The proliferation of Class D digital amplifiers has been a major trend in recent years, and it's easy to see why. Those highly efficient designs run cool, enabling high output power from lightweight amplifiers with small footprints. The massive and costly transformers and heavy heat sinking required for high-powered analog amplifiers are no longer needed. In many of those products, implementations of wall-wart power supplies and off-the-shelf digital amplifier modules produce 100+ watt amplifiers with very respectable specifications. But in my personal experience such undeniably cost-effective designs have not reached the performance refinements I expect in a perfectionist audio system. But top-shelf sonics are available from more ambitious Class D designs, such as my Spectron Musician III amplifiers in bridged monoblock configuration. Those amplifiers provide extraordinary sonic purity and virtually unlimited headroom (2000 wpc, 7000-watt unclipped transient peaks). While the Spectrons' proprietary output modules are class D, the power supply is a traditional linear design incorporating a massive toroidal transformer and Bybee AC Bullets -- which suggests why each amp weighs 50 lbs. The Spectrons normally run cool, but they can get very hot to the touch when pushed hard. And they sell for nearly $12,000 per pair, roughly three times the cost of the Arion RS-500s.
Arion is the brainchild of Michael Kallelis, best known as the North American importer of Analysis Audio planar/ribbon loudspeakers from Greece. Mike's MK Audio comprises Analysis Audio USA, Arion Audio, and the Pon-Tunes footers I reviewed last month. The RS-500s are an uncompromising all-out Class D design, conceived and built with fresh thinking and without any of the off-the-shelf digital modules, cheap power supplies and other cost-driven compromises found in many inexpensive Class D amplifiers. In developing the amplifiers Kallelis collaborated with circuit designers who specialize in PWM (Pulse Width Modulation) circuit design and development used in industrial and military applications.
The switching power supply is one of the most innovative and sophisticated such designs I have seen. It incorporates both over-current and short-circuit protection, and automatically adjusts to any wall voltage from 85 to 240 VRMS -- so no switching or rewiring is needed, for instance, to go from the 117V to 220V European or Asian voltages. Very cool! Other marks of build quality include the use of JPS Labs and proprietary silver hookup wire, Cardas gold-over-solid copper speaker terminals, gold-over-solid copper RCA and XLR input jacks, and premium fasteners throughout.
Description And Review Setup
For the review the RS-500s replaced my Spectron monoblocks. For isolation I used both my familiar Ginkgo Audio Cloud platforms and the Pon-Tunes footers reviewed last month. Both were quite effective, with improved speed and dynamic impact over placing the amps directly on the shelf. The other principal variation was preamps. Initially I listened with the VTL TL 7.5 Series 2; connected with single-ended JPS Aluminata interconnects. Later I switched to Einstein's "The Tube" MK 2 and XLR Aluminatas. The amps performed impeccably in both setups, but ultimately I got best results with the Einstein. The following comments are based on those listening sessions.
Beginning a couple of years ago, first with the Spectron Musician III and now with the Arion RS-500s, I hear an almost uncanny tonal purity. This quality is difficult to describe, but it differs subtly from any of the excellent tube or analog solid-state amplifiers I have owned in the past. Those amplifiers produced gorgeous sounds, and they had their own distinctive sonic "markers" -- such as the "creaminess" and harmonic warmth of the VTL Siegfried tube amps , or the transient "slam" and ultra-low-level detail retrieval of the solid-state Spectral DMA-180 -- but these state-of-the-art class D amps give me something subtly different, and ultimately more musically satisfying because of that defining tonal purity, together with unsurpassed transient speed and background "blackness."
One quality that became apparent early in my evaluation of the RS-500s is their ability to scale accurately to the program material -- an ability that is especially important with my seven-foot-tall Analysis Amphitryon speakers. With large-scale choral/orchestral music such as Ricardo Muti's stunning new CSO Resound recording of the Verdi Requiem. The RS-500s are at least the equal of the VTL Siegfrieds, my previous soundstaging champ, in breadth, depth and precise placement of individual elements within the stage; and they slightly surpass the Musician III monoblocks in depth -- it sounds literally as if the chorus is located well behind the back wall of my listening room. That is not a new perception, but the degree of depth and dimensionality -- and, excitingly, height differentiation with the chorus -- is more vividly audible than before, and highly satisfying.
On the other hand, with Rostropovich's Bach Cello Suites I hear a perfectly centered, close-to-the-floor image. Perfect. And with the Tokyo Quartet's late Beethoven Quartets, the arrangement of the players is captured so precisely that I can visualize them in my mind's eye. The amps are especially symbiotic with my big planar/ribbon speakers in reproducing the piano. I have always regarded that as one of the toughest tests of any audio system, especially when using small cone/dome midrange and tweeter-equipped loudspeakers. The Analysis speakers have the large radiating areas needed to do justice to the piano's sonorities, and the RS-500s capture the instrument's full presence and the hall ambience flawlessly.
Vocal music -- classical, jazz, folk, blues and rock -- constitutes a large share of my listening time, and along with the piano presents the biggest challenge for an audio system. One of my most valuable recordings for critical listening is Patricia Barber's Cole Porter Mix, the best-balanced and most natural-sounding off all that great artist's albums. The system now reproduces it with that uncanny tonal purity I mentioned, on both the vocal and her Quartet's brilliant instrumental contributions. And I am stunned by the ravishing reproduction of Susan Graham's and Thomas Hampson's gorgeous voices in the new recording of Mahler's orchestral songs with Michael Tilson Thomas and the San Francisco Symphony. I have heard both of those singers live numerous times, and I have never heard their voices reproduced more beautifully, even by tube amplifiers. That old digital grain and glare I heard years ago are nowhere to be found with theRS-500s.
About Power Cords And Conditioners?
In a word, yes. Yet it is not nearly as great a difference with either analog amplifiers, or my Spectrons' linear supplies. But still clearly better than with cheap AC cords. I tested the differences in two stages. First, I bypassed my power conditioners and used my Bybee power cables -- which incorporate a specific kind of power conditioning effect -- and then with just cheap AC cables directly into the wall. In the first stage, I would quantify the sonic degradation without power conditioning as somewhere around 10%. Replacing my Bybee cables with el cheapos, the sonic drop-off was probably more in the neighborhood of 20% to 25%. Maybe those low-cost digital amps with their wall-wart power supplies get adequate juice, but state-of-the-art digital amps, it seems, still benefit from improving the quality of incoming AC.