Running cables

[Brad225]

In the listening room I am building I am going to locate the preamp and player along a side wall near my listening position. My plan is to run my XLR cables through the floor framing so they will come up behind the amps at the front of the room. This is nothing more than not wanting to have cables on lifters running along the wall and then out to the middle of the room.

Do any of you think there would be an issue with using either PVC or EMT conduit for the cables to run through?

Would the PVC develop any static charge as it does when when air/material of any type is run through it?

Would the metal EMT be an issue with the unshielded XLR cable laying in it?

I had thought about making wooden channels for the cables to run through but the conduit would be much easier to install.

Any thoughts?

 

[Speedskater]

Many recording studios run their mic level balanced analog audio cables through PVC or EMT conduit.
Balanced XLR analog audio cables are shielded.
Using conduit solves the building code rule problem about in-wall cables.

 

[Brad225]

My cables are Shunyata Altair XLR's and they are not sheilded. That's where my question comes from. Based on that what do you think Speed?

 

[eknuds01]

I think people have been running cables in, or through, plastic materials for many years.

I think as you run the cables away from any electrical lines you won't have any electrical interference issues. I also wouldn't worry about the static charge of the PVC pipe too much. I think you'd have to have some motion, or rubbing, to build up that charge and create an arc of some sort. Also, maybe you could ground the PVC material in some fashion too. Perhaps the use of screws and bare wire would can be used to help ground the pipe.

Erik

 

[sleepysurf]

Brad, you can always conduct an experiment comparing the sound with cables run directly (over carpet +/- elevators) and then via the conduit. Being balanced cables I doubt there'd be any effect, at least "noise" wise.

 

[Speedskater]

Wow, Shunyata Altair XLR's! Aren't they about $500 per yard? I can't find any technical information about them on the web. Are they really symmetrical balanced analog audio interconnects? What's attached to pin#1 ?

 

[slowGEEZR]

Mogami unshielded balanced interconnects sound great in my system. Inexpensive, too. An 8 meter pair of balanced interconnects with Neutrik XLRs is only $239. http://www.10audio.com/market.htm

 

[Brad225]

Fortunately I already have 7 meters of Altairs to make the run. Thanks for the suggestion though Steve I will keep in mind.

 

[Speedskater]

Getting pre-attached XLR connectors through a conduit will take some planning.

 

[Speedskater]

Mogami unshielded balanced interconnects sound great in my system. Inexpensive, too. An 8 meter pair of balanced interconnects with Neutrik XLRs is only $239. http://www.10audio.com/market.htm

Mogami has the best technical cable catalog available:

http://www.mogamicable.com/pdf/Mogami_Tech_cat2011.pdf

But I don't see any "unshielded" balanced interconnect cables?

 

[Brad225]

Getting pre-attached XLR connectors through a conduit will take some planning.

I haven't measured them yet but I think 1" conduit for each cable should do it.
I send an email to Grant at Shunyata to ask about the conduit and what the pin layout is. I will let you know.

 

[slowGEEZR]

Mogami has the best technical cable catalog available:

http://www.mogamicable.com/pdf/Mogami_Tech_cat2011.pdf

But I don't see any "unshielded" balanced interconnect cables?

When I think of shielded cables, I think of some sort of metal shielding, to protect from unwanted RFI, etc. Perhaps we have a disconnect on what a shielded cable means. I may be wrong (it wouldn't be the first time), but I don't think the cable I have has that metal shielding, at least it is not visible nor apparent, as in increased diameter or decreased flexibility, as in my shielded RCA terminated cables.

 

[Speedskater]

The shield is the copper or aluminum wire that is spiraled or braided around the inner conductors. Although sometimes it's a thin aluminum foil. You can see the shield in many of the catalog cut-a-way photos.

 

[zaphod]

a few thoughts.

Brad, on my last room I did similar to what you are considering. popped the unbalanced RCAs on the ceiling near the surrounds and sub. then i mounted the amps on the wall. you can make it out in the pictures of my system. the white hoses are the speaker cables.

i used canare starquad cable which allowed me a shielded unbalanced run. it got rid of the hum problem i had with cheap unshielded unbalanced cables that i had outside of the wall.

I ensured that i stayed far far away from AC lines, and crossed them at 90 degrees when i could not. i drew out the lay of the AC lines and then figrued out the best path for the signal lines which was short and AC free.

One spot that gave me grief was a beam that had 7 (SEVEN) AC lines running on the side away from where every single channel's line level had to go. No way around it. Since it was at 90 degrees, and 7 inches away (with the beam ensuring separation) i should have been good, but to be sure, i ran 10 or so lines of copper tubing for that section of the IC runs. I have pictures somewhere of the construct. i considered also grounding out the copper tubes but didn't in the end didn't need to as the floor level was pretty darn low.

The final thought i have is that if you put in 1" conduit to allow the XLR ends to get through, then for any 2X4 studs, that is approaching 1/3 of the stud width which is where structural strength starts to get hit. no problem for joists.

Sure am glad that where I live there low voltage cable can be run without conduit. The room in our [no longer] new house would kill the budget with conduit alone

Oh, and one final, final thought - for conduit, consider flexible smurf tube for easier runs and always leave a string inside the conduit

 

[slowGEEZR]

The shield is the copper or aluminum wire that is spiraled or braided around the inner conductors. Although sometimes it's a thin aluminum foil. You can see the shield in many of the catalog cut-a-way photos.

Thanks for the catalog link, Speedskater. I checked my cable number and it is the NEGLEX High Def Mic. cable, no. 2534. It is indeed, shielded. It is only about 1/2 the diameter of my shielded RCA interconnects, so I incorrectly assumed it wasn't shielded. Here's a little blurb on the cable...

"Reference Standard NEGLEX Quad High Definition Mic. Cable
NEGLEX No.2534 has become popular around the world as the
standard for high quality digital and analog recording."

 

[Brad225]

Wow, Shunyata Altair XLR's! Aren't they about $500 per yard? I can't find any technical information about them on the web. Are they really symmetrical balanced analog audio interconnects? What's attached to pin#1 ?

Pin#1 is ground according to Shunyat. What is a symmetrical balanced analog audio interconnects?

 

[Speedskater]

Actually Pin #1 is a shield, it's not part of the audio ground. Sometimes the shield is not connected at the receive end.
The symmetrical part is when both signal conductors have the same capacitance to the shield. This is not true in all two conductor shielded cables. Some have different insulation thickness on each of the conductors. The ones with a foil shield and a drain wire are often asymmetrical. This asymmetry affects higher frequency interference rejection. It takes good machines to make good balanced interconnects.

 

[Brad225]

Thanks Zaphod, I had previously noticed your amps on the wall looking at your system pics. Thought it was an interesting approach to mount amps near your speakers.

The conduit should be an easy install as I need to raise the floor of the room 4" with new framing and sub floor. The room had at one time been a porch and is lower than the level of the hallway outside the door. I can place the conduit and junction boxes where I need them and frame over the conduit.

The dedicated circuits wiring in the room runs through the floor framing of the existing floor structure and up into the walls so it shouldn't be an issue.

The smurf tubing being flexible is a good idea. I have used it in the past but had not seen it in 1". I will check into it.

 

[Brad225]

Now that you explained what symmetrical thing is I remember reading on the Shuntata site when Altairs were still in production that the capacitance is the same in both signal conductors. They chose not to use foil shielding for the exact reason you mentioned.

Thanks for the info.

 

[zaphod]

The smurf tubing being flexible is a good idea. I have used it in the past but had not seen it in 1". I will check into it.

we have it in orange for our fiber runs in the 1" size - and 3", but that doesn't interest you unless you are oct-wiring a set of McIntosh towers.