VGA Dist Amp as Composite Vid Dist Amp

[david.elsbury]

Hi there

Could someone please advise me if there is a flaw in my thinking here...

 

For work we want to split one compshite video signal to 12/15 devices (TV wall).

We do not have comp video distribution amps, but we do have VGA amps.

 

Would there be any forseeable problems with making up a set of leads to common all three inputs (R, G, B) and then using the outputs (it's a 1->4 VGA box) seperately?

 

After all, it's still analog video... just that the VGA video is at a higher resolution than composite.

 

Ta

David

[Fletch]

Hi David,

 

I'm afraid this will not work as you have suggested and you could damage your amplifier...

 

There is a chance - and I say chance - that if you just use the G (best bet!), or the R or the B, on the amplifier if might pass through composite video, but don't common any of them together.

 

The reason it will not work:

 

Video has many guises, a composite video signal is very complex. It has many signals modulated together so that in essence R,G & B are all present but down one cable, which is really clever and quite mind bending (this is a very simplified explanation). However, it has a much higher bandwidth as there is much more information down this one cable. RGB on the other hand uses 3 cables for the same purpose. This is higher quality, but not because the image is better, but because there is less electronics involved (and less horrible filters etc) as you are not combining everything onto one cable and then having to do the inverse at the TV end. As RGB is three signals, each independent part has a lower bandwidth, which means it's unlikely that your amp will work with composite video.

 

If you are lucky your VGA amp will have high bandwidth amplifiers on the RGB signals and it will pass composite though using just one of the R, G or B channels. However I suspect this is very unlikely.

 

I don't see why you can't give this a go (can anyone else?) but DO NOT common the RGB connectors together, I have no idea what that might do, just pick one channel as above and see what happens.

 

Best of luck

Fletch

[peternewman]

My assumption was he want to common the inputs together, because he want to distribute to twelve TVs and only has one 1:4 VGA DA, so he can output signals for 4 TVs from each colour.

[Fletch]

Hi,

 

I hadn't quite appreciated what Peter said...

 

 

My assumption was he want to common the inputs together, because he want to distribute to twelve TVs and only has one 1:4 VGA DA, so he can output signals for 4 TVs from each colour.

 

In this case maybe first see if you can get composite video through just one channel , RG or B, that way you know if the amp has a high bandwidth on each channel. Still not quite sure about linking the RG & B together mind...

 

Fletch

[Pete McCrea]

Most of the Extron and Kramer units we own/have used will pass composite on the Green Channel.