Dedicated Audio Power Circuit

[Speedskater]

Most locations in North America permit rigid metal or plastic (PVC) conduit (aka tubing or trunking).
Also permitted are flexible metal or plastic (PVC) conduit.
As is Romex® and other non-metallic sheath cables.

Note that the NEC code book only applies when a location (city or state) passes a law about it. That location may chose what year code book (2005, 2008, 2011 or 2014) to use. That location may also have exceptions and additions to the code book. Chicago & New York cities are examples of locations with lots of additional rules.

 

[puroagave]

"Ground Loops: The Rest of the Story"

that's an interesting paper, i've been looking into adding a dedicated line and twisted wire seems to be the way to go.

I found similar research regarding power cables recommending a twisted or braided matrix to reduce or eliminate ground loops and noise on the line. I found DIY instructions on the bottlehead site and I made up six pairs of braided wire PCs. I'm usually skeptical re cables but the improvements over molded PC was not subtle and at the very least equaled the results I got from two (expensive) aftermarket cables I had on hand.

 

[BlueFox]

This thread has me a little nervous. On Monday I am having a second dedicated 20 amp line installed for my amps. Other than using whatever 10 gauge wire the electrician buys (Home Depot?), and terminating into a Shunyata SR-Z1 outlet, there isn't anything special being done. It better make an improvement to the sound, with zero ground loop issues. Otherwise it is going to be an expensive outlet for the vacuum cleaner.

 

[Speedskater]

'Bud' everything you need to know about AC power and audio/video systems is containd in these papers:

"Power White Paper" from Middle Atlantic.com
http://www.middleatlantic.com/power.htm

The Bill Whitlock of Jensen Transformers paper
"An Overview of Audio System Grounding and Interfacing"
http://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf

The Jim Brown of Audio Systems Group white paper
"Power and Grounding for Audio and Audio/Video Systems"
http://www.audiosystemsgroup.com/SurgeXPowerGround.pdf

The Bill Whitlock paper that I linked in replay #10.

 

[Btselect]

Speedskater great post, for me after years of trial and error I've developed a electrical setup that has worked for everybody who has used it, with no ground loop issues. First and foremost I use a sub panel (installation cost factors) a Square D or GE commercial panel (because of the way the wire is attached to the breaker), a 100 amp feed using #1 copper wire or larger to meet code. The 2 hot wires have red colored insulation, the neutral or return wire has white insulation, and the ground wire has green insulation, all in a conduit that meets code. From the breaker use a minimum 1" conduit to a deep receptacle box, color wire is the same as above, wire of choice here is THHN stranded 10 gauge wire, and each component has its own dedicated circuit. Make sure to balance your load between the 2 legs. Without this setup you won't be able to proceed to the next step in the electrical setup, and believe it or not your electrical supply is severely chocked, and not on a solid foundation for your audio or home theater system.

 

[mep]

that's an interesting paper, i've been looking into adding a dedicated line and twisted wire seems to be the way to go.

I found similar research regarding power cables recommending a twisted or braided matrix to reduce or eliminate ground loops and noise on the line. I found DIY instructions on the bottlehead site and I made up six pairs of braided wire PCs. I'm usually skeptical re cables but the improvements over molded PC was not subtle and at the very least equaled the results I got from two (expensive) aftermarket cables I had on hand.

And that's how many cable companies were formed in the kitchen of their houses. Sounds like your on your way to producing mega-expensive cables.

 

[Dentdog]

First of all I should say hello. And thanks, being it's my first post and all.
I just completed having a new sub panel and six dedicated runs, 20 amp, to selected areas of a music room. After connecting some audio equipment to burn in, it all being very recent purchases, things sound quiet. The electrician does some studio sound applications and seemed unconcerned as to proximity of the romex to parallel wiring. Now, I don't hear any hum or other noise. My question is, given the sheetrock is still off the wall, should I disconnect and twist all the wires, separate the wires [much easier], or just go with it? I think I know the answer and it may be the answer I don't care to hear.

 

[Speedskater]

Are all the wires (cables) in question, Romex® power cables?
Or is a mix of power, interconnect & speaker cables?

In general 'good engineering practice' suggests that twisting any unshielded multi-conductor cable or cord is a good idea.
In general 'good engineering practice' suggests that bundling all AC power cables or cords is a good idea. (not to tight, there are rules about that)
But in most cases the differences will be negligible. (typo - negotiable)

 

[DonH50]

"negligible" ?

 

[Dentdog]

My project is at the electrical power stage, and a new sub panel and dedicated runs have been installed. I did hook up a few components for a test run and it seems pretty quiet to me. I will be installing a 25' RCA from preamp to amp, in the wall, keeping the run away from the electrical power.
As a future consideration am considering a 1 1/2" PVC for cable runs. I'm ready for the sheetrock to be repaired/reinstalled and am looking for best practices.
Don't want to close up the wall and get a ground loop hum later.

Tom

 

[zztop7]

The safest thing would be to install horizontal sections of plywood along the walls for the audio lines / fit it neatly and aesthetically / maybe 1' vertical.
This would create a chase for any future changes, and/or to correct any possible problems.
Two years from now will your components be in the same place with the same audio connections?
Unfortunately houses are very rarely built to accommodate any changes or repairs.
Actual cost of plumbing/electrical/HVAC repairs are usually a small fraction of repairing the walls afterwards.
???And how often are the wall repairs done right & look proper 6 months later???

Best to you,
zz.

 

[Dentdog]

Thanks zz. At this stage that would be easy. I thought about dipping some PVC in liquid teflon and running that. Your solution sounds a bit easier. Only concern is pulling an interconnect around a corner, no way around it however.

 

[zztop7]

Thanks zz. At this stage that would be easy. I thought about dipping some PVC in liquid teflon and running that. Your solution sounds a bit easier. Only concern is pulling an interconnect around a corner, no way around it however.

Go online to study how & where - Google >>> drilling holes in studs <<<.

OK, so it appears that you understand the "chase" is an accessible internal wall channel/passage way - Good.
"interconnect around a corner" - should be no problem. There are more structural members in the corners, but SMALL appropriate holes cut at angles through the members will not harm the structure. BAD contractors routinely TRASH the structural integrity of houses by cutting huge poorly placed holes.

Think about this -you will NOT be pulling wires though the chase / you will be PLACING wires through the holes in the studs in the chase. Changes - just neatly remove the finished plywood. Use the screws with square drives; they look better on the wall than Phillips drive.


My master bath has visible structural stainless steel pieces surrounding large removable panels that give access to all internal plumbing.

zz.

 

[proufo]

Does anyone have opinions as to the best type of electrical wire to use for a dedicated audio circuit? My current dedicated circuit is 20A romex, but I'm considering replacing it with 20A or 30A twisted wire in metal conduit.

Supposedly solid core cable would filter/attenuate higher frequencies (line noise).

 

[DonH50]

Why? I would have expected twisted pairs to have higher capacitance and thus better HF attenuation.

In the real world, unless you are in a very high EMI environment, I would not expect any significant difference between Romex and twisted pairs, though I find the stranded twisted pairs easier to handle than Romex.

 

[CGabriel]

Does anyone have opinions as to the best type of electrical wire to use for a dedicated audio circuit? My current dedicated circuit is 20A romex, but I'm considering replacing it with 20A or 30A twisted wire in metal conduit.

Len,
You can use BX wiring in a 10 gauge. This is a flexible metal clad cable that is relatively easy to install without the complexity of rigid metal conduit. It has very low magnetic field radiation with the added benefit of reduced electric field emissions. There will be no ground loops if you only have a single dedicated line. If you plan to have multiple dedicated lines, make sure that all lines are of the same type and gauge of wire and make sure they are all the same length. Even if there is a difference in distance to the outlets, cut the in wall cable to the same length. If the lines all have the same impedance to ground there will be no ground loop.

If you plan to have 3 or more dedicated lines for an audio system and the distance from the panel to the room is more than ~90 feet, you may want to consider installing a sub-panel dedicated to the audio system.

 

[Speedskater]

Supposedly solid core cable would filter/attenuate higher frequencies (line noise).

Why? I would have expected twisted pairs to have higher capacitance and thus better HF attenuation.

(In general) Cat 5 cable is both solid core and twisted pair, but it's high frequency response is excellent.

The only reasons for a twisted pair to have slightly higher capacitance are because the twisting holds the cores closer together and makes the cores length a little bit longer.

 

[DonH50]

I did not mean to imply that higher capacitance hurts HF response for transmission lines, I am familiar with those equations. What I do not understand is why solid-core cable would better attenuate line noise compared to twisted pairs. One thing that came to mind was skin effect, but that is negligible at LF. I would guess Romex would have higher inductance than twisted-pair, but again am not at all sure it's enough to provide significant difference in noise attenuation compared to twisted pair power lines. We are talking about the AC power lines in your house, yes?

 

[Dentdog]

Don H, yes my questions were mainly to address the AC power lines. Now the room is largely set as to equipment position, with the wall cut out. I do have some concerns as to the long run out of the preamp. To complicate matters the AV will have to be run back from the Plasma or DAC to the Preamp. So an interference issue is always in the back of my mind. I have enough outlets to separate digital from analog, and must admit it all came about pretty inexpensively.
The wood chase suggested above has been decided upon so this weekend should wind thing up. As of now it's very quiet and while I don't pretend to have a "golden ear" I don't hear the least amount of grain. BTW this is a great forum. Some pretty well thought out differences of opinion but a little less contentious than usual for a technical discussion forum.

Best to all,

Tom

 

[Speedskater]

Once again - three excellent papers that anyone doing AC power wiring should read.

***********************************
Middle Atlantic Products:

"Integrating Electronic Equipment and Power into Rack Enclosures"
'Optimized Power Distribution and Grounding for Audio, Video and Electronic Systems'

http://www.middleatlantic.com/pdf/PowerPaper.pdf

************************************
The updated Bill Whitlock seminar paper:
"An Overview of Audio System Grounding and Interfacing"
by
Bill Whitlock, President
Jensen Transformers, Inc.
Life Fellow, Audio Engineering Society
Life Senior Member, Institute of Electrical & Electronic Engineers
http://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf

************************************
This Bill Whitlock and Jamie Fox paper:

"Ground Loops: The Rest of the Story"
Bill Whitlock, AES Fellow and Jamie Fox, P.E.

This paper was presented at the AES 129th Convention, 4-7 November 2010, San Francisco, CA, USA

ABSTRACT

The mechanisms that enable so-called ground loops to cause well-known hum, buzz, and other audio system
noise problems are well known. But what causes power-line related currents to flow in signal cables in the first
place? This paper explains how magnetic induction in ordinary premises AC wiring creates the small voltage
differences normally found among system ground connections, even if “isolated” or “technical” grounding is
used. The theoretical basis is explored, experimental data shown, and an actual case history related. Little
has been written about this “elephant in the room” topic in engineering literature and apparently none in the
context of audio or video systems. It is shown that simply twisting L-N pairs in the premises wiring can
profoundly reduce system noise problems.

http://xa.yimg.com/kq/groups/20963848/268252969/name/Whitlock-Fox+-+Ground+Loops+.pdf