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Prism Sound Orpheus
Setting Action
24 bit
All 24 bits sent to the digital output are transmitted from the S/PDIF or AES3 output.
Channel Status is set to indicate 24 bit output. This setting can be used to pass Dolby or
DTS data to an external decoder since it leaves the audio data from the host unchanged.
Note, however, that the use of Orpheus' local DO mixer, or the assignable level control, or
the SRC in the digital output will prevent bit-identical data from being transmitted.
16 bit
Audio data sent to the digital output is re-dithered using flat TPDF dither to produce a 16 bit
output at the S/PDIF or AES3 output. Channel Status is set to indicate 16 bit output. This
setting is not generally preferable to the SNS settings, since the noise level is not
psycho-acoustically optimized.
SNS1 Audio data sent to the digital output is noise-shaped using Prism Sound's proprietary SNS
(Super Noise Shaping) process to produce a 16 bit output at the S/PDIF or AES3 output.
SNS2
Channel Status is set to indicate 16 bit output. These settings are generally preferable to
the 16 bit setting, since the noise level is psycho-acoustically optimized. SNS1 offers the
SNS3
least optimization, but with the flattest residual noise spectrum, with optimization increasing
SNS4
up to SNS4, which offers the lowest subjective noise floor, but with significant colouration
Note that if the audio data has already been word-length-processed for 16 bit output by the DAW
software, Orpheus' word-length control should be set to 24 bits to prevent unwanted additional
dithering.
For further discussion of dithering and noise shaping, and details of the SNS process, see the
and noise-shaping
section.
5.1.4.3
DO synchronization
Note that it is necessary to ensure that the sample clock of any digital audio device to which Orpheus'
digital outputs are connected is synchronous with Orpheus' own sample clock. This is usually
achieved by synchronizing the receiving equipment to Orpheus' S/PDIF, ADAT or Wordclock output,
but can be achieved by synchronizing Orpheus to the receiving device's clock or house sync (by
setting DI or Wordclock as Orpheus' sync source).
For more information about synchronization, see the main
jitter
section, and the section describing the
5.1.5
Output mixers
Orpheus' output mixers are high-quality, versatile stereo digital mixers available at all of Orpheus'
outputs (excluding ADAT outputs). The signal processing in Orpheus' mixers is as precise and
sophisticated as in a professional digital console. All coefficients are filtered at sample-rate to
minimise unwanted quantization effects such as zipper noise.
In normal operation, Orpheus' output pairs are set in 'DAW' mode, i.e. they output their respective
feeds from the DAW software directly - in this case, Orpheus' output mixers are disabled. By
selecting 'MIX' mode for an output pair, the mixer is enabled: its inputs comprise all eight of Orpheus'
analogue inputs, the two-channel digital input, plus the respective stereo feed from the DAW
software. Each input has a dedicated fader and pan pot, plus mute and solo buttons and
high-resolution level meter. Input pairs can be designated as 'stereo', wherein a single ganged fader
and balance pot are provided, plus a single mute and solo button. The stereo output also has fader,
mute button and high-resolution level meters.
The output mixers are primarily intended to provide low-latency foldback or monitor mixes
incorporating Orpheus' audio inputs in conjunction with feeds from the DAW software - since the mix
is performed locally, the delay involved in passing live audio up to the host computer and back is
removed. However, it is also possible to configure the output mixers for general purpose use, where
inputs can be mixed to outputs without involving the Host's audio at all. Having set up such mixes
© 2008 Prism Media Products Ltd
Operation Manual
Synchronization
Unit Settings tab
of the
Revision 1.05
section , the
Clocking and
Orpheus Control Panel
Dither
applet.
1.26
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