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ULTRAMATCH PRO SRC2496
There is no doubt that digital signal processing guarantees the
lowest distortion and noise values. However, up until now signal
conversion, specifically sampling rate conversion, had partially
led to considerable distortion and interference: If you tried to use
traditional methods, the incoming data quantity would far exceed
any hardware capacity. If data was put into smaller pieces to
avoid storage problems, the necessary turnaround time would
prevent any practical 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 ULTRAMATCHPRO 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 ULTRAMATCHPRO uses the latest versions
of each of the standards, AES/EBU (AES3), IEC 60958 and EIAJ
CP-1201 (Japanese standard).
Type AES/EBU IEC 958 Type II (S/PDIF
)
Connection XLR RCA/optical
Mode Balanced Unbalanced
Impedance 110 Ohms 75 Ohms
Level 0,2 V to 5 Vpp 0,2 V to 0,5 V pp
Clock
accuracy
Not specified
I: ± 50 ppm II: 0,1 %
III: Variable pitch
Jitter ± 20 ns Not specified
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
01234567
0 P/C Audio Locked
1
2
3
4
5
Bit
Emphasis Sampl. freq.
Channel mode Use of user bits
Use of AUX bits Sample length Reserved
Reserved for description of multichannel recording
Audio ref. Reserved
Reserved
Tab. 4.2: Markers in professional format (AES/EBU)
Table 4.3 presents the corresponding consumer-format data,
as normally used with S/PDIF-connections.
Byte
01234567
0 P/C Audio Copy
1Gen.s
t.
2
3
Bit
Emphasis Mode
Category code
Source number Channel number
Sampling frequency Clock acc. Reserved
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 PROs 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 ULTRAMATCHPRO 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.
5. INSTALLATION