Digital Processor Reviews

As I wrote in my review of the Bricasti M1 D/A processor in February 2012, it seemed a good idea in the late 1980s: upgrade the performance of your CD player by feeding its digital output to an outboard digital/analog processor. British manufacturer Arcam, one of the first companies to see the opportunities in this strategy, introduced their Black Box in 1988. When I reviewed the Black Box in February 1989, I found that its low-level linearity was among the best I had measured at that time for a product featuring the 16-bit Philips TDA1541 DAC chip set. However, that linearity still wasn't very good in absolute terms. Back then, it required heroic and expensive engineering to obtain D/A performance that did justice to the 16-bit CD. These days, however, the semiconductor foundries produce a plethora of relatively inexpensive D/A processor chips that both handle 16-bit data with ease and wrest full resolution from 24-bit data.

Am I the only one who values content and convenience over sound quality?

There. I've said it. I am not an audiophile; ie, someone who's in love with recorded sound for its own sake. The search for ideal sound can leave a person burned out and broke.

Back in the summer of 2009, USB-connected D/A processors that could operate at sample rates greater than 48kHz were rare. Ayre Acoustics had just released its groundbreaking QB-9, one of the first DACs to use Gordon Rankin's Streamlength code for Texas Instruments' TAS1020 USB 1.1 receiver chip. Streamlength allowed the chip to operate in the sonically beneficial asynchronous mode, where the PC sourcing the audio data is slaved to the DAC. But high-performance, USB-connected DACs like the Ayre were also relatively expensive back then, so in the January 2010 issue of Stereophile I reviewed a pair of soundcards from major computer manufacturer ASUS , the Xonar Essence ST and STX, which, at $200, offered a much more cost-effective means of playing hi-rez files on a PC.

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.

The past 12 months have seen some remarkable developments in digital playback. Standards of digital musicality are far higher than they were a year ago, both on an absolute performance basis and in terms of what you get at various price levels. No other component category has seen such tremendous gains in value for money or number of new products introduced. It seems hard to believe that since Vol.13 No.6 (12 issues ago), we've reviewed such noteworthy digital processors as the Meridian 203, Proceed PDP 2, Stax DAC-X1t, Theta DSPro Basic, Wadia X-32, Esoteric D-2, PS Audio SuperLink, and VTL D/A. Each of these converters brought a new level of performance to its price point—or, in the case of the Stax and VTL, established a new benchmark of ultimate digital performance.

Just as these units provided stiff competition for previous products, so too will they come under the assault of improving technology. The art of digital processor design is so young that we can continue to expect further improvements coupled with lower prices as designers move up the learning curve.

Unless something is broken, the bits from your computer will be delivered to your DAC intact; the claim behind three new products I recently listened through is that each can reduce noise within the DAC—noise that could otherwise corrupt the analog signal and thus make our music less musical. This notion is not based on audiophool woo-woo, but on the basic electronics of mixed-signal systems: Although its input is digital data, a DAC's output is subject to all the noise problems of analog circuits.