[cpalcott]

What would you all recommend for a dedicated line in a high RF zone? My biggest concern is the electric wiring acting as an antenna, picking up RFI from two radio transmitters (one AM, one FM) , both less than 2 mile from my house.

Cable: Would a Metal-Clad (MC/BX/AC-HCF) be best/sufficient or should I run Flexible Metal Conduit and run my own wires through it? What brand would you recommend for both? I am assuming having twisted Hot/Neutral is a good idea. I have read you can't count on the MC cables having this (some do, some don't). Some have said Romex 4-conoductor cable does come pre-twisted. They just removed the plastic sheath and run the pre-twisted cables through the FMC.

Outlet: Would an Isolated Ground receptacle like the Voodoo Hubbell IG8300H be best? Or would a non-IG outlet like the Porter Ports suffice?

Grounding: What is the best practice for grounding a conduit dedicated line? Do I need to use a 4 conductor cable (hot, nuetral, and two grounds)? Do I need to use a metal box? One ground to the outlet itself, the other to the metal box? Does the grounded metal box act as a farady cage to the outlet itself?

What is the best combination to ward off RFI?

[ctviggen]

In my house, I ran EMT conduit from the breaker box to a metal box where I have two cryogenically treated, isolated ground outlets. I also ran two independent sets of THHN wires (10 gauge) (each set has hot, neutral, ground), which I had cryogenically treated.  Further, I ran a separate ground wire for the metal box (sometimes required to ensure the box remains grounded if the EMT gets separated).  Each outlet is on its own 20 amp circuit, although I put them on the same phase.

There are codes for the diameter of the conduit based on the size and number of wires running in the conduit.  I went one diameter larger.  I had everything inspected. 

Theoretically, the tubing and metal box (and I also used a metal plate for the cover) should be a Faraday shield.   

As for your other questions, I can't answer them.  For instance, I can't see where two grounds for a single outlet would be useful. 

[Mike B.]

We are pretty much screwed living in a tech world with a wide variety of airborne signal devices. My approach for a dedicated line would be to use a new circuit breaker, and run a 10-2 wire to the outlet. I would attack the noise at the outlet. Attention to making all connections tight is important.

[cpalcott]

Just to clarify, you ran two sets of THHN wire, each set containg hot/neutral/ground, plus an additional ground for the box for a totol of seven wires, each outlet/circuit having its own hot/neutral/isolated ground, plus a ground wire for the box. If I am reading this corectly, you had 3 ground wires, right? Did you run the ground wire for the metal box inside the conduit? Did you bond the EMT at the box and the panel? Did you twist the hot/neutrals but not the grounds, or did you twist the sets of three together and run the box ground untwisted?

In my house, I ran EMT conduit from the breaker box to a metal box where I have two cryogenically treated, isolated ground outlets. I also ran two independent sets of THHN wires (10 gauge) (each set has hot, neutral, ground), which I had cryogenically treated.  Further, I ran a separate ground wire for the metal box (sometimes required to ensure the box remains grounded if the EMT gets separated).  Each outlet is on its own 20 amp circuit, although I put them on the same phase.

There are codes for the diameter of the conduit based on the size and number of wires running in the conduit.  I went one diameter larger.  I had everything inspected. 

Theoretically, the tubing and metal box (and I also used a metal plate for the cover) should be a Faraday shield.   

As for your other questions, I can't answer them.  For instance, I can't see where two grounds for a single outlet would be useful.

[ctviggen]

Just to clarify, you ran two sets of THHN wire, each set containg hot/neutral/ground, plus an additional ground for the box for a totol of seven wires, each outlet/circuit having its own hot/neutral/isolated ground, plus a ground wire for the box. If I am reading this corectly, you had 3 ground wires, right? Did you run the ground wire for the metal box inside the conduit? Did you bond the EMT at the box and the panel? Did you twist the hot/neutrals but not the grounds, or did you twist the sets of three together and run the box ground untwisted?

I had three ground wires, one for each of the outlets, and one for the box. I did run the ground wire for the box inside the conduit.  This ground wire is solely in case the EMT would somehow not have a complete ground/get disconnected (in my case, the only way that would happen is if the house is demolished; nonetheless, since you can't see the EMT because it's behind drywall, I ran an extra ground; the inspect said it wasn't required).   The EMT is bonded solely by screw on connections at both the box and the panel.  They do make screw on connectors with grounding screws for ground wires though.  I decided that was probably overkill.  I mean if there's metal to metal contact from the breaker box to the outlet box, there should be no extra reason to add more ground wires. 

I did not twist any wires together.  I'm not sure what purpose that would serve.   Also, you have to create the EMT pathway THEN pull the wires.  I had over 270 degrees of turns (360 is the most you can have without a pull box) (I think 3-90s and a 22.5), and it was very hard to pull 7 10 gauge wires even using the next higher diameter of EMT.  If you decide to twist the wires, I'd seriously consider grease and perhaps going with even larger diameter EMT.  Also, I had less than 30 feet to pull.  If you have 50-100 foot runs, it's going to be a tough pull.

[CSI]

I live in a typical suburban neighborhood which means that everyone on the grid is running computers and other microprocessors by the dozens, all of which tend to dump garbage back onto the line. In addition to the general grunge I was picking up the occasional airborne RFI as well.

My solution:

Ran a dedicated line to my equipment rack.
Put an isolation transformer (117v in 117v out) between the line and my gear.
Kept all IC's and speaker leads as short as possible to avoid the "antenna effect".

Results? Absolute dead silent background. A very worthwhile investment IMHO.

Footnote: You have to find a transformer that is quiet enough to use in your listening space - most transformers are for outside installation and way to noisy. Mine is a Richard Gray (just the iso- transformer, not the power conditioner which may or may not be suitable for your system and which won't solve these problems on its own). Full disclosure: Years ago I did some sales work for Richard Grays Power Company. I have no financial interest in them and have been out of touch for some time.

[cpalcott]

ctviggen...It has been suggested that twisting the hot and neutral will help in warding of RFI.  Fortunatley I would not have as many turns as you had. Basically, mine is just up, over and down. Would there be any potential issue with running the wires for both circuits ib the same conduit? Could they interact with each negatively?

CSI...Yep, I have tried an isolation transformer (Topaz) and power regenerator (PS Audio) and am currently using a paralell power filter (Audience) in conjunction with a whole-house surge protector/filter (Environmental Potentials EP-2050). All have made nice improvements to the sound, but none have taken care of the brittlle and sibilant high end I am experiencing. Something that, after considerable troubleshooting, I am chalking up to airborne RFI effecting either the equipment itself or coming through the AC wiring or both.  Was thinking of trying a BPT unit since it is one of the few that does both iso transformer and paralell RFI filtering as well as RFI shielding. Also will be auditioning an Uberbuss soon.

[Geardaddy]

CSI, have you ever fiddled with whole house ionic grounding systems? 

[Occam]

...am currently using a paralell power filter (Audience) in conjunction with a whole-house surge protector/filter (Environmental Potentials EP-2050)....

Nice kit, but the Audience Adept power conditioners are not parallel power filters, rather they are series inductance [toroidal common mode choke(s)], parallel capacitance (2nd order lowpass) filters. Any filter that provides isolation contains a series impedance element.

FWIW,
Paul

[Meguerra]

This thread has been very helpful in eliminating RFI noise in my system. Thanks guys

[Folsom]

Nice kit, but the Audience Adept power conditioners are not parallel power filters, rather they are series inductance [toroidal common mode choke(s)], parallel capacitance (2nd order lowpass) filters. Any filter that provides isolation contains a series impedance element.

FWIW,
Paul

It's also about the only thing mentioned so far that does something for RF.

The problem with RF is it localizes because of inductance making low resistance wires at DC and 60hz, into higher impedance at RF range. This means more local attenuation has a greater affect. That makes power conditioners and in-component decoupling good.

Well made powercords help, conditioners, shielded cables, and internal filtration/decoupling. Aside from having a safety ground wired directly to stereo outlet and being ran in same romex, a very expensive special block for the earth ground can offer very low impedance. I'm not sure where or how you get that. Recording studios use them when possible.

[Speedskater]

Some of the ideas in the earlier posts came from these papers.
For those interested in Audio/Video systems and AC power and EMI/RFI here are the papers that now apply:

***************************
Middle Atlantic

"Power Distribution and Grounding of Audio, Video and Telecommunications Equipment"
"Addendum to Power Distribution White Paper"
http://www.middleatlantic.com/resources/white-papers.aspx

**************************
Jim Brown

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

"RFI, Ferrites, and Common Mode Chokes For Hams" skip the parts that only apply to Hams
http://www.audiosystemsgroup.com/RFI-Ham.pdf

"RF Interference in Audio Systems"  Power Point
http://www.audiosystemsgroup.com/AES-RFI-SF08.pdf

50 more Jim Brown papers:
http://www.audiosystemsgroup.com/publish.htm

*************************************
Bill Whitlock

"An Overview of Audio System Grounding and Interfacing"
2012 version - more pictures and less words than the 2005 generic seminar paper
http://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf

"UNDERSTANDING, FINDING, & ELIMINATING GROUND LOOPS IN AUDIO & VIDEO SYSTEMS"
'2005 Generic Student Seminar Handout' AN007
http://www.jensen-transformers.com/application-notes/
you now have to register at Jensen Transformers

"Ground Loops: The Rest of the Story"
http://xa.yimg.com/kq/groups/20963848/268252969/name/Whitlock-Fox+-+Ground+Loops+.pdf

***********************************

[Speedskater]

A thread from DaveC113:
"Power Distribution and How Power Cables Can Be Audible"
http://www.audiocircle.com/index.php?topic=128309.0

and a post from DaveC113:
...you will see why it's best to have everything plugged into one receptacle. If you use multiple lines there is more potential for voltage differences between the components that are on each circuit, as the grounds will be tied together way back at the main panel, which may result in more noise. A 20 amp circuit is more than enough for most any home system. If you do need more power then it's best to place a breaker box as close to the receptacles it will be serving as possible. With one line the component's grounds will be tied together as close as possible to the components, which is more ideal.

[Quiet Earth]

...Yep, I have tried an isolation transformer (Topaz) and power regenerator (PS Audio) and am currently using a paralell power filter (Audience) in conjunction with a whole-house surge protector/filter (Environmental Potentials EP-2050). All have made nice improvements to the sound, but none have taken care of the brittlle and sibilant high end I am experiencing. Something that, after considerable troubleshooting, I am chalking up to airborne RFI effecting either the equipment itself or coming through the AC wiring or both.

Hi cpalcott,

I don't want to sound facetious, but how do you know that something in your audio system is not responsible for the brittle sibilant high end? How do you know that the problem must be coming from the AC power line? Is it possible that you are expecting too much from power conditioning alone?

If you are just splitting hairs in refinement then OK, I totally get that. But if you have a real sibilance/brightness issue then perhaps you need to focus your efforts elsewhere. (I don't know what your system is so I am guessing.)


The only thing that I might suspect from your description is that your whole house surge suppressor could be contributing to the problem. I have never used one those but I wonder if it might be responsible for the brittle sibilance issue. It seems to me that most high end audio gear can do without a surge suppressor, so if something in the house really needs one then just use it locally/as needed. (I'll probably get in trouble for saying that.  )

[ctviggen]

I've had multiple whole-house surge suppressors and never noticed a sibilance issue.  (I had multiple surge suppressors because they kept failing, and never from a surge that I could tell.  After three of them failed, I gave up.)

[Early B.]

Well made powercords help, conditioners, shielded cables, and internal filtration/decoupling.

It's interesting that some people spend thousands of dollars on power conditioning, but use cheap ICs and power cords, then expect their systems to have a completely black background. I don't know if that's case here, but just making the point that power conditioning is one part of a "power management" system which includes the "power lines" (ICs, power cords, and speaker cables). In fact, IMO, the foundation of a two-channel audio system is power management, not an amp, source or speakers.

 

[ctviggen]

It's interesting that some people spend thousands of dollars on power conditioning, but use cheap ICs and power cords, then expect their systems to have a completely black background. I don't know if that's case here, but just making the point that power conditioning is one part of a "power management" system which includes the "power lines" (ICs, power cords, and speaker cables). In fact, IMO, the foundation of a two-channel audio system is power management, not an amp, source or speakers.

From an electrical engineering standpoint, I can see that metal conduit and isolated grounds make a difference in electromagnetic field rejection.  It's much harder to see that ICs, power cords, and speaker cables can do the same (except for balanced interconnects).  Or at least it's hard for me to see, as most ICs, power cords and speaker cables really aren't designed that way.

[Speedskater]

Power cords can and do act as interference antennas (but receiving and transmitting).  It's up to the skill of the circuit designer to deal with these problems.  A well designed product should not need a power conditioner.

[Folsom]

I wouldn't be an audiophile if I didn't have power conditioning.

However I have yet to invest in rather expensive power cords. They tend to be doing what a conditioner does, at lower levels.

To say a good stereo doesn't need power conditioing isn't really much of a statement Speedskater. Does it mean all equipment should have built in AC filters? There's so many levels of noise reduction all the way to the speaker, and it's all basically unnecessary for you to have music playback, but all of it makes it better. The arguement that a well designed piece of equipment has ripple capacitors is the biggest damn flop there is since they all do, and they all benefit anyway before and after from forms of noise reduction. That's also despite almost all equipment has improperly designed PCB ground designs in minor and major ways at nearly all price levels.

[Early B.]

I wouldn't be an audiophile if I didn't have power conditioning.

Ain't that the truth!