My take at building audio grade power cord

cortico

I have been thinking about building a shielded power cord for my vintage stereo amps.without safety grounding.

For this effect, I will be using a two twisted 12 AWG (19 strands of 25AWG bare copper) conductors to create a low inductance/high capacitance configuration effective rejecting RFI/EMI, this should be a quantum leap ahead of the original zip lamp cord.



The twisted conductors are shielded with a foil and a tinned copper braid, for maximum RFI rejection. The braid will be connected to the ground prong on the mains side, as follows:

machone

Make sure you use good plugs.

drumminman

Chris VenHaus has good stuff. I've made several of his cables, including Flavor 4's. Might want to consider unshielded ones if you don't have a huge RFI/EMI problem as they're supposed to sound better.

Also, he has a recipe that involves an outer tube of rubber with a separate ground wire wrapped in a spiral opposite to the twist of the inner wires.

mikeyb128

I believe I’ve read unshielded power cables have lower capacitance, which makes for a “faster more dynamic cable” therefore they sound better. Nordost power cables come to mind. In my experience I’ve heard heavily shielded power cables sound just as good as Unshielded ones.

verb

Keep us posted @cortico ! Love DIYer's!

machone

Flavor 4

cortico

Thanks for your notes guys, the true is that I actual don’t have any issues with RFI/EMI noise, I may eleminate the shielding and focus on cable gauge, conductor quality and connections. I understand that the old power cord can negatively impact the power supply filtering rectified voltage charging cycles.

tonyb

DSkip wrote: »

cortico wrote: »

Thanks for your notes guys, the true is that I actual don’t have any issues with RFI/EMI noise, I may eleminate the shielding and focus on cable gauge, conductor quality and connections. I understand that the old power cord can negatively impact the power supply filtering rectified voltage charging cycles.

You don't know you do until its gone. I think everyone has an issue with it, just to what degree.

Skip speaks the truth here. Noise isn't just represented in a hum or buzz that's obvious to the ear. I don't think, if it was me anyway, I'd forgo the shielding.

mikeyb128

DSkip wrote: »

cortico wrote: »

Thanks for your notes guys, the true is that I actual don’t have any issues with RFI/EMI noise, I may eleminate the shielding and focus on cable gauge, conductor quality and connections. I understand that the old power cord can negatively impact the power supply filtering rectified voltage charging cycles.

You don't know you do until its gone. I think everyone has an issue with it, just to what degree.

I was going to say the same. How do you know you don’t have RFI/EMI?

cortico

mikeyb128 wrote: »

DSkip wrote: »

cortico wrote: »

Thanks for your notes guys, the true is that I actual don’t have any issues with RFI/EMI noise, I may eleminate the shielding and focus on cable gauge, conductor quality and connections. I understand that the old power cord can negatively impact the power supply filtering rectified voltage charging cycles.

You don't know you do until its gone. I think everyone has an issue with it, just to what degree.

I was going to say the same. How do you know you don’t have RFI/EMI?

^My setup isn’t revealing it. The background is pitch black, any present interferences are inaudible to me. The shielding would’t hurt, though!.. I’ll make 2 cables and AB it...

xschop

"My setup isn’t revealing it. The background is pitch black, any present interferences are inaudible to me. The shielding would’t hurt, though!.. I’ll make 2 cables and AB it... "

I'll gladly take whichever one you don't use...

delkal

If you do have RFI / EMI in your house electricity you are going to need more than a 3 foot power cord to get rid of it.

Think of it this way. Your actual "power cord" goes from your breaker box to your system. You might have the last 3-6 feet of the best conductive cord available but it is still connected to 30-100 feet of 50 cents a foot 3 stranded Romex cable.

Just because it is behind the wall doesn't mean it is not there.

pitdogg2

Think of it as the first 3-6 feet not the last

cortico

Ok, I made the first experiment using a 14AWG 3 prong contractor grade extension cord rated to 15amps 600v.

The wire has 3 twisted stranded copper conductors and thick pvc insulation, I have cut a 4 foot section and saved the original 3 prong plug. Warped the entire cable length with 2 layers of conductive aluminum self adhesive tape which was connected to the ground conductor but isolated from the amp. At last, I applied a cable sleeve to improve the looks and cover the tape. It ended up not very flexible, I’m afraid aluminum tape won’t survive many bends, in the future I’ll use conductive braid...just a side note.

Conclusion, I bumped gauge from 18 to 14, used better copper, twisted conductors, added shielding and used better connectors. My first impression is that the residual hiss when the volume is all the way up with no input signal is now null. I think I hear better channel separation too, does this make sense?!

Edit: second impressions, I think this cable I built sucks! Jumped back and forth and stock 18awg cord seems to sound more lively with more clarity and better dynamics...

I’m going back to the drawing board...

gp4jesus

machone wrote: »

Flavor 4

where to $ that IEC connector?

machone

Furutech FI-11 CU @ Douglasconnection.com

cortico

I am perplex as I though I would never hear any differences with my lousy diy cords and low end gear.

I can definitely see a pattern that are probably related with the capacitance and inductance of the different schemes:

-18 vs 14 gauges,
(thicker wire benifted low end and soundstage width, slightly tamed upper freqs)

-shielded vs unshielded,
(Shielding muted dynamics, more defenition but mid range seamed setback in the mix)

-parallel vs twisted conductors,
(there’s tone changes, specially high end)

-with exterior insulation vs wihout exterior insulation, (good dynamics and clarity without cable rubber jacket)

These results are related to my specific gear and hears therefore subjective. Changes are not subtle, most tone differences can be compensated with tone controls but the sound stage dimension, focus and dynamics are a hit or miss situation.

Ok, enough of nonsense:)

cortico

FWIW, I have found a run of Romex 12awg wire on the trunk of my father in law’s car, who’s an electrician by trade and decided to give it a try. The cable has 3 solid copper conductors runing in paralel inside a vinyl sleeve. It’s my favorite so far, imparts all the qualities of the previous thicker wires and apparently without noticeable losses I noticed with other schemes... the system sounds bigger!

Clipdat

Interesting observations! Looks like AA sells a snobby Cardas version of it here for $16.26/foot!

http://www.audioadvisor.com/prodinfo.asp?number=CRIW3X10

cortico wrote: »

FWIW, I have found a run of Romex 12awg wire on the trunk of my father in law’s car, who’s an electrician by trade and decided to give it a try. The cable has 3 solid copper conductors runing in paralel inside a vinyl sleeve. It’s my favorite so far, imparts all the qualities of the previous thicker wires and apparently without noticeable losses I noticed with other schemes... the system sounds bigger!

gp4jesus

cortico wrote: »

18 vs 14 gauges, thicker wire benefits low end...

interesting...

Assuming 4 amps, 18 ga versus 14 ga nets a voltage drop reduction of a mere .04 volts. Yet some perport upgrading to 10 or 12 from 14 or 16 isn’t worth it.

Go figure...

delkal

According to this article solid core wires (romex et al) make excellent power cords. Unfortunately you will never find one since solid core wires are not UL approved for power cables. You have to make your own.

From the article.


The reality is that a power cord made from 12-14 gauge solid copper is pretty good. The problem with this is that this wire is not UL approved for cords and is very inflexible indeed. Most electrical Romex runs to the outlet in question are 20-40 feet in length. The power cord adds an additional 6 feet or so, so this is a small percentage of the entire run. It turns out that typical "rubber" stranded copper power cords have significantly higher inductance than the Romex in the wall, even at the same wire gauge, so these are not recommended. Empirically, stranded rubber cords have been demonstrated to limit transient high-power currents (dynamics) compared to solid copper conductors when supplying power to typical audio power amplifiers.

It is fairly easy to build a serviceable cable that will minimize power cord inductance. A simple 3-conductor twisted cable from 12 AWG solid THHN from Home Depot yields a very high quality power cord, although it is so stiff that it must be bent to the desired shape. It is actually superior to the Romex in the wall because the twisting and close proximity of the insulated conductors will reduce the inductance by magnetic coupling between the conductors. In the optimum configuration, the Hot and Neutral are twisted together and then the ground wire run beside or wrapped around them.


empiricalaudio.com/computer-audio/technical-papers/myths-and-snake-oil

cortico

Good article, thanks for sharing!

miner

machone wrote: »

Flavor 4

That is one vintage ZZ Top picture there machine.

machone

Macon, GA in 74ish.

gp4jesus

Great article and...

Oops...

gp4jesus wrote: »

cortico wrote: »

18 vs 14 gauges, thicker wire benefits low end...

interesting...

Assuming 4 amps, 18 ga versus 14 ga nets a voltage drop reduction of a mere .04 volts. Yet some perport upgrading to 10 or 12 from 14 or 16 isn’t worth it.

Go figure...

“Yet some perport upgrading speaker wire from 14 or 16 to 10 or 12 gauge isn’t worth it.”

I can’t figure..