Country of Origin
Reviewer: Simone Ragionieri
Source: Generic 5G router into Taiko Audio network switch both powered by a Zayin Audio Suprareg; Taiko Olympus XDMI Server; LampizatOr Horizon 360 DAC
Headphone amplifier: Riviera Audio Labs AIC-10
Headphones: Spirit Torino Valkyria, Raal 1995 Immanis
Loudspeakers: Diesis Audio Aura SE
Cables: complete Faber's Cables La Potenza loom
Power delivery: Faber's Cables La Potenza power distributor and ground box, Furutech NCF AC wall plugs on a dedicated spur
Room size: 5 x 4.5 x 2.7m
Room treatments: Eight ceiling diffusers, floor-to-ceiling acoustic curtains on sidewalls, Vicoustic VicTotem Ultra VMT in front corners
Review component retail ex VAT: €2'900 Silver RCD interface, €2'000 Star-12 2.9m headphone cable, €450/0.85m Star-8 amp cable
Silver fox? Unlike mine, Simone's coif isn't quite there yet. But more silver was about to invade his life. "The RCD I purchased for driving my Immanis headphones off the Riviera AIC-10 amp is a custom 16Ω which Alex recommended at the time as the best choice since I use the amp's speaker posts. For low-power SET amps specifically, Alex recommends the 8Ω version. In anticipation of my review of Solaja's Master 300b, I asked Alex what he thought of my 16Ω RCD. He replied that it'd work but not be best on the Solaja though—and confirmed by SAEQ— the Astraeus also in for review is perfectly happy at 16Ω. I thus asked Alex whether he could loan me an 8Ω version for the Solaja review. He's happy to and could include his new silver cables if I can review those." That was our man in fashionable Milan asking permission to pursue a review on the new top Raal 1995 interface kit.
To refresh collective memories, the Immanis headphones which Simone and I listen to run thrice-paralleled true ribbons whose native impedance would present a virtual dead short to the amplifier. It's why true ribbon tweeters—not planarmagnetics mislabelled as ribbons—are backed by an impedance-matching transformer. Wearing two of those on our noggin would simply be an uncouth neck dumbbell. Hence Raal relocate that iron into a separate barrel. Fitted with the mushroom stem as shown, it doubles as stand. A length of special cable connects our headphone amp to this RCD, another cable goes from the RCD to the headphone proper. Since most headfi amps designed for harder loads will muster the ~3wpc into 32Ω which Immanis wants to see, the standard transformer interface I have presents our amp with 32Ω. Custom values are available. Apparently the new 300B amp from Serbia's Dragan Solaja prefers to see 8Ω to develop full power into these current-hungry triple ribbons.
October 9th: "We must get out of this magnet-shortage crisis. We were out of magnets for a full 4 months due to Trump's trade war with China halting the export of raw magnets. Unlike most others, we make our own drivers so need raw magnets. We can't order complete drivers or sub-assemblies from China. Those weren't hit as they were considered completed transducers or parts with a different tariff code than raw magnets.
"We are presently clearing a hefty backlog so until done literally have no time to work on other stuff. I expect we'll clear all old orders by the 1st week of November. The new Silver set consists of a new interface and cables. The transformer interface is a completely new development aimed at the least leakage inductance. There are special windings I call "silver multi-strand coaxial" because it's not a classical primary + secondary layering. Our transformer ratio sets by the wire rope we build prior to winding it onto the core. We used to make 32Ω, 8Ω and Viva Egoista 2A3/845 versions but now the 8Ω version is discontinued.
"What you see here is a powder-coated green core and one winding of 28 windings that turns 14 times one way, 14 times the other. At first it looks like one cross-wound secondary winding but isn't. It's a full-blown 32Ω transformer of 308:28 solid-core silver windings with extremely low leakage inductance. What you see here hasn't been potted in epoxy yet to show the winding scheme. The way to minimized leakage inductance is minimized distance between primary and secondary windings. There are other factors like complete coverage of the core etc. but reducing prime/sec distance is the most important goal. We made the existing interfaces with normal winding methods where you lay up the primary winding then cover it with the secondary, using the thinnest insulating layer between them. This works fine, gives very reasonable values and is reasonably simple to manufacture but not yet the state of the art.
"At left you see a short-pitch unidirectional concentric stranding of enamelled wire. The drawing makes the wire look slightly oval. It really is round but due to the pitch angle, the perpendicular cross section of an angled round wire is oval so must be factored when picking a diameter that creates layers without gaps. Blue is a non-magnetic insulated core, preferably non-conducting, that serves as filler so the first strand layer in red lays nicely in a circle that isn't squashed. After we twist the first layer, we twist another layer of 11 wires over it (yellow). Once made, we get 11:5 strands in this rope. If we connect all the inner wires in parallel, we get an 11:1 wire electrically. For an 11:1 transformer ratio which is slightly over what we need for a 32Ω transformer, all 5 wires in the first layer must connect in parallel to create the secondary winding; and 11 wires in the second layer most connect in series for the primary winding. For a 5:1 ratio slightly under what we need for an 8Ω transformer, all 11 wires in the outer secondary layer connect in parallel and all 5 in the primary inner layer in series.
"If you wind this on a transformer core even with a single winding, you still get a true 11:1 or 5:1 ratio if your wires connect correctly. For a decent primary inductance and power handling, this core need 308 turns on its primary to make a 32Ω transformer. That means 28 turns of this 11:1 rope. Once 11 outer wires connect in series and 5 inner wires in parallel, that is 308 primary turns and 28 secondary turns. On my barrel casing for it, I had to somehow explain this so engraved it with "Silver Multi-Strand Coaxial Windings". I use silver for one primary reason. After twisting, pure silver can be annealed at a low temperature and the strain in the metal relieved. Copper needs far higher temperatures well beyond what enamel can withstand. With silver you can use annealing to tweak the sound. Work-hardened silver sounds hard and too bright, annealed and strain-relieved silver becomes smooth and organic. So what we do with our cables we also do with this transformer. The whole point of this complicated exercise is that being coaxial, the primary and secondary windings now have virtually no distance between their magnetic centres and a very small distance between their conductors so leakage inductance is minimized. Another benefit is that HF now more directly couples between windings without in the process engaging the core. The result is a better leading edge on percussive instruments and less crowding so choral vocals separate better."
"I know how hard it was to keep track of all the changes we made across the past 5-6 years on how best to drive our true-ribbon headphones. The problem is that we are still pioneers of this new tech with no prior art on how to best do it. We started with the original resistor interface where you needed a 100wpc speaker amp, then moved to direct-drive amps from Solaja and Schiit, then to the 1st gen transformer interfaces, then to the 2nd. Now I can say with certainty that transformer-based interfaces are the way to go. So my further cable R&D aims at optimized transformer drive. Here we have true 2nd-gen cabling maximized for just that. So I'll explain what the Star-6, -8 and now Star-12 topologies mean.
"When you terminate a cable with 40-50Ω headphones, things are very different than terminating it with 0.015-0.057Ω which our current ribbons represent. In our case otherwise minute cable inductance easily kills the highs. The same inductance value would be ridiculously low for a 50Ω headphone to easily net 300kHz bandwidth. Not with ribbons. We must reduce inductance as much as possible. 0.050Ω doesn't forgive mistakes. One of the best ways to reduce cable inductance is a coaxial topology as used in our Magna Satis copper cable. But that doesn't yet make it best. The best way is a Star topology. A bare minimum uses 4 conductors (2 '+', 2 '-') called a Star-Quad. The property of Star topology is that the magnetic centre of each polarity is in the centre of the array so there is no 'area' of magnetic overlay, hence smallest possible inductance.
"For a combined cross section, the greater the number of conductors, the smaller their inductance. For results better than coax, the dielectric must be ultra thin so we use enamelled silver, not extruded insulation. Resistance to crosstalk or pickup of buzz and hum is better than coax but you still need some reasonable distance between L and R channels. There's one drawback to this scheme: conductors buzzing with signal. The currents we need for our ribbons are about 10 x higher than a standard 32Ω headphone. Immanis sees peak currents of ~3A. With that much current, closely packed ± conductors start to repel and attract each other due to magnetic forces between them. So good twisting around the inert core, annealing silver to soft after twisting so it won't mechanically resonate and jacketing that damps the vibration are all things we do.
"The initial Star-12 goal was simply a greater length option over our existing 1.8m Star-8. To keep the same resistance on a 50% longer cable, I had to increase the combined conductor cross section by 50%. Rather than use the Star-8 topology with larger-diameter wire, I moved to the more complicated Star-12 topology with my existing wire diameter. That option proved better than 8 wires so we quickly figured out how to twist it then spun up my playlist. Now it sounded better than Star-8 to create a challenge.
"I was lucky enough to move in the correct direction right away by increasing the distance between L/R channels, managing mechanical damping and one more item. Because of pursuing better sound not just length, this cable ended up bulky and unwieldy, pretty stiff and very much the opposite of ergonomic. But it does gives us 2.9 metres of higher quality. Now the frequency response of Silver RCDI + Star-12 cable measures up to 90kHz where I see a drop of just 0.35dB vs 1kHz. That's measured at the driver connector, cable terminated with Immanis driver. Also, the impregnation of the windings with complete immobilization of the strands between each other and the core brings down distortion further and doesn't waste any signal energy. With just 0.3Ω on this circuit, it's a tremendous result to, past the sum of transformer and cable, get -3dB at over 100kHz at the driver."
Now we're ready to hear about Simone's silver makeover.
