Kalman Rubinson

Back in 2016, I documented the rise of class-D amps using the early TriPath technology. Used in the Bel Canto eVo 200.2, TriPath cracked open the door to the High End but was never admitted due to a dim and opaque treble. The second wave was based on B&O's ICEpower technology, again via a Bel Canto amplifier, the Ref1000M monoblock. ICEpower had more credibility and was accepted by many but, often, only with, ahem, due consideration for size and efficiency. There was an explosion of new class-D amps in 2016 when Stereophile featured glowing reviews of Bel Canto's e.One Ref600M monoblock, Theta's Prometheus monoblock, and NAD's Masters Series M22 stereo amp, all based on Bruno Putzeys's Hypex NCore technology modules. Finally, it seemed that class-D was "in the room," though, even to this day, there remain critics and quibblers who continue to deny them as true high-fidelity products.

Well, time does not stand still and neither did Bruno Putzeys. He, along with Lars Risbo and Peter Lyngdorf, had founded Purifi in 2015, and in 2019 he unveiled the Purifi Eigentakt power amplifier modules.

In my early years in audio, I witnessed the rise and fall of the AM-FM receiver, first in vacuum tube mono and later in solid state stereo. Some of them grew to be behemoths, supporting multiple inputs, equalizers, dual speaker zones, and powerful amplifiers. When radio sources receded in popularity and with the rise of CDs, cable TV, and DVD, radio receivers were replaced by A/V receivers in the mainstream market.

Today, the ascension of streaming as the conduit for both audio and video content has nudged these, too, from the center stage. One can stream content from the bewildering variety of products with internet access including cell phones, smart TVs, almost any computer, and of course, dedicated streaming devices from the cheap-and-cheerful to seriously audiophile. If your music is on the web or on a NAS, many of these will let you browse for it, find it, and play it.

One thing that interested me about the StormAudio ISP Evo is that, despite its obvious hi-fi function, it's more like a computer than a typical "prepro." While it does offer a few "legacy" analog inputs, it is for the most part all-digital, input to output, including network connections on both ends. Consequently, it is less likely to leave sonic fingerprints on the music than devices that convert digital to/from analog or modulate their signals with active amplification or attenuation. It is notable that, despite its audio function, the Storm completely lacks traditional audio specifications—distortion, dynamic range, and so on.

Yes, that aspect of the product was appealing, but the real trigger for me was that when I began this review, the StormAudio ISP Evo was the only consumer device to fully incorporate the latest version of Dirac Live Active Room Treatment (ART).

I've been watching Estelon since they came on the market in the US. Their striking appearance grabs the eye, but, preoccupied with other brands and reviews, I was able to deny them serious attention until now.

I had my reasons—especially price. The prices of those earlier Estelons were a poor fit for my budget. I was also troubled by the fact that, despite rhetoric about driver and component choice, advanced cabinet materials and construction, and fastidious engineering, Estelon has been stingy with details and specifications—not a complete disqualifier but rather a missed opportunity to appeal to objectivist proclivities.

What changed my mind? First, while Estelon is deservedly known for the elegance of its designs, the AURA is, to me, the cleanest design the company has yet achieved . . . Second, at $19,900/pair, the AURA is much less expensive than the earlier models, including the Forza reviewed by Michael Fremer and the XB Diamond Mk.2 reviewed by Jim Austin.