Limit Bandwidth - RME Audio Fireface 800 User Manual

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.
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 Clock, ADAT1, ADAT2, SPDIF), or if there is a valid and synchronous signal
(Sync). The AutoSync Ref display shows the input and frequency of the current sync source
(see chapter 35.1).
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.
Thanks to its AutoSync technique and lightning fast PLLs, the Fireface 800 is not only capable
of handling standard frequencies, but also any sample rate between 28 and 200 kHz. Even the
word clock input, most often used in varispeed operation, allows any frequency between 28 kHz
and 200 kHz.
At 88.2 or 96 kHz: If the ADAT input has been selected in Pref Sync Ref, the sample frequency
shown in the SPDIF Freq. field differs from the one shown in AutoSync Ref. The unit automati-
cally switches to S/MUX mode here, because ADAT optical inputs and outputs are only speci-
fied 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.

19.4 Limit Bandwidth

This option allows to reduce the amount of bandwidth used on the FireWire bus. A typical ex-
ample is the use of the Fireface with a laptop. Only in rare cases both ADAT ports are needed,
in many cases even both stay unused. The option Analog+SPDIF will reduce the amount of
constantly (!) transferred data from around 5 MByte (10 in both directions) to only 2 MByte (4 in
both directions). The FireWire connection will be more stable, reliable and robust, leaving addi-
tional bandwidth for other devices. At the same time the CPU and system load is reduced, as
less channels have to be processed and to be transferred. In TotalMix, the deactivated software
playback channels will be replaced with empty plates. More details are found in chapter 35.4.
Available Settings
All channels (default) activates all 28 input and output channels.
Analog + SPDIF + ADAT1 disables channels 21–28 (ADAT2).
Analog + SPDIF activates all 10 analog channels plus SPDIF.
Analog 1-8 activates only the first eight analog channels.
User's Guide Fireface 800 © RME
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