wire for multizone?

[dgpretzel]

Suppose I wanted to use Xlobby for multizone audio. Further suppose that I wanted to distribute the output from sound cards (line level) to to remote amps in each of the zones. (In other words, suppose that I would not be distributing speaker level signal.)

Then what would be suitable wire to use to distribute signal to amps? I have a bunch of extra Cat5e around, could/should I use that? Or, perhaps, something like this 22/2 shielded mic wire for balunced/unbalanced apps: http://www.partsexpress.com/pe/showdetl ... er=100-246

Or something else?

Max run length is 40'

Thank you.

DG

[samgreco]

You absolutely MUST use shielded wire for line level signals. If you use the 22-2 you've listed, you can use one wire for left and one for right. Do your best to keep it away from AC lines.

The Parts Express wire you show will be fine.

[dgpretzel]

Thank you, Sam.

DG

[Marbles_00]

You might want to be careful of running low level audio for that distance. One big thing you would have to take into account is the capacitance of the cable. This could effect/interfere at audio frequencies. Your best bet is to either build or buy balanced line drivers/recievers. Below is a simple circuit:
http://sound.westhost.com/project51.htm
and an update to the circuit:
http://sound.westhost.com/project87.htm

AudioControl sells simple line drivers/recievers called the BLD-10, BLR-10 and the BLX-10 (http://www.wholehouseaudiocontrol.com/d ... 66&l1=9966). They all can use CAT5 cable and if you can find someone to sell them to you, they are about $150 each. As I said, if you can find someone to sell them to you as they are considered "professional" equipment which are only sold to certified installers (though I have seen a couple of websites that will sell them). This guy actually used them:
http://www.whiteoaks.com/distaudio/

Also check out:
http://www.avsforum.com/avs-vb/forumdisplay.php?f=28
this is the Tweak and DIY section of AVS forum where you might just find the answers your looking for.

Hope this was helpful, and have fun.

David

[samgreco]

David,

You are absolutely right. But I have had good success running unbalanced lines up to about 50' or 60' if it's well shielded and you keep it away from motors and AC lines, etc..

So, DG, I probably should have been more specific But you can try it before you spend the dough and then only if needed.

That's the cheap side of me talkin' . Now in my recording studio, anything over a few feet is balanced line .

[Marbles_00]

Yeah, I should have also added from my experience, that I've built RCA cable around 25-30' with no problems. I did a capacitance check and they were better than some Phoenix Gold (pricey crap) cable that I used to use in car audio (transfered to home audio now). For that cable I used 4 conductor twisted pair Belden type cable with a shield and the heavy duty RCA connectors from Radio Shack. I think I measured around 4 to 5 pico farads.

When I was going to build my cables, I found some useful articles about the issue of audio cables (both speaker level and line level):
http://www.tnt-audio.com/clinica/intere.html
http://www.tnt-audio.com/clinica/spkcbl_e.html
are just two interesting sites to read. I only wish the internet was around during my car audio days...I would have saved a bundle (to put towards my home theater).

40' you would most likely be OK. There might be a rolloff at the higher frequencies but as we get older, who cares as we get less prone to those frequencies anyways. DG, just remember to only tie the shield at one end of the cable should you go that route or you could introduce ground loops which are a bitch.

[dgpretzel]

Thank you both, Sam and Marbles.

I probably should have been more forthcoming.

I am in a physical build-out stage right now. Building a dedicated HT, and, as part of that process, I have some open ceilings and access to ceiling truss spaces, etc. that I otherwise wouldn't conveniently have.

I know that the next project is going to be whole house audio. I'm not sure if I'm going to use Xlobby and distribute audio signals (either line-level or speaker level), or use a bunch of Squeezebox-like devices installed all around the house. I do already have cat5e wired network installed all around the house (got about 35 drops), so I guess that would be a point in favor of the SB option. [As a sidebar, might anyone comment on the relative advanages, for audio purposes only, of Squeezeboxen vs. multizoned Xlobby.]

Since I have the opportunity now to run wire, I want to cover all my bases. I will be running 12g speaker wire from the central server location to all the target locations (to preserve the centralized amp option). I also want to run appropriate wire for line-level distribution (to preserve the local receiver/amp option). Hence, my initial inquiry.

Now, finally, the follow-up to the initial inquiry and responses. Considering the shielded 22/2 wire I used as an example, should I run one or two lengths to each target location? I'm thinking that a single run might suffice-- two conductors, one for each channel. On the other hand, to run as a balanced line, it would require two of these 22/2 wires, right? Yet, on the other hand, sound cards don't have balanced outputs, right? And, the sort of lower end equipment (receiver or amp) that would be at the target locations (keep the "good stuff" in the HT room) also would probably not have balanced inputs. So, I guess that's where the drivers/receivers would come in, right? But, would there actually be an incremental benefit to running balanced lines between an unbalanced source and unbalanced sink (if that's an acceptable term)?

Summary: To allow for line level distribution from sound cards in the server to local receivers/amps at the target locations, should I run one or two shielded 22/2 cables for each zone? The cost of the extra wire isn't really a factor, and the marginal extra effort isn't really significant, either. But, is there a potential benefit?

Thank you, again.

Dg

[Marbles_00]

I'm thinking that a single run might suffice-- two conductors, one for each channel.

I could be wrong and sorry if I mis-understood you, but you are missing your returns. Unless you were thinking of using the shield as your return for both left and right channel, which is something that I wouldn't do (who would get the return). You have to run two runs. One cable will be for left channel, the other for right. Each channel will have your postive and return conductor. The shield will be tied to ground at one end (usually the source) to protect against EMI. You could get a 4 conductor twisted pair with shield, then you would only need one run. One pair would go to the left channel, the other to the right.

Balanced lines use two wires where the signal will be equal in amplitude, but out of phase. Only out of phase signals are detected at the receiver end. If RF or other noise is induced on the line, it will be picked up by both wires, but this signal would be in phase, which would be filtered by the receiver circuit. This would allow you to run audio signals hundreds of feet (if you wanted). I think the only problem would be a voltage drop due to the increase resistance in the cable, so your receiver circuitry would have to be able to detect very low signals.

You would not see a incremental benefit from converting from unbalanced to balanced back to unbalanced in short runs (around 30' and under). Or should I say, the chances of your hearing a difference would be slim. Longer runs, depending on the distance you may see, or should I say hear an attenuation in the higher frequencies. This all depends on how good the cable is, how good your speakers are, how good your amp and preamp are, and mainly how good your ears are. This is where the benefit of balanced lines would be handy. Not just for immunity for noise, but the effect of the capacitance would have less of an effect, again because of the phasing.

As stated, 40' is hard to tell how much signal you would loose (maybe not any). Not knowing you background to electronics, you may consider trying to build that DIY circuit I posted, and hear for yourself if there is a difference. Just use quality parts.

Hope this was helpful

[samgreco]

Typically in a standard RCA type audio cable, the sheild is the return. It is not uncommon to use a single sheild for both channels.

If you take an ohm meter and check your receiver or preamp, you will find that all of the connectors are common grounded. So therefore, your sheild is connected to the negative on both ends and the inner conducter to positive (the pin on an RCA). You could, theoretically, run one channel completely disconnected from the sheild and it would still work, as long as the other channel is connected. I would run a jumper though.

David - Again you are absolutely correct. But in practice, I've never had an issue running this way under 50'. I could just be lucky

[samgreco]

One more thing. After re-reading this, I realized that you have open walls and such. I would run the extra wire. The cost isn't much more about .12 per foot The wire is cheap, labor's not. Especially after the walls are closed up.

Plus if you decided to go balanced later, you already have the wire.

[dgpretzel]

Once again, thank you, both for helpful, thoughtful, and thorough responses.

DG

[Marbles_00]

I learned something myself. I guess I'm a little old school when it comes to returns and the sort...seen and experienced too many ground loops and noise. Sam's right, most likely the returns are all tied to ground, which you could use a single run.

When looking at cost and time, try and run line level with RCA, who knows, you may not hear any difference and then you don't have to worry about the extra cost of running balanced (or spending the time to make up boards...unless you enjoy that sort of stuff).

I agree with Sam too that since you don't have the drywall up, run as much as you can for future expansion...you just never know.

Have fun with it.

David

[samgreco]

David - Slightly OT. Hamilton, Canada is just outside Toronto, right?

I was up in Kirchner a couple of months ago for training. I love that area. I've always loved Toronto. Great city.

[Marbles_00]

Toronto's not bad....well its more lively then Hamilton...just have to avoid the shootings.

Actually I work in Cambridge, bordering Kitchener. Cambridge is really nice if you can get used to the streets. Lot's of industry in Cambridge too and driving from Hamilton, it a nice drive to boot. If you don't mind me asking, what were you up here training for?

[samgreco]

I am a manufacturers rep for audio stuff and one of the lines I represent is Tannoy speakers on the Hi-Fi side of things. Everything else that my firm reps is Pro Audio/Commercial. Lines like Focusrite, Genelec, QSC, Audix Mics, plus lots more.

It's a fun job.

And I knew it was Kitchener