Clock Modes - Synchronization - RME Audio Hammerfall HDSP 9632 User Manual

9.2 Clock Modes - Synchronization

In the digital world, all devices are either the 'Master' (clock source) or a 'Slave' synchronized
to the master. Whenever several devices are linked within a system, there must always be a
single master clock. The Hammerfall DSP'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 quartz
(AutoSync Ref displays 'Master') to a clock generated from the input signal (AutoSync Ref
displays 'Slave'). This allows on-the-fly recording, even during playback, without having to
synchronize the card to the input signal first. It also allows immediate playback at any sample
rate without having to reconfigure the card.
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
directly to the Hammerfall DSP, AutoSync may cause feedback in the digital carrier, so
synchronization breaks down. To remedy this, switch the HDSP's clock mode over to 'Master'.
Remember that a digital system can only have one master! If the HDSP's clock mode is set
to 'Master', all other devices must be set to 'Slave'.
The HDSP 9632's ADAT optical input and the SPDIF input operate simultaneously. Because
there is no input selector however, the HDSP 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
situations which may arise
in studio practice, setting
'Pref Sync Ref'
essential. One example:
An ADAT recorder
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.
samples will inevitably be
corrupted, because
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.
some
is
is
The
the
User's Guide Hammerfall DSP 9632 © RME
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