This review page is supported in part by the sponsors whose ad banners are displayed below

This is the 32nd in a series of reviews dedicated to the concept of 32Ohm Audio as embodied by the store of that name in downtown Portland/Oregon and described here - Ed.

Reviewer: Nicholas Bedworth
Financial Interests: click here
Source components: Weiss Engineering DAC 202 digital-analogue converter; Bel Canto 1.5 digital-analogue converter; Toshiba Qosmio laptop with Seagate 1.5 TB external digital media storage
Amplifiers: Odyssey Kismet monoblock amplifiers
Speakers: Wilson Audio Specialties Sasha W/P
Cables: AudioQuest Wild Wood single bi-wire speaker cables, AudioQuest Sky analogue line interconnects; Weiss Engineering Chiron, Wireworld Cable Platinum Starlight, AudioQuest Eagle Eye, AudioQuest Raven S/PDIF and AES/EBU digital interconnects; Wireworld Cable Starlight, AudioQuest Carbon USB cables; AudioQuest NRG-10, NRG-100, Audio Magic Clairvoyant Liquid Air power cables
Accessories: Wireworld Cable The Matrix power distribution block; Audio Magic Oracle power conditioner with liquid conductors
Room: 18’ deep, 12’ wide, 9’ to 11’ ceilings.
Review component retail pricing: Audiophilleo1, $895; Audiophilleo 2, $495.

Introduction: The world of audio and entertainment in general is going through a major transformation as "pure digital" playback—no shiny discs required—becomes the norm. Although the future is distributed somewhat unevenly, younger generations are growing up in the context of digital downloads being the only way they know to get tunes. The days of CD players and transports are gradually coming to a close as the convenience and potentially higher performance of file-based music deliver an increasingly powerful value proposition to music lovers of all kinds.

A relatively new product category—USB-to-S/PDIF processors with preamplifier functions enabled in the digital domain—is doing a lot to elbow analogue preamplifiers aside. And before long even digital-to-analogue converters or DACs may come under similar pressure. The only remaining analogue-input component, the amplifier, may soon also be controlled with digital data. In this brave new world everything stays digital until the output stage of the power amplifier. While such a scenario has many benefits including eliminating layers of device and interconnect as well as reducing cost and complexity, the digital regime is not without its own nagging issues as many of us know from experiences both good and bad. The promise of truly excellent lower-cost digital playback is very real but so are the challenges.

Newcomers to the audio design world tend to be increasingly expert in digital engineering and signal processing software, because, among other things, such topics are heavily emphasized core elements of today’s college and graduate school curricula. Savvy students quickly figure out where the future is going and along with that, how they can make a difference in areas that interest them. If they don’t find something that’s interesting, they’ll invent it.

After graduating from Santa Clara University in Silicon Valley, Philip Gruebele, one of the principals of AudioPhilleo LLC and its lead designer, began his career in information technology, robotics and 3-D vision. But he eventually became smitten with high-end audio. Given what he already knew about software and telecommunications technology, Philip began looking at the inherent weaknesses in audio from a start-from-scratch "what if?" perspective and began experimenting with digital crossovers.

At home Philip enjoys playing his Steinway-designed 7’ Boston  grand piano and listening to just about any kind of music provided it’s well performed and well recorded. Ireland’s Damien Rice is one of his favorite artists. However, he’ll eventually admit that his otherwise catholic musical interests do not quite extend all the way to country. Having spent some enjoyable times in Nashville over the years, my personal familiarity with the country and Americana scene makes it a bit easier for me to at least understand Philip’s position. Of course students of music marketing know that apparently more than a few people do enjoy these genres immensely. In the post-1991 SoundScan era, Garth Brooks outsold even the Beatles by a wide margin.

As Philip began getting more intimately involved with high-end electronics in the form of Rogue Audio M-180 tube monoblocks and ribbon-tweeter Monitor Audio PL300 speakers, his attention started to focus on solving some of the fundamental issues of digital playback. These include the interrelated weaknesses of S/PDIF as a bit-streaming protocol; USB interfaces to digital audio servers and computers; and the biggest bugbear of them all, clock noise in all its forms collectively referred to as jitter. You can’t do digital very well without exceptionally stable clocks but they can be difficult beasts to subdue. His first two products under development since 2009 have several unique features. The Audiophilleo 1 and 2 combine elements of several product categories, namely USB computer audio interfaces, conventional preamplifiers and digital signal processors in novel and effective ways. Philip packs a great deal of functionality into very small package.

The Audiophilleo 1 even has a bright full-color OLED display, which is unusual at this price level. Other key technical features include full support for 44.1 through 192kHz, 16 or 24-bit sampling via asynchronous USB; noise-shaped digital attenuation and balance; remote control capability; field-upgradable firmware; differential ECL output; and ultra-low period and phase jitter measured at just 8 to 14ps (picoseconds) RMS depending upon bandwidth. To help understand what these features might mean for audio enthusiasts, let’s start with an overview of jitter and how it’s handled by these two new products.

Dancing with jitter bugs once again: How low does the jitter really need to get before it’s no longer an issue? The Audiophilleo 1 and 2 and a few of the other digital transport devices that recently came to market  reduce clock jitter to handfuls of picoseconds. Now one might wonder whether this is simply another case of specupmanship. Does it really matter? After all, digital audio is usually associated with units of time that are a million (microseconds for high-resolution bit rates) or a billion (milliseconds for sampling intervals) times longer than picoseconds. It does seem surprising that something as evanescent as a picosecond could really be important to audio - or anything else for that matter.

How long is a picosecond? Each one is just 10-12 or a trillionth of a second, a very short period of time indeed. During this interval light only travels about an 1/8th of an inch or 3mm in a vacuum. Because such fleeting moments are way beyond the ken of ordinary audio test gear, specialized equipment must be used to capture the raw data in the first place and then these have to be analyzed by custom analysis software. One can easily spend $100K to get such a test system up and running.

On the conceptual level, think of jitter as unintended variations in those specialized timing signals—clocks—that make just about everything happen on time in digital electronics. Jitter means clock noise for most audio purposes. Making matters worse, most digital devices have several clocks running at different frequencies. They govern the myriad activities within a circuit and also coordinate the transfer of information from one device to another. No, one cannot hear such electronic noise with one’s ears of course but in various insidious ways the tiny perturbations inherent in digital clocks eventually make themselves apparent in the audio spectrum in ways that one generally will not enjoy.