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I N S T A L L A T I O N
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S/PDIF DEVICES
S/PDIF is an industry standard format for
transferring stereo digital audio from one device to
another. While many devices on the market
support S/PDIF, the term
S/PDIF device as used in
this discussion refers to a device that has no other
way of synchronizing digitally with other devices.
Examples of this kind of device are:
■
Digidesign Audiomedia I, II and III cards
■
DAT decks
Devices that have S/PDIF connectors, but also have
word clock connectors, ADAT sync connectors, or
other means of digital audio synchronization,
should be incorporated into a Digital Timepiece
system using these other sync formats.
How S/PDIF sync works
When synchronizing two S/PDIF devices, one acts
as the master and the other serves as a slave. The
slaved device follows the master to maintain
accurate synchronization that won’t drift.
S/PDIF is similar to word clock in the sense that it
is a time base reference, providing an accurate
measurement of the passage of time and the speed
at which samples should go by. S/PDIF can also
contain embedded address information (e.g. “we’re
at 1:05:33:14”). However, many S/PDIF devices,
including most DAT decks, do not support
embedded time code. In order to support as wide a
range of devices as possible, the Digital Timepiece
does not support embedded S/PDIF time code
either. Instead, it uses the S/P DIF sample clock as a
time base and relies on time code (SMPTE time
code or MIDI time code) to make the S/P DIF
device chase, locate and play in sync with the
Digital Timepiece. An example is shown in
Figure 3-22 on page 26.
S/PDIF devices cannot be chained.
S/PDIF thru
S/PDIF differs from word clock because it is not
just a synchronization format: it consists of actual
digital audio signal, which can be recorded from
one device to another. As a result, the Digital
Timepiece has a S/PDIF THRU button on the front
panel that allows the Digital Timepiece to become
transparent and pass any audio signal it receives on
its S/PDIF IN port directly to its S/PDIF OUT port.
When the THRU button is pushed out , the Digital
Timepiece “swallows” incoming S/PDIF signal. If
the Digital Timepiece is currently set to its S/PDIF
time base mode, it will also slave to the S/P DIF
signal that it swallows. When the THRU button is
pushed
in , the THRU LED on the front panel lights
up and the Digital Timepiece ignores whatever it
receives on its S/PDIF input, passing the signal
through, unaltered, to its S/PDIF output as shown
in Figure 3-18. The Digital Timepiece cannot slave
to S/PDIF input when S/PDIF THRU is engaged.
This feature is supplied as a convenience, so you
don’t have to swap cables for different situations. If
you want to slave the Digital Timepiece to an S/
PDIF device, release the THRU button. If you want
to pass the device’s S/PDIF signal to another device
connected to the Digital Timepiece’s S/PDIF Out,
push the THRU button in.
Figure 3-18: An example of bidirectional communication between
two S/PDIF devices. When Digital Timepiece’s S/PDIF THRU button is
pushed in (turned on), device A can send signal to Device B. When the
S/PDIF device A
S/PDIF Out
S/PDIF In
Digital Timepiece
S/PDIF In
S/PDIF device B
S/PDIF Out S/PDIF In
S/PDIF Out
S/PDIF THRU
turned on
(button pushed in)