Aes/Ebu And S/Pdif Standards; Installation; General Connection Notes; Analog Inputs And Outputs - Behringer ULTRAMATCH PRO SRC2496 User Manual

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ULTRAMATCH PRO SRC2496
application. Therefore, programmers continue to experiment with the most
varied of algorithms, ending up, however, always having to make a compromise
between computation efforts and sound quality.
By processing data in real time, the processor used in the BEHRINGER
ULTRAMATCH PRO can process incredible amounts of data.
The noise and interference floor is thus below -117 dBFS, and the
distortion values, even with difficult input signals, are below -104 dBFS.
The ULTRAMATCH PRO remains practically inaudible as such values are not
normally achieved either by the A/D or the D/A converter, and certainly not by the
CD as the final product.

4.2 AES/EBU and S/PDIF standards

In principle there are two standards, the most important electrical characteristics of
which can be seen in tab. 4.1.
AES/EBU is the professional, balanced connection via XLR connectors.
This interface is based on two identical protocols published in November 1985
(EBU Tech. 3250-E) by the European Broadcast Union and in December 1985 by
the Audio Engineering Society (AES3-1985). Sony and Philips oriented themselves
to this standard and developed a further interface with unbalanced signal routing
and a few other major differences, predominantly related to the assignment
of the channel status bits. This interface, named after the two companies and
known as S/PDIF (Sony/Philips Digital Interface), uses either RCA connectors or
optical connections with optical fiber cables. The procedure, standardized in IEC
958, made a name for itself mainly due to efforts to introduce a copy protect
technique. This standard also describes the revised AES/EBU interface, which was
adapted to the S/PDIF format and named IEC 958 Type I (professional). The name
of the S/PDIF interface is then IEC 958 Type II (consumer). Your ULTRAMATCH PRO
uses the latest versions of each of the standards, AES/EBU (AES3), IEC 60958 and
EIAJ CP-1201 (Japanese standard).
Type AES/EBU
Connection XLR
Mode Balanced
Impedance 110 Ohms
Level 0,2 V to 5 Vpp
Clock accuracy Not specified
Jitter ± 20 ns
Tab. 4.1: Important data for AES and IEC 958 Type II specifications
Table 4.2 illustrates part of the structure of the professional format, as it would
normally be used with AES/EBU connections.
Byte
0 1 2
0
P/C Audio Emphasis
1
Channel mode
2
Use of AUX bits
3
Reserved for description of multichannel recording
4
Audio ref.
5
Tab. 4.2: Markers in professional format (AES/EBU)
IEC 958 Type II (S/PDIF)
RCA/optical
Unbalanced
75 Ohms
0,2 V to 0,5 V pp
I: ± 50 ppm II: 0,1%
III: Variable pitch
Not specified
Bit
3 4 5 6 7
Locked Sampl. freq.
Use of user bits
Sample length Reserved
Reserved
Reserved
Table 4.3 presents the corresponding consumer-format data, as normally used
with S/PDIF-connections.
Byte
0 1 2
0
P/C Audio Copy
1
Category code
2
Source number
3
Sampling frequency
Tab. 4.3: Markers in consumer format IEC 958 Type II (S/PDIF)
The first bit already defines whether the following bits are to be understood as
professional or consumer-format bits. As shown, the audio information can be
found at the same position in the data stream, in principle making both formats
compatible. There are, however, information blocks that differ in both norms. If a
piece of equipment, such as a commercially available DAT recorder, has only one
S/PDIF input, the equipment will usually understand that format only. It will thus
usually stop when supplied with professional-format data. The reason is simple:
as shown in the illustrations, processing a professionally-coded signal with
equipment that can only understand consumer format can lead to malfunctions
relating to the copy protect bit and the emphasis!
However, this point is not always readily evident, as is the case with plug-and-
socket connectors (e.g. 1/4" TRS connectors, mini-jacks and special adapters for
Sub-D instead of XLR connectors). A lot of equipment has no stop function while
other equipment can understand both formats despite having only one type
of connector.
In all of these cases using the ULTRAMATCH PRO as the ultimate problem solver
will soon pay off. Virtually, all common digital signals it receives at the input
appear at the output with new, clean markers in the respective chosen format.

5. Installation

5.1 General connection notes

The ULTRAMATCH PRO's digital input and output connections are short-circuit-
proof and transformer-balanced. This rules out any possibility of ground loops
caused by additional ground connections, even when using the RCA connectors.
Furthermore, the completely potential-free concept of the digital connectors
allows for using adapters in order to, e.g. route the RCA connector signal to the
XLR input of another piece of equipment.
Unlike digital connectors, analog connectors are not galvanically separated,
but have a balanced design and are thus unproblematic in regard to
ground loops.

5.2 Analog inputs and outputs

In order to give your audio signals the best possible protection from
electromagnetic interference, the ULTRAMATCH PRO has balanced XLR inputs and
outputs. As previously described, the level at the analog inputs can be adjusted
with the GAIN control. The outputs operate at studio level (+4 dBu). Please see
the following illustrations for the pin assignment of the connectors.
Of course, it is also possible to send signals to the SRC2496 from unbalanced
outputs (e.g. sound cards or mixing console outputs) in order to further process
them in digitized form. Receiving analog signals (e.g. when using a high-end D/A
converter between a CD-Player and amplifier) from the ULTRAMATCH PRO via
unbalanced connectors (e.g. hi-fi amplifier or tape recorder) is not a problem, too.
Bit
3 4 5 6 7
Emphasis Mode
Gen. st.
Channel number
Clock acc. Reserved