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Positive Feedback ISSUE 30
march/april 2007


We sent out the same 20 questions to 50 manufacturers, the following are their responses. The intent of the survey is to address basic questions as to design along with any questions raging on various sites, while minimizing potential chest-thumping and friendly, or unfriendly, bashing of others....

Click here to read the other interviews in the series.


Joe Cohen of Prana Wire
by PFO

PFO Why do cables make a difference? Interconnects, speaker, and AC cords?

Joe Cohen By now we should all know that cables can make or break a system. The finest equipment with inferior cables will yield a result inferior to a lesser system with superior cables. Why? If the cable is not up to the task it will insert and attract various kinds of distortion and noise.

People tend to think that signal travels within the conductor the same way that water runs through the confines of a hose, but that is far too simple an analogy. One of the reasons why so many people have come up with so many different theories about cables and so many different approaches is that the interactions between signal and conductor and all of the materials in the cable and all of the fields that surround the cable, both self generated and ambient are so numerous, varied and complex, that there is no way to properly predict or model them all.

The best thing a cable can do is to get entirely out of the way, but to do that one has to address all of the problems inherent in taking signal from component A to component B including, but not limited to: vibration at the connection, interaction between the conductive material of the connector, its plating, if any, it's insulator, the manner of joining the conductor to the connector, interactions between conductor and dielectric, interactions between conductor and shield, interactions between conductor, shield, dielectric and outer covering, self generated noise, ambient noise, feedback from other components in the chain and so on.

A properly designed cable becomes a "quiet zone" through which signal passes—the majority of self-generated and potentially acquired noise and distortion are not picked up or are left behind. This will explain why 1 meter of power cable can make a difference even though power has originated hundreds of miles away from your outlet.

PFO What about metals ...copper versus silver versus gold versus what? What about blends?

JC Metals are 50% of the equation. The rest is choice of other materials and architecture. Choice of metals is critical. Use of high purity conductors lessens the amount of minute resistances caused by impurities and allows for smoother more extended high frequency performance.

PFO What about dielectrics... Teflon versus what?

JC All materials interact with one another even when there is no signal, so the point is to choose a dielectric material that has a symbiotic relationship with your conductor and other materials used in the design. Reliance on the dielectric constant spec alone will not necessarily yield the best sound. One has to dig deeper.

PFO What about no dielectric?

JC There is no such thing (unless, of course one surrounds the conductor with another conductor, but at some point one has to arrive at (at the least) air which will be the dielectric). Even a vacuum surrounding a conductor is a dielectric by definition.

PFO What about measurements... what do they tell us? what do they not tell us?

JC Measurements cannot unravel the multiple layers of interaction that occur in real world, real system environments.

PFO What about connectors... how important?

JC As the choice of cable can make or break a system, so too can the choice of connector make or break the cable. To date, whether we like it or not, the most expensive connectors, that is the ones with the finest materials and construction (as with everything else) give the best performance.

PFO Why this geometry... ribbon, twisted, braded, spiraled...

JC Each approach has its reason for being whether to reduce capacitance, induce inductance, increase or decrease skin effect, and every approach has its limitation. Take your pick and develop from there.

PFO What about cryoing? What is going on with this?

JC The evidence is there to support the theory that cryogenically treated materials are more pure and have a tighter and more coherent crystal structure. I have yet to experience a negative effect from cryogenic treatment.

PFO Why shielding? Why not shielding?

JC As with everything in cable design, implementation is everything. There is not necessarily one way to arrive at a desired result. In some cases a shielded design may be superior, in another not. Implemented one way the shield may appear to cause congestion in the sound, implemented another it will appear to yield the opposite result.

PFO What about run-in? Why is/isn't it important?

JC A cable is a "put together" thing. Over time the various materials will settle in and become a whole. Signal traveling through conductor may establish its most efficient pathway. Materials surrounding the conductor may actually "charge up" and store energy and finally release that energy in a symbiotic fashion.

PFO How did you get into this?

JC I began building my own cables in the late eighties, experimenting with various multiple gauge solid core designs—getting better results than a number of commercially available cables at the time. One time my friend Ric Schultz, now of Electronic Visionary Systems, came by with a very large diameter wire constructed entirely from bundles of litz made by his friend Sig Modes. This cable completely obliterated all preconceptions I had held up to that time as to how cables might influence the behavior of a high-resolution system. I was practically begging him not to leave my house with this newfound revelation. Sig's cable was, sadly, one of a kind and not available commercially so there was nothing to be done. I didn't have another such revelatory experience until the 1992 CES. in Las Vegas, when I came across A.R.T., an ostensibly Italian line of audio cables. I was drawn into their room by the sound of "La Folia", by Panagua, but stayed to hear an Italian gentleman extol the virtues of the cables and accessories he was peddling. I remember him saying that the high quality of the sound in the room was due more to the cables and accessories than to the amplifiers and speakers. This seemed a little far-fetched at the time, but he gave me a pair of cables to audition. When I got back home and had a chance to listen, I instantly realized I had encountered something very unique. I was so impressed I became the US importer. Over time I acquired more and more of their products, and each time I placed a new cable or accessory into the system it produced the same kind of salutary effect—sounds became more natural, less harsh, less glaring and more rich with information.

Later when I traveled to Italy I learned that the cables were actually produced in Japan and that they were designed by Be Yamamura.

At the time, Mr. Yamamura was building the first of his exponentially curved, cork-covered back loaded horns with modified Lowther drivers called the "Dionisio". There was a pair on hand in his Tuscan hillside home when I visited. Joined with his true air-bearing graphite turntable, current mode electronics and cabling, these speakers produced a kind of realism and organic sound I not experienced up to that time, and which haunted me for years after.

I spent a fair amount of time with Mr. Yamamura, burrowing into the heart of his concepts, developing a deep sense of his understanding of cable design and learning about vibration control and protection of equipment from noise. I wrote a handbook that was distributed worldwide called the Yamamura Method‚ and conceived of and built the first prototype Millennium Tube—used to passively absorb noise at metal-to-metal junctions in audio systems and presented it to Yamamura, who then made a practical model that could be easily manufactured.

After several years of representing Mr. Yamamura I took a hiatus from promoting hi-fi.

For three years there was no audio system in our house, but one day after I had divested myself of most of the high end equipment, I decided to put together a very modest system based around a pair of Totem Acoustic Model One's and a class D amplifier I had in storage. The tweaking impulse was soon to follow, and this, in turn, grew into a raging obsession with cable design. I spent a couple of years researching configuration and materials culminating in the construction of a power cord which delivered more than I had a right to expect. That prototype design was far too complicated to put into production, but it let me know that I was on the right track.

PFO What is your fundamental design goal?

JC To design devices that enable one to forget that one is listening to equipment and get lost in the enjoyment of music.

PFO How do you approach accomplishing those philosophies/goals?

JC I obsess over an issue, give up, revisit it, revisit it again and wait for inspiration.

PFO How successful do you feel you have been at achieving the goals that you have set for yourself?

JC I never started with a goal. I started with an obsession that would not let go of me. Had I been able to have a glimpse of what I'm hearing today when I started out, I night have said it was beyond my wildest dreams. Today I only feel like I'm at the beginning.

PFO How do you plan to push beyond what you have already accomplished?

JC Obsess some more.

PFO Where is this all heading?

JC The grave.

PFO Others that you admire?

JC Winston Ma is a fine gentleman. When I see him he reminds me that it's about the music and people. In the end, that's what it's all about.

Click here to read the other interviews in the series.