Dedicated power circuits

I have Pass Labs mono amps.  Combined they pull 740 Watts at idle.  Nice little heaters.  Until I exceed the Class A bias current that wattage is constant.  I think they are Class A up to around 80 Watts if memory serves.  
My preamps and DAC use tubes so their wattage is a little higher than a typical SS setup.  The line stage and phono stage preamps pull 140 Watts each, for example. 

@gphill do whatever you fell is best for you.

I'm not trying to argue with anyone here, however, ground loops occur if there is a voltage potential between the neutral and ground wires.

The only difference between the two hots coming into a home is the phase difference in the AC legs.  However, when that AC is converted to DC the PHase difference goes completely away.

That is it.

As I mentioned previously, sometimes people would connect to a hot leg that has noisy equipment connected to it or the grounding scheme in some audio equipment was improperly designed which causes ground loop issues.

Dedicated lines have the hot, neutral and ground go back to the service panel without sharing.  All circuit neutrals tie together at the service panel and all grounds tie together at the service panel.

If the leg has noisy components (AND) the internal power supply of certain audio equipment isn't up to snuff to eliminate noise properly, then, you MAY have noise.  if the grounding scheme in a particular audio equipment isn't designed properly (star ground, etc.), then you MAY have a ground loop.

But, like I said before, connecting to two legs is okay as long as you know what is on the legs.  Connecting everything to one leg is fine as long as you don't have arc welder amps that unbalance the system (noise anyone?) by drawing too much on one leg and unbalancing the system.

This is why Refrigerators, microwaves, electric washing machines, etc. as connected as balanced loads on home systems.

But I can tell you that people that claim to hear differences between all on one leg of split leg service, didn't do A/B comparisons (kind of hard to do that) and if they did, there was something else that caused the problem. like a really noisy equipment that was on that particular leg or worse, some audio component that didn't have a properly designed ground scheme.

In older equipment you would find the signal ground (for audio) and the chassis ground was connected.  not a good idea is it?  Many people know that now but back then?  not so much.  Or there were multiple signal ground points in a circuit instead of star grounding at the same point (physically).  Literally asking for a ground loop or hum problem. Has nothing at all to do with which AC leg was used.

In my experience, I have never seen an issue with all low level components tied to a decent power conditioner and then to a dedicated line and separate amps tied to their own dedicated line.

I have however many times found ground loops by the following method.

unplug everything.  Connecting the amp and speakers together only and turn the amp on. Noise?  yes, amp is the problem.  No?  then connect the pre-amp to the amp/speaker combination.  Noise?  yes, pre-amp or (interconnect cables) is the problem.  see where I'm going with this?  

Anyway, enjoy you system.  I know you will.

 

@minorl Wow great post, thanks for that. I found that to be some of the best no nonsense AC information Ive read here. Also took a look at your system on your profile, wow again, any chance for some pics? Thx again!

It’s not hard to make the comparison between 1 leg and 2 when you have gone through multiple systems and step by step made 1 change then listened.  It makes a difference.  And anyone that is caught up on just focusing on the phase line and voltage that is regulated by the equipment power supply is missing everything going on with the neutral and ground and how those 2 play into the system.

Again, you can not hide from power line noise by selecting a phase.  The noise is on the neutral.  Unless the noise is from a 240 volt motor, in which case, it’s on both phase, so again you can not hide from it.

Yes the power supply in the equipment regulates the incoming 120 volts to something else.  But most equipment also has some connection of the equipment power supply of the signal ground that is tied to the chassis ground.  So the signal is tied to the 120 volt power grid.  I have heard it.  Others have heard it.   Just do it.  In my opinion, there is no reason to not use 1 phase.  There is 0 evidence only 1 phase causes any issues.  So why fight it?  To make a point?   If that is the only reason you are arguing, your helping nothing. 

And, people here seem to think it’s great to put metal clad cable in and tie the ground to the shield of the cable which then allows the shield to become an antenna.  Or at a minimum you have introduced a ground loop because the impedance of the shield and the copper wire are different.  And before some "Engineer" gets on a rampage, let me say I have removed more than one annoyingly loud ground loop by eliminating 3 wire MC and replacing it with Romex. 

 

I don't have an engineering degree, so I don't talk as technically proficient as others.  What I have done is consult with many engineers, nuclear and NASA scientist. I have read a lot. I have taken specialized classes on grounding.   I have made alterations, observed the result, then sought out knowledge from these type people to understand why I heard what I heard.  I have also wired maybe 100 systems and have a large data base of evidence to back what works and what does not.   I will say again, putting MC into an electrical supply is a receipt for disaster unless you are very cautious.  IF you only ran 3 wire MC with a hot, neutral, ground and metal shield, you’re likely to have noise and/or ground issues.  If you ran 4 wire and don't use an isolated duplex on even 1 outlet, you may introduce ground and noise issues.  Even 4 wire MC is not a full proof way to eliminate noise.  The jacket is an antenna for RF.   It really does nothing for audio performance.   Commercial facilities use metal for fire protection.  Not because it has better performance characteristics.  Just like your house has AFCI on all the breakers.  They don't make your computer work faster or stereo sound better.  To that matter, I have sat and listened with others and you can hear an AFCI breaker as a small veil on the music.  They hinder audio playback.    But they extinguish arc fires before they propagate to the rest of the house and burn the building down.  They do a great job at that.  As do metal raceways. I have been in a room when the switch was thrown and a faulty piece of MC arched inside the cable jacket.  It was a very large boom and smoke smell.  It took a while to find the fault as the case was fully intact.  Just a small discoloration of the jacket under the flash.  No flame left the jacket where it could ignite combustible materials around it.  That is why you use metal jackets.  It’s fantastic fire protection.

The only shielding that blocks RF to any degree is a copper pipe.  No one runs wire in copper pipe.  Steel and aluminum don't really do anything towards blocking RF.  They do block EMF.  But cable management eliminates issues associated with EMF radiating from your power cable and contaminating other circuits in close proximity.  That's all metal is doing for you.  Maybe you want to run the rest of the house wiring that is in close proximity to your audio outlets in metal.  That is a good solution.

The only real block to RF is putting something such as a Torus Isolation transformer on your rack.  The best location for a isolation transformer is on the rack.  The second best is within 10 to 15 feet of the rack.  After 40 feet, you have potentially lost much of the RF noise mitigation as it has reentered the circuit again.  Metal won't keep it out.  You can coat a room with Faraday shield.  But it’s very hard to do correctly. I have heard of one audio room I want to visit and been in a commercial room that was RF treated.  The one I was in was a government building where they wanted to house sensitive equipment.  My phone still partly worked.  It was very intermittent and definitely impacted it.   But it was not 100%.  I would like to get in the audio room with my RF sniffer and see what is still there.  RF is an interesting phenomena.  In my room, my meter reads about 1700 near my rack.  Even with the equipment turned off.  It’s not my audio equipment.  Walk 24 feet out of the room and into my hallway and it reads about 70.  It’s a massive drop in only a few feet.  Directly above my audio room in a bed room the RF is around 1700.  Something about that side of the house.

 

I just came back from a work trip where a client was crying about a radio station bleeding through his speakers.  I was confident it was not my power supply, but I had to go check.  In the end through various processes of elimination an use of filtration, I was able to validate his system preamp was a mess of noise and his phono preamp was not filtering out the RF from the cartridge, tone arm, phono pre enclosure.  It is my experience through many people asking for my assistance to eliminate some sort of noise, I find the issue is the audio equipment itself that is the culprit.  I have seen it with 3 year old 40K monoblocks to brand new $20K phono stages.  I have never seen a clients noise issues emanate from a well designed electrical infrastructure using NM cable.    Having said that, I have dropped  Torus Isolation transformers on peoples racks and 2/3rds of people end up buying it.  I sold 2 out of 3 on this last trip.  There is a ton of noise on the power line. But it’s not noise you notice as a hum or radio.   It’s a hazy veil most people don't notice.  They just keep buying new gear trying to get better performance.  Once you eliminate the power line noise, the music becomes more clean and quiet.  Not black.  The room feels more calm.  Details are more present in the recordings and the bass becomes tighter and more integrated with the whole.  The music is more natural.  There is noise on your power line.  Lots of it.   But you’re doing nothing to get rid of it by wrapping a few feet of your infrastructure in steel or aluminum.  Those that say shielded wire does not matter because there are hundreds of miles of wire that are exposed to noise injection have a very valid point.

FWIW, that radio station bleeding out my clients speakers.  You won’t fix that with an isolation transformer.  You won’t fix it with any power line filter.  You might fix it with about $25K in Faraday shielding around the room.  That includes over windows, in doors, under the floor.  Everywhere.  You have to encapsulate the entire room.  Or the entire rack.  It’s possible a system set in a closed cabinet that is completely shielded will work.    And then it’s a maybe.  Better to get audio equipment that has a power supply designed to reject RF and not modulate it into the power supply of the audio equipment. 

Here is a good read.  More important, go to the References and read all of those.  I have read a lot of the materials noted in the references.

https://cdn.cableorganizer.com/old-images/midatlantic/PowerSolutions-middle-atlantic.pdf

 

In summation, if you want the best power for your audio

Ground Correctly

Use all copper panels and wiring.  This means the neutral and ground too.

Segregate power

Use an isolation transformer

Use NM #10.  Better to use twisted wire.  Better to use grain oriented twisted wire.

If your dead set on using metal encased wire, use an isolated ground system

This is a very high level list.  It lack all detail on how to set the infrastructure up properly.  It’s basically a one line.

Old White Paper. Middle Atlantic Products, Inc.

https://cdn.cableorganizer.com/old-images/midatlantic/PowerSolutions-middle-atlantic.pdf

( Rev 2b 8/7/2007 )

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Newer white Paper. Middle Atlantic Products, Inc.

Integrating Electronic Equipment and Power into Rack ...

( Rev 4b 2002-2010 )

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Page 12:

Integrating Electronic Equipment and Power into Rack Enclosures © 2002-2010 Middle Atlantic Products, Inc.

AC Power Wiring Types (cont’d)

Metal Clad (MC) is manufactured in both steel and aluminum with twisted conductors that help reduce AC magnetic fields. Although the steel jacket helps reduce AC magnetic fields, the twisting of conductors has the greatest effect on reducing these fields. Another benefit is the constant symmetry of the phase conductors with respect to the grounding conductor which greatly reduces voltage induction on the grounding wire. (NEC article: 330)

Two conductor plus 1 ground MC (Metal Clad) is a good choice for Non-Isolated Ground A/V systems. MC cable contains a safety grounding conductor (wire). The three conductors in the MC cable (Line, Neutral and Ground) are uniformly twisted, reducing both induced voltages on the ground wire and radiated AC magnetic fields. The NEC article 250.118 (10)a prohibits the use of this cable for isolated ground circuits because the metal jacket is not considered a grounding conductor, and it is not rated for fault current.

Two Conductor plus 2 ground MC (Metal Clad) may be used in an Isolated Ground installation, because the cable contains two grounding conductors (one for safety ground and one for isolated ground).

The conductors are twisted, but the average proximity of the hot conductor and the neutral conductor with respect to the isolated grounding conductor is not equal. Under load, this will induce a voltage along the length of the isolated ground wire, partially defeating the intent of isolation (see Ground Voltage Induction section of this paper).

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Again:

Two conductor plus 1 ground MC (Metal Clad) is a good choice for Non-Isolated Ground A/V systems. MC cable contains a safety
grounding conductor (wire). The three conductors in the MC cable (Line, Neutral and Ground) are uniformly twisted, reducing both
induced voltages on the ground wire and radiated AC magnetic fields.

Read page 13. Look at the chart on page 13.

Note the far right hand side of the chart.

Arrow pointing up, Worst. Note where NM Cable is on the chart. Look at the numbers...

Arrow pointing down, BEST. Note where MC Cable is on the chart. Look at the numbers...

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Note the picture of the test board where the NM cable, (Romex) is fastened in place. Note the piece of cable is laying flat on the board. No twists, laying flat. Do you think when an electrician installs, say, 50ft to 75ft he takes care to make sure there is not any twists in the cable? Not hardly.

Look at the picture of Romex, NM cable, on page 32.

An Overview of Audio System Grounding and Interfacing

Note:

There is a magnetic “null zone” exactly midway between line conductors

What happens when the cable has twists ever so often along it’s entire length from the electrical panel to the wall outlet box? Do yo think the “null zone” exactly midway between line conductors is altered in any way?

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/ / / /

An Overview of Audio System Grounding and Interfacing

Read pages 31 thru 36.

Look at the chart on page 35. Note Aluminum MC cable beats out NM cable.

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FWIW, When I wired my dedicated 2 channel audio room in 2011 I ran two 75ft each of 10/2 NM cable. I followed best practices for the installation. 100% no twists? I doubt it.

My system is dead quiet...

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/ / / /

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I have been in a room when the switch was thrown and a faulty piece of MC arched inside the cable jacket.

Yeah and more than likely the ground fault was at the cut off point of where the metal cladding was cut and removed for make up. Was the red insulator installed properly. Was the proper tool used for cutting the metal cladding for removal from the conductors.

3/8 in. Flexible Metal Conduit (FMC) Anti-Short

 

I’ve seen a steel staple buried in the sheath of NM cable, (Romex trade Name), and short out the cable. Don’t blame the cable. Blame the guy that drove the steel staple.

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