User`s guide

User’s Guide HDSP System HDSP 9652 © RME
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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 digital clock source inputs. The
‘AutoSync Ref’ display shows the current sync source and the measured 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 Hammerfall DSP 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 HDSP 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 HDSP’s ADAT3
output. The Hammerfall DSP 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 lightning fast PLLs, the HDSP is not only capable of
handling standard frequencies, but also any sample rate between 25 and 105 kHz. Even the
word clock input, which most users will use in varispeed operation, allows any frequency
between 25 kHz and 103 kHz.
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 ‘AutoSync 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.