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Reviewer: Srajan Ebaen
Financial Interests: click here
Source: Custom PC (Windows XP), Stello CDT100 / DAC100 Signature
Preamp/Integrated: Peachtree Audio Nova, Glow Audio 2008 Amp One [on review]
Speakers: Beyerdynamic DT880 and B&O 19-ohm earphones, Era Design 5 Sat, Glow Audio Sub One [on review]
Cables: Entreq Crossword Discover USB [on review], Zu Audio Pivot, Zu Audio Varial, AntiCables
Desktop: Ikea glass table
Powerline conditioning: Furutech e-TP80
Desktop size: Diagonal corner placement in 4m x 3m room open to main ground floor.
Review Component Retail: $150
It was Christine Han from April Music of Korea. I'd recently tested her Stello CDT 100 and DA100 Signature. Would I be interested to do the tiny Korean Calyx Kong USB headphone amp? That's what she listens to on her office PC. And, she likes it better than her HeadRoom. If I wanted, she'd make the arrangements. What the heck was the world coming to? Fraternizing with the enemy? A big thumbs up to Christine for promoting a competitor. That's exactly the spirit of cooperation the world needs today!
For background, I asked Seungmok Yi, CEO & President of Digital & Analog Co., Ltd. to paint the picture behind the tiny kong. "Digital & Analog Co., Ltd, started in 1999 as a fab-less* digital amplifier company. We have a few class
D patents and proprietary technologies and focused on making single-chip digital amplifiers. To date, we have developed 4 different chips and provide those to various OEM audio makers like Samsung and Daewoo who develop audio products for big brands whose names I must protect. We have shipped more than 10 million chips to these companies.

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* Fab-less means a semi-conductor or IC maker without fabrication facilities. Most IC companies operate that way. Samsung Electronics manufactures D&A's chips in their semiconductor manufacturing facility (FAB) for example, Magna Chips of Korea makes the popular Wolfson Semiconductor integrated circuits.


"Last year, I decided to make high-end products under my own brand. High-end audio has always been my goal since I listened to and was moved by Beethoven's 5th Symphony in 1974. Last year we launched our first product, the Calyx 500. That is a 500-watt mono amplifier running the ASP500 module from ICEPower. Alas, ours is very different from other amplifiers using this module. We add more input and power supply circuitry to improve what we regard as the weak points of the ASP500. As you know, other companies just buy the stock modules and put them in their chassis. Our Calyx 500 hit the Korean market with rave reviews.

"This year we debuted CTI Calyx The Integrated at T.H.E. Show in Las Vegas with Usher BE-718 speakers. During the second day, Magnepan president Mark Winey visited our room, spent some time listening and asked me to visit his room with our CTI. Closing my exhibit at 2:00PM well early, I brought my CTI to Magnepan's demo room. There were several people from Magnepan and some dealers. We all listened to the CTI with their new mini Maggie system. All were amazed by the sound. It was much better than their former big

system with Bryston electronics. Mr. Winey ordered a CTI for himself on the spot. In turn, we used their mini Maggies during this year's Eyear show 2009 in Korea for which Magnepan had generously sent us a set. We had great success together [above].
"For the Calyx Kong, we use TI's PCM2704* USB DAC and some special custom-made Nichicon capacitors. We were very careful to design the circuit board so computer-generated noise would not enter the Calyx Kong. As a chip provider to various audio companies, we have engineered many audio circuits for them without a single claim from our customers. This shows how we are true experts in class D amplifiers. We use both measurements and subjective auditions during the development of our products. As a concert goer, I have been to a lot of famous concert halls. I always try for the best equivalent performance in our products.
"We have some sales contacts for certain countries already but not Europe yet so we take

direct orders at the official US retail of $150. We provide a 1-year warranty but be assured that our company has never yet received a single repair call for products which used our D&A chips."

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*Texas Instruments specifies this as a 16-bit Delta-Sigma 28-pin stereo DAC requiring no dedicated device driver and running an on-chip clock generator from a single 12MHz clock source.

For specifications, the Calyx Kong is a USB-powered integrated amplifier with a USB input on one end, a stereo mini port on the other and three small push-button controls marked + and - for volume, o for mute. A blue/white LED confirms PC power lock. Output impedance is 32Ω. Measured on their Audio Precision bench, Calyx specifies THD+N 0.01 [%] @ 1kHz, S/N -98dB @ 1kHz, channel separation better than 70dB, dynamic range of 98dB and an upper bandwidth -3dB point of 140kHz. The volume control operates from 0 to 64dB and power output is 12mW into 32 ohms with a swing voltage of 600mV. Dimensions are a petite 52 x 86 x 22mm and weight is 167g. The entire affair is ensconced in a machined aluminum body whose bottom plate is covered by a protective non-slip foam pad. Various anodizing colors are available, with the review loaner lime green.

The review context was my desk top with its custom Windows XP PC or a big MacBook running XP Parallels. Stello's DA100 Signature DAC with USB input, Peachtree Audio's Nova or Glow Audio Amp One 2009 integrateds and the Era Design Sat 5 speakers plus Glow Audio Sub One represented the hifi hardware. Direct comparators for D/A conversion thus were the April Music and Peachtree Audio Nova units on the upper end and the USB DAC built into the Glow Audio EL84 amplifier on the lower. To assess headphone drive, I used B&O's stylish 19-ohm clip-on earspeakers and a full-size pair of Beyerdynamic DT880 with convertible mini plug.