NBSAudio: DIY Power Cables


web nbsaudio.com
 
 

Do power cable affects the sound? In general – yes. Let us build a good one. But in order to build an optimal power cable we need to dig a little dipper.
There are five major components related to the power cable that could alter sound:

    1. AV equipment connected to the cable
    2. Power outlet that supplied the AC current
    3. Material of the cable itself
    4. Material of the connectors inside IEC plugs
    5. Coupling of the IEC plugs with the wire inside of the power cord.

I. Let’s talk about each component.

  1. Common observation is that CD player is more sensible to the power cable choice than the power amplifier. It is kind of obvious: inside of typical CD player is anemic power supply that relies on sufficient current flow, and inside of decent power amp you’ll see caps bank with hundred thousand of µF, which would allow such amp to function without any connected power for some (short) time. But still size does matter. In-house wiring is done typically using 14 GA wire, which applied limitation on the carried power/current 5.9 A for transmission. (See see more on wire specs below). Any power cord thicker than 14 GA (12, 10 or 8) wouldn’t improve the situation and fix the possible problems arisen in the AC power delivery path.

    Now how about replacing the typical 18 GA power cord with 14 GA power cord? Stereo amplifier delivering 200 W per channel needs about 4A of 110V current. Standard 18 GA 6’ long power cord has 0.038 ohm resistance, which result in 0.16 V voltage drop over the cord during the pick signals. Replacing that cord with 14 GA 3 ft. long power cord will decrease resistance in 5 times and result in approximately 0.03 V over the power cord. How important this worst case 0.16 V modulation of the 110 V power line, how it’d effect the quality of audio signal? Level of modulation is 0.16/110 = 0.15% and would be further filtered by those huge (10,000 – 100,000 microfarad) capacitors in the amplifier’s power supply, which will put it under declared 0.03% (typical) THD. Can you hear it? I doubt.

    Side note: Could it be an improvement in the sound quality after replacing any power cord? Definitely. Merely plugging and unplugging any cord into the power outlet will clean up oxides from the plug/reciprocal surfaces, and provide a better connection for your power.

  1. Standard US home has 15A power lines (14 AWG wire) running from breaker box to in wall power outlets inside of the iron pipes that served as a proper shield against any EMI. If it’s not a case, than it does not make any sense to bother with power cables. From the other side, it will pay off to install dedicated 20A power line terminated with good (at least of medical grade) power outlets.

  2. Choice of wire inside of the power cable is the most controversial topic. I will discuss it later in the separate article in more details. The basic start points would be the choice of material, AWG, shielded or not shielded flavor of the cable. And let’s do not kid ourselves:  I have a strong suspicion that any name you choose was manufactured in China today.  Some of the samples are shown in the table:


  3. Popular bulk wire choices

    Inside view*

    The Belden 19364 is shielded with an aluminum foil that has a drain wire for connecting to plugs.

    XLO Reference 2 Type 10A silver plated power cable features two black (blue) live conductors, two brown neutral conductors, two green ground conductors (European/UK color code), and a bare (uninsulated) drain wire for the foil shield.

    Furutech FP-314Ag Silver Plated μ–OFC HIFI Power Wire 15 AWG

    Image result for Furutech FP-314Ag Silver Plated μ–OFC HIFI Power Wire Powerflux Cord

    Strange, but I couldn’t find a common value of allowed current for a given AWG. Obviously, the higher current will result in a higher temperature, and the number considered as “safe” will depend on the quality of insulation.  The rated maximum continuous current capacity for 12 AWG copper wire could be assumed as high as 20 amps, but I would follow more conservative estimation of the solid wire power rating shown in the table below:

    Wire AWG gauge

    Wire
    Diameter Inches

    Wire
    Diameter mm

    Ohms per 1000 ft.

    Maximum amps

    Threshold for skin effect for solid  copper wire.

    10

    0.102

    2.59

    0.9989

    15

    2.6 kHz

    12

    0.081

    2.05

    1.588

    9.3

    4.15 kHz

    14

    0.064

    1.63

    2.525

    5.9

    6.7 kHz

    18

    0.040

    1.02

    6.385

    2.3

    17 kHz

    20

    0.032

    0.81

    10.15

    1.5

    27 kHz

    More data could be found here: https://www.powerstream.com/Wire_Size.htm

  4. Material of pin connectors could vary from steel to gold, but I would avoid fancy “pure copper”. In a time of months coper oxide developed on the surface of copper connectors will increase resistance of the cable – plug – power outlet chain and diminish all advantages of the fancy cable. Gold plated is better, but you need to be sure it is real gold and could be soldered, and not some good looking alloy.   
  1. Now when we have all components chosen and collected it is time to put it all together. And here is the most hidden and rare discussed part of the cable: connection of the wire to the pin (contact) inside of the power connector. All bulk cables used compression, and even handmade cable with the fancy connectors (any like Furutech, Oyaide or WattGate) rely on compression by means of tighten the screw on the pin.
  2. Here is what happened with respectable genuine XLO Reference 2 Type 10A power cord after a few years of use:

    You can see that brown wire partially got loose. What is good in using quality wire if it is not connected to the circuit? And that would be with any copper wire connected this way. Copper is a soft metal, after some time under pressure it will give up, plus bare surface will be oxidized.

    The only one old fashion way to solve this problem is to solder wire to the pin.

II. Putting all together

The color coding US and Europe have different standard, and colors may be different. Mine has brown, blue and green. Which one to use as line/neutral if they all have the same type of wire does not matter, as long as both sides connected right. When there are different opinions, I would suggest that drain wire should be connected to the neutral pin only at the wall plug end.

Pinout, reminder for myself: Code:

Image result for IEC plug pinout

Left pin: Neutral

Center pin: Earth/Ground

Right pin: Live

Image result for IEC plug pinout

Option One:

black live conductor,  

brown neutral conductor,

 green ground conductors

Option two:

blue live conductor,  

brown neutral conductor,  

green ground conductors

III. Assembly:

Now you can claim: Made in USA – I made it in Chicago!

__________________________________________________________

*Pictures taken from vendor sites are duplicated on the Web so many times that is was impossible for me to identify the origin of some images. My apology. If somebody would provide me a references to such origins I will be happy to include them.

  Copyright © 2001-2017 NBSAudio. All Rights Reserved.