User's Guide HDSPe MADIface
© RME
67
29.4 DS - Double Speed
When activating the
Double Speed
mode the MADIface operates at double sample rate. The
internal clock 44.1 kHz turns to 88.2 kHz, 48 kHz to 96 kHz. The internal resolution is still 24 bit.
Sample rates above 48 kHz were not always taken for granted, and are still not widely used
because of the CD format (44.1 kHz) dominating everything. Before 1998 there were no re-
ceiver/transmitter circuits available that could receive or transmit more than 48 kHz. Therefore a
work-around was used: instead of two channels, one AES line only carries one channel, whose
odd and even samples are being distributed to the former left and right channels. By this, you
get the double amount of data, i. e. also double sample rate. Of course in order to transmit a
stereo signal two AES/EBU ports are necessary then.
This transmission mode is called
Double Wire
in the professional studio world, and is also
known as
S/MUX
(abbreviation for
Sample Multiplexing
) in connection with the multichannel
ADAT format. The AES3 specification uses the uncommon term
Single channel double sam-
pling frequency mode
.
Not before February 1998, Crystal shipped the first 'single wire' receiver/transmitters that could
also work with double sample rate. It was then possible to transmit two channels of 96 kHz data
via one AES/EBU port.
But
Double Wire
is still far from being dead. On one hand, there are still many devices which
can't handle more than 48 kHz, e. g. digital tape recorders. But also other common interfaces
like ADAT or TDIF are still using this technique.
With MADI, sample multiplexing is often used as well to offer sample rates higher than 48 kHz.
The MADIface supports all formats. 96 kHz can be received and transmitted both as 48K Frame
(using S/MUX) and as native 96K Frame. In 48K Frame Double Speed mode, the MADIface
distributes the data of one channel to two consecutive MADI channels. This reduces the avail-
able channel count from 64 to 32.
As the transmission of double rate signals with 48K Frame is done at standard sample rate
(Single Speed), the MADI ports still operate at 44.1 kHz or 48 kHz.
Summary of Contents for Hammerfall HDSPe MADIface
Page 5: ...User s Guide HDSPe MADIface RME 5 User s Guide HDSPe MADIface General...
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Page 35: ...User s Guide HDSPe MADIface RME 35 User s Guide HDSPe MADIface Connections and TotalMix...
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