Specifications

1.28
Operation Manual
© 2008 Prism Media Products Ltd
Revision 1.05Prism Sound Orpheus
5.2 Synchronization
This section seeks to clarify some potentially confusing issues to do with synchronization.
Sync sources, masters and slaves
A single Orpheus connected to a host computer supports a range of reference sync options:
Sync Source
Master/Slave
Description
Local
Master
System is sync'ed to Orpheus' local clock
Wordclock
Master
System is sync'ed to external wordclock applied to Orpheus
DI
Master
System is sync'ed to external S/PDIF applied to Orpheus
ADAT
Master
System is sync'ed to external ADAT (ADAT input must be enabled)
PC DAW
Slave
Orpheus is slaved to system clock from host PC
CSP
Master
System is sync'ed to Orpheus' 1394 clock (not recommended)
When multiple Orpheus units are connected to a single host, only one unit (or the host) can be
master. The remainder are slaves to the master's reference sync which is transmitted on the
FireWire bus.
Thus every port of every Orpheus in the system must operate at a common sample rate.
An exception to this is when a sample rate converter (SRC) is configured in Orpheus' digital input or
output. In the former case, the SRC simply converts any incoming digital signal of whatever sample
rate to the sample rate of the Orpheus system. But if the SRC is in the digital output, it is necessary
to specify what the output sample rate must be. Furthermore, it may be necessary to lock the output
rate to an arbitrary external reference. Orpheus allows for this; as described in the Output Setup tab
section of the Orpheus Control Panel chapter.
'Master' in the table reflects the state of the unit's front panel ''Master' indicator. If the device's is
providing the sample clock to the FireWire for the host (and any other Orpheus devices), the master
indicator is lit. If the device is receiving its sample clock from the bus, the indicator is not lit. Note
that if an Orpheus is being clocked from its wordclock or DI input, and thus is providing the clock via
the FireWire to other interfaces, it is considered to be a master.
Wordclock output
As well as outputting a clock at the selected sample rate, Orpheus' wordclock output can be
configured to produce a '256x clock' (a clock at 256x the selected sample rate, e.g. a 'superclock') or
a 'base clock' (44.1kHz if the sample rate is a 44.1kHz multiple, or 48kHz if the sample rate is a
48kHz multiple)
TAKE NOTE
It is not possible to change the sample rate in a Windows system whilst any of Orpheus' ports
are in use in WDM mode. In this case it is necessary to disconnect the ports from the
application before changing the sample rate.
In Mac OS X, the Audio MIDI Setup panel contains a drop control for selection of the desired
Sync Source. However, in versions to date, the names of the selectable Sync Sources may
not exactly match those in the Sync Source control within the Orpheus Control Panel applet.
For this reason, it is recommended that the Orpheus Control Panel applet be used for setting
the desired Sync Source.