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If several digital 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. RME's exclusive SyncCheck technology, first
implemented in the Hammerfall, enables an easy to use check and display of the current clock
status. The 'SyncCheck' field indicates whether no signal ('No Lock'), a valid signal ('Lock') or a
valid and synchronous signal ('Sync') is present at each of the three ADAT optical inputs. The
'Sync Ref' display shows the current sync source's input and frequency.
In practice, SyncCheck provides the user with an easy way of checking whether all digital
devices 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.
An example to illustrate this: The ADAT1 and ADAT2 inputs are receiving signals from a digital
mixing desk that has been set to clock mode 'Internal' or 'Master'. An ADAT recorder is
connected to the ADAT3 input. The DIGI9652 is set to AutoSync mode. As expected,
SyncCheck shows that the ADAT1 and ADAT2 inputs are in sync (as they are driven by the
same clock from the mixing desk), but shows 'Lock' instead of 'Sync' for the ADAT3 input.
Because the ADAT
recorder
is
not
receiving any signals
from
Hammerfall
or
from the mixer, it will
generate
its
own
clock at a rate which
is (almost) the same
as
the
sample
frequency
of
the
mixing desk - but not
identical.
Remedy:
To drive the ADAT
recorder
from
its
digital input, set it to
slave mode (DIG),
and connect the input to the Hammerfall's ADAT3 output. Hammerfall is already in
sync with the mixing desk, so it will send an identical (synchronous) signal to ADAT3 out. The
ADAT recorder will lock onto this, its output will also be in sync. The signal from the ADAT
recorder is now fully in sync with the signals from the mixing desk.
Thanks to the its AutoSync technique and a lightning fast PLL, the Hammerfall is not only
capable of handling standard frequencies, but also any sample rate between 25 and 105 kHz.
The input selected in 'Pref Sync Ref' serves as synchronization source. If the Expansion Board
has been installed, and the word clock input is selected (clock mode 'Word Clock'), this will
serve as the synchronization source, allowing any sample frequency between 25 kHz and 56
kHz in varispeed operation.
The current sample frequency at the S/PDIF input (displayed in the 'SPDIF In' field) is useful
for troubleshooting and checking the configuration of all connected digital devices. If an input
without a valid signal (or a faulty one) is selected, 'No Lock' will appear. In varispeed mode, or
if the sample frequency is way out of tune, 'Lock' is displayed.
At 88.2 or 96 kHz: If one of the ADAT inputs has been selected in 'Pref Sync Ref', the sample
frequency shown in the 'SPDIF In' field differs from the one shown in 'Sync Ref'. The card
automatically switches to its Sample Split mode here, because ADAT optical inputs and outputs
are only specified up to 48 kHz. Data from/to a single input/output is spread over two channels,
the internal frequency stays at 44.1 or 48 kHz. In such cases, the ADAT sample frequency is
only half the SPDIF frequency.
User's Guide DIGI9652 © RME
15
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