Digital Processor Reviews

The audiophile does not pursue music reproduction because it is useful; he pursues it because he delights in it, and he delights in it because it is beautiful. If music were not beautiful it would not be worth knowing, and if music were not worth knowing life would not be worth living.

My apologies for corrupting the well-known statement by French mathematician Jules Henri Poincaré (1854–1912), in which he described his relationship with science and nature. But substituting audiophile for scientist and music for nature, I feel the sentiment expresses what drives many audiophiles to the extremes for which mere mortals often chide us.

"This product is an industry disrupter."

Thus spoke AudioQuest's Steve Silberman, VP of development, of their brand-new USB D/A converter, the DragonFly. "There are a lot of very good DACs out there," he continued. "There are even a lot of very good affordable DACs. But the problem is, people outside of audio don't want them: They don't want old-style components like that.

With the introduction of Audio Alchemy's Digital Transmission Interface (DTI) more than three years ago, the company created an entirely new category of hi-fi product: the jitter filter. The original DTI was a good start, but didn't always improve the sound of the better-quality digital front-ends.

When it comes to getting audio from a PC via its USB port, the buzzword du jour is asynchronous. This cryptic term refers to which device has control over the timing of the audio data being streamed from the computer: the computer itself, or the device receiving the data. It might seem logical to have the computer control the timing, but this is not so. When digital audio data are converted to analog by a D/A converter, control over exactly when each dataword is converted is critical for the best quality of sound. Any uncertainty in that timing manifests itself as analog distortion, aka jitter.

Who wants only a digital-to-analog converter when you can have a DAC with benefits? How about if those benefits also come with some high-resolution attitude?

That's what I pondered while setting up the NAD M51 ($2000). Sure, it's a basic DAC, but it also has extras—like HDMI inputs, remote-controlled volume, a polarity switch, and one of my favorite features on any DAC: a display that tells you which sampling rate the thing is locked to.

There are as many ways of designing a digital-to-analog converter as there are engineers. One approach is to select parts from manufacturers' data books and build the product according to the "application notes" provided by the parts manufacturers. This is the electronic equivalent of a paint-by-numbers kit.

A more creative engineer may add a few tricks of his own to the standard brew. Bigger and better regulated power supplies, careful circuit-board layout, tweaky passive components, and attention to detail will likely make this designer's product sound better than the same basic building blocks implemented without this care. Indeed, the vast range of sonic flavors from digital processors containing very nearly the same parts attests to the designer's influence over a digital processor's sound.

Many years ago I bought the first model of the Audio/Pulse ambience synthesizer. Like many audiophiles, I was convinced (and still am) that the standard two-speaker stereo experience provides an unsatisfying concert-hall impression. But the Audio/Pulse didn't remain long in my stereo system. You see, at best the unit provided a fair reproduction of the sound of my upstairs bathroom, topped off with a nasty flutter echo. I already get that sound every morning in the shower.