RME Audio Hammerfall HDSPe AES, User Manual

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User's Guide HDSPe AES
© RME
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11.3 Clock Modes - Synchronisation
In the digital world, all devices must be either Master (clock source) or Slave (clock receiver).
Whenever several devices are linked within a system, there must always be a single master
clock.
A digital system can only have one master! If the card’s clock mode is set to 'Master', all
other devices must be set to ‘Slave’.
The HDSPe AES utilizes a very user-friendly, intelligent clock control, called AutoSync . In
AutoSync mode, the system constantly scans the digital input for a valid signal. If any valid sig-
nal is found, the card switches from the internal quartz (
Clock Mode – Current Internal) to a
clock extracted from the input signal ( Clock Mode – Current AES, Word, TCO or Sync In). The
difference to a usual slave mode is that whenever the clock reference fails, the system will
automatically use its internal clock and operate in clock mode Master.
AutoSync guarantees that normal record and record-while-play will always work correctly. In
certain cases however,
AutoSync may cause feedback in the digital carrier, so synchronization
breaks down. To remedy this, switch the HDSP’s clock mode to 'Master'.
RME’s exclusive
SyncCheck technology enables an easy to use check and display of the cur-
rent clock status. SyncCheck indicates whether there is a valid signal (Lock, No Lock) for each
input (Word, AES, TCO, Sync In), or if there is a valid and synchronous signal (Sync). In the
field Clock Mode the clock reference is shown. See chapter 30.2.
Via
Clock Source 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’.
Under WDM the card will (has to) set
the sample rate. Therefore the error
shown to the right can occur. A stable
signal with a sample rate of 32 kHz is
detected at the Word Clock input
(Sync), but Windows audio had been
set to 44100 Hz before. The red
colour of the text label signals the
error condition, and prompts the user
to set 32000 Hz manually as sample
rate.
Under ASIO the audio software sets the sample rate, so that such an error will usually not hap-
pen – but it can too. In slave mode the external sample rate has priority. Feeding 44.1 kHz will
prevent the ASIO software to set 48 kHz – obviously, as the only way to do so would be to enter
a different clock mode (Master/Internal).
In practice, SyncCheck provides the user with an easy way of checking whether all digital de-
vices 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.