Digital Processor Reviews

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.

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.

Without having intended to, I seem to have collected several "statement" products. I've already reported on the Weiss">http://www.stereophile.com/digitalsourcereviews/781">Weiss Medea and Theta">http://www.stereophile.com/digitalsourcereviews/204theta">Theta Digital Generation VIII digital-to-analog converters. I saw and expressed interest in the Nagra DAC at the 2002 Consumer Electronics Show, when prototypes of it were shown along with a forthcoming multichannel version, the Nagra Digital Audio Processor (DAP). The two units are based on the same chassis and interface, the DAP including additional modules and processing.

For a couple of years, I have been following Prague-based Okto Research. At first, Pavel Krasensky, the founder and hardware developer, offered audio design ideas and DIY modules that I found tantalizing. For example, there was a dandy-looking ESS 9038Pro Sabre–based output module and some appealing power supply modules—but to use those, the buyer had to manage inputs and integration on their own.

Then, finally, last year, Krasensky released the dac8 PRO, an 8-channel D/A processor with USB input and output, 8 channels of AES/EBU input, and 8 channels of balanced (XLR) analog output as well as a headphone output.

"Dinner's fried chicken, honey."

Oh boy, another new DAC review. Some folks think DACs, once you get past the features, all sound pretty much the same. I mean, it's just digital. Well, they're right. Pretty much. Just as two new cars of a particular make, model, color, and options package both look the same, sitting there on the lot.

But if you discover a ding in the door of one of them, where most folks still see only a new car, you now see the ding. It might have been there all along, undetected the first few times you walked around the car—maybe your buddy even had to point it out to you. It's insignificant in the scheme of all that a new car is, but once you've seen it, you always see it. Now you can easily tell the two cars apart, and we both know which one you'll drive home.

At the Consumer Electronics show in Las Vegas in January 1999, Mark Schifter, erstwhile president of Audio Alchemy, was handing out a press release announcing what seemed like a groundbreaking product from his new company, Perpetual Technologies. The product was the P-1A, a digital-to-digital processor that would do resolution enhancement, loudspeaker correction (amplitude and phase), and room correction—all for less than $1k. It sounded too good to be true.