a single source). The Clock Source selection is used to define
a preferred input for the automatic clock system. This input will stay active as long as a valid
signal is found.
To cope with some situations which may arise in
studio practice, defining a sync reference is essential.
One example: An ADAT recorder is connected to the
ADAT input (ADAT immediately becomes the
AutoSync source) and a CD player is connected to
the SPDIF input. Try recording a few samples from
the CD and you will be disappointed - few CD players
can be synchronized. The samples will inevitably be
corrupted, because the signal from the CD player is
read with the (wrong) clock from the ADAT i.e. out of
sync. In this case, the Clock Source should be set
temporarily to SPDIF.
RME’s exclusive SyncCheck technology (first implemented in the Hammerfall) enables an easy
to use check and display of the current clock status. Input Status indicates whether there is a
valid signal (Lock, No Lock) for each input (Word Clock, ADAT, SPDIF and LTC), or if there is a
valid and synchronous signal (Sync). In the field Clock Mode the clock reference is shown (Cur-
rent…). See chapter 31.1.
In practice, SyncCheck provides the user with an easy way of checking whether all digital de-
vices 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.