User manual

8X96 ADC and DAC User Manual Page 47 of 54
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S/MUX ™ encoder and decoder
The S/MUX ™ sample splitting method was originally developed by Sonorus Inc, in
order to provide means of transmitting 24/96 data over 48k ADAT lightpipe. S/MUX
stands for “sample multiplexing”. S/MUX ™ sample splitting has been design to allow
96k operation using standard 48k ADAT interface transmission. where one high speed
96k channel is split between 2 48k channels (tracks). This technique is compatible with
dual wire AES, Prism Sound Split96 (tm) and the recording technique used in Tascam
DA98HR. Mytek also incorporates S/MUX splitting on the TDIF card in order to record
24/96 using new Tascam HR MDM machines.
S/MUX is currently (Nov 2000) implemented in Mytek ADAT and TDIF interfaces.
S/MUX function is automatically engaged whenever 2X sampling switch is on. For
detailed options on using S/MUX with various 48k equipment see: “Dip switch options”.
The 8X96 ADC equipped with an ADAT or TDIF Card can both encode and decode
S/MUX signals. Similarly, the 8X96 DAC can also encode and decode S/MUX.
S/MUX was developed method of de/multiplexing hi-sampling rates data in order to feed
them through a standard 44/48k ADAT Lightpipe interface and onto a 48k machine or
inside a computer DAW through the Sonorus Studi/o PCI interface card. In short, a 24
bit 96k signal is demultiplexed: odd samples are sent at 48kHz via the odd channel (e.g.
#1) and even samples are sent via the even channel (e.g. #2). As a result, a single ADAT
Lightpipe can carry 4 channels of 24 bit, 88/96kHz signal. The Mytek ADAT daughter
card and Sonorus Studi/o PCI Interface both have two sets of Lightpipes, and thus are
capable of transmitting 8 channels of 24 bit 96kHz audio. This method is the foundation
of the Mytek/Sonorus collaboration on a hardware front end for the multichannel
DAW9624™ which is described later in the manual.
More information on S/MUX ™ can be obtained from Sonorus Inc. at:
http://www.sonorus.com/audio/smux.pdf
An excerpt from this paper follows:
S/MUX is our shorthand for Sample Multiplexing. Multiplexing is the process of
combining multiple streams into one stream (in this case, the streams are audio samples).
Demultiplexing is the opposite process of splitting a single stream into multiple streams.
The basic idea of S/MUX is to join together multiple audio channels in order to represent
a single higher bandwidth channel. Unlike current bit-splitting technology, with S/MUX
each sample is contained within one of the ‘bonded’ channels (bchans), not spread out
among them. The audio channels joined together thus determine the resolution of the
S/MUX channels (schans). If they are 24 bit, the S/MUX channels are 24 bit. If they’re
20 bit, the S/MUX channels are 20 bit, and so on. All the bonded channels (bchans) are,
of course, the same resolution.
This simple idea is made practical through a few conventions: