Digital Processor Reviews

Pro-Jecting
The Pro-Ject Play app's home screen offers buttons for selecting Music Library, Web Radio, Bluetooth, USB/PC (echoing the function of the Stream Box's front-panel button), and Shairport-Sync. Selecting Bluetooth and pairing with my iPhone 6S let me stream music without any problem. Selecting Music Library brings up the usual menu of Favorites, Playlists, Artists, Albums, and Genres, as well as buttons for Media Servers and Internal. Selecting a track to play and then pressing Playback at the bottom of the screen displays the total playing time and elapsed time, as well as the song and album titles and cover art; to play more than one track, you add them to the Queue.

Listening
The Pro-Ject combo played 24/192 PCM and DSD64 and DSD128 music without any problems (I had no DSD256 files), and fully unfolded MQA-encoded files, illuminating the blue "Authenticated" light on the Pre Box's front-panel display when appropriate.

The late Charley Hansen, founder and CEO of Ayre Acoustics, used to hold that a properly implemented USB connection would sound superior to audio signals sent via Ethernet. However, with the USB-connected dCS and PS Audio processors, the Stream Box S2 Ultra, used with its iPad app, gave sound that was indistinguishable from that using my Nucleus+ with Roon to stream audio over my Ethernet-wired network. Not bad for something that costs only one-third the Roon server's price.

Using the Stream Box with the inexpensive Pre Box S2 Digital was intriguing as the latter offered superb measured performance. As I wrote in the measurements section accompanying KM's review of the Pre Box S2 Digital in the April issue, "The low noise and the superb channel-separation measurement are extraordinarily good, considering that the Pre Box S2 Digital is powered by a tiny wall-wart supply. Someone at Pro-Ject knows how to optimize a printed-circuit-board layout!" Wondering if this little DAC was a giant killer, therefore, I'd asked Herb Reichert to give it a listen. In his Follow-Up in the May issue, Herb concluded: "The Pro-Ject Pre Box S2 Digital's main sense-oriented effects were its impact and its beat-emphasizing drive, both of which I regard as distinctly masculine traits. What was missing was a radiant, sensuous, feminine side. To me, the Pre Box S2 Digital is simply a good DAC-headphone amplifier at its price point but it didn't kill any giants."

Giants may not have been slain, but I still enjoyed using the Pre Box S2 Digital with the Stream Box S2 Ultra. The combination did have a good sense of drive, yet there was no "digital edge"—I could listen for extended periods with my Audeze LCD-X headphones without fatigue.

I also experimented with the Pre Box S2 Digital's various reconstruction filters. Both Herb and Ken had preferred the Pro-Ject's Optimal Transient filter, which is a slow-rolloff, short-impulse-response type. However, I felt that the Hybrid filter, which has an apodizing null at the Nyquist frequency of 22.05kHz, revealed a slightly fuller-sounding bass guitar in the superb cover of Marvin Gaye's "What's Goin' On" on Quincy Jones's Smackwater Jack (16/44.1 ALAC file from CD, A&M 393 037-2) than did the Optimal Transient filter. I agreed with Herb that the BrickWall and Fast Rolloff (Linear Phase) filters sounded somewhat artificial compared with Optimal Transient, but did most of my auditioning with the Hybrid filter. With Hybrid, Paul Simon's voice in "Rene and Georgette Magritte with Their Dog After the War," from his Negotiations and Love Songs 1971–1986 (16/44.1 ALAC from CD, Warner Bros. 25789-2), sounded natural, the backing voices were farther back on the soundstage, and Anthony Jackson's bass guitar sounded gentle yet powerful.

The Pro-Ject Play app worked well, but I decided to continue my auditioning using Roon. I launched Roon on my iPad, but the Stream Box didn't appear in Roon's Settings menu as an audio device despite being on the same network. I rebooted the Roon Nucleus+ and the Stream Box S2 Ultra, and for good measure reinstalled the Roon app on the iPad. Now all worked properly, and I could select the Pro-Ject server as a Roon audio endpoint.

Interestingly, when I did so, not only the Stream Box but also the USB-connected Pre Box S2 Digital DAC appeared on the Roon home screen. However, the Stream Box was indicated as having fixed volume, and the Pre Box's volume control was not accessible with Roon.

Also interestingly, when I selected a track with Roon, then exited the Roon app and opened the Pro-Ject Play app, the latter's Playback screen showed what was playing with Roon, and Roon's random-play Radio function was still functioning.

Summing up
As I finish writing this review, I'm listening on my Audeze LCD-X headphones to the MQA files of Robert Silverman performing Beethoven's Piano Sonata 32, Op.111 (Audio High), unfolded to 24-bit/88.2kHz by the Pre Box S2 Digital, sourced from the Pro-Ject Stream Box S2 Ultra's internal storage, and controlled with the Pro-Ject Play app. At $1248, the two Pro-Ject components cost about the same as the headphones, and take up less space on my desk than Robert Silverman's SACD boxed set of Mozart Piano Sonatas from IsoMike, which I'll be playing on the big rig once I've sent this review to copyeditor Richard Lehnert.

But for now, Silverman's Beethoven performance through the Pro-Ject–Audeze system is giving me pretty much all I need. Strongly recommended to those who don't want to drop big bucks on a networked digital music system.