10
ULTRAMATCH PRO SRC2496
3. APPLICATIONS
3.2 Sample rate conversion
No matter which 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:
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Conversion of 48 kHz DAT recordings to the CD standard of
44.1 kHz.
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Conversion of older digital recordings from 44.056 kHz to
32, 44.1, 48, 88.2 or 96 kHz.
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Conversion of foreign material with 32 kHz to 44.1, 48,
88.2 or 96 kHz.
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Conversion of audio data with a word length of 24 bits to 20
or 16 bits for recording on a digital medium.
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Conversion of S/PDIF format to AES/EBU for easy mani-
pulation of various parameters and improved (balanced)
signal transmission.
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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 any 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
DAT recorder. With uncritical audio material, you can thus 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 48 kHz).
3.2.3 Master/slave problem solver
When a digital mixing console is used, it is at this pointif not
beforethat 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 met by
connecting the equipment to one central sync source. For example,
the console could be the master supplying the remaining devices
with a reference signal (wordclock). However, this will only work if
these other devices have a sync input, i.e. can be used as slaves.
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 ULTRAMATCH PRO SRC2496
between the device to be synchronized and the mixing console input,
however, 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 a kind of intermediate
gear 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 device to any other,
irrespective of any other options available.
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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 a case, the
ULTRAMATCH PRO 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 ULTRAMATCH PRO 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
.
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We want to point out again that the copyright of third
parties must not be infringeddespite the possibility of
removing the copy protect bit with the help of the
ULTRAMATCH PRO! This device was not developed to
produce unauthorized copies!
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
