Digital Processor Reviews

Obsolescence is obsolete—at least according to the slogan coined by PS Audio's Paul McGowan when he introduced their PerfectWave DirectStream DAC ($5999). Allowing for a bit of marketing hyperbole, he had a point. While the DirectStream's hardware platform has stayed the same, the use of field-programmable gate arrays (FPGAs) has allowed its designer, Ted Smith, to come up with ever more refined versions of the firmware (they now call it an operating system), each major revision bringing audible benefits. Best of all, these updates are free.

I made my acquaintance with the PerfectWave DirectStream DAC in fall 2014, when its operating system was v.1.1.4, upgraded a few weeks later to v.1.2.1. I wrote about the DirectStream in the February 2015 issue, and about v.1.2.1 in March 2015, an issue that also included John Atkinson's measurements of it. Then came the Pikes Peak upgrade, PS Audio having decided on nonnumerical designations for that and subsequent OS upgrades.

Now we have the latest upgrade, Yale (named for Colorado's Mount Yale, not the university in Connecticut). What's new with Yale? Here's the description from Ted Smith, who has made a valiant effort to describe some highly technical aspects of design.

"There are changes in how the upsamplings from 44.1 to 48kHz and from 88.2 to 96kHz are handled in Pikes Peak and Yale. This led to the use of more accurate filters in Yale.

"Yale also includes a new approach to lower jitter and noise generation that does the work in slices of different size. There's a more studied placement of the processing steps, which lowers jitter and noise production. Yale incorporates the first half of reworking the FPGA code, to generate less jitter and noise by changing when things are done instead of what things are done."

Smith points out that jitter and noise in the FPGA don't necessarily show up in the analog output noise in any obvious way. A lot of the FPGA work is in contouring the low-level noise and minimizing any interaction or modulation of the digital output signals.

Before I describe what Yale sounded like, a bit about how PS Audio develops their products—to my knowledge, a process unique in the industry for the way the company listen to the opinions of their customers. PS Audio has a very active Community Forum, in which McGowan and Smith participate. When a new OS is released, it's initially made available for download on the website as a Beta "soft release" on which anyone can comment—and many do. In typical audiophile fashion, everyone has an opinion of the sound, and those opinions are often quite varied, even diametrically opposed. Most forum contributors think that each upgrade is an improvement over the one before, but there are always some who point out what they believe are problems with the sound and suggest changes.

It must be a great challenge for McGowan, Smith, and their team to glean from the great volume of customer feedback suggestions that are genuinely useful rather than merely represent the posters' idiosyncratic tastes. But for those who, for whatever reason, are dissatisfied with the latest OS, preferring the previous one or even the one before that, all operating systems remain available for free download from PSA's website.

I was happy with Pikes Peak, and felt that it represented a genuine advance over v.1.2.1—and I liked the Yale version even more. (All of my listening was to CDs, played through PS Audio's PerfectWave Memory CD/DVD transport ($3999), a Convergent Audio Technology SL1 Renaissance preamp, a McIntosh Laboratory MC275 LE power amp, and Avantgarde Uno Nano speakers; all cables and interconnects were Nordost Valhalla 2.)

The Yale tonal balance was very similar to that of Pikes Peak: bass about the same, treble a bit softer and a bit more subtly detailed. In comparison, Pikes Peak was a bit brighter, more forward. In my review of the Pikes Peak upgrade in the May 2015 issue, I said that listeners whose systems are on the borderline of being too bright might prefer v.1.2.1. Yale was like v.1.2.1 in that respect, but its slightly softer sound was combined with higher resolution and even better dynamics—a difficult trick to achieve. It's easy for DirectStream users to ask Ted Smith for "a little less/more treble, please," or "Can you give us more rhythm and pace?," but putting such audiophile concepts into practice is no mere matter of tweaking a few dials.

The Yale operating system was superior to Pikes Peak and to v.1.2.1 in depth and width of soundstage, and in the precision of positioning of images on soundstages. Of course, this is also a function of the speakers and their setup. The Fujitsu Ten Eclipse TD712z Mk.2 speakers, which I was using when I wrote my Follow-Up on Pikes Peak, are champions at soundstaging and imaging; the Avantgarde Uno Nanos are good, but no match in this respect for the single-driver Fujitsus. However, with the same speakers, the Yale OS revealed its superiority at soundstaging and imaging. In "General Image and Resolution Test," track 47 of Best of Chesky Jazz and More Audiophile Tests, Volume 2 (CD, Chesky JD 68), the people marching around the room and playing their percussion instruments had a scary presence, their movements precisely defined in space.

I leave the concluding comments to Ted Smith: "As good as DirectStream was at the outset, it has steadily gotten better. . . . and I'm already working on ideas that should make it much, much better still. I'm excited to be working on a product that will never become obsolete, and will continue to provide state-of-the-art performance forever."— Robert Deutsch