M-AUDIO Delta TDIF - Manual (Page 13)

with the mixer’s output recorded into the user’s application software.
The digital audio mixer is configured and controlled by the included
Delta Control Panel Software.
The Patchbay / Router
In addition to the built-in monitor mixer, the Delta TDIF PCI Audio Card
includes an output patchbay/router. The patchbay/router allows each
output (analog or digital) to be connected to a variety of input sources.
The Delta TDIF’s outputs may accept audio from software sources (these
output devices are visible in your audio software applications) or from
hardware sources such as the analog and digital inputs (TDIF or S/PDIF),
or the monitor mixer. This capability makes the Delta TDIF quite flexible
for WAV or AIFF output, monitoring, or directly connecting inputs to
outputs for system test purposes.
Synchronization
For proper operation, the entire Delta TDIF system is always
synchronized to a single master clock. The master clock is chosen via the
Delta Control Panel software, and this clock may be derived from the
Delta TDIF’s internal crystal oscillators, S/PDIF In, or TDIF In. Much of
the time, the master clock is taken from the internal crystal oscillators.
However, the S/PDIF and TDIF options are used in situations where the
Delta TDIF must be synchronized to external digital audio or sample
rates derived from an external device.
Using the initial default setting, the master clock is derived from the
internal crystal oscillators. Operation in this mode is similar to that of a
generic sound card – for instance, when a WAV or AIFF file is played
through the Delta drivers, the software application playing the WAV or
AIFF file is responsible for setting the sample rate in the sound card
hardware. The Delta TDIF supports these sample rates by using either of
its internal crystal oscillators and dividing the rate of that oscillator by
some value to derive the proper sample rate.
In situations where S/PDIF In is being used, the Delta TDIF Audio Card
must be configured to get its master clock from the S/PDIF In data
stream. The reason for this is simple – a S/PDIF data stream coming from
an external source is rarely going to be in sync with the Delta TDIF card
(or other digital audio devices in the system for that matter), even if the
sample rates are set the same. If the master clock were set to use the
internal crystal, then the incoming S/PDIF audio would have "pops,"
"crackles," and other undesirable audio artifacts present in it. Instead,
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