User's Guide HDSP System Multiface II
© RME
79
34.4 AES/EBU - SPDIF
The most important electrical properties of 'AES' and 'SPDIF' can be seen in the table below.
AES/EBU is the professional balanced connection using XLR plugs. The standard is being set
by the
Audio Engineering Society
based on the AES3-1992. For the 'home user', SONY and
Philips have omitted the balanced connection and use either Phono plugs or optical cables
(TOSLINK). The format called S/P-DIF (SONY/Philips Digital Interface) is described by IEC
60958.
Type
AES3-1992
IEC 60958
Connection
XLR
RCA / Optical
Mode
Balanced
Un-balanced
Impedance
110 Ohm
75 Ohm
Level
0.2 V up to 5 Vss
0.2 V up to 0.5 Vss
Clock accuracy
not specified
I:
±
50ppm
II: 0,1%
III: Variable Pitch
Jitter
< 0.025 UI (4.4 ns @ 44.1 kHz) not specified
Besides the electrical differences, both formats also have a slightly different setup. The two
formats are compatible in principle, because the audio information is stored in the same place
in the data stream. However, there are blocks of additional information, which are different for
both standards. In the table, the meaning of the first byte (#0) is shown for both formats. The
first bit already determines whether the following bits should be read as Professional or Con-
sumer information.
Byte
Mode
Bit 0
1
2
3
4
5
6
7
0
Pro
P/C
Audio?
Emphasis
Locked Sample Freq.
0
Con
P/C
Audio?
Copy
Emphasis
Mode
It becomes obvious that the meaning of the following bits differs quite substantially between the
two formats. If a device like a common DAT recorder only has an SPDIF input, it usually un-
derstands only this format. In most cases, it will switch off when being fed Professional-coded
data. The table shows that a Professional-coded signal would lead to malfunctions for copy
prohibition and emphasis, if being read as Consumer-coded data.
Nowadays many devices with SPDIF input can handle Professional subcode. Devices with
AES3 input almost always accept Consumer SPDIF (passive cable adapter necessary).
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