Reviewers' ChoiceCalyx Audio FemtoMy review of Calyx Audio’s DAC 24/192 appeared September 1 on our sister site SoundStage! Xperience. The DAC 24/192 wasn’t flawless -- it lacked certain key features I would have liked -- but it was a fine product for its asking price of $1950 USD, and showed a lot of promise: its sound approached the state of the art.

As I finished writing up the DAC 24/192, the Korean firm’s Canadian distributor, Charisma Audio, offered to send me the company’s new Femto DAC, which retails for $6850 -- more than three times as much as the DAC 24/192. Could it justify that hefty price?


The Femto looks nothing like the DAC 24/192, which looks more or less like an Apple TV box milled from a solid block of aluminum. Instead, the Femto has a large, rectangular, extremely well-built case that measures about 17"W x 4"H x 16"D, and whose looks I liked quite a bit more. The case’s thick panels are made of pieces of solid, superbly finished aluminum that fit together perfectly, and no doubt contribute to its substantial weight: some 40 pounds. My review sample came in silver; the Femto is also available in black. The Femto’s level of build quality is probably overkill for a DAC, but it’s fitting, given current expectations for how high-priced, ultra-high-end components should be built. So even though the two products look nothing alike and are priced miles apart, I can say about the Femto’s build quality what I said about the DAC 24/192’s: "I find it refreshing to see a quality of case commensurate with the price."

Calyx Audio Femto

I also like the Femto’s feature set more. The power button is discreetly placed toward the front of the left side panel. This helps unclutter the front panel, and it’s as easy to get to as if it were on the front. The DAC 24/192 has a single LED on its front panel to indicate a lock to either a computer or a disc transport, which kept its look exceedingly simple and clean, but I found that limiting -- I wanted a front-mounted source identifier (the DAC 24/192’s was on the rear), as well as a sample-rate indicator. In stark contrast, the Femto has a beautiful glass display with easy-to-read, orange-tinted characters that indicate the selected input, incoming sample rate, digital filter (three are selectable), phase setting, and volume level. Its built-in digital volume control (which works in 0.5dB increments) means that the Femto can be connected directly to a power amp, though I think most users will run it through a preamp, which is what I did. The DAC 24/192 is sparse in features, the Femto comparatively rich. The latter’s different inputs and settings can be selected using the front-panel controls to the right of the display, or with the small, beautifully finished, all-aluminum remote control (the DAC 24/192 has no remote).

Calyx Audio Femto

On the Femto’s rear panel are the inputs: two coaxial, two AES/EBU, two optical, one BNC, and one USB, all supporting resolutions up to 24-bit/192kHz. There are also balanced (XLR) and unbalanced (RCA) analog outputs, along with the IEC-compatible power-cord inlet. All digital inputs and analog outputs are labeled right-side up (above the connectors) and upside down (below), and thus can be easily read whether you’re directly facing the Femto rear’s panel, or leaning over the Femto from the front to peer down at the rear. Smart!

As in the DAC 24/192, the Femto’s unbalanced outputs deliver up to 2V, which is more or less the industry standard for digital sources, but its balanced outputs deliver up to 6.8V, which could overload some preamps -- you might want to try this DAC with your own gear before buying. Both outputs boast impressive specs (e.g., distortion of less than 0.0003% at 1kHz), but because the balanced outputs have slightly better numbers for signal/noise ratio, channel separation, and dynamic range, they’re what I used for most of my listening.

Calyx Audio Femto

The DAC 24/192’s power supply is outboard. The Femto’s substantially larger case contains its supply, placed somewhat away from the main circuit board -- which is located near the back, alongside the connectors, for the shortest signal path -- and fully enclosed within a metal shield, to keep noise from leaking into the sensitive audio circuitry. According to Seungmok Yi, Calyx’s president and chief designer, separate transformers are used for the digital and analog sections.

The Femto’s circuit board is quite a bit larger than the DAC 24/192’s and, from what I could tell, is decked out with top-quality parts. Yi told me that dual Sabre Reference ESS9018 DAC chips are used, one per channel, for better channel separation and dynamic range, instead of the DAC 24/192’s single chip. As I mentioned in my review of the DAC 24/192, Sabre’s DAC chips are turning up in many of today’s top digital sources. XMOS’s technology is used for the USB input, which operates asynchronously; i.e., the DAC controls the flow of data from the computer and not the other way around, resulting in a lower amount of jitter for such a hookup. Resolutions of up to 24/192 via USB are supported natively with Apple’s OS X (v.10.6.4 and higher). For resolutions higher than 24/96 using Windows XP, Vista, or 7, the Thesycon driver, which Calyx Audio provides, must first be installed. Because I no longer spin discs, I used USB to connect to my Sony Vaio laptop, which runs Windows Vista and JRiver Media Center 17.

Calyx Audio Femto

Then there are the "femto" clocks (hence the DAC’s name), which Seungmok Yi says he "borrowed" from military and aerospace GPS technology. He says these clocks have only 500 femtoseconds of jitter. That may sound like a lot, until you realize that it’s less than 1 picosecond, which itself is incredibly brief. (One femtosecond is one quadrillionth of a second, or 0.000000000000001s.) Yi said that these clocks are "covered with milled aluminum to secure them from outside EMI or any other noise."

In build quality, styling, size, and features, the Femto is a clear step up from the DAC 24/192. It’s also a step up in something else: the warranty. When I reviewed the DAC 24/192, I criticized Calyx’s parent company, Digital & Analog Co., for the paltriness of their one-year warranty. They immediately increased the warranties of the DAC 24/192 and Femto to three years. That’s more like it. Good on them.


I began this section of my DAC 24/192 review by saying that the DACs I’d reviewed over the past year or so were sounding quite a bit different from one another than the ones I’d reviewed in previous years, which tended to sound close to the same. However, the DAC 24/192 and Femto sounded quite similar, which is not all that surprising -- the Femto is something of a souped-up DAC 24/192. What I said about the DAC 24/192 sounding "exceedingly neutral and utterly clean in my system" held true for the Femto. No matter what kind of music I played, there was no hint of grain, hash, or edge -- unless, of course, those qualities were already in the recording itself.

Likewise, the Femto sounded more forward than the Simaudio Moon Evolution 650D ($9000), which I reviewed earlier this year and found to be pretty much a statement-level digital source, if slightly less upfront than the Eximus DP1 ($3000), which is quite lively in its sound. When components’ sounds differ in this way, it’s hard, if not impossible, to know which is "right" -- but after listening to many recordings through all three sources, I suspect that the Femto and the DAC 24/192 were the most neutral; also, their soundstages began right at the plane defined by the speakers’ front baffles and extended rearward from there.

These observations held true as I worked my way through the Femto’s three digital filters, each of which sounded slightly different. I preferred Filter 1 overall, and wasn’t surprised to see that it’s the Femto’s default filter -- it had the best balance of bass to high frequencies, the clearest midrange, and the best resolution. Filter 2 sounded a touch tipped up in the highest frequencies, which made it sound livelier in my system with my music -- but also somewhat splashier, which was particularly noticeable with poorly recorded cymbals. It was hard to tell if Filter 3’s highs were more pronounced than Filter 2’s, but they at least sounded similar, and not as refined as Filter 1’s. Mostly, though, I noticed that Filter 3’s midrange made voices sound ever-so-slightly homogenized and compressed. I used Filter 1 for most of my listening.

Calyx Audio Femto

But sounding similar to the DAC 24/192 didn’t mean that the Femto sounded the same. The Femto’s soundstage extended rearward quite a bit more than the DAC 24/192’s, with far better image specificity and separation among instruments and voices. This held true regardless of which filter I used, but it was most noticeable with Filter 1. When I played Crux Fidelis, from our 2L-TWBAS 2012 Sampler (24/176.4 FLAC, 2L/, I was more than impressed to hear soundstage width and depth that outclassed the DAC 24/192’s, but I was flabbergasted when I realized that the re-creation of space was on a par with the Simaudio 650D’s, which until then no other DAC had even approached. What’s more, the Femto’s image specificity was more precise than the 650D’s, and its delineation of voices was also superior -- which also surprised me, given how good the 650D is in just those areas. Such performance points squarely to one thing: greater resolution. I could hear more detail through the Femto than through the DAC 24/192, and as much as, and sometimes a little more, than through the Moon Evolution 650D.

Of course, 2L-TWBAS 2012 Sampler is a superb-sounding high-resolution recording (24/88.2 and 24/176.4 resolutions are available) -- you’d expect to hear a lot of detail. But the Femto’s ability to unearth extraordinary amounts of detail and present a soundstage wider than I was used to could also be heard even with very poor CDs, such as Sade’s Diamond Life (16/44.1 FLAC, Epic). That album was first released on CD in the mid-1980s, when the CD format was in its infancy, but was remastered and reissued in 2000, by which time engineers had more experience with digital sound. I’ve ripped both versions to my computer system, and although the remastering is better than the original edition, both sound thin and edgy, with little image dimensionality, soundstage depth, or clear separation among the musicians.

The Femto didn’t make a silk purse of this sow’s ear, but its reproduction of tracks such as "Smooth Operator" and "Frankie’s First Affair" was the best I’d ever heard. I believe that had mostly to do with its extremely high resolution and utterly pure and grain-free sound -- the Femto let me hear everything with breathtaking transparency and uncanny image focus. As a result, Sade Adu’s voice was rendered more cleanly, and with greater presence, than by any other digital source I’ve heard, and the delineation between herself and the other musicians was far easier to discern. There was also a little more air and depth than I’d ever thought this recording contained. Similar impressions held true for Blue Rodeo’s Diamond Mine (16/44.1 FLAC, WEA), a musically superb album marred by the threadbare, metallic sound that plagued so many CDs in the ’80s and ’90s. Once again, the Femto couldn’t alter the recording’s inherent quality, but it did unravel more detail than I ever thought was there, and the voices, drums, and guitars sounded far more present and natural.

Calyx Audio Femto

Better-sounding CD-resolution recordings sounded so much more detailed than I’m used to that, if I hadn’t known better, I’d have sworn I was listening to a hi-rez recording or a first-rate remastering. For example, Bruce Cockburn’s centrally placed voice in "Pacing the Cage," from his The Charity of Night (16/44.1 FLAC, Rykodisc), had greater presence, focus, and separation from the surrounding space than the DAC 24/192 -- or even the Simaudio 650D -- could muster up. The guitar hovered holographically to his right, with a clarity and immediacy the likes of which I’d never heard from any digital source. Ola Gjeilo’s robust, rich-sounding piano in "North Country II," from his Stone Rose, sounded almost as detailed and present in 16/44.1 as in the 24/88.2 and 24/176.4 versions of that track on our 2L-TWBAS 2012 Sampler. Color me impressed.

As struck as I was by the Femto’s ability to unveil extraordinary details even from 16/44.1 material, I was just as captivated by its ability to provide those details without sacrificing musicality or inducing any kind of fatigue. Sometimes components with highly detailed sounds, while sounding impressive, can be tiresome or even troublesome to listen to over time, and produce listener fatigue. But the Femto, like the DAC 24/192, sounded utterly neutral and extremely clean.

Another word that seems to describe the Femto’s sound is pure. All told, there was never anything objectionable about that sound, and its extreme resolution allowed me to simply hear more of what my recordings already contained. In fact, every piece of music I played through the Femto sounded better than it ever had before -- which is why I have to say that this is the best-sounding (and best-looking) DAC I’ve ever heard.


Whereas Calyx Audio’s DAC 24/192 was a fine product for its price, it had flaws that precluded me from giving it an unconditional recommendation. The Femto, on the other hand, bowled me over, despite its costing 3.5 times as much. I welcomed its sterling casework, superb styling, and rich feature set, but I was most taken aback by its spectacular sound, which, though cut from the same cloth as the DAC 24/192’s, was superior in a number of ways. In particular, the Femto’s high level of resolution, without sacrificing musicality or long-term listenability, was inspiring with hi-rez recordings, and a revelation with standard-rez fare.

The DAC 24/192 showed promise. The Femto fulfills that promise in being a more developed, fully mature product that has left me with nothing to quibble about, aesthetically or cosmetically -- something that happens seldom. And even if the Femto can’t be considered cheap by any measure, it’s worth the asking price for anyone who wants a statement-grade DAC.

. . . Doug Schneider

Associated Equipment

  • Speakers -- PMC twenty.24, KEF R500, Audio Solutions Rhapsody 80
  • Amplifiers -- Copland CTA 506, Eximus S1, Bryston 4B SST2
  • Preamplifiers -- Simaudio Moon 350P, JE Audio VL10.1, Eximus DP1
  • Digital-to-analog converters -- Simaudio Moon Evolution 650D, Eximus DP1, Calyx Audio DAC 24/192
  • Computer -- Sony Vaio laptop running Windows Vista and JRiver Media Center 17
  • Digital interconnects -- AudioQuest Carbon USB, AudioQuest Diamond USB
  • Analog interconnects -- Nordost Valhalla, Nirvana S-L
  • Speaker cables -- Nirvana S-L, AudioQuest Comet

Calyx Audio Femto Digital-to-Analog Converter
Price: $6850 USD.
Warranty: Three years parts and labor.

Calyx Audio
Digital & Analog Co.
4F, Bohyun Building
1458-4 Gwanyan-dong, Dongan-gu, Anyan-si
Gyeonggi-do, 431-060
South Korea


US distributor:
On Song Audio Distribution
Phone: (269) 569-5540


Canadian distributor:
Charisma Audio
Suite 86, Unit A14
4261 Highway 7
Markham, Ontario L3R 9W6
Phone: (905) 470-0825
Fax: (905) 470-7966