Video over audio wire???

Plus4dB · Post by **Plus4dB** » Wed Mar 26, 2008 11:34 am

One of my clients asked if we can use his existing audio tie lines for composite video. I know there are many manufacturers making product to send good quality composite video over CAT5, but I've never heard of anyone doing it over regular shielded audio cable. I've got several pairs (four?) of balanced, shielded 22g audio wire installed.
Anybody know if: 1) I can treat four audio wire pairs as CAT5 twisted pairs and just break out a short CAT5 cable to audio cable or 2) if there is some other way to send video over audio or 3) am I likely to get interference in the audio or in the video in any possible solution?
Any help would be greatly appreciated.
Thanks,
Mark

Speedskater · Post by **Speedskater** » Wed Mar 26, 2008 10:19 pm

Well, composite video is not that big a quality deal anymore. It's won't cost much to try one line. Get a pair of video co-ax to Cat5 "balun" transformers and give it a go. The pair of transformers may only cost $60 US. The shielding may reduce the maximum distance though.

Plus4dB · Post by **Plus4dB** » Thu Mar 27, 2008 11:57 am

I guess you mean try sending one line of composite video over the four single-pair audio lines, by splicing the CAT5 pairs into the audio pairs.
Thanks, I will suggest to the client that we try this. Pulling new cable of any kind is not an option, so he has nothing to lose except the cost of the baluns and my labor, which will be minimal.

Speedskater · Post by **Speedskater** » Sat Mar 29, 2008 2:35 am

Composite video only uses one cable, component video uses 3 cables. I think that a short jumper wire adapter from the balun transformer output to your balanced audio connector at each end would work. If the in-wall cables have no connectors, just wire them straight to the transformers.

tcdyer · Post by **tcdyer** » Sun Mar 30, 2008 8:30 am

Hi,

This may be a stupid question; but why do you need transformers? why can't you just connect the compsite output strait into the audio cables?

As far as i know, audio cables are usualy of higher quality than video ones and both types are coax, so shouldn't it work just fine?

Speedskater · Post by **Speedskater** » Sun Mar 30, 2008 11:33 pm

tcdyer wrote:Hi,

This may be a stupid question; but why do you need transformers? why can't you just connect the compsite output strait into the audio cables?
As far as i know, audio cables are usualy of higher quality than video ones and both types are coax, so shouldn't it work just fine?

I think that in this case the audio cables are balanced 2 conductor cables. Even then you should get a fair picture. But without the transformers ground loops will be a big problem and picture quality will be lower. Why would you think the technical quality of audio cables is higher than video cable? Video's wide bandwidth places far greater demand on the cable than analog audio. Even digital audio is more tolerant of low quality cable than video. Here I'm talking technical quality not construction or material quality.

Plus4dB · Post by **Plus4dB** » Mon Mar 31, 2008 8:58 am

Hi Again and thanks for the responses. Thanks, Speedskater, but I am not sure I'm understanding your proposed solution. Yes, composite video uses a single coax video cable and component video uses three coax video cables (R/G/B, Y/Pb/Pr, etc.) But CAT5 uses FOUR twisted pairs of data wire (shielded or unshielded). I have FOUR pairs of shielded 22 g audio wire run from point to point. What I am confused about is this: When you suggest using "baluns," are you suggesting using a product such as the Intelix AVO-V1-F and treating the FOUR AUDIO PAIRS as if they were FOUR CAT5 PAIRS, or are you suggesting some other type of balun that would interface the composite video on COAX to only ONE of the AUDIO PAIRs? If you are refering to some other type of device (i.e., something other than the what the Intelix AVO-V1-F would do) would you mind giving me a specific manufacturer/model # so I can have an example? Thanks a lot.

tcdyer, you may be confusing COAX with UNBALANCED. Speedskater is absolutely correct, the bandwidth of video, especially hi-def video, are much greater than any audio, analog or digital. Much useful info can be found about video and audio formats and cabling just by Googling specific terms and going to sites like Wikipedia. Also, if you want to get a crash course in audio, Google "gain staging" and click on the first hit. This Recording Studio Forum is a great site for specific questions - I am quickly becoming a dedicated user and fan! Also, I am happy to answer any questions that I can.
Thanks,
Mark

Speedskater · Post by **Speedskater** » Mon Mar 31, 2008 10:45 pm

The Intelix AVO-V1 is exactly what I was think of! I don't have a unit or instructions, but I had assumed the each unit used only one pair of conductors.
I have been using some old mic transformers to send analog audio down Cat3 wire for years.

Matt Whritenour · Post by **Matt Whritenour** » Sat Apr 05, 2008 11:48 am

copper is copper, the video and audio are most likely both around the same gauge, it'll probably work fine

Plus4dB · Post by **Plus4dB** » Sat Apr 05, 2008 12:31 pm

Thanks for the replies. I'm going to suggest to the client he gets the Intelix baluns and I'll break out the audio pairs to corresponding CAT5 pairs and it will work, most def. Only question is if the quality will be adequate, and that is for the client, not me, to decide!

Yeah, CAT3 or 5 can easily be used for line-level audio. Have you actually used it for mic-level audio?

Speedskater · Post by **Speedskater** » Sat Apr 05, 2008 11:42 pm

Plus4dB wrote:Thanks for the replies.
(snip)
Yeah, CAT3 or 5 can easily be used for line-level audio. Have you actually used it for mic-level audio?

No, only line level un-balanced audio. The xformers are pre 1960 and large. The impedance ratios looked good and they were just sitting there. Maybe I should buy some baluns and sell the transformers to some tube DIY's.