The Digital Monitor Mixer; The Patchbay / Router; Synchronization - M-Audio Delta Audiophile 2496 Manual

The Digital Monitor Mixer

The Audiophile 2496 Digital Recording System has a hardware digital audio mixer
built into its PCI controller chip. It accepts digital audio streams from all hardware
inputs and all outgoing software audio devices, mixes them with 36-bit internal
precision and then provides the mixed output to the analog outputs (H/W
OUT1/OUT2 as a stereo pair) and/or the S/PDIF outputs. At the same time the
mixer may be used for stereo mix-down, 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 Audiophile 2496 Digital Recording
Interface includes an output patchbay/router. The patchbay/router allows each
output (analog or digital) to be connected to a variety of input sources. The
Audiophile 2496's outputs may accept audio from software sources (the output
devices visible in your audio software applications) or from hardware sources such
as the analog and digital inputs or the monitor mixer. This capability makes the
Audiophile 2496 quite flexible for WAV output, monitoring, or directly connecting
inputs to outputs for "system test" purposes.

Synchronization

For proper operation, the entire Audiophile 2496 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 either the Audiophile 2496's internal crystal
oscillators or from S/PDIF In. Most of the time the master clock is taken from the
internal crystal oscillators. However, the S/PDIF option must be used in situations
where the Audiophile 2496 is monitoring or recording from the S/PDIF input port.
As stated, most of the time the master clock is derived from the internal crystal
oscillators. Operation in this mode is similar to that of a generic sound card and should
be used whenever the S/PDIF In is not being used. In this mode, the audio software
application selects one of the supported Audiophile sample rates and starts playback
and/or recording. The Audiophile 2496 hardware then achieves this sample rate by
activating one of its internal crystal oscillators and dividing the rate of that oscillator
by some integer value.
In situations where S/PDIF In is being used (either to record or just monitor), the
Audiophile 2496 should be configured to get its master clock from the S/PDIF In data
stream. Without this setting, S/PDIF input will not function. Setting the Audiophile
to derive its master clock from the incoming S/PDIF stream keeps the Audiophile in
tight synchronization with that external S/PDIF device, and no drift occurs. Digital
transfers are therefore precise and bit-accurate.
12