Clock Modes - Synchronization - RME Audio HDSPe AIO Pro User Manual

14.2 Clock Modes - Synchronisation
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 HDSPe's clock mode is set to 'Master',
all other devices must be set to 'Slave'.
The HDSPe AIO Pro's intelligent clock control is very user-friendly, being able to switch between
clock modes automatically. Selecting AutoSync will activate this mode.
In AutoSync mode, the system constantly scans all digital inputs for a valid signal. If this signal
corresponds with the current playback sample rate, the card switches from the internal clock
(System Clock - Mode Master) to a clock generated from the input signal (System Clock - Mode
Slave). A difference to usual slave behaviour is that when the input signal is lost the card will
immediately switch back to the internal clock, into Master mode.
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 solve this problem switch the HDSPe clock mode to 'Internal'.
With the HDSPe AIO Pro all inputs operate simultaneously. However, as there is no input selec-
tor, the HDSPe has to be told which of the signals is the sync reference (a digital device can only
be clocked from a single source). Via Pref. Sync Ref (preferred synchronization reference) a
preferred input can be defined. As long as the card 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 card automatically switches clock mode to 'Master'.
To cope with some situations which may arise in studio practice, setting 'Pref Sync Ref' is es-
sential. One example: An ADAT recorder is connected to the ADAT input (ADAT immediately
becomes the sync 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, 'Pref Sync Ref' should be temporarily
set to SPDIF.
RME's exclusive SyncCheck technology enables an easy to use check and display of the cur-
rent clock status. The status box labelled Input Status indicates whether no signal ('No Lock'), a
valid signal ('Lock') or a valid and synchronous signal ('Sync') is present at each of the digital
clock source inputs.
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.
User's Guide HDSPe AIO Pro © RME
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