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Published March 1, 2001

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Ayre K-1x Preamplifier with Phono Section and Remote Control

You'd think I'd learn from experience, but nooooooooo! Back in 1996, I was entranced by the original Ayre K-1 when I reviewed it in Stereophile. I hadn't really wanted to -- after all, all the design excitement seemed to be in the digital and speaker realms. Preamps just didn't seem thrilling, somehow.

Then Charles Hansen, Ayre's Research Director, popped the top off a K-1 and I saw just how quirky and strange the preamplifier was.

Well, Charlie has upgraded that preamp and when he asked me if I'd like to hear the new version, I said yes, of course, but not with any great anticipation. I'd forgotten both its strangeness and the incredible beauty that was its direct result. Until I installed it into my system, that is -- that's when I fell in love all over again.

I still remember my first look under the hood of the K-1's main chassis (it has a separate power supply). The box was large and chunky -- its faceplate was a slab of 1/2-inch aluminum and the sides of its chassis were coated in a pebbled black finish. Inside -- well inside was the damnedest thing I'd ever seen. There was a small circuit board snuggled up against the front panel -- that handled the logic controls for the remote and mute. Attached to the left and right sidewalls were circuit-boards that held the phono modules and, hardwired to the outputs at the rear panel, was a large double-sided circuit board, stuffed with high quality components -- this was the brain of the preamp, where all of its gain amplification took place. Attached to it, back in the near-empty central compartment, was a second panel that looked like a cast-off from the set of Brazil, more a mechanical contraption laced with stepper-belts and gears than an electronic device. That was the motor/volume control system.

It seemed a strange way to implement volume control -- after all, most companies use a straightforward microprocessor/resistor ladder control these days. That microprocessor, Hansen maintains, is the problem. "Most remote controls," maintains Hansen, "use microprocessors, which means there's a high-frequency quartz-oscillator generating a 4MHz signal -- and a 4MHz RF generator is a terrible thing to have inside a preamp. Some manufacturers have the right idea, they have them shut down except when they are asked to change values. We designed a discrete logic circuit that operates at 100Hz and then only long enough to perform the function."

The logic circuit controls a stepper motor that moves the 46-position rotary volume knob. The nature of stepper motors presented Hansen with a problem, which is that the motors themselves cycle through four positions: A, B, C, and D. Hansen needed a way to ensure that the motor and the volume control didn't get out of sync with one another when the motor wasn't used to change the volume, so he used ladder belts to gear the stepper motor so it would cycle through a complete four-step sequence for every click on the volume knob. That way, as Hansen put it, "the motor is always set to A and the two never get out of phase."

It's pure Rube Goldberg -- and it's expensive to boot. It's a custom-built 46-position Shallco rotary switch with self-cleaning solid-silver wipers and silver contacts. Each position is a calibrated 1.0dB step. "It's stupidly expensive and it's stupidly impractical and it's kind of quirky and it makes a lot of noise when it changes position and the feel isn't that good -- but it's the highest performance volume control anyone's ever done! And we'll never do it again!" says Hansen.

"But I strongly believe in balanced circuits and the only way to handle volume control with balanced circuitry is to use a stepped attenuator -- at least it's the only way I can think of."

There's music in the air

I've done it again! Just like the first time I stared down into the K-1, I've focused on that volume control and become paralyzed by its quirkiness. Let's stand back for a second and examine the K-1 and its upgrade, the K-1x.

It is a two box unit -- the audio circuitry is in the big chassis, and the power supply, connected by an umbilical, is in the smaller one. Most of what differentiates the K-1x from the original model resides in the power supply. (Owners of the K-1 can have their units upgraded for the $1500 price difference.) The umbilical, for instance, is new -- a custom cable sourced from Cardas and kitted out with Teflon insulation and a multi-pin computer-type connector. Ayre also now uses special high-speed circuit boards in the power supply, as it always has in the main chassis.

The power supply is housed in its separate enclosure to ensure it doesn't interfere with the musical signal. Schottky high-speed rectifiers, combined with inductor (choke)-input filtering, produce pure DC. Discrete FET master regulators are located in the external power supply enclosure and, additionally, each channel's amplification stage has its own discrete zero-feedback FET regulator.

The K-1x has four times the capacitance of the K-1 and it has been outfitted with what Hansen describes as "Ayre-conditioning." It's a non-ferrous RF filter that "is completely free of the magnetic hysteresis of ferrous-based devices, but like a ferrite filter, it absorbs RF energy," he explained. "It turns it into heat, it doesn't try to block it or shunt it to ground or anything like that. It actually gets rid of RF energy and it's completely non-magnetic. And it doesn't inhibit dynamics. It's the only power line filter I know of that does nothing but good things -- there are no tradeoffs involved."

Ayre is quite proud of what it calls Direct-Path Technology™. This involves simplifying the circuitry and the signal path to increase resolution and clarity. The entire line stage, including every connector and control, is direct-soldered to that single circuit board mounted parallel to the chassis' rear panel. Surface-mount technology keeps the amount of space devoted to circuitry to a minimum -- everything from input to output is contained within six inches of board space.

The fully-balanced signal path is a pure FET design, employing no negative feedback. The circuit consists of a cascoded differential input stage followed by a source-follower output stage. You can't get much simpler than that!

The K-1's phono stage is a $1600 option, which is the price of a good separate phono section. It, too, is a pure FET design that features a balanced input. It's billed as an ultra-low-noise design that can accommodate just about any cartridge out there. Gain is easily adjustable through resistor changes. The manufacturer can supply Ayre Reference Series phono cables that accommodate the preamp's balanced inputs -- they also supply extremely high quality RCA-to-XLR converters.

The Ayre K-1x offers three balanced XLR inputs and three single-ended RCA inputs; two balanced XLR outputs and one single-ended RCA output are also provided.

Who shall silence all the airs … that whisper softness in chambers?

I talk to a certain number of audiophiles who question the need for a preamplifier at all in the 21^st century stereo system. After all, they reason, they don't have a turntable, so they don't need a phono section. If everything's line level and all a preamp does is switch sources and attenuate signal, who needs one, much less a $7000 model?

It's a natural question. But the fact is, I've used a number of passive preamplifiers and I've used CD players with both analog and digital volume controls and I've yet to find a system that didn't benefit from a high quality preamplifier. The music simply sounds sweeter, is more focused, and has greater impact. Part of this is undoubtedly because of a preamplifier's ability to drive the cable that connects it to the power amplifier, and part of it is unquestionably due to the seductive nature of gain. Hansen has another idea. "I think the K-1x's sweetness and air on the top end is the result of the FET circuit, zero-feedback and the overall design's ability to remove RF from the signal upstream and keep it from getting downstream. The K-1x is a wide bandwidth design -- its 3dB down point is 250kHz -- and from an RF standpoint, 250kHz is nothing. So basically, it's keeping RF from entering the system."

I think he's on to something there. The K-1x's sound is sweet and extended -- the same properties that distinguished my system when I attacked RF seriously with Versalabs' anti-RF products.

Sounds and sweet aires, that give delight, hurt not

Sweet? Lord, yes. Extended? Absolutely. Also authoritative, smooth, and timbrally true. The K-1x is an extremely polished performer, comparable in soundstaging and holographic imaging to the very finest tube preamps I've heard.

I listened to one of my favorite CD performances, the Simon Rattle/City of Birmingham Symphony Orchestra/Cécille Ousset performance of Ravel's Piano Concerto in G [EMI CDC 754158-2], and made an interesting discovery. I've always loved this disc for Ousset's controlled passion and the time-stopping, tooth-aching sweetness of her reading of the second movement, but I've never considered it a particularly distinguished example of soundstaging. The Ayre says otherwise. Oh, the recording's still multi-miked, and the focus is not entirely natural, but through the K-1x I could clearly hear the rows of instrumentalists and their interaction with the hall and with Ms. Ousset in a remarkably visual way.

And in her unaccompanied portions of the adagio assai, I heard Ms. Ousset's piano tone as I have almost never heard it before. The piano is such a mechanical contraption -- like the K-1x itself -- how is it possible for all those levers and hammers to create a living, breathing line? Yet every touch, every pedaled swell and stop, every internal harmonic floated gloriously free from the instrument like sighs rising to the heavens. It was one of those moments where you just want to stop time, since life couldn't possibly get any better.

But the great thing about hi-fi is that it's not a matter of life and death. You can, of course, recreate that same experience again -- or another similar one.

That particular evening, I went on to listen to more of Robert Silverman's Beethoven cycle [Orpheum Masters KSP 830]. And no, it wasn't the same experience. Ravel, as much as I love him, isn't Beethoven. And Silverman's majestic approach to him couldn't have been more different from Ms. Ousset's Ravel -- he was imperious, thundering, monumental.

Here the Ayre's amazing capacity to sort out inner detail clearly put the piano in its little casket of a room -- but that didn't kill the music! No, Bob and Beethoven and the Bösendorfer were all too big for the room, but they rose above that detail. And speaking of details, I don't think I've ever been more aware that every hammer fell on more than one string than listening to this disc through the K-1x -- not that I heard the separate strings at the expense of the blended tone. I clearly heard the blend and its constituent parts -- it was all a matter of perspective.

Bring with thee aires from heaven or blasts from hell

That's all through the Ayre's line stage, but good as the line stage is, the phono section's even better. It may, in fact, be the best I've ever heard -- certainly, it ranks among the quietest.

The phono boards take advantage of phono cartridges' inherent balanced nature and connect to one of the three XLR inputs on the rear-panel. You can either re-terminate your tonearm to Ayre's own Reference Series balanced cables or use, as I did, high-quality RCA/XLR adaptors (Ayre supplied me with the nicest I've ever used). Both gain and cartridge-loading can be adjusted by swapping small metal-film resistors that plug into terminal strips on the boards. Gain is factory set at 50dB, but resistors are available to offer gain adjustment in 10dB increments from 40-60dB. Need more than that? Talk to Ayre, they're adaptable.

The default cartridge loading is 50 kohms, but the unit comes with resistors that give you 100, 249, 499, and 1000 ohm loads -- and if you need something less common, you can simply purchase the appropriate resistors and install them. The phono-boards are easy to get to, so adjustment is a snap.

I recently received the Classic reissue of Led Zeppelin [SD 8216], a record I've been seeking a clean copy of for decades. Connoisseurs say the UK Atlantic/Polydor is the one to go for, but I've always preferred the original Atco pressing. The only thing is, in thirty years of searching, I've never had a clean, unwarped copy -- sheesh, you'd think that LZ fans actually listened to the damn things.

The Classic was everything a Zep I ought to be: crunchy; full-bodied; with huge, deep, slammin' drum sound and bright shimmering harmonics being thrown off of Page's pick. Man o man o man -- if you like power trio music taken to its limits, you need this reissue. It's as perfect as they get.

We call the music heavy, but I've always felt that LZI was amplified chamber music. There so much space and air in the recording -- and so much body in Robert Plant's vocals -- that it's far more like a string trio recording than the sludgy mound of sound that ossified the heavy metal movement a few years after this recording. In comparison, LZI is as light and delicate as a Mozart serenade.

I reveled in the pile of to be played albums that had grown since my move. I'd kept putting off setting up the turntable, but the Ayre forced me to get it working and … Geez, we keep talking about all the advances digital is making (and it's all true), but there's still something about a properly played LP that is intensely satisfying. No, I'm not going to retreat into audio-Luddism and chant digital bad/record good, but at their best, I still love records and the way they sound.

The new Speakers Corner reissue of Ella Fitzgerald Sings the Cole Porter Songbook [MGV 4001/2] beckoned. I love this recording, although Ella was a strange choice for Porter, since words weren't her primary focus in most songs. Still, she was in great voice in these sessions, and the Ayre constructed an Ella-sized body between the speakers and floated her voice on a sumptuous cushion of Buddy Bregman-arranged instruments. Tasty, tasty, indeed.

Here, the Ayre was, once again, a champion at constructing a soundstage -- one that seemed horseshoe-shaped around Ms. Fitzgerald. That's probably a microphone-induced distortion of how the group was really seated, but it's quite solid and unwavering. And detailed -- without ever sounding etched.

God, I'm such an audioweenie. After hearing the Speakers Corner version, I had to compare it to my old Verve (not an original). Hmmm, that's a hard choice. My Verve pressing had more air, especially surrounding Ms. Fitzgerald, but it also seemed a tad smeared in terms of instrumental detail. The reissue seemed lusher and warmer, but also sharper around the edges of the instruments images -- perhaps a bit like the excessive use of edge enhancement on a DVD's picture. The edges almost shimmered. I guess I'll keep my old copy, but the new one is nothing to sneeze at -- and the Ayre allowed me to hear the differences clearly.

And ever against eating cares, wrap me in soft lydian airs

There just ain't no way around it. I've fallen in love again. The Ayre K-1x has reminded me just how good the original was, and it seems to have improved upon that original formula without introducing any new shortcomings. It is sweet and detailed, tonally spot on, and capable of resolving the smallest details without ever stinting the big picture. If it has any shortcomings, I couldn't find them.

Will you prefer it to all other preamplifiers? I couldn't say. Component interaction and personal taste account for more at this level of performance than any good/better/best ranking. It won't be everyone's cup of tea.

If you cannot take advantage of its balanced operation, either through a source component or an amplifier, you may decide to look elsewhere -- although it sounded great feeding my single-ended MF Nu-Vista 300. The Rube Goldberg-esque volume control is physically hard to turn by hand, and that might put off some shoppers, although most people will use its remote control exclusively. And some folks will be put off by the fact that they have to switch sources manually (the remote only controls volume and muting).

Then there's the matter of cost -- at $7000 as a line stage, $8600 with phono section, the K-1x isn't cheap. Yet it's solidly built and employs expensive, predominantly custom-built components. The price doesn't seem unreasonable. Some reference preamps do cost far, far more. And some people may be looking for a preamplifier with more of an identifiable "sound." That's their decision, of course, and not Ayre's fault. That's what preference is all about.

But for the rest of us, I think the Ayre K-1x might be just right. If you're easily satisfied with the very best, put the K-1x on your shortlist and see how it stacks up to the competition. You're in for a treat.

...Wes Phillips
wes@onhifi.com

Ayre K-1x Preamplifier
Price: $6750 USD (linestage w/o remote); $7000 (w/remote); $8600 (w/remote and phono section)
Warranty: Five years parts and labor

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

E-mail: info@ayre.com
Website: www.ayre.com

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