Film-Tech Forum ARCHIVE: How To Make Correct Y Connection without Video Loss?

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Posted by Demetris Thoupis (Member # 833) on 12-22-2008, 06:05 AM:

I have this Component switcher that can switch either Component or S-Video with Composite. What I wish to do is switch both component and composite. I will connect the component inputs in inputs 1-4 for example and the composite inputs in inputs 5-8. I know that if I use a Y connector to split the output of the green component connector to both green and composite I most probably will have video loss on the other end. Is there a way to install some resistors to prevent this video loss?
Demetris

Posted by Steve Guttag (Member # 268) on 12-22-2008, 08:57 AM:

There is no way to split a signal without loss...they defies physics...sorry. Distribution amplifiers are there for making multiple copies of signals without signal loss. Remember, with video, one is trying to always form a perfect transmission line so one must match impedances very well to get the signal to the other end in tact.

Steve

Posted by Austin Pelnar (Member # 5043) on 12-22-2008, 09:09 AM:

Problem is not so much loss per`se youll end up with a double termination resulting in video and sync levels being reduced to almost half. Best way is to use a distribution amplifier. Next best is to build out with a 75 ohm resistor and 2200 uf capacitor in series with each leg of your splitter. Youll still end up with a change in video level if you unterminate one leg but not near as bad as just using a 75 ohm resistor or a straight y cable.
Austin

Posted by Bruce Hansen (Member # 281) on 12-22-2008, 05:43 PM:

You cannot "split" video. Can you use another output such as a Y/C output to give you another "Y" out? If you use a DA, you may have some delay going through the DA that you will not have on the R-Y and B-Y lines. This may not amount to much. Look at objects to see if the color and B&W are out of alignment (horz.). If this is a problem you may have to add a little delay, or just DA everything, with the same sort of DAs.

Posted by Austin Pelnar (Member # 5043) on 12-22-2008, 09:45 PM:

Im not sure why one would DA just one part of a component signal, with a basic DA I dont the belive Y channel delay would be noticable.
In my bag of dirty tricks I have the following VGA DA's make great component DA's as well. Nothing fancy just a basic wall wart powered splitter. If your really stuck for a composite output just tie Y and C together.

Posted by Bruce Hansen (Member # 281) on 12-26-2008, 03:33 PM:

If you just hook Y and C together they will load each other down. They needed to be added together through filters. There are some "adders" on the market that sell for about $5.

Posted by Phil Blake (Member # 2012) on 01-03-2009, 07:27 PM:

I am curious as to if this would apply also to VGA leads , I was looking at installing a Y lead on my digital media player to split output 1. to projector and 2. to VGA monitor intending only to use either one or the other but not both at the same time . ie, use monitor to setup and test media play lists and use projector just to run shows, would this incur and picture loss ?

Posted by Austin Pelnar (Member # 5043) on 01-03-2009, 08:54 PM:

Sounds like you just need a switch.
For permanent use go for DA's Most of my dirty tricks are for emergencies or temporary use.
RE Y/C combining thats all your 5$ adaptor does most Y/C outputs are built out at 75 ohms and wont load down. Comb filtering is involved in separating composite into Y/C, honestly passive comb filtering doesnt work that great very lossy and group delay causes unpredictable phase shifts. Active filtering and resync works soooo much better.