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Power Cord Plus
The good stuff for your AC interface.

Article by Gordon Rankin, Wavelength Audio
From Sound Practices Issue 1, Summer 1992

 

  Over the last several years, many manufacturers of high end equipment have adopted IEC type power connectors. This move toward a standard AC mains connector led to experimentation with aftermarket power cord designs. I t is now widely recognized that important shielding advantages and impressive sonic improvements are available through the use of high quality AC wires.

These advantages became apparent to me about two years ago while 1 was demonstrating a pre-production discrete FET preamplifier at a local dealer. Initially, the result was pleasing. Then we installed the preamp just above an ARC Classic 60 amplifier. This time the preamp sounded terrible - there was considerable noise even without any sources attached. The unit does have high impedance areas which were susceptible to noise pickup. We changed the power cord to a Belden shielded unit. The noise disappeared suddenly and the unit sounded good again.

After this experience, I investigated what was available on the market. I was surmised to find a number of power cords ranging from $100 to over $300 for a six foot length. I bought several of these entries and tested them in the configuration that caused problems with the stock cord I had been using. I couldn't believe the improvement over the Belden shielded cord. The noise radiation problem was eliminated, but there was also substantial sonic improvement in a number of areas. This was starting to get interesting.

I polled several equipment makers and learned that most were using standard grade high gauge wire or off-the-shelf IEC cords for their units. Clearly, one could do better. In my first attempt at building power cords, I used Romex wire, inspired by a write up in IAR suggesting that since it is what is running in the walls it should suffice. The result was good but not as good as some of the store bought cords. 1 am against tearing open cables and devices and copying them so 1 went back to the drawing board. I tried some average grade 12 gauge solid core wire with a copper braid shield and the result was better than expected.

One day, I got some Cardas wire for a prototype amplifier we were building and tried this as a power cord conductor. In this attempt, I adopted a few aspects of construction and aesthetics from the Cogan-Hall Intermezzo speaker wire kit. The copper braid shield was a plus in the above mentioned effort so 1 retained it in the prototype of this design.

I braided the three Cardas conductors to cancel any radiation and I used a Wonder Wire" drain wire for the ground connection. Stretching and taping the braid down every few inches helps the drain wire maintain contact with the braid and keeps the signal wires wrapped tightly. At this point the cable was functional but not very pretty. A nylon braid sheath a la Cogan Hall over the copper braid gave the unit a finished and "professional" appearance. Compared with the other cables I had been auditioning, this cable provided a more spatial sound with enhanced definition. On track 5 of Ricki Lee Jones Flying Cowboys, the oscillation of the vibrato controller was cleanly articulated. The other cables were somewhat smeared in the vibe passages in comparison. Overall, there were surprising differences for such a simple change. On extended listening, I liked this cord so much that I now include it with my Wavelength Audio products. The cord is not available separately but here are plans for you to build your own or provide inspiration for your experiments.

 

Description
The Power Cord Plus uses Cardas 14.5 ga. wire for hot and neutral leads and 18ga Wonder Wire as a drain, a tinned copper braid shield, and a nylon braid covering. The wall end is terminated with a hospital grade mains plug and the female end is terminated in a high grade IEC connector. This configuration will work with all equipment using male IEC connector.

 

Parts For An X Foot Cord
1 - Three lengths of 14.5ga Cardas Golden Stranded Chassis wire at (X+0.7St') each
2- X feet of tubular copper braid 0.375" dia.
3- X feet of nylon braid 0.5" dia.
4- X feet of Wonder Wire or other tinned solid 18ga. conductor
5- Hospital Grade three prong power plug
6- IEC female connector (15A-25A) with as large an opening as possible
7- Electrical tape precut in 1.5" lengths (approx. 10-15 pieces)
8- Heat shrink tubing: One 1.5" piece of 0.75" dia., two pieces of 0.25" dia.

 

Equipment Required

 

Construction
Dimensions are given in terms of offsets so that the user can create any length of cord. Prepare the three 14 ga. conductors in the following manner: Cut lengths about 3/4" longer than the proposed length of the cable. Strip about 0.25" from each end of the wires. Using a solder pot or a high wattage soldering gun, tin both ends of all three conductors. Mark two of the three wires with a marker or heat shrink, unless you have two or more colors of Cardas wire. I use red and yellow heat shrink to mark hot and neutral conductors.

Line up the ends of the three wires and tape them together about 1" from one end in a tight bundle. This will be the wall end. Braid the three conductors up to the other end and tape them together about 1.25" from the end. This will be the equipment (IEC) end.

Line up the 18 ga. drain wire with the unmarked (ground) 14 ga. wire. Tape it in place about 1" from the wall end, then spiral it around the braided wires. Tape it in place about 1" from the other end and clip off any excess.

Temporarily tape over the ends of all conductors at the wall end. This will facilitate threading these wires through the copper braid.

Trim the copper braid to 1" less than the proposed length of the cable. Start at the end you just taped over and feed the cable through the braid. Tape the braid tightly around the wires about 1" in from the equipment end then, while pulling the braid tight, tape every six inches or so. This will ensure good contact between the braid and the drain wire. Trim any excess braid off at the wall end and tape it down about 1" from the end. Make absolutely sure that the braid can not come into contact with any power leads. The copper braid will get your hands really dirty, so go wash them after this section of the operation.

Trim the nylon braid to 1" less than the proposed cable length. Starting at the wall end, inch the nylon over the copper braid. Make sure that the copper braid does not bunch up while doing so. Pull the end of the nylon just over the end of the copper braid and tape it off very tightly. Be sure that the tape does not show beyond the rubber sleeve of the female IEC connector. Smooth out the nylon braid over the length of the cable, tape it down 1" from the wall end and trim any excess.

Remove the temporary tape from the wall ends of the wires. Place the heat shrink tubing over then end of the wires and adjust so that about 3/4" of the conductors is showing. Shrink the tubing until the nylon pattern begins to show through the tubing. At this point, take apart the female IEC connector. Take the rubber sleeve out and position it on the equipment end of the cable. There should be about 1/2" of conductor showing. Insert the conductors into the channels of the IEC connector and bolt them down. I find it useful to square the ends of the connectors using a pair of pliers for better fit and greater surface area for the screw down contact. Close the IEC connector and bolt it together. The connector should close completely, though I have had battles with my needle nose pliers getting everything squeezed in when using large gauge wire.

Figure 2Take apart the wall plug and place the strain relief portion over the cable. Make connections per Figure 2. Make sure that the drain and chassis ground conductor are fed into the center position. Use an ohmmeter to make certain that all connections are correct and that no shorts between conductors exist. It is easier to change connections on the wall end of the power cord if necessary. This completes construction of the cable. Plug it in. Enjoy.

The Power Cord Plus can be used with any source, preamplifier, or amp up to 100W. For amps bigger than 100W, heavier wire is indicated because of increased current. Be prepared to get frustrated over the limited working area of the female IEC connector when using wire heavier than 14 gauge.

 

For Further Experimentation
Here are a few suggestions worth trying which I have not yet implemented:

1- Put IRON cores around the signal leads to filter out HF noise components. Fix placement with heat shrink.

2- Put a low value resistor in series with the chassis ground connection to filter out digital noise in CD and DSP units. Some digital AC cords omit the chassis ground connection entirely.

3 - Run multiple thinner conductors in parallel for each conductor. Tightly twist or braid these together.

4- Michael Percy reports excellent results using a pair of .l caps from chassis ground to neutral and hot leads. Be sure to use AC rated caps or units rated cat least 600 VDC for a 120 V line.

 

Parts Sources
Parts for Power Cord Plus are available from Michael Percy, Triode Electronics, and many other audiophile suppliers. If you have any problems sourcing parts feel free to contact me at Wavelength Audio.

Gordon Rankin
Wavelength Audio
4539 Plainville Road
Cincinnati, OH 45227
513-271-4186 phone/fax/voice mail

Michael Percy
Box 526
Inverness, CA 94937
415-669-7181
415-669-7558 fax

 

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