Kramer Electronics, Ltd.
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INTRODUCTION
Congratulations on your purchase of this Kramer Electronics line amplifier. 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 line amplifiers, such as the one you have just purchased, Kramer also offers a full line of high quality
distribution amplifiers, switchers, processors, interfaces, controllers and computer-related products. This manual
includes configuration, operation and information for the following products from Kramer. Kramer line
amplifiers are all are similar in operation and features.
VM-9S - Video/Audio Amplifier
103YC - YC Line Amplifier
VM-9YC - Y/C Line Amplifier
104L - Video Line Amplifier
1.1 A Word on Line Amplifiers
Line Amplifiers are usually used when video or audio units are connected via long cables. Due to imperfections
and stray capacitance, video cables degrade signal quality, causing image “smear”, fine detail loss and color
distortion. No special care is needed for Composite video signals when using good cables, up to 10 or 15
meters. Beyond this distance, in order to avoid potential losses, a line amplifier should be used. Kramer’s line
amplifiers may be used up to distances of 300m when using good quality cables. If a longer distance is needed,
then either another amplifier may be inserted in series, at the far end - effectively doubling the range - or a
different solution is needed. Other solutions are twisted-pair cable solutions and, if longer distances are needed
(5-25 km), then the optic-fiber solution is the preferred one. The line amplifiers are equipped with controls for
signal level compensation (linear amplification) and for fine detail loss and distortion – cable compensation
(Equalization), which null out the adverse effects of the cables. When a Y/C (s-Video) signal is involved, other
problems can arise. Due to the nature of the Y/C signal, which travels on two wires: one carrying the black and
white and the sync information (Luminance or “Y”) and the other carrying the color information (Chrominance
or “C”,) signal handling is more complicated. The Luminance channel may be treated as Composite video in the
sense of signal loss and fine detail degradation, but the Chrominance signal, besides level deterioration, may
suffer from additional problems. The Chrominance information may get phase shifted or delayed more or less
than the Luminance information, resulting in an image with incorrect tint and/or a image at the end of the line
with its color misprinted. As the Y/C signal is usually used for short distance operations, it uses a dual, thin, low
quality cable. Therefore, a line amplifier for Y/C is necessary when distances above 5-7 meters are involved.
For distances beyond 25 meters, it is highly recommended to use two discrete coax cables (RG-59 or similar) of
precisely the same length.
The basic rule in effectively using a line amplifier is to install it as close as possible to the signal source and not
to the acceptor side. (If the amplifier is installed close to the acceptor (the remote location) then all the noise
accumulated along the cable will be amplified with the signal).
1.2 Factors Affecting Quality of Results
Many factors affect the quality of results when signals are transmitted from a source to an acceptor:
Connection cables
- Low quality cables are susceptible to interference; they degrade signal quality due to
poor matching and cause elevated noise levels. They should therefore be of the best quality.
Sockets and connectors of the sources and acceptors
- So often ignored, they should be of highest
quality, since "Zero Ohm" connection resistance is the objective. Sockets and connectors should also
match the required impedance (75ohm in video). Cheap, low quality connectors tend to rust, thus causing
flaws in the signal path.
Amplifying circuitry
- Must have quality performance when the desired end result is high linearity, low
distortion and low noise operation.
Distance between sources and acceptors
- Plays a major role in the final result. For long distances
between sources and acceptors, special measures should be taken in order to avoid cable losses. These
include using higher quality cables or adding line amplifiers.
Interference from neighboring electrical appliances
- These can have an adverse effect on signal
quality. Balanced audio lines are less prone to interference, but unbalanced audio should be installed far
from any mains power cables, electric motors, transmitters, etc. even when the cables are shielded.
