When the amorphous Stealth Indra interconnect first hit the scene, certain cynics and skeptics immediately cried wolf and voodoo. But the subject is for real. Eliminating all crystalline boundaries in metal conductors seems to be audible. This complete elimination of the molecular lattice work can otherwise only be accomplished by eschewing metal altogether, say in favor of Carbon, other synthetic fibers or fiber optics (which could introduce their own issues).

Of course the equation amorphous + audio = results isn't new. Amorphous core transformers from the likes of Tango and Tamura have long since been deluxe choices for bespoke transformer-coupled amplifiers. But how many people have listened to an amplifier outfitted with silicone steel-core transformers (the standard) and compared it directly to the equivalent amorphous core transformers while disregarding the in-between solution of permalloy cores?

Swedish transformer house Lundahl of Norrtälje now offers amorphous iron as well: "This version provides enhanced audio performance based on the greater inherent magnetic homogeneity of amorphous materials. The normal crystal boundaries that develop in conventional magnetic materials when they are fabricated are absent from amorphous magnetic materials. This is accomplished by cooling the molten iron at a rate of one million degrees per second as it is formed. The absence of crystals that behave to some degree as autonomous magnetic entities, allows amorphous materials to magnetize and demagnetize in a more 'linear', coherent fashion." On a data sheet for the LL9206 unit, it further states "this type of core does not store energy (unlike conventional mu-metal cores) so the low frequency resonance with external series capacitors is practically eliminated."

Because the AM versions use "coils and frames identical to those used in the standard silicon iron transformers", an comparative A/B audition can truly focuses on just one variable - the core material. One of our readers owns custom tube amps and has performed exactly that comparison. Not endowed with the - ahem, flowery gift of gab of certain reviewers, this fellow summarized the differences as equivalent to a speaker upgrade. In short, anything but subtle. Descriptors such as "breathing", "flowing freely", "more natural", "organic" and such peppered his approach to that final statement. Come to think of it, curiously reminiscent of my own attempts in the Indra review to quantify why it sounded different. That amorphous metal sounds different seems quite demonstrable. Describing accurately how is anything but easy since these differences don't operate in the usual domain of audiophile attributes.

One more fleck of evidence -- in my book at least -- that the emerging science of amorphous materials (DuPont for example sells amorphous Teflon with measurably different electrical behavior than the non-amorphous standard flavors) has promising implications not just for space travel and military applications but also for our harmless hobby. The only negative? The hi-tech manufacturing processes involved to produce amorphous materials is said to be very costly and advanced. Hence, those materials carry a hefty price tag when compared to their crystalline brethren and will thus likely limit their appearance to more upscale audio products.

No sooner had that last statement's ink dried on the virtual page that a reader working for Acrosound pointed out the error of my ways (which is one of my favorites things about our site - our readers are very generous and share their knowledge quickly): "The statement above is simply false. Over the last few weeks I have received prices quotes on custom C-cores made from various core materials including amorphous iron, low nickel, high nickel and nano iron. Here are just a few examples: Sample A - amorphous iron $39.50 each; 50% nickel $46 each; nano iron $58.50 each. As you can, see the 50% nickel core is in fact more expensive than the amorphous core.

Sample B - low nickel $12.75 each; high nickel $16.92 each; amorphous iron $15.25 each; nano iron $18.62 each - again, the conventional high nickel core is more expensive than the amorphous iron substitute. The pricing trend in the industry is that the amorphous iron cores are becoming the less expensive material compared to the high perm 'conventional' alloys. Just today I spoke to an industry rep regarding this pricing trend and expressed to him that I was somewhat surprised by this. To which he responded that it was logical because the amorphous iron dispenses with the most expensive material in the manufacturing process (i.e. nickel as a raw material is much more expensive than iron) and that the manufacturing process itself is becoming more cost effective (almost akin to sputtering a conductor onto a dielectric film) as opposed to the traditional method of manufacturing and processing the 'traditional' sheet forms of electrical lamination materials.

You also did not touch on the weaknesses of the amorphous and nanocrystalline core materials and failed to mention that amongst the amorphous and nano materials, there are still different alloys. Amorphous and nano is available in iron, cobalt or nickel cores. What you are seeing on the market (generally speaking) are amorphous iron cores. Amorphous cores have a notoriously poor stacking factor (K factor), hence you need to use a larger core cross section to regain the lost "effective core area". This of course entails some disadvantages in that your coil must now be larger and it changes all of the coil dynamics and electrical properties.

Also, the amorphous cores (even iron ones) cannot be run as hard as you would M6 flux density wise. This means that you should either derate your design's power when you switch over to an amorphous iron core or you should use a bigger core if you need to retain the same power rating as for example your M6 design had. Another point that is often lauded is that amorphous iron cores have exceptionally low core losses but according to material engineers at Mag Metals, domain-refined M4 steel lams will have even lower core losses below 400Hz. The losses in a transformer are related to how hard the core is run. The lower in frequency you go, the more work the core must do. In the frequency range wherein the core must perform the most 'work', the amorphous does not have the advantage claimed by some."

It appears, once again, that there is no free lunch, no magic bullet. The only thing that seems fair to say then at this point is that if Serguei Timachev's Stealth Indra does what it does because of the amorphous factor (rather than some other ingredient or combination of ingredients to do with the cable's geometry and termination), then DIYers and manufacturers of transformer-coupled amplifiers might be well advised to at least experiment with the new crop of amorphous and nano-core transformers to determine whether, in any given application, the audible results are preferable to traditional cores - especially if the pricing structure for amorphous variants is shifting.