ALESIS Hammerfall DSP System - Manual (Page 32)

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User's Guide HDSP MADI © RME
Application examples
DDS allows for a simultaneous change of speed and tune during record and playback. From
alignment to other sources up to creative effects – everything is possible..
DDS allows to intentionally de-tune the complete DAW. This way, the DAW can match instru-
ments which have a wrong or unchangeable tuning.
DDS allows to define a specific sample rate. This feature can be is useful in case the system
randomly changes the sample rate – for unknown reasons. It also prevents a change from Dou-
ble Speed (96 kHz) to Single Speed (48 kHz), which would cause configuration and routing
problems by the changed amount of MADI channels.
19.3 Clock Modes - Synchronisation
AutoSync
The HDSP MADI has been equipped with AutoSync, an automatic clock source selection, which
adopts the first available input with a valid digital signal as the clock reference input. The input
currently used as sync reference is shown in the AutoSync Ref status field, together with its
current sample frequency.
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 over to 'Master'.
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, oth-
erwise 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’.
Thanks to its AutoSync technique and lightning fast PLLs, the HDSP is not only capable of han-
dling standard frequencies, but also any sample rate between 28 and 105 kHz. Even the word
clock input, which most users will use in varispeed operation, allows any frequency between 28
kHz and 105 kHz.
The HDSP MADI's outstanding clock control allows for a synchronization of the output signal to
the word clock's input signal not only at identical sample rates, but also at half, quarter, double
and quad sample rates. A playback of 96 kHz can easily be synchronized via a 48 kHz word
clock signal.
SyncCheck
If several digital devices are to be used simultaneously in a system, they not only have to oper-
ate with the same sample frequency but also be synchronous with each other. This is why digi-
tal systems always need a single device defined as ‘master’, which sends the same clock signal
to all the other (‘slave’) devices.
Remember that a digital system can only have one master! If the HDSP MADI’s clock
mode is set to Master, all other devices must be set to Slave.
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 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.