Ayre Acoustics Codex D/A headphone amplifier

I first spied the Ayre Codex two Januarys ago, at the 2015 Consumer Electronics Show, and its scrappy proletarian vibe sure made it look different from any other Ayre creation. On learning that its price would be well under $2000, I was immediately curious what Charley Hansen and his gang—makers of the $3450 QB-9DSD USB digital-to-analog converter, plus a few five-figure amps and preamps—could create when cost is an object.

Indeed, as Hansen says, "The Codex was deliberately built to the lowest price point we've ever done. Doing so imposes specific constraints. No matter how clever one gets with the circuitry, the fact that there are cost constraints limits the ultimate performance level."

I wondered: would this turn out to be trickled-down technology at its best, or would some essential Ayre magic be lost in the process?

The Codex retails for $1795 and sits nicely on a desk, like a thick hardback book stood on its long edge: it's much taller than it is wide, and deeper than it is tall. Other DAC–headphone amps have gone this route, including Denon's DA-300USB and NuForce's Icon. But unlike DACs that can be placed horizontally or vertically, the Codex must be stood on edge, where its four rubber feet reside. One benefit: you can use the Codex as a headphone stand, knowing that your 'phones will be nice and toasty, all warmed up, when you put them over your ears. (My sample of the Codex got hot to the touch—about 108°—after a couple hours.)

On the front, across the top, is the Codex's name in large white letters; below that—and featuring notably smaller characters—is the unit's multi-function display. During normal listening, the display shows the sample rate. Then, as you turn the large volume knob directly below it, the display temporarily indicates the volume level in increments of 1.0dB, from 0 to 100. Every time you power up the Ayre or insert headphone plugs in one of its jacks, the volume resets to a friendly 66. That's probably a safe, sane feature, but it meant I had to keep returning the volume to my calibration target as I switched back and forth for comparisons: other DAC volume controls always stay where I leave them.

The volume knob is wrapped with a couple of rubber rings, for good grippiness. Ayre claims this stepped digital control retains a full 24 bits of resolution down to –60dB. Pushing in the knob mutes the Codex, and holding it down for a couple seconds accesses other functions: input and output selection, display brightness, and firmware version. Though this is a hefty little DAC, pushing the knob hard enough to get it to click caused the Codex to slide a bit across my desk each time. I learned to hold it down with one hand.

You can set up the Codex to bypass its volume control for use as a straight DAC in a system with preamp. With the Codex in this mode, inserting headphones will temporarily turn on the volume control and reset it to 66. Remove the headphones and DAC mode resumes. Very convenient.

Listening to headphones and using the output jacks at the same time is not recommended. The user manual warns that, when trying to use both, "In single-ended mode, the rear-panel jacks will not output the correct signals. While this will not damage any equipment, you will not hear the proper sound quality from your speakers in this situation."

Below the Volume/Select knob is a small LED that indicates when the headphone output is configured for Balanced mode. Below that are two 3.5mm headphone jacks, which can be used for shared listening with two sets of headphones—or, in Balanced mode, one jack for the left channel and one for the right. Each time you plug any headphones into one of the 3.5mm jacks, the displays flashes "BAL" and lets you choose balanced or unbalanced operation.

Below the smaller jacks is a regular ¼" stereo jack for unbalanced headphones. If you've set the 3.5mm jacks for Balanced mode, you can still use the ¼" jack for unbalanced headphones, though you can listen only to one set—balanced or unbalanced—at a time. As soon as you pull the unbalanced headphones out, the Balanced light comes back on; when you insert the balanced headphones into the 3.5mm jacks, the display flashes "BAL," you push the volume knob once, and you're back in business.

On the rear panel are both balanced (XLR) and unbalanced (RCA) audio outputs and, below those, the USB and optical inputs, as well as an IEC power connector and switch. Up to 24-bit/384kHz PCM and DSD64 and DSD128 are accommodated, which I tested via USB (I didn't test the optical input). Inside is ESS's ES9018K2M 32-bit DAC chip, along with the same fully balanced, zero-feedback topology used in Ayre's R Series models.

But according to Charley Hansen, the key to the Codex is the linear power supply stuffed into its little case. "Remember that every circuit is a modulated power supply," Hansen told me. "When you have a fully differential balanced circuit from input to output it makes a massive difference. We put the very best power supply in the Codex that we know how to make, the AyreLock regulator that is in our Twenty series products. When you run balanced, it is like making the best power supply literally 1,000 times better."

A final note about the Codex's exterior design: The case is quite simple and direct, and our own Michael Lavorgna blames the front-panel fonts (they're kinda large) for spoiling an otherwise serviceable design. I have to agree. I wouldn't say the Codex is ugly, but maybe it looks a little plain—certainly not as stylish as Ayre's pricier stuff. I see this as more a missed opportunity than a dud; the question is, can the Codex make up in sound quality what it lacks in looks?

Installation and setup
Setup was easy, and once I got the hang of the Volume knob/pushbutton and how the balanced operation works, it all made sense. And, as noted, Ayre highly recommends using the Codex's Balanced mode with headphones when possible, which I was eager to put to the test.

When using headphones or listening to my main system, I primarily listened to the Codex with it hooked up to my MacBook via USB and running the Roon app. My library has files of pretty much every sample rate and format, and the Codex properly switched on the fly—with never a pop or a click—and indicated the result on its display.

In an effort to rack up a few hundred hours of break-in before critical listening, as Ayre recommends, I left the Codex on continually over the course of several weeks, and used it casually with various headphones: AKG K 240, Audeze LCD-X, AudioQuest NightHawk, Grado HP1, NAD Viso HP50, and Sennheiser Amperior. Ayre also sent a custom set of Cardas Clear balanced headphone cables, to mate with the Audeze connectors and the Codex's dual 3.5mm jacks.

A note about Ayre's warranty: You're automatically covered for 90 days, but if you send in the registration card and a copy of the receipt from an authorized Ayre dealer within 30 days of purchase, the warranty extends to five years. Don't toss that card!

I began with a stroll through Pentangle's lush English meadow of music. The first incarnation of the group, formed in late 1966 or early 1967, created a handful of essential folky-jazzy-rocky albums featuring great acoustic (and occasionally electric) guitar playing layered around Jacqui McShee's bright, clear voice. The title track of their fourth album, Cruel Sister (CD, Sanctuary 634), begins with just McShee's voice and Bert Jansch's guitar, more voices and instruments steadily added throughout the track's seven minutes. As I listened through the Codex, everything imaged clearly from extreme left to extreme right, wonderfully suspended in a wide, open, dreamlike space.

First things first. Listening to "Cruel Sister" with the Audeze LCD-Xes, I switched back and forth between balanced and unbalanced operation, and found, as Charley Hansen had suggested, that the advantage indeed went to balanced. As I ran through a selection of my standard demo cuts, I found that the difference was a cleaner, slightly more focused sound that was unforced and very natural during balanced operation. All my other headphones mated fine with the Codex during unbalanced operation—but if you can, get a balanced cable fitted to whatever 'phones you use, and try it.

Ayre Acoustics, Inc.
2300-B Central Avenue
Boulder, CO 80301
(303) 442-7300

headphile's picture

It seems like a missed opportunity to not have Tyll Hertsens at least co-author headphone reviews when they are posted to Stereophile instead of Innerfidelity (Stereophile's review of the Chord Hugo TT is another example of this). I am an avid reader of The Enthusiast Network's audiophile websites and I have consistently found Tyll to be a trusted reviewer with invaluable headphone experience. His reviews include accurate comparisons and measurements that give useful context that can be used to make informed purchase decisions. I hope in the future more reviews like this will at least be co-authored by Tyll or posted to Innerfidelity.

Jon Iverson's picture
Great idea - will see if this is possible for the next headphone/DAC review.
cgh's picture

... watch stuff grow.

lennykp's picture

Did you try AYRE Codex as balance preamp? how does it perform?
Please ask manufacturer if USA model work on 240V also?

acuvox's picture

Ayre Acoustics has always scrupulously minimized or avoided generating RFI signals in its boxes. This means putting the control micro to sleep or hibernating, analog power supplies and static, non-matrixed displays.

This example is retro visually. The seven segment LED display goes back to the first pocket calculators from Bowmar in 1971, and the first digital watch in 1967. Pin count was a major issue, so calculator displays where multiplexed, switching the digits on and off in succession on the first microprocessors.

For only two digits, you just need 14 pins for the segments to run on DC. The extra 5 pins are insignificantly expensive in parts cost and circuit board space, but this critical design decision improves sound quality better than expensive internal mu metal shielding.