Clock Modes - Synchronization - RME Audio Hammerfall HDSPe RayDAT User Manual

19.3 Clock Modes - Synchronisation
In the digital world, all devices are either the 'Master' (clock source) or a 'Slave'. If several digi-
tal devices are to be used simultaneously in a system, they not only have to operate with the
same sample frequency but also be synchronous with each other. This is why digital systems
always need a single device defined as 'master', which sends the same clock signal to all the
other ('slave') devices.
Remember that 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's intelligent clock control is very user-friendly, being able to switch between clock
modes automatically. Selecting AutoSync will activate this mode.
AutoSync guarantees that normal 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 di-
rectly to the Hammerfall DSP, AutoSync may cause feedback in the digital carrier, so synchro-
nization breaks down. To remedy this, switch the HDSP's clock mode over to 'Master'.
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 quartz
(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.
With the HDSPe RayDAT all
inputs operate simultaneously.
However, as there is no input
selector, 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)
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 ADAT1 input (ADAT1 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.
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User's Guide HDSPe RayDAT © RME