Kramer Electronics VP-31 - Manual (Page 3)

INTRODUCTION
Congratulations on your purchase of this Kramer switcher. 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
switcher, such as the one you have just purchased, Kramer also offers a full line of high quality distribution
amplifiers, processors, interfaces, controllers and computer-related products.
This manual includes configuration, operation and option information for the following products from the
Kramer VP line of switchers. All these VP switchers are similar in operation and features.
VP-31 - 3x1 VGA/XGA Switcher
VP-32xl - 3x1 VGA/XGA/Audio Stereo Switcher
VP-61RS - 6x1 VGA/XGA Switcher
A Word on VGA/XGA/Audio Switchers
VGA/XGA/Audio Switchers route signals to one or more selected users. They vary in the number of inputs,
looping capability, programming capability, number of outputs, operating format, bandwidth and input/output
coupling. VGA/XGA/Audio Switchers are used to select which source is to be switched to which acceptor for
recording or monitoring, with no discernible signal degradation. A good quality VGA/XGA/Audio Switcher
amplifies the incoming signal, pre-compensates the signal for potential losses (resulting from the use of long
cables, noisy source, etc.) and routes the signal(s) to buffered and amplified outputs. Often, a signal processor
is inserted between the source and the VGA/XGA/Audio switcher for correction and fine tuning of the source
signal before routing. The front panels of these Kramer switchers are designed to be simple to operate. Some
of the switchers are RS232 controlled for remote PC operation. The machines described in this manual switch
one of several PC's to a monitor. The machines excel in high source isolation for minimal crosstalk and very
large bandwidth.
Handling Graphics signals
A computer generated graphics signal is usually comprised of 5 signals: Red, Green, Blue -which are analog
level signals and two TTL (logic) level signals - Horizontal Sync and Vertical Sync signals. (Digital graphics
cards and monitors use a different signal format, and will not be discussed here as they are not relevant to the
DA.). Computer graphics resolution is measured in pixels and signal bandwidth.
The more pixels (picture elements) on the screen, the more the image is detailed. VGA, S-VGA, XGA, S-XGA
and U-XGA are terms describing the graphics resolution and the color depth. Color depth represents the
maximum number of simultaneously displayed colors on the screen and is measured in bits. 24 and 32-36 bits
of color depth represent millions to billions of color shades available on the screen at any given moment. It
should be born in mind though that the human eye can resolve only a few thousands colors! The more the
image is detailed (higher resolution) and higher the color depth the more real the image will look. The
standard VGA highest resolution was 640x480 pixels with 4 bits of color (16 colors). The VGA standard was
able to use more colors (256) but at a lower resolution- around 320x200 pixels, which was very crude.
Common resolutions used nowadays for computer graphics vary between 1024x768 up to 2000x1600 pixels
with “high color” - 16 bits of color, representing 64,000 different colors, up to “true color” - 24 bits or more,
representing from 16.7 million colors up to several billion. Displaying such a detailed and colorful image on
the screen needs enormous graphics memory per frame, as well as very high speeds for “writing” so many
pixels on the screen in real time. The amplifiers that carry those signals should be able to handle those speeds
and hence signal bandwidth. The standard VGA at 640x480 resolution needed amplifiers with 20-30MHz
bandwidth.
At 1600x1200 or even at 1280x1024 (S-XGA), those amplifiers will completely fail. In order to faithfully
amplify and transmit modern high-resolution graphics, amplifiers with bandwidths of 300 MHz and more are
needed. Those amplifiers, besides the enormous bandwidth they should handle, need to be linear, to have very
low distortion and be stable. Stability of an amplifier is its ability to avoid bursting into uncontrolled
oscillation, which is in adverse relationship to the speed it can handle. The tendency to oscillate is further
enhanced by the load impedance. The load impedance of a system is usually not just a resistor. A cable