Reviewers' ChoiceEarlier this year, I reviewed Ayre Acoustics’ stellar KX-5 preamplifier ($7950 USD, discontinued). It was the quietest preamplifier I’d ever reviewed, and set the stage for many good things to come, with one exception: having to give it back. Difficult as it was, I parted with the KX-5 -- only to be asked, a few months later, if I’d be interested in reviewing its successor, the KX-5 Twenty. My response was an immediate yes.

But seeing a new version of the KX-5 only 18 months after the release of the original took me a bit aback. Ayre is one of the few audio companies that avoids the economic temptation to make a few minor internal changes, add a new faceplate and a higher price tag, and call the result “all new!” Instead, they claim that they don’t release a new model or version until what they do release is a considerable improvement on its predecessor(s). This has usually involved revising circuits, upgrading parts, and sometimes redesigning all of the circuitry from the ground up. But Ayre had rarely, if ever, replaced a product -- especially one that had so well established itself -- as quickly as it did the KX-5. What gives?

Ayre KX-5 Twenty

While waiting for my review sample to arrive, I posed the question to Alex Brinkman, Ayre’s manager of North American sales. Within minutes, I learned that the KX-5 Twenty is no mere revision of the KX-5, but the result of a top-down redesign inspired by Ayre’s R Twenty models, which were released in celebration of the company’s 20th anniversary.

411 on the Twenty

The Twenty series was introduced with Ayre’s current flagship preamplifier, the KX-R Twenty ($27,500), almost two years ago. Soon after, the Twenty technologies had been incorporated into the remaining R models, and have since trickled down into Ayre’s less costly X-5 series. The AX-5 Twenty integrated amplifier ($12,950), VX-5 Twenty power amplifier ($8950), and KX-5 Twenty preamp ($8950) have each received slight variations of these technologies.

When I first took delivery of the KX-5 Twenty (which costs $1000 more than the KX-5), I could find nothing that visually differentiated it from the original KX-5 other than the new, gold “Twenty” designation occupying the far right of the faceplate. Both versions measure 17.25”W x 3.75”H x 13.25”D and weigh 23 pounds; are contained in the same case of high-quality, anodized aluminum and stainless steel; have the same chunky, backlit remote control; and can be ordered in a black or silver finish. The rear panel, too, remains unchanged, offering four balanced and two unbalanced inputs, twin AyreLink inputs for convenient control of other AyreLink-equipped models, a 15A IEC power receptacle, twin balanced outputs (XLR), and one pair of unbalanced outputs (RCA). Unfortunately, the KX-5’s nonintuitive menu system was also carried over, prompting me to reach for the manual more than I would have liked -- but this ergonomic niggle was largely offset by the fact that it will be rare for a user to need to enter this menu more than once. I also appreciated the large, three-stage LED display, which is easily readable from across the room.

Inside, the KX-5 Twenty is replete with Ayre’s familiar design fundamentals, such as zero-feedback, fully balanced, discrete circuitry -- a core topology that Charles Hansen, founder-owner of Ayre and designer of the KX-5 Twenty, believes to be essential in the elimination of timing-related errors. Also carried forward is Ayre’s fully complementary analog circuitry, which has been proven to greatly contribute to the rejection of contamination by the power supply, in much the way that balanced circuits in a recording studio reject hum picked up from external magnetic fields. Although this circuitry doubles the number of parts, in particular transistors, and requires the hand-matching of devices and thus dramatically increases cost, Hansen considers this approach an absolute necessity for optimal performance. When I asked him what effect it all has on the signal path, he reminded me that each “stage” of a circuit makes a more powerful copy of the input signal. The more stages, the more copies, and each time a new copy is created, it increases the chance of signal degradation -- much as would taking a photograph of a photograph, and then a photo of that second photo. While a complementary, balanced circuit contains four times as many active devices, the signal doesn’t necessarily have to go through all of these devices in series. In fact, most designs orient these stages in parallel with each other, so that each stage can propagate simultaneously. This ensures that no extra steps are required as the signal makes its way from input to output, and thus keeps the signal path as short as possible.

Ayre KX-5 Twenty

The KX-5 Twenty comes equipped with the Ayre Conditioner. Essentially a built-in power conditioner, the Ayre Conditioner filters out radio-frequency interference (RFI) to ensure that clean, quiet power is supplied to all of the KX-5 Twenty’s circuits. One such circuit is Ayre’s tried-and-true EquiLock, which, in a nutshell, is designed to help maintain the signal’s stability by adding a transistor between the gain transistor and the load itself. This additional transistor maintains the voltage of the gain transistor at a fixed level, while the rest of the circuit simultaneously conveys to the load the variations in current. In sum, EquiLock provides for a fully stabilized gain transistor, which greatly contributes to maintaining very low levels of noise.

The KX-5 Twenty also retains Ayre’s formidable Variable-Gain Transconductance (VGT) volume control. I wrote about this at length in my review of the original KX-5; here, I’ll say only that the VGT control is unique in enabling the circuit’s bias to remain constant, thus allowing the signal traveling through it to sound identical at all volume levels. The VGT is also claimed to produce less real-world noise as the gain is reduced. Other than similar assembly processes, use of a few common parts (e.g., high-speed circuit boards, FET-based switches, and high-quality relays), this concludes the list of what the KX-5 Twenty contains of the original KX-5.

In designing the KX-5 Twenty’s circuitry, Charles Hansen set out to significantly raise the level of performance offered by the already brilliant KX-5. He knew that the task would not be easy or cheap, so rather than reinvent the wheel, he decided to pillage superior-sounding parts from his far more costly R series. He began by replacing the KX-5’s output stage with the same circuitry found in the flagship KX-R Twenty preamp. This was part and parcel of replacing the KX-5’s power supply with Ayre’s bespoke AyreLock technology. Also first introduced in the KX-R Twenty, the AyreLock power supply is unique in exploiting a new type of discrete voltage regulation by way of discrete, zero-feedback AyreLock regulators for all analog and critical digital circuits. These distinctive regulators are claimed to result in better sound quality than the original discrete, zero-feedback regulators used in the KX-5, and to yield significant improvements when compared to more conventional “three-pin” regulators. As Hansen explained it,

When we developed the AyreLock voltage regulator for the KX-R Twenty, we further refined the Diamond Output stage to its present level of performance. For the upgrade from the KX-5 to the KX-5 Twenty, the unit receives the upgraded Diamond Output stage plus replaces the original discrete zero-feedback regulators with discrete AyreLock regulators. The culmination of this technology is called the “AyreLock” because the regulator “locks” the output voltage in a radical new way. Conventional regulators add an adjustable resistance in series with the audio circuit (load for the power supply). If the audio circuit draws more current, the regulator’s resistance is lowered to keep a constant voltage at the output of the regulator. Such a conventional regulator is limited to only pulling the output voltage “up” (higher), but cannot pull it “down” (lower).

Hansen went on to explain that the AyreLock regulator operates differently in using a unique push-pull output stage that can both pull the output “up” (higher) and also pull the output “down” (lower), depending on the circuit’s current demands. This dual-action regulator is a significant breakthrough for Ayre, and they think it moves the performance mark forward greatly. The combination of improving the quality of some key passive parts, maintaining Ayre’s core technologies (zero feedback, balanced analog circuitry, complementary analog circuitry, EquiLock, VGT), and supplementing them with Ayre’s latest technological advancements (Diamond Output, AyreLock) constitute the DNA of not only the KX-5 Twenty, but of the entire Twenty series. These technologies represent the culmination of more than two decades of continuous technological R&D at Ayre Acoustics.

Ayre KX-5 Twenty

Ayresting results

Eager to hear the KX-5 Twenty in action, I began my listening sessions with the same recordings I used to review the KX-5. Unfortunately, some recent upgrades to my system negated the possibility of any direct A/B comparisons of the KX-5 and KX-5 Twenty, but my listening notes from the KX-5 review gave me a good launch pad.

Starting again with “Riders on the Storm,” from The Best of the Doors (CD, Elektra WTVD 62568), I was startled by what the KX-5 Twenty put forward. Up till now I’d always assumed that, other than to add a bit of ambiance to Jim Morrison’s words, the point of providing the sounds of rain and thunder in the background was to imply that the Doors were perhaps performing the song outdoors -- at least, that was the picture I’d always painted in my head. But through the KX-5 Twenty, the individual elements of the storm imaged so deep in the soundstage that they seemed to emanate from an abyss. This in itself was a bit spooky -- but when the instruments and Morrison’s voice entered in the foreground, an entirely new set of images began to form in my mind’s eye. Ray Manzarek’s Fender Rhodes electric piano filled the left front of the stage with notes that floated so holographically I could swear I was listening through a Dolby Atmos system. As these notes fell to the ground, Morrison’s voice appeared out of nowhere, brimming with immediacy, image specificity, and density, sounding as if he were standing just 5’ in front of me. Hearing his voice and Manzarek’s piano layered against the vast depth of the storm, replete with wonderfully articulated individual raindrops and dark, distant rumbles of thunder, conjured an image of the Doors rehearsing the song in a rented apartment, the storm audible and visible through a large window opening behind them. The varying layers of depth, density, proportion, and resolution combined to convey a level of realism that now left very little to the imagination. It was, in a word, mesmerizing.

As I rambled through other tracks I’d listened to when reviewing the original KX-5, I noticed comparable levels of immediacy and dimensionality, and of variations in tonal density, particularly when listening to Randy Brecker’s trumpet in the opening minutes of “Your Latest Trick,” from Dire Straits’ Brothers in Arms (SACD/CD, Vertigo 9871498). The contrasts in scale and image focus, in the timing of decays and the rasp of Brecker’s trumpet before and after he moves up-front and center on the soundstage, were present to a level I’m accustomed to hearing only through much higher-priced gear, such as my Simaudio Moon Evolution P-8 preamplifier ($16,000, discontinued). As per the recording engineer’s intentions, Brecker’s trumpet was at first presented with exaggerated grandeur, lacking solidity and focus. As the track progressed and Brecker moved to the fore, the composition of his trumpet’s sound changed rapidly, as if focused by a high-speed aural lens, transformed once again into a dimensional, svelte-sounding horn with senses of immediacy, texture, and solidity so real I felt I could almost reach out and touch it.

Ayre KX-5 Twenty

Similarly, Bob Dylan’s harmonica in “Man in the Long Black Coat,” from his Oh Mercy (SACD/CD, Columbia 5123436), sounded massively dynamic, almost to the point of being too much of a good thing. Equally ear-grabbing was the speed and accuracy with which the transients of plucked bass- and electric-guitar strings were communicated. Reveling in the depths that Tony Hall’s bass guitar on this album demands from my Rockport Technologies Atria speakers, it was easy to forget that the KX-5 Twenty was even in the signal path. I could hear textural details and pitch fluctuations that most often get smoothed over by inferior electronics, and Hall’s unforgivingly low bassline, sustained during the opening seconds of this track, sounded flat-out visceral. I could spend this entire review trying to communicate all of the nuances I could hear through the KX-5 Twenty, but suffice it to say that listening to Hall’s bass against such a still background -- and, later, among other instruments -- reminded me just how much I love this hobby. This was real performance, and reminded me of something I said in my review of the KX-5: that it provided me “with a new benchmark with which to measure transparency in future reviews.”

The KX-5 Twenty raised that benchmark even higher, yet not entirely by sounding more transparent. It took me a while to put my finger on it, but what enabled the KX-5 Twenty to perform at such a high level was its ability to balance each of its attributes with all of the others, then present the music with levels of accuracy and refinement so satisfying that the music pulled at my heartstrings. Once I realized this, I began to understand how and why the KX-5 Twenty sounded so distinct and so special.

Moving on to some newer music, I cued up “Sleep Away,” from Bob Acri’s self-titled album (16-bit/44.1kHz FLAC, Blujazz). Here, the KX-5 Twenty laid to waste any worries I may have had about such an utterly transparent product highlighting a recording’s smallest imperfections. The notes from Acri’s piano floated in air with exquisite fluidity, warmth, and silkiness, all of which helped make this track simply melodic. Obvious in its expanse was the soundstage in which Arci’s piano resided, the KX-5 Twenty’s reproduction of which pushed the boundaries of my room’s walls rather than plumbing its depth. The near silence of the KX-5 Twenty’s noise floor contributed greatly to my being able to appreciate the shimmer, air, and delicacy of Ed Thigpen’s delicate taps of his cymbals. Each tap, despite possessing only mild dynamic inflections, sprang to life by way of its expertly delineated transient, well-defined tonal color, and lingering decay. Then, as I sat back and tried to forget about dissecting the track for a moment, I found myself sucked into George Mraz’s plucking of his double bass. I particularly noted how balanced the sound of the bass was reproduced: richness and pitch definition were deftly juggled with healthy doses of solidity and impact. Through lesser electronics, “Sleep Away” can be a bit confused in the bottom end, sounding too supple and rounded. I heard no such muddling through the KX-5 Twenty.

Ayre KX-5 Twenty

As I continued rummaging through my music collection, it occurred to me that perhaps I should pause to repeat what the KX-5 Twenty didn’t do. Outside of physical build quality, that is the true measure of how good any preamplifier is. From the moment I integrated the KX-5 Twenty into my system, it, like the KX-5, proved to be the quietest preamplifier I had reviewed to date. And Ayre’s own KX-R and KX-R Twenty aside, the KX-5 Twenty was the quietest preamplifier I have ever heard when operated in its Processor Pass Thru mode, adding little to no noise. Aside from passing along all signals with a silky refinement, the KX-5 Twenty lacked any obvious coloration, any tendency to lean toward the cool or warm side of neutrality.

These high levels of performance were not available from the get-go: The KX-5 Twenty took close to 300 hours to break in. Even now, after almost 500 hours of use, there are times when I hear new improvements in how well objects are fleshed out.


Not at this price. What Ayre has achieved in the KX-5 Twenty is nothing short of remarkable. I have heard nothing else for under $10,000 that so convincingly closes the gap between solid-state and tube preamplification. After substituting my Simaudio Moon P-8 preamplifier for the properly broken in KX-5 Twenty, I was hard-pressed to tell them apart. This is a good thing -- it tells me that these two products are reaching the same goal: transparency. But after a period of pleasurable torment in which I tried to hear any difference between them, I did find a few things.

The KX-5 Twenty was a wisp quieter than the Moon Evolution P-8. It was also smoother, sounding more like an exceedingly refined tube than a solid-state preamp. The Moon P-8’s more vivid overall character at times allows it to sound a hint more dynamic and full than did the KX-5 Twenty, but no more resolved, refined, or articulate. It was in the lower frequencies that the gap widened a bit -- despite going toe-to-toe with the Simaudio in overall slam, tonal accuracy, and pitch definition, the Ayre lacked the last iota of textural detail and speed that the P-8 put forward. But remember that the Moon P-8 is a 74-pound, double-chassised juggernaut that, when available, cost $16,000 -- nearly twice as much as the KX-5 Twenty. The fact that the Ayre can confidently hold its own against such a bruiser demands respect.


In his e-mails to me, Charles Hansen noted more than once that his goal with the Twenty series was to produce products that “ensure that the musical engagement and beauty of tubes has been surpassed, while all of tubes’ drawbacks are completely sidestepped.” While I can’t comment on Ayre’s other Twenty-series models, I can unequivocally state that the KX-5 Twenty does just what Hansen set out to achieve. Much like the KX-5 before it, the KX-5 Twenty strives for purity of sound through purity of signal, and emphasizes that the first step toward true transparency is silence. The levels of build quality, and the close attention paid to selection and implementation of parts and materials, have resulted in what I consider to be the industry benchmark in solid-state preamplification for less than $10,000. The KX-5 Twenty is not only the best preamplifier I have reviewed, it may be the best component of any type that I’ve reviewed. It’s only logical, then, that I give the KX-5 Twenty my highest recommendation, and bestow on it a Reviewers’ Choice award. Charles Hansen, I can’t wait to see -- and hear -- what you come up with next.

. . . Aron Garrecht

Associated Equipment

  • Speakers -- Rockport Technologies Atria
  • Subwoofers -- JL Audio Fathom f112 (2)
  • Amplifiers -- Rotel RMB-1585, Simaudio Moon Evolution W-7M (2)
  • Preamplifiers -- Marantz AV8801, Simaudio Moon Evolution P-8
  • Sources -- Oppo Digital BDP-103 universal BD player, Simaudio MiND 180 music server
  • Digital-to-analog converter -- Calyx Audio Femto
  • Cables -- Analysis Plus Digital Crystal S/PDIF and AES/EBU and Silver Oval-In interconnects, Kimber Kable Select KS-6063 speaker cables, Cardas Clear Blue Beyond power cables
  • Power conditioner -- Torus Power AVR2 20A

Ayre Acoustics KX-5 Twenty Preamplifier
Price: $8950 USD.
Warranty: Five years parts and labor.

Ayre Acoustics, Inc.
2300-B Central Ave.
Boulder, CO 80301
Phone: (303) 442-7300
Fax: (303) 442-7301