Dedicated Power Line Project


I’m going to be adding a dedicated AC line to feed my audio system. Currently, the system is fed by a 75 foot run of 14 gauge romex that is likely daisy chained a few times in the wall between outlets. Needless to say when I turn the volume up, dynamics suffer and the overall sound quality is much less than I know my system is capable of. At louder volumes, bass notes will make the lamps dim and if I go louder, it seems like the system struggles and the bass notes get rounded off or sound “fuzzy.” My calculations tell me that with 75 feet of 14g romex, the voltage at the end of the line could be dropping by 5-10 volts, maybe more, during transient peaks. What I think is happening is that the power amps’ power supply caps are draining and there isn’t enough current to recharge them quickly enough and the amps start to draw directly from the AC line which causes a large voltage drop. 

Initially I was looking at a 10 gauge or 12 gauge line with a 20 amp breaker. After running the numbers, even a 10 gauge run could see some significant voltage sag at 75 feet during transients. At that point I considered 8 gauge, but the problem with that is that no electrical outlets will accept anything larger than 10 gauge, so I’ll have to do something fancy like place a junction box and step down to 10 gauge at the breaker panel and just before the outlet. Then I thought if I’m going to that much trouble with an 8 gauge, why not run 6 gauge? My calcs tell me 6 gauge could have a volt or two less variance than an 8 gauge and it wouldn’t be much more cost. So as of now, the plan is to run a 6/2 solid core romex line and run all the equipment of that. (I could run another line for the front end in the future but that isn’t the plan right now).  I have a few questions if anyone would be so kind to reply:

1) Are there any foreseeable issues with running “too large” a power line? I’m not sure if it’s accurate, but I’ve heard that large gauge is good for bass and small gauge is good for treble. Since I’ll be running everything (including the low current draw components like sources, preamps, etc) off this one line, is there any chance I’ll change the sound signature in a negative way?

2) What is better? In-wall romex or THHN inside a grounded conduit? I’m leaning towards romex because my gut tells me having the wire surrounded by something could hinder transients or hurt clarity but I’m not sure that’s accurate - that may just be from my personal experience with low level signal cables where too much insulation can be a bad thing. 
3) Are there any other “gotchas” that you can think of?

I’ve read the MSB Technology article and I’m subscribing to that theory which is this in a nutshell:

“It is the subject and goal of this paper. The gauge of the wire is FAR MORE IMPORTANT than the fact that the line is “dedicated”. The subject of this paper works on the theory that the varying musical demands of your amplifier are actually modulating the incoming power line, divorced from the utility (power company) by some resistance (12 or 14 gauge wall wiring at some length from the breaker panel has too much resistance for audio purposes).”

Thank you and wish me luck!
mkgus

Showing 6 responses by jea48

@emailists

I assume you live in the US. My post only applies if you live in the US.

If you use Romex, (Romex is a Trade Name for NM sheathed cable), it is not designed or manufactured, or UL Listed, for use as you would like to do as basically a power cord extending from the wall electrical box. I only point that out so you know what most likely the electrical governing body in your area allows. (The AHJ, Authority Having Jurisdiction.)

With that out of the way.

Solid core #10 copper wire is pretty stiff and resists bending. Care would need to be taken when/if there is any bending at the IEC female connector. Any movements can, will, cause the tightness of the #10 solid wire to the mechanical lug terminations of the IEC connector to loosen. (It’s just the nature of a solid wire terminated in a mechanical lug). The only way to maintain a tight secure connection would be to solder the wire to the mechanical lug connection after mechanically tightening the connection first.

IF you want to meet electrical safety codes in your area you could cut/remove the plug off a good quality after market power cord and hard wire the conductors from the cord to the #10 solid copper branch circuit wires in the electrical wall box. Use spring wire electrical connectors. Nothing in the NEC Prohibits it providing the conductors in the power cord are rated for the ampacity of the branch circuit breaker.

You would need to install an extension box to the flush electrical wall box. You would need to install an approved strain relief cord connector to connect the power cord to the extension box.

Last but not least I would highly recommend you hire an electrician to do the job. He/she will know what is required/allowed by the AHJ in your area.

Example of a spring wire electrical connector.
https://www.homedepot.com/p/Ideal-Twister-Wire-Connectors-341-Tan-100-Per-Package-30-341P/202894284?...


You can get 8/2 and 6/2 romex in solid core.
@ mkgus OP    

I'm pretty sure it is not manufactured with solid conductors.

Per the NEC as well as NEMA,  single conductor insulated #8awg solid copper is the largest allowed building wire. Good luck finding any one that carries it. You may find some old  #8 solid copper insulated TW or THW  single conductor wire. I can tell you from experience it a bear to work with.

Be careful when buying 600V rated so called audio grade building wire. NEC says it shall be Listed by a recognized NRTL testing laboratory like UL to name one. Some AHJ (Authority Having Jurisdiction) specify UL only.


Jim
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mkgus OP173 posts

01-20-2020
5:51pm

Here’s 6/2 solid core Romex:

https://www.lowes.com/pd/Southwire-Romex-SIMpull-6-2-Non-Metallic-Wire-By-the-Roll/3127529
@ mkgus OP

I can’t explain the ad. IMO, it’s a misprint. Should say stranded.

Here is a link to the Southwire Manufacturer’s web site. Note conductors are stranded. I can’t imagine working with 6-2 with ground solid copper NM cable. (Romex is a Trade Name)

https://www.mysouthwire.com/medias/sys_master/product-specifications/product-specifications/h77/hfc/...



jea483,237 posts

01-20-2020  
 4:42pm

Per the NEC as well as NEMA, single conductor insulated #8awg solid copper is the largest allowed building wire. Good luck finding any one that carries it. You may find some old #8 solid copper insulated TW or THW single conductor wire. I can tell you from experience it a bear to work with.

I should have checked before I posted. The old memory ain’t what it used to be.
The NEC for many years has stated conductors pulled in raceways #8 and large shall be stranded. (Key words, in raceways)

I had to go all the way back to the 1971 NEC to find where it said # 6 and larger shall be stranded when installed in a raceway. In the 1971 code it says in 1973 the requirement will change to # 8 and larger shall be stranded when installed in a raceway.

. I did a quick search and didn’t find anything in the 2017 NEC requiring #8 and larger NM sheathed cable (Romex) shall be stranded wire. I’ll spend some time tomorrow and see If I can find anything to the contrary.

There is a Lowes in my area and they show they have 6-2 with ground Romex in stock. I’ll stop by and see if the conductors are stranded or solid.
Curiosity killed the cat.......


Jim
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I stopped by Lowes and here is what I found.

8-2 with ground Romex.
Two #8 stranded conductors with one #10 solid bare equipment grounding conductor.

8-3 with ground Romex.
Three #8 stranded conductors with one #10 solid bare equipment grounding conductor.

6-2 with ground Romex.
Two #6 stranded conductors with one #10 solid bare equipment grounding conductor.

6-3 with ground Romex.
Three #6 stranded conductors with one #10 solid bare equipment grounding conductor.

All of the above matches Southwire manufacturer website information.
https://www.mysouthwire.com/medias/sys_master/product-specifications/product-specifications/h77/hfc/...

Jim

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Can you use 10/3 romex for two dedicated hots and a shared neutral and ground? Is that even code?

Code? Yes.....

A 3 wire multi wire branch circuit is not recommended for feeding audio and or video equipment.

The two hot conductor of the multi wire circuit must be fed from both Lines, legs. One from Line 1 (L1), and the other from Line 2 (L2).

Only the unbalanced load current will return on the neutral conductor to the electrical panel. The balanced load of L1 to neutral and L2 to neutral will be in series with one another. The balanced series loads will be fed by 240V, nominal. This works greats for tying the power supply of digital equipment to the power supply of analog equipment.

Here is a video showing how a multi wire branch circuit works.
https://www.youtube.com/watch?v=eVamt9IdQd8


Jim
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