John Sayers' Recording Studio Design Forum Archive

Hey Aaron! (and forum!)
Yea, it's been a LONG time since we've talked. I kinda feel like an ol' man when I come on here now. Guys that were on here when I uh, "started"...in 2005 have FINISHED their studios LONG ago. Life, children, grandchildren, my Church, my job have simply PUSHED ASIDE my dream of years ago, BUT a decision had to be made concerning all the money I had already invested in construction and whether to tear it down and make a "movie room" or FINISH the studio. Now Aaron, I know YOU know where my vote went...TO FINISH IT!! So, here I am, back asking what I need to get this done.

I'm at the point now where I'm ready to do the electrical. Man, I tell ya, finding an electrician to do the Star Ground system using MC cable or FMC with THHN conductors threaded has been an ABSOLUTE, WITHOUT A DOUBT, SURE FIRE, BETCHA HOUSE ON IT, 100% NIGHTMARE!!!! I simply decided that I would just run/route the wiring myself (with consultation from a licensed electrician). I don't plan on hooking anything up to the sub panel or any receptacles or light switches, but I CAN route them up to their termination point. I have 1 or 2 estimates I may get for someone to do ALL of it, but I'm tired of calling to GET estimates.

(Ok, I'm done with my preamble...on with my question...)

In trying to save $$$ to get this done, I saw I could eliminate some receptacles that are not "priority" receptacles by using romex instead of MC cable or FMC with THHN conductors. I have 10 breakers that will be dedicated to the studio itself. ALL breakers that will power mixers, keyboards, instrument modules, amps etc etc etc will run on selected 20 amp breakers using MC cable or FMC with no. 12 THHN conductors. For all other receptacles (general-use stuff), I was thinking about using romex. "General use" means these are receptacles that will hardly ever be used (there for code reasons), or will be used for something that will NOT be for recording (ie: ethernet switcher, satellite tv reciever, etc). ANY electronic item that is used in the recording domain will be plugged into an IG receptacle. The lighting will be on it's own seperate breakers also. I am running 3 dimmer lights on the same breaker using (3) Staco Variac 501 or 501C transformers. The dimmer wiring will be using MC cable or ran in STEEL FMC (using no.12 THHN conductors). The other lighting will be on other breakers and wired with ROMEX.

If the studio IG receptacles are on THEIR OWN seperate breakers and ALL lighting are on different breakers, would it cause a problem with me trying to maintain "no ground loops" (using the Star Ground system) by having some of the receptacles and lighting in the sub panel box wired using regular romex BUT on their OWN seperate breakers?

I wouln't think it would matter as long as any IG receptacles and romex receptacles are NOT in the same breaker, but man, I could be "wrong as all outdoors" (we say that in Kentucky).

(By the way...the ISOLATED conductor on the IG receptacles are running to a seperate box with a ground bar that's tied to the same stake in the ground outside the house that the main breaker panel is tied to...via Rod's book)

Anyway, Aaron or anyone else who wants to chime in, feel free to do so. I'm off this week and next week so I've got TIME to get this done...If I don't get it done, and ya'll don't hear from me soon, you'll know the "beatdown" from my wife has begun and you can look for my next post..."Recording Equipment For Sale"...

This sounds bad, very bad. You are way over thinking the whole project. Too many this and too many that's. Just calm down, I'll get back to you tomorrow.

Just what are you building? One control room and one studio? or what?
Any basic drawing or equipment lists or anything?

Sounds "bad"...very "bad"???
Hmmmmmmmm....
Well Speedskater, no disrespect, but I guess we'll have to agree that we DIS-agree...

Ok, I'll do this quickly...
I'm doing a Star Ground system with IG receptacles. I'm trying to save "some" money by running regular receptacles using the standard hot, neutral and safety ground hook up via Romex. This will save me from buying extra IG receptacles and additional MC cable that I don't need (I already explained why in my previous post).

All I'm asking is if I put the standard receptacles on seperate breakers from the IG receptacles would that effect the integrity of my Star Ground system/ground loops. (Maybe it wouldn't effect the integrity, but I would be skeptical to put IG receptacle wiring in the same breaker with standard receptacle wiring...at this point)

What am I building? Well, a studio, that has a control room and vocal booth. I can get into more detail (Man, do I have data and drawings...) when I know specifically what you feel is "bad" and "overthinking" about my post.

Now, I'll admit I might have rambled somewhat, but I try to be very detailed about what I'm doing...(uh, maybe sometimes TOO detailed)...

SO...if you take being DETAILED + RAMBLING (a little) I guess you MIGHT come up with "This sounds bad, very bad. You are way over thinking the whole project. Too many this and too many that's. Just calm down"

I really look forward to your suggestions on simplifying my "overthinking" for this area of my project.

Thanx for the input tho'!!!

I'll try to only touch one point at a time.
This is mostly about the US type AC power system.

Three most excellent papers about AC power and audio/video systems:

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

The Bill Whitlock of Jensen Transformers Seminar paper
http://www.jensen-transformers.com/an/g ... eminar.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

For other readers.
Some US AC power wire types.

'NM' - Non-Metallic - Romex®
'MC' - Metal Clad - a flexible spiral cable supplied with wires. Most 'MC' is not suitable for Isolated Ground (IG)
'FMC' - Flexible Metal Conduit - a flexible spiral conduit but no wires. restrictions on grounding.
'EMT' - Electrical Metal Tubing - a stiff metal conduit but no wires.
'ENT' - Electrical Non-Metallic Tubing - PVC - LB - a stiff plastic conduit but no wires.
'AC-HCF' - Armor Clad for Health Care Facilities' - at one time this was thought to be the best choice but after further investigation, it's not.

I'll skip the or less popular systems.

For a long time 'EMT' was also thought to be the best choice. But a recent Bill Whitlock paper suggests that for most of us, Romex®(NM) is the way to go.

Some US AC power wire types.

Thanks for that list, Speedskater! You crazy yanks seem to have a terminology all of your own, for electrics.... Very useful to get those acronyms.

Here in Chile, most wiring is done with the equivalent of your ENT (PVC conduit), which goes in fast and makes for easy wiring replacement / change / upgrade. Sort of "future proofs" the place. I use it all the time. The wiring itself done with three individual conductors PVC coated solid copper conductors (live, neutral, ground). Outlets are non-polarized, center pin is ground. Ground is bridged to neutral at the main panel. Everything is 220 V, 50 Hz single phase (380 V three-phase). Makes it darn simple to wire places here, compared with some of the loops you guys have to jump through!

---

Stan, now that I understand some of those abbreviations you were using, I tend to agree with Speedskater: what you propose is unnecessarily complex for a small studio. For example, I don't see the need for 10 breakers in a studio that consists of one control room and one booth. 4 or 5 would be plenty, I expect.

But to answer your question: No, putting circuits on separate breakers does not affect your grounding system, since the ground does not go through any breakers: only the live conductor is interrupted by the breaker. Grounds and Neutrals are continuous, and go to their own buses in the panel. The breakers have no effect on the grounds (unless your breakers in the USA are a whole lot different than what I'm used to from Australia, South Africa and Chile!).

- Stuart -

I meant to get back to this thread sooner, but got distracted.

I want to cover some common mis-understanding, mis-conceptions and myths that some IT technicians, industrial instrumentation technicians, audiophiles, pro-audio engineers and we can't leave out electricians have about AC power. This is mostly directed at US type AC power systems.

Let's start with:

a] Ground rods in the dirt.
b] Isolated Ground (IG) circuits.
c] Star grounds.
d] Maximum circuit current or power.

I type real slow, so I'll only do one at a time.

Ground rods in the dirt

This is about the electrical system ground rod or rods (or system, it may be more than just rods). The ground rod is connected at the building AC power service entrance area to the main breaker box (panel board) via the GEC (Grounding Electrode Conductor) wire.

As a side note: people may not recognize there is a difference between the terms grounded and grounding.
Bonded simply means to tie together, and we are usually talking about grounding conductors when we use the term.
I do agree that using the full term "equipment grounding conductor" seems to clarify things a little better, which I think the NEC does this pretty well, but many still only see the word "ground" in there and seem to disregard all the supporting text.
People seem to understand what is usually being talked about when you use the word "neutral" problem is there are things like corner grounded delta systems that still have a "grounded conductor" but do not have a "neutral". But the rules for this "grounded conductor" are the same as they are for a neutral in a system where the neutral is the "grounded conductor".

From 2008 NEC:
Bonded: Connected to establish electrical continuity and conductivity.
Ground: The earth.
Grounding: Connecting to ground or to a connective body that extends the ground connection.
Grounded conductor: One of the conductors needed for energy transfer that is connected to ground.
Grounding conductor: An additional conductor connected to ground at one end, with the other available for safety grounding.

Now back to the 'ground rod'. The ground rod's only purpose is to hold the electrical system potential near Mother Earth's potential during nearby thunder storms or power company high-voltage accidents. This is NOT the same function as a 'lightning rod' during a direct strike!

In every serious book about AC power and IT systems or industrial instrumentation systems or audio system the author writes my above statement (only with much better wording).

The myth is that the noise and leakage and interference will go to the 'ground rod' then use it as a sump or sink and just disappear!

The truth is that all these noise and leakage and interference currents just want to get back to their voltage sources and the dirt is seldom a good path. In fact that dirt is often a very noisy place with leakage currents going all sorts of directions.

Good audio quality does not require a connect to the dirt, but safety sure does.

Good info Speedskater...
I'm NO electrician, but I'm checkin' it out...at least what I can understand!!... uh, as I have time to read it...
Thanx man...keep it comin...I got my on ya!

Soundman2020...
I've got reasons why I'm using 10 breakers. They may be valid...maybe not...
I'll post more info about this when Speedskater is thru posting his info...
Thanx tho'...

I keep meaning to get back to this, but right now I have to go:


SPEEDSKATING (Summer Ice)

Resources

These are the best three papers on AC power and audio/video systems:
*************************
The Middle Atlantic paper:

You can download the paper without signing in.

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

http://www.middleatlantic.com/power.htm
http://www.middleatlantic.com/pdf/PowerPaper.pdf
http://www.middleatlantic.com/pdf/Power ... dendum.pdf

**************************
The Bill Whitlock seminar:

"UNDERSTANDING, FINDING, & ELIMINATING GROUND LOOPS IN AUDIO & VIDEO SYSTEMS"
2005 Generic Seminar Template
Instructor - Bill Whitlock
http://www.jensen-transformers.com/an/g ... eminar.pdf

also a newer PowerPoint with notes of his seminar:
http://centralindianaaes.files.wordpres ... s-v1-0.pdf
****************************
The Jim Brown paper:

'Power and Grounding For Audio and Audio/Video Systems -- A White Paper for the Real World'
http://www.audiosystemsgroup.com/SurgeXPowerGround.pdf

Now this is special...
About a year ago I got into a discussion on here about Romex & MC cable. I did a little research and posted some info HERE... viewtopic.php?f=16&t=18496
and HERE...viewtopic.php?f=16&t=18485

Well, SPEEDSKATER turned me on to Bill Whitlock of Jensen Transformers (PROPS to ya' SPEEDSKATER! Also thanx to Soundman2020 for his help also!). I decided to send email to Bill Whitlock concerning questions I had about things talked about in the posts. Mr. Jenson knows what he's talking about...make NO doubts about that. If ya' NEVER HEARD OF HIM, look him up! You can start here...

"UNDERSTANDING, FINDING, & ELIMINATING GROUND LOOPS IN AUDIO & VIDEO SYSTEMS"
2005 Generic Seminar Template
Instructor - Bill Whitlock
http://www.jensen-transformers.com/an/g ... eminar.pdf

also a newer PowerPoint with notes of his seminar:
http://centralindianaaes.files.wordpres ... s-v1-0.pdf

Basically, Mr. Whitlock's response to my email answers questions concerning the use of Romex cable, MC cable and THHN wiring (THHN wiring in conduit). The chart on page 35 in the link below shows how the different cables/wiring are ranked. You can read the info in this post along with the other two electrical forum posts listed above if necessary. Hopefully you'll get a clearer idea of what "I", "we" were rambling about in all the posts. All page references to my questions below can be found here...

http://centralindianaaes.files.wordpres ... s-v1-0.pdf

Anyway, below is the email I sent that he actually took the time to read and respond to. The letter is in it's entirety excluding non-pertinent info and contact info...
--------------------------------------------------------------------------------------------------------------------------------------------

Hi Stanley,

Thanks for writing. The questions you pose indicate that you’ve read my piece quite thoroughly … thank you. I’ve attached a copy of the 2011 AES paper “Ground Loops: The Rest of the Story” where the comparison graph originally appeared. It contains additional details about the tests and (hopefully) other useful information. You certainly may post my replies in the blog.

All that being said, I’ll happily answer your questions within your original message below (in red text).

Cordially,

Bill Whitlock, Technology Manager

Jensen Transformers, Inc.


From: Stanley
Sent: Friday, October 24, 2014 8:48 AM
To:
Subject: Re-Submitted Question from 10/27/13 for Bill Whitlock

Greetings!
As I stated...I know it's unlikely this email will get to Bill Whitlock, but I'm hoping for an "early Christmas present", so I'm gonna' go for it!

I'll try to be brief...

I'm a "seasoned" musician in the process of trying to build a home recording studio. The seminar notes for "Overview of Audio System Grounding & Interfacing" were forwarded to me to check out. I am NOT an electrician in any shape, form or fashion, so I can't speak in any "technical" terms for what I am talking about in this email. There is a web site with those of us that are trying to build Recording Studios where, let's say "questions" were raised on Romex being better than MC cable. For some of us (who are interested) the answer to my questions may determine the type of wiring that we may use when building our Studios.

Basically, this is it...
On page 35 you have a chart that shows different wiring types and their effect with magnetic induction. The test that were done looked to be using 3 conductor wiring including the MC cable. On the chart, MC cable was slightly better than Romex.

Ok, let me back up...

Page 31...

• Imperfect cancellation magnetically induces voltage over the

length of the nearby safety ground conductor

• Strongly affected by geometry and proximity of wires

• Highest voltages with randomly positioned wires in conduit

• Lower voltages with uniform geometry of Romex®


Page 32... shows the magnetic "null" zone in Romex...


Page 33...

Wires randomly positioned in conduit

produce the worst possible results!

Page 34... shows how the test were done...

As I stated...On page 35 it shows the chart with different types of wiring tested for magnetic induction. The best wiring type was twisted load-neutral (I think that's what the LN means... yes)
I checked with 3 different MC cable manufacturers on their manufacturing process to see if
they "twisted" any of the wiring in their MC cable...

Here is what I wrote in a blog response about this issue...
"Anyway, an update...
Southwire engineering called me back and stated their wire is twisted. He said it's twisted clockwise so many feet then counterclockwise so many feet.

(In pictures of twisting machinery I’ve seen, a rotating platform of wire reels pays out the individual wires as the twisted cable is pulled onto another reel. This “reversal” thing is new to me, but there may be a good reason.)

AFC engineering called me and calculated their "conductor twist" in MC cable is twisted 2.3 to 2.4 times per foot.

So, all 3 cable manufacturers (AFC, Southwire and Encore) stated they do twist their wire in the MC armor. This MAY have something to do with why the Aluminum MC produced the 2nd best results in the test Bill Whitlock conducted."

Ok, here's my questions...
1.) Is the reason MC cable was second best of the wiring types tested due to, or is partially due to the twisting of the wire?

To minimize induction of noise into the ground wire, there are two strategies: 1. Because, at any instant in time they carry the same current in opposite directions, put these two wires as close to each other as possible so their magnetic fields neutralize/cancel each other. Tight twisting is the most practical way to do this; and 2. Put the “victim” ground wire as far away as possible from the current-carrying pair. Because the magnetic fields are very intense close to this pair, the closer the ground wire gets to them, the more critical its exact positioning becomes. Since MC includes the ground (green) wire in the twist, it’s not as good as letting the green wire assume a random position farther from a twisted pair. For the same reason, Romex (type NM) is subject to minor position deviations of the “centered” ground wire simply because it’s so close to the pair. The graph plot for Romex was for a pretty pristine straight length. In typical application, Romex gets bent, which will surely make it fare worse since bending will slightly alter positioning. I may do a follow-up study of this as well as the effect of “stacking” and bundling of Romex in real-world residential wiring.

2.) Would multiple conductor MC cable in steel galvanized armor (let's say 12/4 with ground MC) be worse (as far as magnetic induction and due possibly to the "bad proximity of the wires") than 3 conductor or 4 conductor Romex with it's "uniform geometry"?

I have to confess that I’m unfamiliar with the geometry of these multi-conductor types (I’ve never seen 3 or 4-conductor Romex. But, once you understand the principles I summarized in the previous answer, you can fairly-accurately predict the behavior of any arrangement.

3.) For those who desire to pull THHN wiring through Conduit; Is the best way to set up "twisted" wire in the conduit to have all the grounds in the middle with the hot wrapped around the grounds in one direction and the neutral wrapped around the grounds in the opposite direction?
(If this is wrong, how should the twist be done?)

Nothing that exotic is necessary! As shown in Fig. 4 of the attached paper, the ideal is to pre-twist the current-carrying pairs (typically BLK and WHI) only and then pull the pairs and their ground (GRN) wires into the conduit, letting the ground wires assume random positions. My co-author, Jamie Fox, was the specifying engineer for the AC power at the new Bing Auditorium at Stanford University. He specified twisted L-N pairs for all the AV circuits as well as isolated grounding. He had the L-N pairs pre-twisted by Sourcery Wire & Cable (http://www.sourcery-llc.com/) in Los Angeles. According to reports, the AV systems were remarkably noise-free right from the start with no troubleshooting of noise problems or modifications required. Bear in mind that, if multiple circuits run in the same conduit, all of the circuits must have twisted L-N pairs. Otherwise, one branch circuit can induce noise into the ground of another. And, of course, little or none of this benefit will be realized unless isolated-ground (IG) outlets are used … if J-boxes and metallic conduit are used. In residential settings with no metallic conduit and plastic J-boxes, the system is already “isolated ground” by definition.

4.) Which is better for the inner (THHN) wiring in MC cable...Aluminum armor or Galvanized Steel armor?

You can see from the plots in the attached paper that steel has little effect compared to plastic or aluminum. Steel increases coupling by 4 or 5 dB at frequencies below 10 kHz but decreases coupling above 10 kHz. The change above 10 kHz is likely due to eddy current effects – both aluminum and steel would likely do this. More subtle details to study!

5.) "If" you respond...Hmmmmmmm...
Scratch that...I'm "gonna" BELIEVE...
WHEN you respond, can I put your response on the Studio Blog?

Yes, I just hope folks will appreciate that this is real science, not audiophile magical thinking, and that I have little to gain from making the information public. Seems to me that some enterprising electricians could specialize in low-noise wiring for AV systems – learning this technique as well as using isolated grounding, separately-derived power, etc. as discussed in the Middle-Atlantic white paper, which I helped write, listed as a reference in the Whitlock-Fox (attached) paper.

Well, that's it...
I'll let you go now with a "Thanx" in advance!
Sincerely,
Stanley
--------------------------------------------------------------------------------------------------------------------------------------------
Well, that's the end of the email. A big thanx again to Bill Whitlock on answering the questions and giving a clearer picture of Romex compared to MC cable and THHN wiring (THHN wiring in conduit).

_________________
Take Care and GOD Bless
Stan