KRAMER ELECTRONICS LTD.
P/N: 2900-006002
KRAMER ELECTRONICS Ltd.
USER MANUAL
Digital (SDI) to Analog Converter
Model:
SD-7401
IMPORTANT: Before proceeding, please read paragraph entitled
"Unpacking and Contents"
KRAMER ELECTRONICS LTD. 1
Table Of Contents
Section Name Page
1 INTRODUCTION 2
1.1 Digital and Analog Signals 2
1.2 Several Points to Consider when Working with Digital Signals 2
1.3 SDI Standards 4
1.4 Factors Affecting Quality of Results 4
2 SPECIFICATIONS 5
3 HOW DO I GET STARTED? 5
4 UNPACKING AND CONTENTS 5
5 OPTIONAL ACCESSORIES 5
6 SDI TO ANALOG CONVERTER 6
6.1 Getting to Know Your SD-7401 Converter 6
7 INSTALLATION 7
8 CONNECTING TO DIGITAL VIDEO DEVICES 7
9 TURNING ON THE MACHINES 7
9.1 Operation of the SDI to Analog Converter 8
9.2 Dip-Switch settings 8
10 TAKING CARE OF YOUR MACHINE 8
11 TROUBLESHOOTING 8
11.1 Power and Indicators 9
11.2 SDI and Video signals 9
11.3 Noise and Hum 9
Limited Warranty 10
List Of Illustrations
Figure Page
1
Digital “eye” Diagram
3
2
The Digital “eye” after accumulating noise and jitter
3
3 SD-7401 Front/Rear Panel Features 7
List Of Tables
Table Page
1 SD-7401 Front/Rear Panel Features 7
2 SD-7401 Dip Switch settings 8
KRAMER ELECTRONICS LTD. 2
1 INTRODUCTION
Congratulations on your purchase of this Kramer Electronics SDI / Analog converter. Since 1981,
Kramer has been dedicated to the development and manufacture of high quality video/audio equipment.
The Kramer line has become an integral part of many of the best production and presentation facilities
around the world. In recent years, Kramer has redesigned and upgraded most of the line, making the best
even better. Kramer’s line of professional video/audio electronics is one of the most versatile and
complete available, and is a true leader in terms of quality, workmanship, price/performance ratio and
innovation. In addition to the Kramer line of high quality distributors, such as the one you have just
purchased, Kramer also offers a full line of high quality switchers, processors, interfaces, controllers and
computer-related products.
This manual includes configuration, operation and option information for the SD-7401 SDI to
Analog converter
1.1 Digital and Analog signals
An analog signal varies continuously. It may have any value (within its physical bounds) and can
change at any instant. A digital signal is made up of a finite number of discrete levels, usually – but not
always – changing only at discrete time periods. An example of a digitized waveform is shown below.
1.2 Several points to consider when working with digital signals
The minimum noise introduced by quantizing is 1 bit (1 level), so the higher the number of bits, the
lower the inherent noise, and the higher the resolution.
Since A/D and D/A conversions create artifacts, it is important not to convert back and forth. In a
“mixed” outfit, the video should be digitized, and all the digital processing done before converting back to
analog.
“Multi-media” systems usually quantize the video to 8 bits (i.e. 2
8
= 256) levels. Some “levels” are
dedicated to special codes (SAV, EAV – similar to syncs in analog video), leaving 220 quantization levels
(~3mV steps) for the luminance signals. Audio is usually quantized to 16 bits for multi-media systems.
Broadcast systems usually use 10-bit video, and 20- to 24- bit audio.
The advantages of working in a digital domain are obvious – a digital signal may be transported
very easily, and saved and retrieved reliably with no generation losses.
The transmission of a digital video signal is reliable up to a certain length of cable. Beyond this
length, the signal is destroyed. This phenomenon is known as the “cliff-effect”. To avoid the “crash” at
the cliff, an “equalizer and reclocker” should be inserted at a distance less than the “cliff” length. From
ANALOG SIGNAL
DIGITAL SIGNAL
KRAMER ELECTRONICS LTD. 3
this point it is again possible to drive a cable up to the “cliff” length. This is similar to the “repeater”
analogy for analog signals. (Note: the term “equalizer” is usually dropped, and the “equalizer and
reclocker” is often referred to simply as a “reclocker”).
“Equalization” is a process of amplifying the input signal to overcome losses on the cable. For
digital signals, this is possible, since the correct amplitude of the signal is known!
“Reclocking” is a process of “cleaning up” the signal in the time-domain, i.e., removing the jitter
which was introduced as a result of the long cable. To do this, the timing source must be recovered from
the signal, and the signal is regenerated with stable timing.
A graphic representation of the timing and amplitude distortions is shown in an “eye diagram”, as
below:
Figure 1: Digital “eye” Diagram
Increase in jitter and decrease in amplitude cause the eye to “close”. It is clear that jitter of more
than ±50% would result in an irretrievable signal (cliff effect).
Figure 2: The Digital “eye” after accumulating noise and jitter
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