Aes/Ebu - Spdif - RME Audio ADI-4 DD User Manual

11.2 AES/EBU - SPDIF

The most important electrical properties of 'AES' and 'SPDIF' can be seen in the below table.
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
Connection
Mode
Impedance
Level
Clock accuracy
Jitter
Besides the electrical differences, both formats also have a slightly different setup. The two
formats are principally compatible, 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. Already in the
first bit there is the decision, whether the following bits should be read as Professional or Con-
sumer information.
Byte Mode Bit 0
0 Pro P/C
0 Con P/C
As can be seen, the meaning of the following bits differs quite substantially in both formats. If a
device like a common DAT recorder only has an SPDIF input, it usually understands 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. This actually happened in former times, but if
found today then it was implemented to force the costumer to buy a more expensive device.
Nowadays many devices with SPDIF input can handle Professional subcode. Devices with
AES3 input almost always accept Consumer SPDIF (passive cable adapter necessary).
20
AES3-1992
XLR
Balanced
110 Ohm
0.2 V up to 5 Vss
not specified
< 0.025 UI (4.4 ns @ 44.1 kHz)
1 2
Audio? Emphasis
Audio? Copy
User's Guide ADI-4 DD © RME
IEC 60958
RCA / Optical
Un-balanced
75 Ohm
0.2 V up to 0.5 Vss
I: ± 50ppm
II: 0,1%
III: Variable Pitch
not specified
3 4 5
Locked
Emphasis
6 7
Sample Freq.
Mode