Dedicated power circuits

@8th-note,

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Is this what you are looking to buy? You do know it is 120/240V? Best practices is to feed audio equipment, (that is connected together by wire ICs), is to feed the 120V equipment from branch circuit breakers fed from same Line. All from Line 1 or all from Line 2. Not from both.

 

You mentioned Michael Fremer’s new electrical service. All his audio equipment is fed from one 120V Line. I have no idea how big his total load is though. Just a guess a lot more than yours.

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I watched the video again today and picked up a few things I missed the first two previous times. I believe there are a few things worth noting.

Near the end of the video Fremer shows the new sub panel for his audio room. It is fed 120V only. *(1)* Electrical Inspector did make the electrician install the other 120V hot conductor. It will not be used though. I think it was just an AHJ Inspector thing. I couldn’t find anything in the NEC that requires it.)

Note the 120V feeder for the sub panel is installed in PVC conduit. All the branch circuit wiring is installed in non metallic flexible conduit.

Example, non metallic flexible conduit:

1/2-in x 25-ft Ultratite Non-metallic Schedule 80 Liquid-tight Conduit

From what I could see the outlet boxes are also non ferrous as well as the outlet cover plates. I did see something I didn’t agree with though. Two dedicated circuits for the two mono amps were pulled in the same raceway, conduit. That doesn’t follow best practices. I did notice though the 120V Hot, Neutral, and Ground branch circuit wiring used for each 120V circuit was apparently tightly twisted together. That would be a whole lot better than if single conductors for both dedicated circuits were all pulled loosely together in the conduit. That definitely is a no, no. A sure way to induce an AC voltage onto the equipment grounding conductors and cause ground loop hum.

Image of audio room sub panel, front cover removed. Note the two 120V dedicated circuits bottom right side of panel in the flex conduit connector.

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Not to bad mouth the electrician. He may have had his reasons... I did notice a few things on the installation of the new electrical service I didn’t care for.

The use of a rigid no-thread coupling on the Mast rigid Conduit. (Yeah it meets code. But...)

The use of the offset nipple into the top of the meter socket enclosure hub. Not pretty...

And I found myself scratching my head why the electrician used PVC conduit nipple from the bottom of the meter socket enclosure to the Myers Hub on the main service equipment panel. A galvanized rigid nipple would have looked a lot better, jmho... As well as electrically bonding the two metal enclosures together.

 

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*(1)* Electrical Inspector did make the electrician install the other 120V hot conductor.

I have a friend in Texas that has a 15KVA 240V to 120V single phase pad mount outdoors isolation transformer strictly for feeding his two channel audio room equipment. The electrician only installed one, Hot, neutral, and ground, conductor to feed the 120V only electrical panel. The electrical inspector made the electrician add the additional spare conductor for the other hot Line, ( for future), not used, not connected.

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@lowrider57 Wrote:

@ditusa

Please explain why MC Galvanized Steel Metal Clad Cable. A metal conduit is not required to meet code in this situation. And cost will be higher than Romex 10/2.

The MC Galvanized Steel Metal Clad cable provides better shielding versus 10/2 Romex, in my opinion the benefits outweigh the extra cost of the MC which is minimal. The advantage of MC cable is low line noise and reduced antenna effect on AC dedicated branch circuits feeding your audio equipment. Also, I prefer to use metal boxes with MC cable, not plastic, they both meet code but if shielding is not important then the 10/2 Romex with plastic boxes will be more then adequate. I just try to get the most out of my audio system as I can with minimal cost. 😎 See MC cable below: Hope that helps

FWIW: Another reason for multiple circuits besides dedicated power see my previous post below:

ditusa

1,073 posts

12-20-2022 at 08:35pm

 

@jea48Wrote:

Probably the biggest reason for installing more than one Dedicated Branch Circuit is to decouple the power supplies of audio equipment from one another. Example digital source(s) equipment from analog equipment.

I agree!

That was one of the reasons I ran four 60’ runs of galvanized steel armored MC cable 10AWG. That’s four true dedicated branch circuits, one for each mono block amp, one for analog and one for digital. It helps to reduce noise on the AC lines, by reducing the amount of transformers and power supplies on each circuit. Also, the MC helps to reduce hashing noise EMI, and electric fields, on the dedicated branch circuits feeding your audio equipment. You don’t realize how much hashing noise is on the AC lines, until it’s reduced. No ground loop hum. No noise. System is dead quiet with ear against speaker horn, I have tube and SS amps. (The efficiency of my speakers is 2.7% sensitivity 96dB). 😎

Mike

 

@ditusa 

Thanks for the detailed explanation. I'm using two identical runs from 20A breakers, one for analogue and one digital. Tube amp plugged into wall. Audio system is only 20' from panel so I used 12/2 Romex. No ground loop, no RFI (tested with a meter).

ditusa,

Your installation is almost identical with mine. I'm running 10/3 MC 240v. A 20 amp circuit dedicated to each mono block, 20 amp circuit for pre amp, and a 20 amp circuit for digital. All galvanized gang boxes. 

I desigbed and build that all in one AudioUltra panel.  I have modified it since inception.  It can't be beat when installed  in the right application.  That application is on a wall between monoblock amps and subs.  I don't use a power cord.  Its bolted directly to a feeder wire and capable of passing 225 amps. 

 

An all in one Torus distribution is great, but not so great.  Its a better suited product in recording studios where many have been installed.  There are much better ways to integrate a Torus in a residence. 

I had to have the second phase run at Fremers because I could not get a letter from SqD  saying a Square D subpanrl rated 120/240 was suitable for 120 only.  In response to this, I manufacture a 225A all copper panel with a UL label rated for 120 volt only.   Yes you only use one phase. 

I went back to Fremers and changed out that panel in the image above. .  I now rework those SqD QO MLO 125 to 200A subpanels with damping compounds and install all copper neutrals and grounds.  Its a shockingly good panel for the money when rebuilt.  Stock they are little better than a couple others.  There is crap ou there like Homeline and Eaton/Siemens/CH BR style.  Waste of money.  And they limit performance.  

The primary feed from the utility to the receptacle in the wall can be very sensitive to how the wiring is installed.  The best electrician out there is going to do it wrong  because he does not have experience powering something as sensitive as an electron microscope.  Thats your stereo.  He will do what all electricians do, meet code minimum.  Anything more in their mind is a waste of money.  They don't get it.  That twisted wire at Fremers.  I grain orient it.  Tell an electrician that and their eyes glaze over.  Tell that to a cable manufacturer and they will acknowledge you know one of their secrets.   When wire is drawn through dies to size it, it gets a grain.  I have heard it called a Chevron.  Its audible and measurable.  I am the only person in the US I know of who is talking UL THHN/THWN solid 10 awg and determining its grain, then orienting all 3 hot, neutral and ground before installation.  Others have stuck wires in a drill and twisted them.  My tools are more clean and precise.  I built a custom bobbin and twist the wire 1 turn every 2 inch.    I am soon going to Cryogenic immersion bath this wire. 

I don't like MC cable or wire in a steel pipe.  I use it when I have to such as in NYNY.  Otherwise its a can of worms.  It creates ground loop issues.  It really blocks no RF.  Its there to stop fires as an arch in the conductors rarely propagate ouside the metal case.  Steel will block a small amount of emf from one branch circuit to another.  But the steel case is interacting with the electro magnetic field around the wire and compressing it. In my mind Its not ideal.   But I do need to test it more.

I do not like 8 awg and larger.  MSB may have written a paper saying you want to upsize to larger gauges for longer runs, but every wire is audible.  8 is analytical.   It grabs your attention and makes you aware of different parts and pieces in the music.  Its harder to relax and enjoy.  10 is plenty of current.  Romex is decent wire.  If your on a budget, use it.  Its a little hard and slightly analytical,  but not like 8.  Romex is great for subs.  8 can be too.  They speed up the bass.  Grain oriented twisted is more whole and complete in tone.  Its easier to digest the whole of the presentstion and relax while listening.  Its a little fuller, but looses no resolution. 

The all copper panels I mentioned are nice as you eliminate the galvanic reaction between the copper and aluminum.   Its audible.  Its heard as a sleigh  veil and haze.  A small amount of lost resolution and softening of the music.  If you have SET amps and horns, you might find it tames some of their potential "Hot" dynamics.  It could be consodered a tone control.  I prefer to rid noise and work on taming the speaker/room issues in the room.  Not in the electrical infrastructure.   

Rex