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Author
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Topic: Q. about intallation of a video projector
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Frank Angel
Film God
Posts: 5305
From: Brooklyn NY USA
Registered: Dec 1999
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posted 04-14-2004 08:21 AM
We are permanently installing an Ekik LC-XT3 in the booth and up till now we have just run coax cable from the composite output of a video switcher to the composite input on the projector. Of course this was temporary and now I want to run component and also S-Video.
Q. What is the correct cable to use to make the component RGB connection? I am assuming it needs to be 75ohm coax cable, but does it have to be some special type or can I use standard RG58/9 coax like I use for RF? I also understand that the three cables need to be exactly the same length. How critical is this? I mean, are we talking about microns? And how do you cut them so that they are precisely equal? Do they make cables containing three coaxs combined specifically for RGB, just as the do multi-cable for audio?
Now what about S-Video cable? I am assuming Belden or any of the other wire manufactures can supply S-V cable in bulk. Any recommendations? And how critical is wiring the S-V connectors -- same requirement of each conductor being the exact same length when wiring on the connectors and it is for component cables?
Lastly, we are going to need to replace the composite switcher with one that will switch component inputs to the projector. However, some of the equipment, like the S-VHS deck and the old LaserDisc only output a composite signal. Are switchers normally designed so that you can input any one of the common signal types (composite, S-Video and RGB) and convert any of them to the one RGB output for the v-projector, or will I have to get a switcher for each format? Or is that the function of a scaler? Ok, I admit it....this is where I am at a total loss. Scaler, switcher, the three different formats.....can this all be integrated into one unit or do I need separate switchers for the different formats plus a scaler? Doesn't the scaler do the converting? Or is it better to just keep each type of signal native -- in other words, the player that can only output composite needs to be fed to the composite input on the projector; the player whose best output is S-Video should be fed to the S-Video input on the projector, and the player whose best output is RGB needs to be fed into the RGB input on the projector.
Any clarification would be appreciated.
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Steve Guttag
We forgot the crackers Gromit!!!
Posts: 12814
From: Annapolis, MD
Registered: Dec 1999
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posted 04-14-2004 12:39 PM
Frank,
First things first....the impedance of the cable for video is 75-Ohms...so you have a choice of RG-59 or RG-6. RG-58 is 50-Ohm cable and will not do.
If your three signal types will be Component (3-wire), S-Video (2-wire) and Composite (single wire) then may I suggest rather than running three cables, use a 6-wire cable...normally used for RGBHV and Composite (for things like monitors) but it would handle all three of your listed signals...if you need 5-wire too, then run a second cable of 5-wire (or 6-wire and leave one unused).
You do have a choice of cable manufacturers and sizes. With analog video, size does matter...the longer the run, the better the bulky cable does. For relatively short runs then a mini-coax will be just fine if you are not using any really high-bandwidth signals.
Using this cable will keep all of your lengths exact. The more exact your cable lengths are, the better you color alignment will be..again, higher frequencies will require more precision.
For S-Video...I recommend avoiding the mini-din S-video connector as much as possible...it isn't terribly secure and you don't want to make it. So, using whatever coax you are going to use and crimp on BNC connectors then use a BNC->S-Video adapter as needed...you'll be happy you did.
As to the various signal types and switchers...you have a wide choice of how to do it.
There are switchers that will switch only one type, some that switch two-types....and on up to any combination of 1-5 wire signal types.
Some switchers even have the ability to "talk" to your projector to make sure it is looking at the correct input for the signal type it is sending.
Another type of switcher is the switcher/scaler. You tell it on an input-by-input basis what signal you are feeding it and you tell it what type of signal your projector wants and it will scale each input as needed so they all have the same effective resolution (the scaler will also deinterlace, remove 3:2 pull-down artifacts...etc). This makes for the easiest installation. You only have one 5-wire cable feeding your projector and some will even give you projector controls at the switcher too.
Another way is to use a switcher of your choosing and put a scaler on its output. The Extron DVS 204 is a good scaler for this. It has 4 inputs...Composite, S-Video, Component...all scaled and an RGB pass-through. You can put in autoswitch mode and it will automatically switch to which ever input is active. You can even put it on the output of your typical A/V home receiver and as you select the sources...it will follow and scale whatever to the projector resolution with just one 5-wire cable.
If I have a crack at selling any of this stuff (cables too)...e-mail me. I have a Extron System 7SC, new, that I'd be willing to sell discounted. http://www.extron.com/product/product.asp?id=system7sc
Steve
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Steve Guttag
We forgot the crackers Gromit!!!
Posts: 12814
From: Annapolis, MD
Registered: Dec 1999
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posted 04-15-2004 08:14 AM
Bruk,
I can't tell if your post is a joke or if your are serious...and RCA connection (aka phono) is about the worst though popular with consumer equipment since it works entirely by friction.
Your post also appears to recommend using just a composite (single wire) signal. While it is true that that is the easiest, by far, it is also of the lowest quality within the video world next to just "RF". With composite, you will have numerous artifacts in the video signal, most notably Chroma Crawl. Chroma Crawl is that rainbow like effect one can see on any TV when smaller high contrast object appear (like a checkerboard pattern). The detail on a composite signal is also notably pretty bad. Lastly, the color on composite signals are notably all over the place.
In the analog video world, the more cables carrying the information, the better. The results with a 5-wire system (Red, Green, Blue, Horizontal Sync, Vertical Sync) at the top of the heap and compare favorably to even digital signals...at least SDI digital signals...HDSDI is pretty spectacular but boy is the cable and signal touchy at the moment.
For video, the BNC connector is still at the top, unless you are doing fiberoptics.
On Gord's suggestion, note that it is a passive switcher he is pointing to. That is fine if all you are doing is to avoid repatching signals. Also note, your ability to use mixed signal types (composite, S-Video and Component) will be not be satisfied.
Ocean matix does have other switchers available though and we have also had decent results from them.
Again, there are many ways to set up a video system and depending on what you use will change your user overhead (how many buttons and actions must they remember to do) and how good the final result will look.
Steve
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Leo Enticknap
Film God
Posts: 7474
From: Loma Linda, CA
Registered: Jul 2000
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posted 04-15-2004 10:28 AM
Apropos RCA connectors, my experience with them is that they're fine if (i) you use good quality plugs, not cheap plastic shafted crap, and (ii) they are for a permanent installation and not constantly being reconfigured. As Steve points out, the connections are maintained entirely by friction, and can loosen with repeated plugging and unplugging. For patch board type operations, XLR or BNC connectors are far more secure.
I once did a silent show in which the pianist plugged the output of her Clavinova into a mixer input at the front of the stage, which was XLR. The output from the piano was RCA only, though. She had a set of leads with her, which we used. About half way through the show, the left channel suddenly went dead (the mixer board in the booth was plumbed into the L + R nonsync input of a CP45). It turned out that one of the two RCA plugs on her patch leads had just fallen out of the back of the piano - simple as that. This was probably because it had been inserted and removed tens if not hundreds of times, thereby loosening the plug.
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