Written by Aron Garrecht Aron Garrecht
Category: Full-Length Equipment Reviews Full-Length Equipment Reviews
Created: 01 January 2015 01 January 2015

Ayre KX-5Reviewers' ChoiceMy experience with Ayre Acoustics’ KX-5 preamplifier ($7950 USD) began with Alex Brinkman, Ayre’s North American Sales Manager, flying up from Ayre’s home base of Boulder, Colorado, to deliver and set up the KX-5 in my system. Brinkman was very helpful in showing me the KX-5’s ins and outs, and provided valuable information about its origins and features. This was followed by Charles Hansen, owner of Ayre Acoustics and designer of the KX-5, taking the time to answer my myriad technical questions.

Hansen and Brinkman told me that several aspects of the KX-5 are unique. First, particular attention was paid to the materials used. Although the KX-5 isn’t carved from a billet of solid aluminum, as is done with its much costlier big brother, the KX-R Twenty ($27,500), all of the pieces comprising the KX-5’s case are made of solid aluminum plates locked together with stainless-steel fasteners. This was done for two reasons. First, aluminum is a strong, resilient material that retains its shape, color, and texture indefinitely, and won’t tarnish or bubble. Second, aluminum is nonmagnetic, which is key -- magnetic materials can adversely affect audio signals. In fact, Hansen saw to it that none of the materials used inside the KX-5 have magnetic properties -- save the EI transformer, of course.

Measuring a slim 17.25”W x 3.75”H x 13.25”D, the 23-pound KX-5 takes up little space, and can be ordered in silver or black. The KX-5 has a single-line display machined into the center of its faceplate, flanked by a pair of identical rotating knobs and two small buttons to the lower inside of each.

Brinkman and I linked the review sample to my Calyx Femto DAC, Ayre C-5xeMP SACD player, and Classé CA-M300 monoblocks using Kimber Kable Select 1126 balanced interconnects. Analysis Plus Silver Oval balanced interconnects served to link the KX-5 and my Marantz AV8801 home-theater processor, enabling me to evaluate the KX-5’s home-theater bypass. All power cables were Cardas Clear Beyond.

After letting the KX-5 warm up for a couple hours as Brinkman and I chatted, and before he left, I decided to play a quick demo of Master and Commander: The Far Side of the World. Switching to Unity Gain mode, a function that can be assigned to any of the KX-5’s inputs, I heard no noise coming from the tweeters of my Rockport Technologies Atria speakers. I assumed something had gone awry -- I’ve grown accustomed to hearing at least some hiss from most other preamps with this option. It turned out that nothing at all was wrong -- the KX-5 had simply delivered its first surprise, and a welcome one: an unprecedentedly low noise floor.

So impressed was I by the KX-5’s silence in this mode that my first question to Hansen was: How was this possible? He paused for a moment, then explained that it was due to Ayre’s Variable Gain Transconductance (VGT) volume control. Not really understanding how a volume control could have so profound an effect on a preamp’s noise level, I asked him to explain. He took me through the KX-5’s entire signal path, along the way elaborating on several key features.

A signal, balanced or unbalanced, enters the KX-5 through one of its four balanced or two single-ended input jacks on the rear panel. On the inner surface of that panel, each input is directly connected to a series of electronic FET-based switches that are controlled using a series of pulses sent by either the remote control, or the input selector on the far left of the faceplate. Each time a different input is selected, there is a short click as the relay makes a ground connection between the selected source component and the preamplifier. Hansen said that these relays are very robust and can handle large ground-leakage currents, but are used only outside the signal path, as they can significantly degrade the audio signal. Also of note is that, once a source has been selected, all other source components are completely disconnected from the system, including the ground connection. This eliminates the possibility of any noise creeping into the audio signal from other source components’ power supplies, such as possible ground loops or RFI. This elaborate process of selecting among completely isolated sources results in exceedingly short and precisely directed signal paths -- the first of many ways noise is kept to a minimum in the KX-5.

After the signal is sent through the selected input, it is immediately converted to a fully balanced signal (if the input is single-ended), and kept in balanced mode throughout the rest of the circuitry. The signal is then sent to the line stage, which in the KX-5 is Ayre’s VGT line circuit. This circuit dictates the volume level using solid-silver-contact rotary switches driven by a series of toothed pulleys and gears, these in turn driven by stepper motors that rotate a specific resistor into the amplifier circuitry. As each resistor is selected, the stepper motor produces an audible knock as the resistor locks in place. Volume levels are altered because each resistor alters the circuit’s transconductance by a specific amount, thereby altering the gain. Because the only thing changing is the resistor in the amplifier circuitry, unity gain -- or any other volume level, for that matter -- can be achieved with exceptionally low levels of noise.

After the desired volume is set, the audio signal is directed to Ayre’s Diamond output stage -- essentially, an emitter follower that drives a secondary emitter follower. The PNP on one side of the circuit, along with the NPN on the other side, drive a secondary emitter follower that is cross-coupled in reverse orientation. This eliminates most of the noise or distortion residing in the circuit, and is the end of the signal’s path through the KX-5 before it exits through either a pair of Cardas single-ended output connectors or one of two pairs of Neutrik balanced output connectors. All circuitry within the KX-5 is fully balanced from input to output, with zero feedback, and is all discrete. Even the LED display used to show the input and volume levels was chosen because it was the quietest among those considered, emitting almost zero noise. Power delivery is kept quiet in the KX-5 by using a combination of a high-quality EI transformer and Ayre’s own Ayre Conditioner power-line RFI filter. The gain circuit uses Ayre’s EquiLock circuit, which Hansen explained: “Normally, as you run a signal across an amplification device such as a transistor or a tube, the voltage across the device changes. The EquiLock circuit maintains the voltage across the amplification device it is paired with, and allows only the current to change, providing for very stable power delivery.”

Because the KX-5 shares many Ayre technologies -- VGT, the EquiLock circuit, the Diamond output stage -- with other Ayre models, I asked Hansen if the KX-5 shares any of its other parts with other current Ayre products. He said that the KX-5 is so closely related to the AX-5 integrated amplifier ($9950) that, with the exception of a slightly larger enclosure and a few modifications of parts, the KX-5 is essentially an AX-5 with the latter’s amplification modules removed. They share the VGT circuit, but in the KX-5 the VGT is a low-powered affair that simply drives the cables and the external power amp. In the AX-5, the VGT circuit changes the gain of the amplifier stage itself, which outputs 125Wpc. Though the two models also share the fundamental design of the Diamond output stage, their vast differences in power output mean that the circuitry is implemented in completely different ways. A similar approach was taken in the volume-control assembly shared by the KX-5 and the KX-R Twenty. The assemblies themselves are virtually identical, but the KX-5’s has 46 volume positions, employing different resistors, whereas the KX-R Twenty has 60 volume steps, and uses superior, far more costly resistors.

All Ayre products are also manufactured similarly. The billet-aluminum chassis of Ayre’s R models are milled by a private contractor not far from Ayre’s headquarters. The aluminum case panels for all other Ayre models are made by another contractor, in California. All Ayre circuit boards are designed in-house and made off-site by yet another contractor -- but rather than keep their hands entirely off their hardware, Ayre hand-picks in-house every part for each circuit board, and assembles them into kits before shipping them off for final assembly and soldering. This is done using a computer-controlled process that involves wave soldering to ensure the utmost consistency and quality. All circuit boards are then sent back to Ayre, where each is tested, then installed by hand. The end product is tested again, burned in for at least 24 hours, then tested again before the final assembly is approved.

In use

With so high a level of quality control, it came as no surprise that the KX-5 functioned flawlessly during my few months with it. Watching movies using the near-silent unity-gain setting offered new levels of detail retrieval from more Blu-rays and DVDs than I can remember -- I can’t recommend this preamp enough to those incorporating a two-channel preamp into a home-theater environment. However, I should point out that initially setting up the unity-gain feature is a bit of an exercise -- the KX-5’s means of communicating with the user is less than intuitive. The information displayed is limited, and it took me and Alex Brinkman some time to figure out how to program a chosen input. The good news is, once your sources are configured, you rarely have to access the menu again; I chalk this up to a labor of love.

Listening to the KX-5 was the antithesis of setting it up. It was one of the quietest, most straightforward preamps I have reviewed. The Ayre’s inky-black background let details emerge with newfound clarity -- such as the falling raindrops in the first 30 seconds of “Riders on the Storm,” from The Best of the Doors (CD, Elektra WTVD 62568). Through other preamplifiers, including my own Classé CP-800, the rain can sound a bit blurred, lacking any sense of individual drops. But with the KX-5 I could now hear raindrops hitting the ground one by one -- there seemed to be more space between them, and the space into which they fell sounded larger, more three-dimensional.

Ayre KX-5

With such a quiet and resolute preamplifier in my system, the gulf dividing “Red Book” from high-resolution audio files never seemed wider. Randy Brecker’s trumpet in the first minute of “Your Latest Trick,” from Dire Straits’ Brothers in Arms (SACD, Vertigo 9871498), popped out of thin air with arresting levels of solidity and focus. I was also able to hear previously unheard textures in Mark Knopfler’s voice that contributed to benchmark levels of realism in my system. In fact, the KX-5 consistently excelled at delivering nuances, microlevel details, and a sense of delicacy that drew me into the music.

That said, the KX-5 wasn’t all about providing the last iota of detail at low levels against a stark background -- it also liked to get down and boogie with the best. While listening to “Man in the Long Black Coat,” from Bob Dylan’s Oh Mercy (CD, Columbia CK 45281), I was treated to an acoustically dynamic sound replete with a deep, rhythmic, tactile bass line, firm plucks of guitar strings that then subtly decayed, and a palpable voice placed center stage. Dylan’s briefly appearing harmonica floated in the air with a vivid, organic, and grander character than I’m used to hearing. There was also a subtle resonance to his harmonica that helped limn the boundaries of the recording space, providing me with a new benchmark with which to measure transparency in future reviews. Experiencing these unexpected nuances evoked in me a sense of intrigue that had me hitting Next rather than Stop with pretty much every album I played. And as I did, I quickly realized that what I’d heard so far weren’t the only surprises the KX-5 had in store for me.

Regardless of the type of music I played -- and, for the most part, the quality of the recording -- the Ayre KX-5 seemed hell bent on letting the speakers dissolve into thin air, leaving nothing but a precisely illustrated image of whatever I’d decided to play. Moving from “Ora,” from Ludovico Einaudi’s Una Mattina (CD, Decca Music 475629-2), to an electronic remix of La Roux’s “In for the Kill” (16-bit/44.1kHz FLAC), couldn’t have driven this observation home harder. “Ora” is a piano solo that draws me in with Einaudi’s undulating tempo and dynamic keystrokes. Two things can keep this track from sounding mundane: proper definition of the leading edges of the keystrokes, and accurate reproduction of the full depth of each note. With the KX-5 in the loop, Einaudi’s keystrokes were consistently presented with the requisite level of note saturation and tonal color. Moreover, each note had a fast initial transient attack followed by a supple decay; together, they let each note float in a very specific space in air. This image specificity helped keep scale in check, something often exaggerated by lesser electronics -- the sound was more that of an instrument than notes merely floating in space.

By contrast, “In for the Kill” was recorded with the intent of making the voice sound huge, and that’s exactly what I heard. The track opens with a synth-bass line that digs well below 30Hz and undulates like a sinewave -- within seconds, La Roux’s voice enters, seeming to occupy the entire soundstage and sounding focused and immense in scale. The KX-5 reproduced La Roux’s voice with an endearing liquidity, instead of the more visceral, in-your-face character I’ve grown used to. It sounded almost as if the electronics were taken out of the electronica. At volumes past the point of sanity, this track can make you think your ears are about to bleed -- but as I crept closer and closer to maximum gain, I heard no deafening edginess in the voice, no bloat in or lack of control of the bass line, and definitely no homogenization of the soundstage. Everything sounded as close to real as I’ve heard it in my room, all above a noise floor that just didn’t seem to exist.


I’m able to make the above observations and the following comparisons only because I’ve let these tracks rip many times before, through other components and speakers. My current reference preamplifier is my Classé CP-800 ($6000), and no matter how you slice it, it and the Ayre KX-5 could not be more different. Ergonomically, the Classé uses a fancy touchscreen and a single volume knob for repetitive selections, setup, and adjustments, compared to the Ayre’s more minimalist and symmetrical approach. The Classé offers an endless array of customizable options: parametric EQ, tone controls, bass management, and a formidable onboard DAC capable of playing high-resolution files up to 24/192 asynchronously via USB. The KX-5 offers none of that, instead focusing strictly on attenuating an analog signal and doing it quietly. The most obvious example of this was when I compared the two models’ unity-gain features. With the Ayre in the chain, I could detect almost no noise coming from the tweeters of my Atrias, unless my ear was almost touching them. When I swapped in the Classé, I could hear noise from my listening chair, more than 9’ away.

To level the playing field for listening to music, I bypassed all of the Classé’s digital circuitry by running it strictly in Digital Bypass mode, and used each preamp with the same cables and ancillaries. I matched output levels with a sound-pressure-level meter -- the numbers of steps needed to achieve maximum gain with these preamps are very different, making level matching by volume display impossible.

When I listened to each of the tracks mentioned above, the KX-5 was consistently more transparent, resolute, and quiet. The Doors’ raindrops, which I could so easily hear through the KX-5, were less obvious, and a bit lost in the Classé’s higher noise floor at higher volumes. Michael Brecker’s tenor sax in “Your Latest Trick” seemed to have a hint less bite through the Classé, and the bass guitar, while equally controlled, had less punch. The added level of textural detail in Knopfler’s voice that I’d heard through the Ayre was present with the Classé but a smidge less obvious -- I might have missed it if I hadn’t been listening for it. When I listened again to La Roux’s “In for the Kill,” the leading edges of the drums seemed a degree more focused through the Ayre, and were supported by quicker transients, added impact with each drumbeat, and a resonant decay to each stroke on the skin that took ages to fade into a background clearly superior in volume.

While the Classé CP-800 offers exceptional value and terrific performance among its peers, Ayre’s KX-5 has proven to be clearly better.

In the end

The attention to detail, quality, and performance that I have experienced while reviewing the formidable KX-5 preamplifier has reaffirmed my position that Ayre Acoustics makes some of the best audio gear money can buy. Putting aside my quibbles about ergonomics, I found nothing to dislike in the KX-5 -- it performed flawlessly, exhibited outstanding sound quality, and proved to be the quietest preamplifier I have ever heard in my system. Add to this a five-year warranty, and an undeniable dedication to customer service, and I can enthusiastically recommend it not only to you, but also for a Reviewers’ Choice award.

. . . Aron Garrecht

Associated Equipment

Ayre Acoustics KX-5 Preamplifier
Price: $7950 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