ThomJ Posted October 15, 2006 Share Posted October 15, 2006 Hi Guys I'm thinking of making a multi-core for our conference work is it possible/good idea to run video signal down shielded audio signal cable. I'm looking to send 5 video signals (RGBHV) possibly two runs (send and return) with BNC at both ends and a parallel audio with 6 lines. Any thoughts Thom Link to comment Share on other sites More sharing options...
paulears Posted October 15, 2006 Share Posted October 15, 2006 There isn't a reason for saying a categoric no - but there are a number of pitfalls. 1 The main one has nothing to do with the electrical performance - it's putting the plugs on that is the problem. Video cable has pretty standard physical dimensions, made to fit the common BNC connectors - audio multicore is pretty random in the construction. 2. cores - most audio multi is balanced. The extra core again gets in the way. Monocore multi is available, but not that common. 3. performance - may be good - may be bad. No real way of telling without buying the right length and trying it - not good. video is reasonably happy in non 75 ohm cable (and audio cable isn't likley to be this standard). My experience is that some audio cable actually works quite well - I had some long lengths of ex BBC 7 core audio - the cream coloured stuff. It worked well feeding video 20m or so - however, this was separate composite sources. RGB didn't work as well. Not sure why, but the image was degraded quite a bit, coloured fringing on vertical lines the main issue. Using proper video cable cured this. I couldn't see a difference on totally separate sources. HTH Link to comment Share on other sites More sharing options...
soundo26 Posted October 15, 2006 Share Posted October 15, 2006 Hi Guys I'm thinking of making a multi-core for our conference work is it possible/good idea to run video signal down shielded audio signal cable. I'm looking to send 5 video signals (RGBHV) possibly two runs (send and return) with BNC at both ends and a parallel audio with 6 lines. Any thoughts Thom Video cable needs to have an impedance of 75 Ohms, Audio cable is not suitable. VDC & Canford do offer Multicores that have multi Audio / video cores of the correct types, if I were you I'd check them out or possibly look at one of the cat 5 Converter options (Kramer or CPC) Link to comment Share on other sites More sharing options...
paulears Posted October 15, 2006 Share Posted October 15, 2006 video is a nominal 75 ohm impedance - but as I said, having non-standard cable isn't as doom and gloom as it first appears. Much does depend on the terminating equipment. quite severe cable mismatches are not always unworkable. After all, people often use T-pieces as splitters to feed two items of kit. as long as the sync pulse is still acceptable as a solid source all is well, bar a little drop in brightness as the p-p moves away from the 1v mark. Although normally short - very few camcorders even use 75 ohm conenctors - most use 3 or 4 way 3.5mm sockets and phonos -none of which are 75 ohm constant impedance connectors. multicore video cable isn't cheap. For me, the connector issue is critical - bncs falling off, or pulling free are the main problem with non-video cable Link to comment Share on other sites More sharing options...
dbuckley Posted October 16, 2006 Share Posted October 16, 2006 Of course audio multicore isn't suitable, but it works, and unfortunately it works far too well for too many people to be dismissed. At least for composite video. And DMX512. <sigh> You would be advised to use video baluns so the signal is at least balanced on the muticore. Link to comment Share on other sites More sharing options...
slim_mcslim Posted October 16, 2006 Share Posted October 16, 2006 As has been said there is no reson not to, however its not a very professional way of doing it, and as such in a professional conference environment is that what you want to be hiring to your clients ? VDC makes some lovely 5 core video cables just for this purpose which means it will work everytime, and people won't laugh at you when they see your video multi. I have had quite good success in the past sending raw composite video down XLR audio cable and cat5 network cable, but I wouldn't be happy using either on any of my events. P. Link to comment Share on other sites More sharing options...
fogg Posted October 16, 2006 Share Posted October 16, 2006 Just had a quick search on ebay found this stuff Linkany use? Link to comment Share on other sites More sharing options...
Toxopholist Posted October 16, 2006 Share Posted October 16, 2006 I suppose a solution to the BNC connector v. Audio cable problem could be to use a solder type connector like Phono then add Phono-BNC adaptors on the end... But as has already been said countless times before it is really only a bodge to be used in those "criminey the client wants it where!? but I havent got the copper!" type situations... Regarding why it doesnt work as well for RGBHV applications would be variations in the length of the cores in audio multi (at a guess) causing skew issues as revealed by a lack of convergence between the red green and blue signals giving that "fringing" look. This can also happen if you use some of the CAT 5 adaptors mentioned above, if you go down that route make sure you invest in a CAT 5 system that has some skew compensation built in... HTH Charlie Link to comment Share on other sites More sharing options...
ThomJ Posted October 16, 2006 Author Share Posted October 16, 2006 Thanks guys I thought that would be the case but had to ask. This is not for hire use but for our own convenience lay line, Had looked into cat 5 and decided to go with 5 core (RGBHV) BNC cable this was just an idea and your thoughts and comments are most helpful. The proper AV/audio cable mentioned is great (all be it pricey) Thanks again Thom Link to comment Share on other sites More sharing options...
eviljohn2 Posted October 16, 2006 Share Posted October 16, 2006 For the cost of a good length of audio multi and video multi you could probably get a small audio multi (or even the suitable number of individual cables) and suitable VGA over Cat5 gadgetry which would work well. :) Link to comment Share on other sites More sharing options...
fogg Posted October 17, 2006 Share Posted October 17, 2006 Hi there I just found this adaptor on thomann, looks like it just what you need to send video down an XLR... or a could be tottaly wrong! Anyway take a look Adaptor Link to comment Share on other sites More sharing options...
Pete McCrea Posted October 17, 2006 Share Posted October 17, 2006 From Here it looks like it's designed for putting Digital audio down co-axial cable rather than video down Ballanced XLR lines. Link to comment Share on other sites More sharing options...
Toxopholist Posted October 17, 2006 Share Posted October 17, 2006 these are indeed only suitable for audio sending/receiving over coax Link to comment Share on other sites More sharing options...
fogg Posted October 17, 2006 Share Posted October 17, 2006 Ahh yes silly me, nevermind! worth a look anyway! Link to comment Share on other sites More sharing options...
pumphouse Posted October 23, 2006 Share Posted October 23, 2006 these are indeed only suitable for audio sending/receiving over coax Just how would the adaptors know which way round they are supposed to work? The laws of physics don't generally allow for these things to work only 1 way round (same way as I don't believe in audio cables with arrows printed on the side!). I would venture that if they are passive impedance converters then provided they don't have any band limiting in them, then they would work either way round. The video conversion would work particularly well on 110 ohm audio cable, but would probably work fine (for composite anyway) on normal multicores. I'm not saying it's good - or right, but it would probably work. Definitely not recommended for RGBHV signals or higher bandwidths though. Jason Link to comment Share on other sites More sharing options...
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