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ULTRAMATCH PRO SRC2496
3. APPLICATIONS
3.2 Sample rate conversion
No matter what type of digital audio signal you feed into the
ULTRAMATCH PRO, it will convert it to a common standard format.
Numerous conversion examples can be found in daily studio
practice:
s Conversion of 48 kHz DAT recordings to the CD standard
of 44.1 kHz.
s Conversion of older digital recordings from 44.056 kHz to
32, 44.1, 48, 88.2 or 96 kHz.
s Conversion of foreign material with 32 kHz to 44.1, 48,
88.2 or 96 kHz.
s Conversion of audio data with a word length of 24 bits to
20 or 16 bits for recording on a digital medium.
s Conversion of S/PDIF format to AES/EBU for easy mani-
pulation of various parameters and improved (balanced)
signal transmission.
s Setting or removing copy protect bits for further processing
of recordings in a studio environment.
3.2.1 Typical studio application with DAT
Only recently has it become possible to use less expensive
DAT recorders for direct recording from analog sources with a
sampling rate of 44.1 kHz. Most consumer-level DAT recorders,
however, record at 48 kHz. Usually, such recordings have to be
transferred via an analog connection from DAT to a professional
recorder. This process results in an unnecessary deterioration
of the original quality of the material due to the additional D/A and
A/D converters involved. With the ULTRAMATCH PRO you can
eliminate this problem by converting the sampling rate purely in
the digital domain, which allows for a considerably higher quality
than you could achieve with analog converters.
Further problems, such as incorrect formats, significantly deviating
or unstable sampling rates (as long as they do not deviate by more
than ±12.5% from the current sampling rate), will also be corrected
by the ULTRAMATCH PRO in real time, thus ensuring the
successful transfer of your audio data.
3.2.2 Hard-disk recording
Hard-disk recording applications also require a uniform sampling
rate, if possible the one used by the subsequent playback medium
(CD). As it can convert audio material from 32, 48, 88.2 or 96 kHz
to the standard 44.1 kHz, the ULTRAMATCH PRO makes sure
that all sources can be used to feed audio material by way of a
digital connection.
Of course, the ULTRAMATCH PRO can be inserted at any point
in the audio processing path, i.e. also between the PC and
the DAT recorder. Therefore, with uncritical audio material you
can process the material at 32 kHz in the recording system (or
higher, depending on which sampling rates can be processed by
the HD recording system), and subsequently convert the
completely edited material while transferring it to a DAT recorder
at 44.1 kHz (or even at 48 kHz).
3.2.3 Master/slave problem solver
When a digital mixing console is used, it is at this pointif not
earlierthat master/slave problems will be encountered. The
explanation is simple: When using CD players, DAT recorder and
HD recording systems in their normal applications, the
responsibilities are clearly defined. The playback device is the
master, the recording device is the slave, i.e. the CD player
provides a clock rate of 44.1 kHz to which the DAT recorder is
synchronized.
When using a mixing console, the CD player is the master, the
console is the slave. However, this model collapses all of a
sudden as soon as a DAT recorder is hooked up, which does
not record but plays back too. The console can synchronize to
one source only, the audio data from the other source would be
processed incorrectly because the two devices are not in sync.
The need for synchronization in a digital studio is done justice
connecting the equipment to one central sync source. For
example, the console could be the master-supplying the remaining
equipment with a reference signal (wordclock). However, this
will only work if your other equipment has a sync input, i.e. can
be used as a slave. In a studio with a digital tape machine, digital
effects and hard-disk recording system it is impossible to connect
commercially available CD players or DAT recorders to the mixing
section of the console simply because they cannot be
synchronized.
By inserting the BEHRINGER ULTRAMATCHPRO SRC2496
between the equipment to be synchronized and the mixing console
input, the SRC2496 can deliver the audio signal with the studio
clock rate entered via the external sync input (WORDCLOCK, ).
In this case, the ULTRAMATCH PRO works as intermediate gear of
sorts, whose toothed transmission always ensures that there is
an appropriate gap in the gearwheel. It synchronizes the signal
coming from the devices to be synchronized, while converting to
the desired sampling rate in compliance with the wordclock signal.
In a studio with a central clock generator, it is therefore possible
to use the ULTRAMATCH PRO to connect any unit to any other,
regardless of any other options available.
+ Even if the central clock does not correspond exactly
to one of the sampling rates, the ULTRAMATCH PRO
will assign a corresponding marker to the output
signal! This marker depends on the automatically
detected and displayed sampling rate, which is
important because DAT recorders usually refuse
to enter record mode if an incorrect sampling rate
has been indicated.
3.2.4 Bridging unformatted passages
DAT recorders, in particular, produce tiny format gaps between
individual recorded passages on the tape when intermittent
recordings are made. Also, when you transfer older recordings it
can happen that short passages with a different sampling rate than
that of the current recording remain stored on tape. In such cases,
the ULTRAMATCHPRO converts this host of single pieces of
information into a continuous data stream with a fixed sampling
rate. Even if the DAT recorder or any other digital source is stopped
or switched off, the ULTRAMATCHPRO will continue to generate a
continuous signal (depending on the digital signal, if synchronized
to it).
3.3 Removing copy protect information
The original copy protect mechanism used in DAT recorders
was simple but effective: It was impossible to make digital
recordings from a CD. Later, a step-by-step mechanism was
introduced with SCMS, which allowed at least for one digital
copy from CD. The routine implemented in SCMS depends on the
generation (x
th
copy) and the origin (category) of the digital audio
material. In professional studio engineering a copy protect
mechanism does not make any sense, which is why there is
none defined in the AES/EBU standard.
Since many studios use inexpensive consumer devices for
cost reasons, copy protect and/or format incompatibility problems
(professional/consumer) are encountered frequently. The
SRC2496 can ignore all types of copy protect information and
generate a new, completely free marker that allows for multiple
copying. Thus, you can use your ULTRAMATCH PRO to copy
material from one consumer DAT to another. Further information
on this subject can be found in chapter 2.1.3, section .
3.4 Noise reduction with emphasis
A very special feature is the option to influence the set
emphasis bit. Emphasis here means a noise reduction process
with a treble boost step involved prior to recording. This treble
boost is undone during playback. A specific bit (emphasis bit) in
the digital data stream contains the information whether or not