Digital Processor Reviews

I felt like I'd just been offered a choice of 31 flavors of Baskin-Robbins ice cream topped with up to 57 varieties of Heinz ketchup, 57 condiments, and 47 brands of coddled cream. My head began to spin, my stomach churned, and my mouth grew very dry as I read that Gold Note's DS-10 ($2995) was a "chameleon DAC" with 192 setup options that enable it to "completely blend in with different music genres, giving the listener the opportunity to adapt the behavior of the unit to the music playing, to one's stereo system and, most of all, to the listener's taste."

In contrast to phono cartridges and analog tape recorders, digital audio converters distinguish themselves by the fact that they can be fashioned in an almost infinite number of ways. Therefore, the odds against two manufacturers' DACs or ADCs sounding exactly the same are extremely large.

Hi-fi system resolution has long been the cause of heated arguments. But when it comes to converting digital data to an analog signal, there can be no argument. Data go in at one end of a DAC and an analog signal comes out of the other end, with a noise floor directly rated to the combination of the converter's digital and analog resolution. Ever since I started measuring digital products for Stereophile, I have been expressing a D/A processor's effective resolution in terms of the equivalent number of bits.

This unique device is a solution to a problem that previously couldn't be solved.

There are, of course, any number of little boxes that can extract audio from the HDMI video bitstream; they began to appear on the market to fill a need for a way to route audio from a player's HDMI output In the recent past, you could buy a good-quality—even audiophile-grade—universal player and listen to SACDs via its good-sounding analog outputs. But good-sounding universal players are becoming scarce.

The idea of using digital signal processing (DSP) to convert digital audio data sampled at 44.1kHz or 48kHz to a higher sample rate is not new. I first heard the beneficial effects of upsampling at Stereophile's 1998 hi-fi show in Los Angeles, where a pro-audio dCS 972 digital-to-digital processor was being used to convert 16-bit/44.1kHz CD data to a 24/192 datastream.

Even as digital/analog processors were becoming a hot product category in the early 1990s, audiophiles were also learning that timing uncertainties in the AES/EBU and S/PDIF serial datastreams—jitter—would compromise any improvement in sound quality offered by these DACs. Some companies therefore introduced products to reduce or eliminate jitter—in the November 1994 issue of Stereophile, Robert Harley reviewed three such products: the Audio Alchemy DTI Pro, the Digital Domain VSP, and the Sonic Frontiers UltrajitterBug. I still have Stereophile's review samples of the UltraJitterBug and VSP, along with two contemporary DACs: a PS Audio UltraLink and a Parts Connection Assemblage DAC-1.

As our reviews of these products were published before Paul Miller's and the late Julian Dunn's development of the "J-Test" diagnostic signal, I performed J-Test jitter measurements to bring that 1994 review into the 21st Century. You can see what I found here.

What kind of creature is this? Gryphon Audio Designs' new Ethos ($39,000)—pronounced EE-toss by its Danish manufacturers—is marketed as a CD player and digital-to-analog converter. It's decidedly au courant in that it includes two 32-bit/768kHz ES9038PRO Sabre DAC chips—one for each channel—with each holding eight individual DAC chips; offers optional upsampling to either 24/384 PCM or DSD128; and decodes up to 32/384 PCM and quadruple DSD (DSD512) via its USB input, or up to 24/192 (and no DSD) via AES/EBU or S/PDIF.