shielding rca/component video

Greetings!

I'm building a snake box for my rca gear. I'm going from rca female on the box to a multi cable and probably back again and I can use a panel-mount rca, solder a shielded (or unshielded?) wire to an output connector (below) (db 25).

What about a Double shielded twisted pair DB25? if not please recommend an available cable/connector.

If I use plain unshielded cable inside the (metal) box, could I run into problems?

Do I have to worry about shielding, say, composite video from component or audio (-10 or +4) inside the box?

What do you think my distance limitations will be for component video, composite, -10/+4 audio, digital coax, svideo on the DB25 cable?? I'm thinking 3f patch +1ft in box + 10ft +1ft in box + 3f patch for a total of 18 Feet.

Thank you for your time,

-Jessop

Reply to
J
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"gear"? audio? video?

"back again"? not sure what that means? back where? "the box"? can you give us a better hint what you are doing?

What is the signal? audio? video? something else? "output connector"? output to where? what kind of cable does the db25 connect to?

DB25 connectors are neither shielded or non-shielded. DB25 connectors are neither twisted pair or otherwise. You seem to be describing some sort of cable which connects to the DB25?

You have left out too many details for us to have any idea what you are trying to do here?

What kind of signal? audio? video? something else? How far?

If they are the same picture, probably not. If they are different video signals, then, probably yes.

Depends on how far from the video. I would use shielded cable just to be safe.

Impossible to answer. We have no clue what your "DB25 cable" is.

You have provided only ~40% of the details necessary to answer your questions properly. I would be far more concerned about the nature of the 10 ft of snake cable than about the details of the boxes and connectors.

Reply to
Richard Crowley

Yes -- there are db-25 type connectors with coax fittings for 75 ohm, so you may need baluns to do this properly. I wouldn't use RCA type connectors for this purpose in any case. They're really not sufficiently well shielded and you can't lock them in place.

You're going to have lots of different signals inside the box, right? Shield. And be sure to ground one end of the shield.

No need to worry. Just do it.

Reply to
Mike Berger

My goal is a box to which I can connect my stereo receiver inputs and outputs that will simplify the connection from one entertainment cabinet to another - condensing to a single cable (my dreaded DB25 cable ;). Then there's a box on the other end of the multicable which expands the connectors back out to their respective composite video, svideo, component video, audio(red white), digital multichannel audio, etc. rca panelmount connectors.

My question is: While building the box 1) Must I shield individual lines soldered from rca panel-mounts to my db25 connector inside the metal box, AND 2), Would a doubleshielded twisted pair cable (with db25 connector, standard issue printer switch cable) effectively transmit things like component, composite, svideo, digital audio which were originally on 75ohm coaxial cables?

How effective is shielding on a cable when the + solder points are not shielded inside of a box?

I plan to make the connections in the box with Belkin 8451. 22 ga shielded 2 conductor.

Respectfully, Jessop

PS I very much respect the people involved on these lists. I expect very little as I know that it is charity. I understand, and have for years, that I am poorly organized -as are my writings, but you are making sport of my question. Before writing this paragraph, I looked at your other posts. People, indeed, ask a lot of stupid questions, and you are quick to point out that they need to pause and reorganize. However, if you read the entire question before replying impulsively (as I am replying impulsively here), you'll see that your ostensible bewilderment is not justified in all cases. What kind of gear was implied when I asked about specific signal types: Component video, Composite, Svideo, and audio -10,+4. Translation from one set of discrete connectors to a unified multi-cable and 'back again' to a bunch of discrete connectors is generally what snakes do. The websites I've seen are selling twisted pair double shielded DB25M-DB25M cables. I think you can surmise that a double shielded twisted pair DB25 Cable is some sort of cable that is double shielded with twisted pairs and DB25 Connectors on the ends. ;)

Reply to
J

Yes -- there are db-25 type connectors with coax fittings for 75 ohm, so you may need baluns to do this properly.

*** Had to read up on baluns, and have no clue where to get the db25s w/ coax fittings.... I wouldn't have to build anything if I found a simple way to get LOTS of coax rcas down to a single cable. So far I only see 10c rg59, which I could put rca compression ends onto, OR the ready made hosa 8channel rca snake, but that looks flimsy - and I'm not sure it's best for all kinds of transmission. Don't all those different hifi connectors (below) generally enjoy different impedences? ***

I wouldn't use RCA type connectors for this purpose in any case. They're really not sufficiently well shielded and you can't lock them in place. You're going to have lots of different signals inside the box, right? Shield. And be sure to ground one end of the shield.

***

I wasn't very clear, as Crowley pointed out, but I want to take various connector from a Home Theater Receiver as one cable to the TV (component video, s, composite, audio, digital, whatever) So, I have to use rca connectors /i somewhere /i.

It sounds like $100 dollars for an 8 in, 8 out, 2 box snake is quite unreasonable. My figures were $280 for a complete set 1 main box, 4 separate output boxes and 4 DB25M - DB25M cables when accounting for $20/hr labor for soldering, wire prep, box hole drilling, applying decals.

Sobering reality.

Thanks.

-Jessop

Reply to
J

If you keep the audio at one end and the video at the other end you *might* be able to get away without shielding the internal wiring.

It is questionable whether it will work acceptably well for audio in your application. (See more complete discussion below.) I would bet that it will make a hash out of any video (particuarly high-quality video) that you try to run through it.

Still quite effective. It is over the length of the cable that the shielding is beneficial, not just at the connection point.

Assuming you mean "Belden", a well regarded maker of wire and cable. That would be great for the audio lines. I wouldn't use it for video if I had a choice of proper coaxial cable (whether 75-ohm or some other impedance which doesn't really matter for short pieces).

No, I was trying to clarify what you are asking. It may appear to you that some of the information you left out was not important, but that is because you may not understand the scope of the questions you are asking.

Now, there ARE some people on Usenet who DO make sport of people's questions (and far worse). I suggest that you need to develop considerably thicker skin and get a pair of asbestos undershorts if you intend to hang around some of these newsgroups very much. ;-)

If we can assume from your mention of component video that you have high-end video equipment (as contrasted with a cheapo 12" TV set), then any thought of running video through any kind of printer cable should be put out of your mind. The video will look like a "dog's breakfast" when you are done and you will have wasted both your time and your money.

People frequently come here [I am reading and posting from rec.audio.tech] and ask about very expensive audio and video cables and whether they are worth the extra expense. The overwhelming answer is: No, their high price only enriches the people selling the premium cables and they do nothing discernable for your audio or video.

OTOH, you can't expect to run high-quality video over cable which was never designed for that kind of band- width or impedance-control. Just as there is a threshold above with you cannot *improve* your video signals, so also there is a threshold below which you are just wasting your time and money.

If you object to the way I cross-examined you or responded to your questions, I apologize, I was trying to do a complete job of understanding the circumstances in order to give an accurate answer.

You are operating so close to the edge that it was not safe to make that kind of assumption. Those cables are likely very nice for parallel printers. Maybe even overkill (as for the "premium" audio and video cables discussed above)

That cable *might* even be OK for audio, although the lack of shielding between the twisted pairs may give you more crosstalk than you would like. Particularly with unbalanced sources and inputs. And running something like an unshielded tape output and a tape input line next to each other could even cause oscillation, audible or supersonic, which could actually damage speaker tweeters or other parts of your system.

I would definitely NOT recommend the type of cable you want to use for either audio or video use.

If you want to make something that has several audio and video cables in a long, flat form-factor, you could consider taking 10-ft lengths of proper audio and video coax and "weaving" them together with cable-lacing twine, where the cables form the long dimension, and the lacing twine weaves across them to hold them in a flexible ribbon shape.

Reply to
Richard Crowley

J: If you use well shielded audio and video cables, and part of the goal is to have a nice neat equipment wiring harness, you could pick-up plastic split-channel or spiral wrap and use that instead of going to all the trouble of lacing wires. Plastic channel is available in a few different diameters. Keep the equipment power lines and amplifier output wires separate from the others. Another step to include is to make sure that you label all connector ends, this will save your sanity and avoid guessing games.

Reply to
HangingJester

why not use a SCART plug?

how fast is a car with 4 wheels?

Bye. Jasen

Reply to
Jasen Betts

In article , snipped-for-privacy@cox.net wrote: Without busting into this thread and being a big pain, let me pass along a bit of what I know about this stuff. I was a studio integrator out of Mpls. for the last 25 years. Built just about every major recording studio in the midwest, as well as television stations. I had a couple of the best instructors/mentors in the world, Dave Hill from Crane Song Audio, J. Jamison, Doug Ordon, etc. One particular person had been a "lifer" electronics instructor in the Navy, and he was charged with checking out how we had been doing our rack wiring harnesses, as well as single point grounded patchfields. The first thing he did was to start ripping all of the wire ties off the nice bundles we had made that went from anything with an RCA connector to the patch panels. He then took one of our cables, and hooked it up to 'scope and a signal/sweep generator, as well as an Amber Audio test set. With the cables bundled as we had constructed them, using a factory tie wrapping gun or just by hand, by sending a swept audio signal into a standard hi-impedence Teac single conductor/shielded cable, the max freq. response started to roll off at about 19khz!! We were all pretty much dumbfounded, and he proceded to show us how we had constructed a very neat looking, series of low pass filters using a series of wire ties. Because of the soft foam insulation between the shield/foil and the single conductor, it acts as a capacitor, variable by the distance between the two. By pinching down on the cable with the wire ties, we were changing the capacitance of the cable in exactly the direction not wanted. While watching the sweep, he slowy removed each wire tie that was positioned at 5 inch intervals over about a

18ft run of cable. By the time he was halfway through, the sweel was now clean and flat up to about 50khz. When they were all finally removed, and the kinks worked out, it was flat out to beyond 100khz which was the limit of the sweep generator. Needless to say, we learned our lesson well that day, especially when we had to go back and remove some >4000 wire ties from the audio racks of the new Neve installation at MN NPR Radio. What we did replace it with, was this green surgical tape from 3M. It's basically gauze, soaked in some type of green wax. I've seen it sold under all sorts of various names, and it works great for bundling cables, doing preform wiring bundles (as it's removable as well). It was somewhere between going back and doing the older style lacing, which I still do on projects for Disney as that's part of their construction spec. I haven't tossed out using wire tires, as they are still good on power and ground cables, but on anything that's coax, using anything that changes the relationship of the single internal conductor to the outside shield is a very bad thing. Now, if anyones interested, I can tell you the benefits of building audio/video single point ground systems (which would be the best way to run your junction box).

Regards, Doug

Reply to
DougD

I've only seen scart in pictures. I'm in the US and none of our gear has it. I'd love to, but it looks like my idea is cost-prohibitive.

4 wheels, right - point taken.

-Jessop

Reply to
J

As it stands with my initial design, component, audio, composite, svideo, and digital between 2 boxes would cost $100 after labor, connectors, etc. To build it properly would cost a lot more, it seems.

Haven't been getting much sleep...

Evidentally.

Donned.

I was basing my design on connectors available on the back of sony's new $2000 hifi receiver.

No monster then, hosa is fine? I'm too weak to use monster's toothed RCAs anyways. ;)

I withdraw my objection. Thanks for your patience.

That was one of my concerns - what does double shielded mean? I was hoping the pairs were shielded, then the whole was shielded. Evidentally not.

sounds pretty, but it's not a component you can just 'install'.

NOW I see why the product I'm looking for isn't available. The market won't meet the price for the quality, variety, and assembly of the components required. You'd have to charge several grand for one with 48 specialized connectors and 6 breakout boxes.

I'm just looking for a way to speed hifi installation/ modification. Hoping there's an alternative to crawling around behind someone's tv and entertainment center for hours...

Oh well.

-Jessop

Reply to
J

yeah, I've seen those. Better than nothing, but not quite the one cable simplicity I'm looking for. What can I say, I'm a perfectionist and a malcontent.

-Jessop

Reply to
J

Great post, thanks for the info.

_Jessop

Reply to
J

Monster defines the level where you are paying for the name and not for any discernable benefit to you.

OTOH, if you are a San Francisco 49ers fan, you get the benefit of going to "Monster Park" where Noel Lee (who started "Monster Cable") likely has a luxurious skybox.

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While I admire Mr. Lee's business success, I am not inclined to support it.

Hosa defines the lower level of acceptable quality. It is likely OK for fixed-installations (I use it myself), but many have reported failures (breaking at the moulded connectors) in repeated portable use.

"Double-shielded" in a (relatively) inexpensive computer cable almost always means two layers of aluminum foil over the entire cable. I've never seen a comptuer cable with individually-shielded pairs. At least not in 30 years. Digital signals don't need it, so there is no profit in doing it.

I'd bet that somebody could come up with an efficient cable "weaving" machine and make a bit of profit providing custom flat-cable combinations. Could become the next Noel Lee and have their own sports stadium! :-)

Reply to
Richard Crowley

Cat5/e STP (Shielded Twisted Pair; each of the 4 pairs is shielded plus a shield around the bundle) cable would certainly support the bandwidth requirements, but you'd probably have trouble with the 100-ohm impedance. I suppose you could rig up some impedance-matching terminations.

Some info on grounding shielded cable:

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Reply to
Ray L. Volts

Also, check these devices out:

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Reply to
Ray L. Volts

SCART connector and cables are designed to carry video signal and stereo audio. There are actually wires for audio and video (composite video) for both directions. And there are also some unidirectional control signals and RGB video lines for one direction.

The idea of SCART is good. The real life implementation of it leaves something to be desired. The connector used for SCART is not mechanically or electrically very good (connector gets easily loose when cable is moved and then pins are not making good contact).

Then some equipment could have designed the use of some control signals better in their equipment...

And audio/video connections were pretty clear (composite video and RGB well specified, nicely degrading to use composite video if one of the equipment on one end did not support RGB) until someone later added S-video support for some SCART connectors on some equipment... not amy equipment support those... anyway the way S-video was added to scart has caused many people to wonder why they get blac&white video where they expect to get color video...

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Tomi Engdahl (http://www.iki.fi/then/)
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Reply to
Tomi Holger Engdahl

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