Digital Processor Reviews

I stayed with Music for almost all my listening. But without a preamp in the system, and using instead the QX-5's volume control, the balance was definitely on the forward side even after two weeks of continuous use. If not quite "ruthlessly revealing," as the cliché has it, the Ayre taken directly into the MBL Corona C15 monoblocks driving the Rockport Avior II speakers resulted in a slightly relentless quality. In part this was due to the MBLs, but with Giuliano Carmignola and Mayumi Hirasaki's brisk performance of J.S. Bach's Double Violin Concerto, BWV 1043, accompanied by Concerto Köln (Tidal HiFi stream, Archiv 0289 479 2695 5), I found myself playing the music at a lower level than I'd been used to.

I had reviewed Ayre's KX-R Twenty preamplifier in December 2014, and had recently been discussing with Alex Brinkman (then Ayre's sale manager but now with AudioQuest) the possibility of my reviewing the KX-5 Twenty fully balanced preamplifier ($8950). To my astonishment, the KX-R Twenty had sounded better than no preamplifier, so as the KX-5 Twenty also has Ayre's Diamond output stage and Variable Gain Transimpedance (VGT) volume control, I thought it might prove a synergistic match with the QX-5 Twenty.

And so it proved. The balance was still on the forward side, but with the QX-5 set to DAC mode, the preamplifier allowed the system to step out of the way of the music. I was using Roon in Radio mode, which chooses tracks musically related to what has just been played, and it found in my library an old favorite I hadn't played in too long a time: "Downtown Lights," from Annie Lennox's Medusa (ALAC file ripped from CD, Arista 25717-2). This song depends heavily on the bass line to define its harmonic progression, as the accompanying chords are based almost entirely on suspensions. However, there's a harmonic twist in the verse after the first bridge: at a cadence, the bass drops to the relative minor instead of to the expected tonic. This surprise can be obscured when an amplifier fails to exert sufficient control of the low frequencies; it was superbly clear through the QX-5 Twenty, yet without that clarity of bass being achieved by leaning out the balance.

Playing files with Roon also revealed that the sound had more authority via the QX-5's network input than via USB. Christian McBride's solo double bass at the start of "All or Nothing at All," from Diana Krall's Love Scenes (DSD64 file, Impulse!/Acoustic Sounds), had a slightly more optimal combination of weight and definition via Ethernet than via USB; in fact, playing CD files over the network connection sounded pretty much identical to playing the original CDs in my Ayre transport and feeding the data to the QX-5 Twenty via an AES/EBU link, with much the same sense of authority. Via USB, that authority was slightly diminished.

As the QX-5 will decode HDCDs, I reached for one of my favorite Joni Mitchell recordings, Shadows and Light (2 HDCDs, Asylum 704-2), loaded it into the Ayre player, and selected the QX-5's AES 1 input. The proper green LED lit up, "hd 44" appeared on the DAC's display as advertised, and . . . wow! The sonic benefits of HDCD may have been oversold 25 years ago, even in this magazine, but this was even better sound—more resolved, more palpable—than I remembered ever hearing from this set. The small pitch inflections in Mitchell's voice in "Dreamland," the changes in vocal texture as she's doubled by some of the band in the choruses, were effortlessly laid bare.

Comparisons
My primary comparisons, with levels matched at 1kHz, were performed with the PS Audio PerfectWave DirectStream D/A converter, which I bought following Art Dudley's 2014 review and recently updated with the Bridge II network adapter card ($6899 as auditioned). I also did some comparisons with an Ayre QB-9^DSD DAC ($3450, no longer available), and the Chord DAVE ($10,588), I reviewed in May 2017. As the QB-9^DSD and DAVE lack network ports, for fast A/B comparisons I fed them USB data, and the QX-5 Ethernet data. I also did longer listening tests using USB data for all three DACs.

Following the arrival of the QX-5 Twenty, I had the Chord DAVE in-house for only a week or so. In my review of the Chord, I'd commented on its superb re-creation of soundstage depth, its sense of musical drive, and the clarity with which it presented detail. This was with the DAVE driving the MBL amplifiers directly. Switching to the QX-5 and its Music filter, and again with no preamplifier in the system, I was struck by how similar the two DACs sounded, despite having reconstruction filters totally opposed in design philosophy: the Ayre's is a minimum-phase type as short as possible, the Chord's a linear-phase type as long as possible. But after a while I felt that, while the DAVE scored in its retrieval of detail and sense of low-frequency drive, the QX-5's imaging was a tad more palpable. However, with the Rockport speakers and MBL monoblocks, the Ayre's tonal balance was definitely too forward. As I remarked above, while this aspect was ameliorated by inserting the Ayre KX-5 Twenty preamplifier in the system and disabling the QX-5's volume control, the DAVE had long since been returned to Chord when the Ayre preamp arrived.

For the DirectStream and QB-9^DSD comparisons, I used the Ayre preamp to match levels. The PS Audio has a "comfortable" quality that perhaps sacrifices ultimate resolution in favor of a sound that's always inviting and always allows the music to breathe, especially when connected directly to the power amps. When I switched to the QX-5 Twenty the soundstage deepened, and individual acoustic objects on that stage were a bit more palpable. The PS Audio's low frequencies sounded warmer, however, my Fender bass guitar recording on Editor's Choice (ALAC file ripped from CD, Stereophile STPH016-2) having more upper-bass energy. By contrast, the Ayre focused slightly more on the notes' leading edges.

Most of my listening with the PS Audio was performed using its Torreys firmware, but at the very end of the review schedule I installed the latest version. The Huron firmware took the DirectStream's retrieval of detail close to the QX-5's, but also took away some of the low-frequency warmth, its sound now falling behind the Ayre's in bass authority.

Turning to the QB-9^DSD and using its Listen filter, which is identical to the QX-5's Music filter, the double bass in Diana Krall's version of "All or Nothing at All" sounded louder, despite the levels being matched at 1kHz with PCM data. (This is a DSD64 file.) I loaded a 1kHz, 0dBFS, DSD64 tone into both the computer running Roon and the Aurender server, and checked the levels. To my surprise, the tone was 3dB higher when output from the QB-9^DSD. When this was compensated for, the two DACs' tonal signatures were identical, but Krall's voice still sounded slightly more forceful, less nuanced through the QB-9^DSD. I got the same impressions listening to some of the tracks from Sasha Matson's baseball opera, Cooperstown (24/96 master files, Albany TROY1553/54), which I produced a few years back. As good as the QB-9^DSD sounded in isolation, when I switched to the QX-5 Twenty, the singers' pitch inflections were that bit better developed.

Headphone Listening
Pressing the left-hand button on the QX-5 Twenty's faceplate illuminates it in red, to indicate that the headphone outputs are active and the main XLR and RCA outputs muted. My Audeze LCD-X headphones worked well with the QX-5's balanced outputs, there being an excellent sense of clarity coupled with an involving sense of musical flow. Ayre's Codex D/A headphone amplifier ($1795) left my system long ago, but I was reminded of its qualities. As Jon Iverson wrote in his review of the Codex, "everything imaged clearly from extreme left to extreme right, wonderfully suspended in a wide, open, dreamlike space."

In a fit of nostalgia—I'd used the album to reach my conclusions in one of my very first reviews, of the Krell KSA-50 amplifier, published in Hi-Fi News in 1983—I cued up harpist Andreas Vollenweider's Behind the Gardens—Behind the Wall—Under the Tree . . . (ALAC file ripped from CD, CBS MK 37793). Via the QX-5's balanced headphone outputs, I was drawn into Vollenweider's soundscapes, the found sounds at the start of track 1 setting the stage to the sides beyond my head. "Wide, open"? Yes. "Dreamlike"? Definitely. And that driving groove set up in the lower register of Vollenweider's electrified harp? Present in full measure.

Conclusions
After I'd resolved the issues of system synergy, there was no doubt in my mind: Ayre Acoustics' QX-5 Twenty is one of the finest-sounding, most versatile digital audio products I have had the pleasure of using. No, it doesn't offer MQA, which may be a problem for some. But my experience of feeding audio data over my network to the QX-5 with Roon has convinced me that this, rather than USB connections, is the way forward. Class A+ with a bullet!