VGA Splitting Best Practices?

[M J]

I'm trying to figure out what the best way of splitting a VGA signal is.

I'm looking into the idea of allowing multiple workstations (Keyboard, Monitor, Mouse) to control multiple systems (Case, Computer, Box, Machine, etc...). I'm considering doing this with 1-3 systems at 2-3 workstations.

The idea is to setup each workstation with a KVM switch that is capable of controling multiple different systems. Then also have on each system a way of splitting the KVM signal to multiple different workstations' KVM switches. There would be the potential of allowing multiple workstations to control the same system simultaniously... which is intended for some uses, but primarily the ability for each workstation having the ability to control the shared systems.

I currently have a Belkin Pro2 KVM switch and like its performance, but I have never tried sharing the same system with multiple workstations before. I have hooked up two mice to the same system and was able to control the system simultaniously with both, so I don't think I'll have a problem with the keyboard, mouse side of things.

My big curiosity is in regards to the splitting of the VGA signal. I know the KVM switching companies make a big tado about the switching of the VGA signal, and how it supports up to x resolution at x refresh rate, etc...

I've come across a couple options for VGA splitting:
http://www.buyraritan.com/nav/item.asp?item=4918
http://www.national-tech.com/catalog/vgasplitters.htm
http://www.pc-extras.com/prods/cbvgas.html

Each one has a considerable price difference.

I would imagine that using the VGA splitter cable wouldn't be the best choice since it just splits the pins to two cables, and I doubt most video cards are meant to send the signal to two seperate monitors at the same time. I wonder if anyone has done any research to back up this theory.

That leaves us with the electronic splitters that also ampliphy the VGA signal. I am curious if anyone has had any experience using this type of VGA splitter, and possibly what the PROs and CONs are of using one.

Also it would be nice to get any suggestions on any brands that might be a better quality than the others.

[GoSharks]

Extension Cables and switchboxes are notorious for causing ghosting or streaking on the screen. This is almost always due to an impedance mismatch at the cable connection to the extension cable or switchbox rather than the cable itself.

This type of problem usually gets worse as you increase resolution or refresh rates.

Impedance miss matches will send small video ripples (for lack of a better term) up and down the video cable. These ripples are amplified by the monitor and show on the screen as very small ghost images or streaks particularly after a bright to dark, or dark to light transitions.

I would recommend you avoid extension cables and switch boxes for video.

Jim Witkowski
Chief Hardware Engineer
MonitorsDirect.com

[M J]

I realize the problem with signal degredation (impedance) whatever can cause problems. You see it at any of the computer stores where the dump 30 monitors on the same input. I have the need to use switches and splitters, I just need to know how to minimize the problems as much as possible.

What affect would the number of connections be on the problem?
What about the length of the cables used?
Quality of cables?
Quality of switches/splitters?
How might I determine the quality of a switches/splitter?

[GoSharks]

It is almost always the number of connections that cause the problem. Cable length / quality are much less an issue. Buy the highest quality splitters you can find and check the manufactures return policy before you give them your credit card. There is no way to determine what spitter will be best for your individual setup. This almost always comes down to experimentation. Stick with low resolution for best performance.

Good Luck

Jim Witkowski
Chief hardware engineer
monitorsdirect.com