Idiot subcontractor cut my in-wall SPDIF!! PLEASE HELP ME! (1 Viewer)

[Eric_L]

OK - I am in FREAK-OUT mode right now. As some of you know my home was badly damaged during hurricane Charley. After countless long delays (insurance, window shortage, etc.) we finally are nearing the end. I recently took advantage of the situation when the drywall was being replaced to run speakerwire throughout. I even ran it to several alternate locations - being careful to mark all ends with bands of tape so I could identify them even if they are painted. I ran a total of eight lines plus a subwoofer cable and a 50' run of SPDIF coax RCA ends - for audio. (I keep my DVD player near the projector) It was a real nice cable - cost me well over $100. I cut a generous length in the speaker lines to give me plenty of working slack in the set up on both ends. I bundled the ends nicely - but there was too much to cram into the outlet box.

Today I go over to inspect the work the drywallers are doing. They had already dry-ed in the entertainment center when I got there.

The JERKOFFS cut off all but six inches of my wires including the ends of the SPDIF and Sub line!!! They just chopped it off!! Just to fit on a 2X3 piece of drywall! Nevermind that it was neatly bundled coming from an outlet box in a built in entertainment center!!!

Tweedledee -"WTF is all this wire?"
Tweedledumb-"Fukit! I don't know. Must be nothing. Lets chop it off!"
Tweedledee -"Should't we ask?"
Tweedledumb-"Nah, why would they want all this wire in their entertainment center? Lets clean it up for them!"

OMFG! I am going to have a heart attack! I figure I can get a couple of speaker outlets and put them in with the small amount of slack they left. (Whats a few hours trying to figure out which line leads where?) I can then wire to those outlets when I set up. The Sub cable isn't so bad either because the sub is right near the entertainment center and we can easily rout to it.

The biggie is the audio coax. I had a 50 foot run going under the subfloor through the downstairs ceiling and up the wall where the projector and DVD player are to be located. (yes, they cut the other end off too! Assholes!)

So now my builder (who also is insanely pissed at them) is looking to see if he can find an AV guy to replace it Sunday. If not then I am S.O.L. We can't hold up the job for a week while I order a new one (the longest run avaliable in town is 25' at Circut City) We've been out of our home nearly a year and have other subs lined up after this job is supposed to be done. One week delay could domino into a month!!! So if we don't get it tomorrow we may not have it at all.

Maybe there is a shortcut. I know some folks like to make their own coax audio. Could I just splice the ends back on? There is well over 6" slack between the cut and the ends. Would it have a noticeable effect on the performance and be no different than any other cable where someone put their own plugs on?

Or maybe I can make my own? I've heard of people doing that with regular coax - would it be any good?

Gawd I hope that I can fix this! Not for the subcontractors sake - but my own. We can't afford any more delays than we've already faced, and I hate the thought of having the cable across my livingroom again.

Please, is there a way to restore my SPDIF cable or making a replacement? I am panicked -

"Help me HTF - You're my only hope!

 

[Glenn Overholt]

Ouch!

At best, any AV company could have the wire sent to them via overnight delivery, and get an early delivery time (like 7AM Tuesday) and put it in then - but since the rest of the wiring is all unknon now, I'd have that replaced too, all at their expense, of course.

The drywallers should stay on the job - even if that means that they are working until 3 AM, to get it done.

It might be possible to get the wire even faster, like having the distributor take the cable to the airport to get it off on the next flight - just to avoid more delays in construction.

Maybe the other sub contractors can work around your wiring, and get to that last?

Glenn

 

[Eric_L]

Buzz - because it is a remodel (actually restore) things are a bit different. Also, the general contractor is a friend and has given me broad latitude.

I'm still hopeful someone here could tell me if splicing the cables together would give acceptable results. If not then I think I will have a new one overnighted.

I looked a bit online last night and it seems to be 75 OHM coax line with RCA jacks is acceptable. Apparently the jacks have to be put on in a special fashion which I cannot get any info on - other than not to crimp them on or overheat the soldering iron... I don't know if that would give beter results than splicing my line or just buying a new one...

Can anyone advise me?

 

[Justin Lane]

Eric,

Make a run to Radio Shack, pick up some RCA ends (solder or solderless) and terminate your cable. These ends usually have a digram for cable prep/connection. Try playing a DVD, and if you get a digital audio signal, you are good to go. A lot of places market digital coax, put in real-world applications, a simple composite video cable will do the trick.

J

 

[PhillJones]

I agree with Buzz about this.

Can't you get an RCA chassis jack and make a s/pdif outlet? Perhaps have a pannel with your speaker, subwoofer and spdiff outlets all in one place. Perhaps it would even be neater.

I've been told that, because sub-woofer cables carry low frequency signals, they're not as critical as your other cables. s/pdif is even less critical. I've tested expensive s/pdif against a bit of cheap video cable bundled with an old vcr and couldn't tell the difference. I got several freinds to also take the s/pdif challenge. Everybody failed. So if you're worried about loss due to extra connections, I wouldn't.

 

[Eric_L]

Thanks for the input everyone. (pun - hehe)

I appreciate the idea of just capping some RCA jacks onto the ends, but I also have to splice on some extra length - they left me with only 6" of slack at the outlet - barely enough to stick out the faceplate.

I recovered the ends. Would a splice of some cable length and ends on each end have a noticeable effect?

I understand that when there is signal issues it can be intermitant. So far I've only heard of that happening with standard RCA cables - I found nothing about a repaired coax audio cable. I suppose I could drag my DVD and audio system over, but hooking up in a construction zone is quite a task/risk - and it may not be conclusive. Listening could be problematic also. I'm hoping for a educated guess from someone with more experience than me (read: any) before I try that option.

Thanks


ah, I just reread Phil's post. I planned on a speaker outlet panel - but handn't considered a spdif panel. Hmmm. I'll have to look one up. That soulds workable.

 

[Eric_L]

http://www.radioshack.com/product.as...ct%5Fid=40-990

Here is the only RCA wall outlet I've found - will it work w SPDIF signal?

It needs a RCA jack to plug into the back. I'd have to get that too. I'm sure that part is easy enough to find.

All these connections aren't going to whack my signal beyond recognition, no?

 

[Jeff Ulmer]

Obviously, the fewer connections the better, but as long as you use decent qualty connectors, there should not be an issue.

 

[Eric_L]

WOOT! Look at what I found!

http://www.smarthome.com/8551.html

I think this solves my problem! YAY!

Thanks everyone!

 

[Bob McElfresh]

Email http://www.BlueJeansCable.com. Kurt is a member here and has many satisfied members because of the quality of his work and the quick turn around. I cannot make promises for him - but he would be the first person I would turn to if this was my problem.

Blue Jeans Cable:

206) 284-2924 voice
(206) 284-2931 FAX

 

[PhillJones]

Bob,
That's interesting, so what you're saying is that because RCA isn't impedence matched, it's a rubishy way to connect s/pdiff and video cable.

I guess that means that Eric still has both choices but should use BNC or F-connectors, whether he's going to do it in-line or use make a terminal plate, rather than RCA like we were all thinking.

I guess if he did go for the wall plate idea, he'd want a piece of 75 Ohm BNC to RCA, like the stuff used for component video cables for expensive display devices.

That's what I'd be tempted to do anyway, I think it'd look nicer and be more conveinient.

Just out of curiosity, what is the best way to terminate audio cable then, which is supposed to be 50 ohm?

Don't mean to Hijack the thread Eric, I'm just interested as hiding wires in the walls might be something I'll do in a few years.

 

[Eric Kahn]

when my brothers new house was built, we added many audio cables in the walls before the drywall was put in, sounds like someones contrator wants to overcharge you to install this stuff instead of you doing it yourself

 

[Wayne A. Pflughaupt]

Lesson hard learned. From what I’ve seen here and at other Forums, I think anyone having any drywall work done in combination with a home theater installation needs a special contract for the drywall contractor. It should stipulate that if they cut or otherwise damage any of the AV cabling they’re required to pull in a brand new run of the same exact cable stock at their own expense (i.e., not splice or otherwise “Band-Aid” it, or be charged a $1000 fine, deducted from their payment.
Any solder- or crimp-on RCA is fine for audio from a functional standpoint. However some RCA’s are nicer and better constructed than others.

Regards,
Wayne A. Pflughaupt

 

[ChristopherDAC]

According to all resources on TV, CATV, and video work I have read, if you want to splice a 75-ohm cable, don't. That is what screw-type F connectors and barrels were designed for: to take the place of splices in 75-ohm cable. Crimp-ons are entirely satisfactory, applying them is very simple, and you can splice any lengths together. There are RCA connectors designed for 75-ohm surge impedance, and they are in general use with consumer digital and video connexions. If you are going with BNCs you have to make sure that you are using the 75-ohm variety, and not the more common 50- and 100-ohm types used for computer cables and oscilloscopes. In this particular situation I would prefer to install [in fact, just as I have in my own home] F-connector plates -- you can get them with 2 to a plate, maybe more -- and then whatever adaptor is necessary. F-to-RCA and F-to-BNC are easy to get, and even F-to-PL259 is not hard. I have many adaptors, and the signal loss is minimal as long as they are the correct ones for the application.

 

[KurtBJC]

Ach! Contractors! You know, one of the most common mishaps we run into is the fella who says to the contractor, "hey, I'll need to run a/v cable, so put some conduit in from here to there"...and the contractor runs 3/4 inch conduit...into which are supposed to go an HDMI cable, a couple of component runs, and maybe a few other things...you need some serious magic to get all that cable into that conduit.

Anyhow, Bob mentioned this thread to me and I thought I probably should weigh in on a couple of issues.

Doing a wallplate-type installation is going to work just fine--in fact, it's really a nicer-looking installation that way anyhow, if that's any consolation for the inexcusable cable-hacking done by your drywallers.

On the choice of connector at the wallplate: I'd suggest using a BNC if you can, just because BNCs give a better engagement and are less likely to come loose inside the wall than an F or an RCA. But I wouldn't worry too much about the specific connector type from an impedance match standpoint, just because the bandwidth of the SPDIF signal isn't so great--around 3.5 MHz, if I recall correctly, which would make the quarter-wave about 21 meters long. A impedance mismatch like this, not being more than a couple of inches long, shouldn't cause any grief.

On the "what to terminate audio cable with" question, the answer is that characteristic impedance doesn't matter in analog audio unless you're going to run signal for a distance of several miles (in which case I'd imagine that characteristic impedance is the least of your problems). I often hear it said that analog audio cable traditionally is 50 ohms, but in fact 50 ohm cable (usually built for radio transmission or data) isn't very good for analog audio--not because of characteristic impedance, which as I've said is irrelevant, but because 50 ohm cable is relatively high in capacitance (around 30 pF/ft typically, compared to around 16 to 21 pF/ft in 75 ohm cable). While that isn't going to make a meaningful difference in a short run, it does become meaningful as interconnects get longer. RCA plugs are just fine for unbalanced audio as long as the connection is mechanically and electrically solid.

...and if you do have any other problems with this, or need some advice or assistance, give us a call any time.

Kurt
Blue Jeans Cable

 

[Glenn Overholt]

The wallplates and connectors are available at Radio Shack and Home Depot - but this will mean more work for you - which you shouldn't have to go through. You had a great, easy and simple idea.

Every time you make a connection, it increases the chances of something going wrong too. When you get done making the connections behind the wall plate, you'll have to snap the connectors in place on the wallplate and feed the wire back into the wall when you go to secure the wall plate to the junction box. If you don't have any rude obstructions or turns, this should not be a problem, but all in all, it is more work.

Maybe you should just hire a professional and bill the contractor.

Glenn

 

[Bob McElfresh]

There are some 'tricks' that the better RCA plugs can use to approach 75 ohms. But since the input jacks are already installed on consumer electronics - video cables come with RCA plugs and companies hope consumers wont be able to detect any problems.

(And truth be told - as long as everything else is designed for the frequencies in mind, 2 RCA plugs will only cause a bit of a problem - but it is a less-than-optimal type of connection.)

Cut a piece of coax and what do you see? A center wire, encased in white stuff, then a outer "pipe" of foil/wire braid.

The goal is to keep a fixed distance from the center wire to the outer pipe This helps to maintain the impedence along the entire cable.

Look at a female-to-female "F" barrel connector. What do you see? A small hole for the wire, encased in white stuff, then an outer "pipe" with screw threads. A signal traveling down the coax, hitting one of these will not see a major difference between the barrel connector and the coax on either side.

Now look at 2 RCA plugs and a "barrel connector". The fat banana plug in the center is WAY thicker than the center wire. And the distance to the outer 'fingers' on the plug is a heck of a lot smaller than the center-wire-to-pipe distance of the coax on either side.

You CAN get some high quality RCA plugs ($2+ each) and ..perhaps a barrel connector that try with funny dielectric constants to maintain 75 ohms. But it is only a close aproximation, hard to find, and not ideal.

Two BNC connectors (high quality) run about $0.49 ea and the barrel connector for BNC another $0.50. This is much cheaper, easier to find and much better because it was designed to maintain the impedence. Professional gear has been using them for years.

Does this make sense?

 

[Wayne A. Pflughaupt]

Indeed it does - thanks Bob.

 

[Eric_L]

The hacks are all outside the wall. Since I'm terminating on the wallplate I don't worry too much about them coming loose inside the wall.

As I understand your post then there is not much difference if I do RCA, F or BNC terminal there. I think I'd prefer to do RCA since all of the ready-made SPDIF cables have RCA connectors on them. It simplifies things not just for me but for possible future owners.

That will mean that the signal will travel through four RCA connectors (DVD to wall to wall to Decoder) but you seem to think that will not be an issue so long as I use quality RCA connections.

Are there specific ones you'd suggest? Are the ones I linked to earlier high enough quality? I hope so - I like those wallplates. You are right - in the end it will look more attractive - even if it means there is a pair of 'speedbumps' in my system now. If I understand your post they won't pose much problem.

Oh, and the contractor is a friend, he'll be right there with me running the test speaker from one corner to another while we sort out thie mess. He's bringing the beer. He also offered me a body part of my choice of the drywaller who cut the cables. If it is true that the cut cables will not impede my system and I ended up with a more attractive terminal - then I may just offer the drywaller a beer and take an IOU...

 

[Richard Beckman]

Given quality cable and quality connections you should be able to extend the coax with good results.