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Unlike the Style Audio competitor also from Korea I'd reviewed earlier, the Calyx Kong had sufficient output to get even the big Beyerdynamic phones to useful levels. The DT880s of course will not be what most potential owners would ever use. They simply were the only 'serious' cans in my arsenal that integrate the necessary big-to-mini plug adaptor to run off the Calyx. Standing in for the far more typical in/on-ear 'phones one expects for the Kong user, I used Bang & Olufsen's cool clip-on units. But first...

... nit alert. By opting for sleek, the Calyx push-button volume -- rather than protruding rotary knob or recessed wheel -- gives zero indication where within its range one might be. Worse, the mute function has no visual feedback either. If you get no sound at first, you'll have to call up your PC's volume setting window. Ascertain whether there's a check mark in the mute all square (clicking/unclicking the mute on the Kong immediately puts the check mark there). If you still have no sound, go into the Sound Devices menu to insure that your PC has recognized and set itself to the USB DAC [below].


The big Beyers ran at the very top of the range, i.e. in attenuation bypass or full throttle mode with zero headroom left. On most recordings, I personally wasn't left wanting for more power. I did however stay away from classical recordings. Due to their usually far higher recorded dynamic range, those tend to have a rather lower median level. A mellow adagio at max volume with the DT880s might fall below the threshold of what you find fully satisfying.


Using the above window, I tracked how switching to the B&Os affected the speaker volume setting for levels equal to the Beyers. I clicked the Kong volume minus 6 times and the software slider ended up just below the second mark from the top [right].
Translated, for my tastes the Calyx Kong could get uncomfortably loud on the minis to have sufficient headroom. Of course the tonal balance of the Danish 'phones vs. the bigger drive units of the Beyers upshifted noticeably. Bass fullness evaporated and even voices leaned out. That was simple Physics of course, not the Kong's doing. More relevant, the Korean box nicely avoided the subtle scratchiness or treble dirt I expect from inferior USB converters.


For meaningful listening sessions however, I had to return to the Beyers (which themselves are outclassed by my audiotechnica ATH-W1000s). From the lower midrange on down, the B&Os simply leave too much under the table to make the cut.


In Beyer/Kong mode, I was struck by how very listenable things were - slightly soft, mellow and decidedly not sharp, aggressive, forward or with hyped transients. On my big Woo Audio headphone amp with EAT 300Bs and twin 5U4G Emission Labs rectifiers, the Beyers are leaner, thinner and less communicative than the warmer Cherry-wood clad Japanese cans. They're somewhat flat and staid where the W1000s are spacy and nubile.
Over the Calyx, the Beyers mysteriously acquired a modicum of W1000 traits. Was this because lack of ultimate drive incurred an overall mellifluousness? I couldn't say. Frankly, I didn't really care either. The combination was pleasing and even bass-buster tracks surprised to suggest that whatever op amp drives the output is fully capable of the low stuff.

How about a bigger (real speaker) desk top system?

Here the Calyx connected to an input of the Peachtree Audio Nova to compare to the latter's inbuilt Sabre DAC. Another comparison involved the Stello DA100 Signature DAC's USB input. Yet another comparison inserted Glow Audio's 2009 version Amp One over Miu Audio's 805 speakers.

Obviously the Calyx got murdered two ways (Nova and Stello). Yet it also did some killing of its own (Glow).

Here is the comparison setup, with Glow Audio's Sub One hiding dead center on the floor beneath the desk. The Glow Audio sub is great also for headphone listening. Running it through the Nova's pre-out (which does not mute when the headphones are inserted) feeds back sufficiently into the ears even when full-size headphones cover them. It makes for stupendous low-end can jamming. It's not friendly to cohabitators of course who will just hear the subwoofer.

The converters built into the Peachtree and Stello units had plainly more drive, presence and focus. They also expanded the soundstage particularly in the depth domain. Ambiance like hall sound surrounding a singer's voice improved significantly, exactly what higher resolution should buy. Everything got bigger, more substantial and meaningful. Outclassing a $150 unit without dedicated power supply (i.e. running exclusively off the 5V power line inside the USB cable) with two that benefit from dedicated supplies and class A output stages admittedly was a cheap and dirty trick. It simply demonstrated the limits of the Calyx within a bigger, far more expensive picture.

A rather more meaningful comparison was by way of setup N°2 where my MacBook in Windows Media Player mode fed the Glow Audio Amp One and Miu Audio 805 speakers via USB either directly into the Glow or through the Calyx. Because Glow Audio strangely opted for an A-type USB input, I had to run an A-to-A cable for it and a standard A-to-B cable into the Calyx. And because the Glow stupidly defaults its non-switchable inputs to USB automatically, I had to disconnect that input each time I wanted to hear the Calyx. I likewise had to rematch levels.

Long story short, the Calyx outperformed the USB converter inside the Glow but the former 'kill' slang suggests far too massive a performance delta. The Calyx was more precise and better timed on the leading edge where the Glow played it fuzzier. Music over the Calyx also had a straighter stiffer back in general. It was grippier. Over the Glow the musical posture became more slumped back into the chair. It didn't lean forward to feel more alert. In audio lingo, the Glow was more diffuse, less sorted and separated. More amorphous. The Calyx had better definition and articulation. It was an upgrade over the internal Glow converter but reduced achievable max levels in turn.

If its primary application had been regular rather than PC/mobile audio, the Calyx Kong should pack more gain. However, its solitary mini-jack output reminds one that it really is a miniature headphone amplifier for portable use. All other described uses are possible but more fringe benefits than core focus.


There are 25 click stops of volume including full attenuation. Continuous press traverses them all in a little more than one second. In certain applications, these individual steps could be just a bit coarser than ideal. A future Gen 2 wish list would include higher gain and a recessed continuous volume wheel with an engraved marker and perhaps 'push' for mute where mute also extinguishes the indicator LED for visual feedback.


These paid-to-find-fault issues are of little consequence however. The Calyx Kong operates beautifully as is and neither my PC or laptop had any recognition or handshake issues. It was plug 'n' play all the way including endless unplugs and reseats of the USB cable during A/B comparisons.


To recap, the Calyx Kong is a very solid step up from the headphone jacks of computer sound cards and mobile audio devices like the iPod and its derivatives. Its monolithic metal casing is luxuriously finished to have that pride of ownership cool factor down pat. Its performance is surprisingly refined and well articulated.


I was most impressed by its showing over the Beyerdynamic DT880s. Those aren't famous for being the easiest of cans to drive. While for such headphones, maximally attainable output voltage would ideally be higher to accommodate weaker recordings, sound quality was persuasive - robust yet gentle, articulate yet not overly PRaTty to support longer listening sessions.
Priced exactly right for what it delivers, Seungmok Yi's Calyx Kong is an ideal bridge product. It was sized, profiled and designed specifically for USB audio which presupposes PC or mobile sources. If one industry insider I spoke to at the Munich show this year had it right, the only items currently enjoying an upswing are USB converters and headphones; the two bits which hifi-centric companies can easily improve upon in that arena. The Calyx Kong then is perfectly timely. It's a fine seed that implants future hifi lust in mobile and computer audio users by quietly preaching the gospel of higher performance.

Calyx website