Solid State Preamp Reviews

The KX-R Twenty loved women's voices. The aggressive edge to Chrissie Hynde's thin-sounding pipes in "Back on the Chain Gang," from the Pretenders' The Singles (ALAC file ripped from CD, Sire/WEA), was tamed; it was easy to put to one side the fact that "Love Letters," from Ketty Lester's Torch Songs, with Lincoln Mayorga on piano (320kbps AAC file), was lossy compressed mono. And with well-recorded female voices, such as Mary Chapin Carpenter's take on Jagger and Richards' own torch song "Party Doll," from her Party Doll and Other Favorites (ALAC file ripped from CD, Columbia CK 68751), the singer spoke directly to my heart.

I was going to say that the leading edges of the double bass in "Love Letters" were well defined, except that I hadn't before heard the instrument as clearly on this recording as I did with the Ayre preamp. There was a tangibility to the Twenty's low frequencies, even with minimonitors like KEF's LS50, a pair of which recently returned to my listening room two years after I reviewed the speaker for Stereophile. The walking bass line in Vaughan Williams's mystical arrangement of the Welsh folk tune "Rhosymedre," played by Philip Ledger on Organ Music from King's (24/192 QA-9 needle drop from LP, EMI HQS-1356), seemed fully present with the Twenty, even though the speakers were missing a full octave of measured bass extension. And with the full-range Nola and Triangle speakers that I reviewed recently, well-recorded rock such as "Go Away," from Polish singer Kasia Lins's Take My Tears (24/96 AIFF download from Linn), the kick drum and bass guitar acquired additional authority with the Ayre preamp in the system.

Some highly resolving audio components achieve their transparency to what has been captured on a recording by emphasizing detail. The Ayre simply cleaned the window, naturally increasing saturation and contrast. The image of the solo Fender Rhodes piano that kicks off "Go Away" was tangible without being spotlit, as was the subtle entry of the Hammond organ behind the Rhodes at the end of the intro.

Back in May, I was invited to record the Portland State Chamber Choir, conducted by Ethan Sperry. This was one of those rare projects where everything went as planned. Not only had Ethan rehearsed the singers to that state where they had this sublime material down without it becoming mundane, the sessions took place in St. Stephen's Catholic Church in Portland, Oregon, which has a synergistic combination of a very low noise floor and a wonderfully warm, supportive acoustic. I used my usual microphone technique, combining an ORTF pair of Neumann M147 tubed cardioids with a widely spaced pair of high-voltage DPA omnis. Mike preamps were all Millennia Media, and the master A/D converter was the sample of the Ayre QA-9 that I'd purchased following my 2012 review. Stereophile writer Erick Lichte produced, mixed, and edited the performances, then sent me the 24/88.2 files to decimate to 44.1kHz, noise-shape to 16 bits, and prepare the CD master. (The CD, Into Unknown Worlds, was released in September.)

I had used the Ayre KX-R Twenty for monitoring while deciding which flavor of noiseshaping sounded best in reducing the bit depth from 24 to 16. Perhaps my favorite track is Henry Purcell's "Hear My Prayer, O Lord." This brief setting of Psalm 102 sounds surprisingly modern, with its exploratory harmonies and complex layering of parts, yet was composed in 1682! Because of the church's long reverberation time, I had placed the microphone array fairly close to the choir to get a good balance between the direct and reflected sounds of the singers. Listening to the 24/88.2 WAV file with the KX-R Twenty in the system, there was no ambiguity in the presentation of the voices, in both the acoustic and musical spaces. And it was easy to decide which algorithm most preserved the qualities of the high-resolution master on the CD.

Music I never heard
I would like to have compared the KX-R Twenty ($27,500) with the Dan D'Agostino Momentum preamplifier ($32,000) that Michael Fremer reviewed and the Lamm LL1 Signature that Bob Reina reviewed ($42,790), both in the August 2014 issue, as well as the Simaudio Moon Evolution 850P ($28,000) that Brian Damkroger reviewed in December 2013. But such are the logistics of magazine reviews that these cost-no-object preamps had long since been returned by the time the KX-R Twenty took up residence in my system. And while a comparison with an original KX-R would have been appropriate, this also was not possible.

However, as I wrote earlier, the Pass Labs XP-30, designed by Wayne Colburn, was the only other preamplifier I've used since my experience with the original KX-R that I felt rivaled it in overall quality. And as Pass Labs had allowed me to hang on to the review sample to use while I wrote about their power amplifiers, the XP-30 was still to hand. I spent a weekend comparing the two preamplifiers, with levels matched to within 0.1dB using the 1kHz warble tone on Editor's Choice (CD, Stereophile STPH016-2).

These are both superb-sounding preamplifiers, if you take into consideration that the perfect preamplifier should have no identifiable sound of its own. Ultimately, I felt the difference between them was in how they handled recorded spaces. The Pass Labs' presentation was a touch more ethereal and lighter-balanced, with individual acoustic objects within a recorded acoustic slightly more delicately outlined. The soprano soloist in Ericks Esanvald's inspired arrangement of "Amazing Grace," with its endless cascade of modulations, from Into Unknown Worlds (24/88.2 WAV master), was slightly more clearly set within the church acoustic. While the KX-R Twenty wasn't far behind the XP-30 in this regard, it did make the aural image of the soprano more tangible, and more like her sound as I remember it from having engineered this recording.

Earlier in this review I described this aspect of audio reproduction as robust, but the word doesn't quite capture all the nuances of what I mean. Take Tony Faulkner's recording of the Chamber Soloists of the Royal Philharmonic performing the Adagio from Mozart's Gran Partita, K.361. With the KX-R Twenty in the system, the sounds of the winds on this recording (Wind Serenades, 24/88.2 AIFF file from Naim 2007) took me back to the very first time I heard this transcendental work, when, aged 17, I was dating a clarinet player in a student wind band. With the Pass Labs, I could appreciate what a great job my friend Tony had done engineering this recording. But the Ayre evoked the words Peter Schaffer has Antonio Salieri saying, in Amadeus, about the entry of the solo oboe in this music: "This was a music I'd never heard. Filled with such longing, such unfulfillable longing. It seemed to me that I was hearing the voice of God." So, no, robust doesn't quite get my intended meaning.

Unfulfillable longing?
Reviewing superbly engineered solid-state preamplifiers can be time consuming. All of the first-order sonic attributes—frequency balance, linearity, lack of coloration, etc.—are beyond reproach, which means one needs to focus on such higher-order qualities as the presentation of the soundstage and the accuracy of the imaging, neither of which can be measured. But with Ayre's KX-R Twenty, I had no difficulty reaching a conclusion: While $27,500 is a high price to pay for a line preamplifier, the KX-R Twenty is as good as a preamplifier can get.