DIGI9636
User’s Guide
© RME
11
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
DIGI9636)
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
DIGI9636
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 its AutoSync technique and a lightning fast PLL, the
DIGI9636
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 ‘S/PDIF 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 ‘S/PDIF 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 S/PDIF frequency.