Ulrik Poulsen and his Amazing Alpha-Core Cables
Ulrik Poulsen: It's actually close to three years now...It's a spinoff from other products we make. Actually, Alpha-Core manufactures magnetic cores and various materials and components for transformers...And we have a daughter company called Tortran that manufactures toroidal transformers. Anyway, five years ago we introduced a new product called Laminax. It's a combination of copper and aluminum with various kinds of dielectrics. This is laminated together continuously in various fashions to produce a material that's used as shielding for EMI and RFI in the electronics industry.
We were selling this special material all over the world, as we'd developed a method for combining special types of thin films and metals without using any adhesives at all!
Poulsen: We export this material, and we also developed machines to manufacture it. Then 2½ years ago I developed and patented a cable design of two parallel conductors inside a single sheath. I thought that cable might have applications in various areas of the electrical industry. The thing about it was, it utilized the same technology we use to make the Laminax products. But I didn't find any takers when I showed the cable around, until a friend of mine thought it might just be the cable the world was waiting fora speaker cable. And his name is Goertz!
Scull: I see...
Poulsen: Yes, he's an accomplished Danish electronics and audio engineer. He told us what characteristics would be required for audio applications, and we manufactured a cable to those specs. We sent it to him for testing, and he was able to show that it totally eliminated the type of distortion that in this country is called high-frequency roll-off.
Scull: That was the original copper cable?
Scull: We have the more expensive silver cable, so perhaps you'll tell us about that?
Poulsen: Sureit's what we call MI Ag II Matched Impedance type. The basic thought behind the development of the entire cable linesilver and copperwas that if you have a characteristic impedance that matches that of the load, you get a better-functioning cable. That's basically transmission-line theory, where you match the impedance of either the load or the source in order to prevent mismatch reflections. That's why for certain applicationstelevision or antenna wiring, for exampleyou need a 300 ohm or 75 ohm cable. That's the same theory, mostly used at much higher frequencies. But it's also valid at lower frequencies within the audio spectrum. We were able to demonstrate the effects of both the mismatch reflections and the absence of high frequency rolloff reaching well below 10 kilocycles, which is smack in the audible range, of course.
But you asked about the silver cablethat's the same geometry as the original copper cablea 10-gauge 2.5-ohm characteristic impedance speaker cable. It consists of two solid conductors ¾" wide and 10/1000" thick. Placing those two conductors a mere 3/1000 of an inch apart really drives the inductance way down. At the same time, it raises the capacitance of the cable. And since the characteristic impedance is the square root of the inductance divided by the capacitance, that combination enabled us to reach a characteristic impedance that's in the single-digits. And that is not the case with most other audio cables.
Scull: I wonder if that's why it works so well with the Jadis single-ended amps, which have a typically high output impedance?
Poulsen: Yes, but you see, the output impedance of the amplifier is of no real significance in this case as long as the load impedance is of the same order of magnitude as the characteristic impedance of the cable. It's sufficient if you have an impedance match at only one end of the link. You can compare them if you take an optical point of view. If you have mirrors at both end of the cable, you'd have multiple reflectionsyou'd be able to see yourself repeated hundreds of times.
Scull: I understand...
Poulsen: If you have just one side with an absorbing characteristic instead of a reflective characteristic, that breaks the chain, and you avoid having those repeated reflections. And that's sufficientif you have a match on either the load end or the source end.
Scull: Okay, let me carry out my earlier threat and come back to dreaded RFI. Obviously your cable isn't a twisted pair of a type that fights RFI, so...?
Poulsen: Because they have a low inductance, which pulls both ways, the radiated fields of the cable itself are virtually zero. By the same token, it also makes the cables insensitive to outside fields. You can easily test this by bundling the cables with power cordsyou don't get any line-frequency hum. And you can bundle them with other signal-carrying cables, and you get no crosstalk whatsoever. You can also easily check that they're impervious to broadcast frequencies, because you can hear that there's no dirt getting into your feedback loop at all.
Scull: As I understood from speaking with you earlier, you were saying that the dielectric of your speaker cable affects break-in time?
Poulsen: Well, Jonathan, there's a few things I personally don't believe in at all. I don't believe in the importance of directionality, and I also don't believe in having a cable sit on full-load for weeks on end before it sounds right.
Scull: It's true your cable sounds just terrific from the get-go, Ulrik. But I have to tell you, I thought you were kidding when you said they required no break-in.
Poulsen: We've looked into this, of course. A lot of people whose opinion I respect believe in running-in cables very thoroughly, but they thought as you did about our cable...
Scull: Well, Ulrik, let me qualify that. In my experience, with some cables it's absolutely necessarysome can take ages to break in.
Poulsen: You're probably right. If that's the case, there's only one explanation I can think of that's physically responsible. I don't think much actually happens to the metal in a cable, but all the organic material that's carried in the dielectric and the insulation may well change during the break-in period. And if that is so, that might explain why our cables break-in so fast. The fact is that in our cable the dielectric is only there in minute amounts. When you have 3/1000" between the conductors, that means that there's only a small, small percentage of the total amount of the dielectric that is active in our cable compared to the amount that's active in other cables.
Scull: Ah-hah. What's the actual material of the dielectric?
Poulsen: It's called polyether terephthalate.
Scull: Oh...sure...that old stuff. Can you spell that for me, Ulrik? [laughter]
Poulsen: Actually, it's not an uncommon materialnothing particularly fancy. The reason we're using it is that it's available in a very thin film, and as I mentioned, we found a very good way of bonding it directly to the metal without using any adhesives.
Scull: But you're not saying how you do that?
Poulsen: [very quickly] No!
Poulsen: This material enables us to have a very high dielectric strength. That means you can apply thousands of volts between the two conductors and yet you won't have any breakthrough.
Scull: That's amazing, just 3/1000" between the conductors...
Poulsen: Actually, 2.4 thousandths, because each layer of insulation that surrounds each conductor is only 1.2 thousandths of an inch thick. Then the whole thing is encased in a common jacket, and for that we are using Lexan, which is a polycarbonate.
Scull: What about some of the electrical properties of the MI Ag? What's the capacitance of the cable?
Poulsen: For the cable you have, it's about one nanofarad [1nF] per foot.
Scull: Of course! You know, that means absolutely nothing to me! [laughs]
Poulsen: Well, it's high compared to other cables, but the inductance, that's the important feature. That's only six nanohenries (6nH) per foot.
Scull: Ahh, yes, nanohenriesI've heard of those!
Poulsen: [laughs.] Yes, we all know about old Henry! [laughs.]
Scull: Ulrik, can you simply state why it's true that low inductance is superior to low capacitance?
Poulsen: Yes: because it's been proven that if you have a high inductance in a high-frequency circuit, it will act as a high-frequency partial short! Yes, it will short out some of the signal components as the signal passes through the cables. And any electrical engineer can make the calculation that high inductance is much more of a problem than high capacitance. The reason that high capacitance has been considered harmful by some is that it can sometimes cause a poorly designed solid-state amplifier to oscillate. If you have a correctly designed amplifier which does not violate the Nyquist rule on the amount of negative feedback you can use, you don't have a problem.
Scull: That's quite a spade lug you supply on the cables. What's its construction?
Poulsen: Yes, it's a solid, almost forged piece of high-quality brass that's rhodium-plated, because rhodium is generally considered to be a better contact material than gold. It's also more wear-resistant. You know, rhodium is from the platinum groupa noble metaland we consider it far better than gold for audio applications.
Scull: How much are the silver cables retail, Ulrik?
Poulsen: Well, with the silver cables it depends how you buy it. If you purchase a 75' can for professional installation, it's $4668, to be exact. For the typical audiophile who needs 6' terminated, it's $760/paira hell of a lot of money for cable. But we know from many of our customers, those who paid $10,000 or $20,000 for their systems, that they just don't want any weak links in the chain.
Scull: What reception has your novel design received in the audio community?
Poulsen: We brought the cable over to Dick Sequerra, who loved it. He A/B'd them with what he was using, and he made a lot of measurements to illustrate the differences. We have a lot of other fans too, like Vince [Bruzzese] at Totem, who also loves the cables. We use his Model 1 speakers in our evaluations, by the way. We know that Thiel also feels that our cable is the right way to go, and then there's Dan D'Agostino at Krell, who has become so enthused that we are now developing a special 7-gauge cable especially for him. It'll be called Krell/Goertz.
Scull: Congratulations. Any last stones to toss?
Poulsen: Laughs Actually, I can talk my head off on the subject, but the proof of the pudding is in the listening.