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composite video over mic cable


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just been decided for a show at the end of the week, to add projection, have the DVD player, and the projector, but not a long enough cable for the run.

 

the throw is approx 3m , the cable run approx 25m. Would running the composite video (audio is through the PA) along this length of good quality mic cable be ok, or would there be a lot of signal loss? if so would a standard RF amp work, or not?

 

sorry for the questions, I've not really done projection before!

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Simple answer?

Yes it would probably work OK.

 

Not-so-simple answer - using the correct cable will make the end-product more reliable and of a higher quality.

 

It's just the same as the DMX vs mic cable debate.

If it's a 'get-me-sorted-quick' job, then give it a go.

If it's something that needs to last and work properly every time, then invest in the proper stuff.

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There's a few topics knocking around of this theme, the general consensus is it works, with some signal degradation.

 

If you can cope with the loss, then fine. That said, as always, when using something out of spec you can't guarantee it will work every time.

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You can probably hire a 30m BNC cable for under a £10 for a week.... A Line Driver for around £10-20 week. Is there no budget for hire available?

 

Running a Comp video feed through a House Multicore of about 40m gave an appalling result. Personally I won't be trying it again. We even tried Driving it properly with a line driver with minimal improvement in the signal.

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In my experience it is not worth messing around when good quality composite cable is not that expensive.

 

The problem is that any degradation of a video signal is obvious to the audience where as degradation in DMX is only obvious to the light in that it either works or does not. I have also found that most projectors simply cut out when the signal gets below a certain level and this never happens during the setup it always happens in the middle of the show. That is if you do get it working, you may have to spend ages messing about to get it to work.

 

Your biggest problem is probably going to be reflections caused by impedance mismatches between the XLR cable and the projector input. This will show up in the form of annoying lines over the video image. Once you get these no amount of signal amplifying will help the situation. Your only option will be to put in the correct impedance cable.

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I've sent composite video approx 45m over standard mic cable with n problems at all, most of that run was down a multicore. - give it a go and see what happens - however make sure that you wire the phono - XLRs with shield on pin 1 and hot on pin 2, do not connect anything to pin 3. - thats how mine work anyway...
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