PS Audio NuWave DSD D/A processor

Researchers at MIT recently discovered a "music channel" in the human brain. These neural pathways respond to all kinds of music—and only to music. "A listener may relish the sampled genre or revile it," Natalie Angier wrote in the New York Times. "No matter. When a musical passage is played, a distinct set of neurons tucked inside a furrow of a listener's auditory cortex will fire in response" (footnote 1).

"Why do we have music?" Nancy Kanwisher, one of the scientists behind the research, asked in an interview with Angier. Is our "sensitivity to music . . . tunable with experience? These are the really cool first-order questions we can begin to address."

To me, the research provokes other questions: What is it about an auditory experience that tells our brain it's music? Would a serious audiophile's functional magnetic resonance imaging—the technique used in the study to scan the auditory cortex—look the same as other people's fMRIs? Might it someday be possible to observe differences in the brain as it responds to different presentations of the same music?

For the past several weeks, I've been auditioning PS Audio's NuWave DSD digital-to-analog converter ($1299), and the experience has me waxing philosophical on one of my favorite subjects: the connection between reproduced sound and our perception of music. The NuWave DSD, I've found, presents music in a striking and characterful way. What aspects of its sound—and the underlying electronic design—cause the music to come across the way it does? I'll return to that question in a moment—but first . . .

Drums and wires
PS Audio's flagship D/A converter, the DirectStream DAC ($5999), created a stir in the months following its 2014 debut—not only for the quality of its sound, which was widely deemed excellent by reviewers, but also for the novelty of its design. Instead of relying on PCM-based input processors, as most DACs do, the DirectStream converts all incoming data streams to DSDx10, which, conveniently, is the least common multiple of two common sampling frequencies, 176.4 and 192kHz. Instead of a dedicated DAC chip, the DirectStream uses a field-programmable gate array (FPGA), which allowed designer Ted Smith to use, as he told me via e-mail, "accurate math instead of the approximations that most DAC chips and upsamplers use." The FPGA approach also allows the DirectStream to be upgraded in the field by updating its firmware, as has already happened three times in the months since the model's launch, each upgrade reportedly dramatically improving the sound. The DirectStream's output stage includes expensive transformers as part of a low-pass filter that smooths the reclocked, downsampled DSD data to make music.

Marketing copy on PS Audio's website says that in designing the NuWave DSD they've "taken the lessons learned from one of the world's best DACs, the DirectStream, and applied them to a smaller-scale, lower-cost unit" (footnote 2). I don't doubt that claim, but the NuWave DSD and the DirectStream are very different DACs. The NuWave DSD does not convert incoming signals to DSD. It does use a dedicated DAC chip (a Sabre32 Hyperstream, from ESS Technology). And while the NuWave does employ a programmable integrated circuit—a complex programmable logic device (CPLD)—that component is smaller and less capable than an FPGA. The CPLD, PS Audio says, "discovers sample rate and format, reclocks all incoming data, reduces jitter, waveshapes data output to the DAC chip, and utilizes high speed/low gate count logic to reduce propagation delay for faster throughput." Both DACs use passive filtering at the output, but the NuWave DSD does it more cheaply.

In contrast to the DirectStream, "The NuWave DSD cannot be updated in the field," according to Bill Leebens, PS Audio's director of marketing. "It can be reprogrammed at the factory, but we don't anticipate any firmware updates on the basis of sound quality; we're happy with that." He added, "you can only go so far for a grand and change."

The NuWave DSD plays DSD files (hence its name), whether they arrive in native form (at single or double rate) via an HDMI cable serving as an I2S interface (you'll need a similarly equipped transport, of which few exist; PSA has announced one for October release), or via DSD-over-PCM (DoP), in which the DSD stream is broken into chunks and buried in PCM code transmitted via USB. Some say DoP is inferior to native DSD, but if the reassembled DSD stream is identical to the original stream (which it is), and both streams are reclocked in the same way (which they are), there should be no difference in the sound.

Of course, the NuWave DSD accepts PCM data, too, up to 24 bits and 192kHz via S/PDIF, asynchronous USB, and I2S. (The TosLink input accepts 24-bit data up to 96kHz.) Some converters go higher in bit depth and frequency, but 24/192 should be more than enough for transparency.

For years, PS Audio has focused on AC power problems, because dirty power lines can compromise the performance of even the best audio component. The company's most sophisticated standalone solutions to those problems, their Power Plant AC regenerators, store the energy from the rough, 60Hz sinewave that comes out of your wall and use it to make a much cleaner sinewave. It's not surprising that a company that so emphasizes power is attentive to the power driving its audio components. The NuWave DSD employs seven voltage regulators and "massive power supplies"—the phrase is from an e-mail from Paul McGowan, CEO of PS Audio—to ensure a consistent and precise rail voltage.

"There's nothing we've ever made that eliminates jitter," McGowan said in another e-mail. "And so cables still matter, though less so." I was determined to give the NuWave DSD a completely fair audition, so I asked AudioQuest to loan me a high-quality USB cable. They sent three: their Cinnamon, Carbon, and Coffee, each 10' long. (Coffee is the company's second-best USB cable, second only to Diamond. I like their priorities.)

We got the beat
I listened to ripped CDs and other PCM files up to 24/192. I tested DoP with Kim André Arnesen's Magnificat, with Anita Brevik conducting the Nidaros Cathedral Girls Choir and the Trondheim Soloists (DSD128 download, 2L 2L-106). It worked fine and sounded great. I wasn't able to lay hands on a source that could deliver DSD over HDMI, so I wasn't able to try DSD in native mode.

Operationally, the NuWave DSD performed without flaw: It swallowed whatever I fed it in whatever format via whatever input, and it output music, without one glitch or pop. I tested all the inputs (except I2S over HDMI), but did most of my listening via USB, as I suspect most listeners will in the Tidal era.

Footnote 1: Natalie Angier, "New Ways Into the Brain's 'Music Room'," New York Times, February 8, 2016.

Footnote 2: A few days before I turned in this review, PS Audio announced the DirectStream's true trickled-down heir: the DirectStream Junior ($3999).

PS Audio
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