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Reviewer: Srajan Ebaen
Financial Interests: click here
Source: April Music Stello CDT100 | DA100 Signature
Headphone outputs: Peachtree Audio Nova, Yamamoto HA-02, Woo Audio Model 5, Aura Note Premiere [on review]
Headphones: Audio-Technica AHT-W1000, BeyerDynamic DT880
Cables: ASI Liveline loom
Powerline conditioning: Furutech eTP-80
Sundry accessories: Extensive use of Acoustic System Resonators, noise filters and phase inverters throughout the house, additional unconventional products by BioGenesis and Tachyonics
Room size: The sound platform is 3 x 4.5m with a 2-story slanted ceiling above; four steps below continue into an 8m long combined open kitchen, dining room and office, an area which widens to 5.2m with a 2.8m ceiling; the sound platform space is open to a 2nd story landing and, via spiral stair case, to a 3rd-floor studio; concrete floor, concrete and brick walls from a converted barn with no parallel walls nor perfect right angles; short-wall setup with speaker backs facing the 8-meter expanse and 2nd-story landing.
Review Component Retail: $890


Not tongue-tied but christened tongue in cheek, perhaps the Headquarters* HQ-1 by KingRex gives no quarter but chops off competitors' heads? Prior reviews in these pages have extensively chronicled this Taiwanese high-value company. They made a name with very affordable Tripath amps and USB DACs. For KingRex, this new headphone amplifier with pre-outs positions itself higher on price. It suggests rather more serious ambitions. The clever name meanwhile creates parallels to the just as cleverly named PREference preamp sibling with top-mounted phono adjustments and outboard PSU. Is KingRex moving upmarket now?

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* After reading the above intro, the company's crest-fallen Christine Wu e-mailed me. Misunderstanding my play on words—and despite my assurance that no competitor could possibly harbor any ill feelings toward KingRex for its naming of Headquarter—her bosses decided to chuck the existing inventory of face plates and add an 's' to the new batch to make the name Headquarters. Possibilities for double entrendres continue for devious word smiths but KingRex feels this name now better conveys their intended meaning of "being the headquarters for a headphone-based or mini hifi system".

"Our next product will be a high-end 50wpc Tripath stereo amplifier, with higher power monos in the wings. The QS-01 power amp will likely be announced by early September. I believe many people will be shocked by our new products. They were originally scheduled for roll-out by June but we postponed the launch schedule to tune them for even better sound. We will not only enter the PC audio sector in earnest but also progress deeper into the High-End sector. Right now, there is plenty of cheap audio gear on the market but not all of it has high C/P. KingRex began to redress that balance with all of our initial offerings. You are correct to note that our prices now are higher but the truth is that we also exponentially increased our costs for material, design, labor and circuit originality. We really spend lots of money on quality parts and the pricing for our more ambitious machines now reflects that. Still, we are quite certain that when users get their components, they will find the cost to be disproportionately low relative to their satisfaction and our quality."

Let's look at the HQ-1's nuts and bolts. Obviously, this newcomer is a two-box affair of equal half-width foot prints. It allows convenient stacking or going cheek to cheek on a standard audio rack shelf. The circuit is classic class A with Mosfet outputs, meaning it must dissipate at least twice its rated output at idle. Because headphone voltages operate in the micro-watt range—though preamp duties could raise those when engaged—power consumption remains below 10 watts. That's low-light-bulb green in the energy consumption stakes.


The power supply is of the linear kind and runs off a 48VA toroid, with five 2.200uF caps filtering incoming AC, three 4.700uF units smoothing outgoing DC. Eight "hifi-grade Nippon Chemicon electrolytics" create a total power supply capacitance of 25.100uF. Naturally, output power varies with headphone impedance so we get 100mW at 300 ohms, 170mw at 150 ohms, 360mW at 60 ohms and 570mW at 30 ohms. At 2Vrms output, THD+N is 0.005%. Dynamic range is 110dB, channel separation >92dB at 1kHz and >76dB at 10kHz and S/N ratio 115dB.

Circuit gain is 18.5dB, making it a standard medium gain one-source preamplifier if so used. I/o impedances are 15K and 1.8 ohm respectively, frequency response is 20Hz (-0.7dB) to 80kHz (+0.1dB). AC line tolerance is ±10% at the respective 110 or 220 international voltages. Dimension are 183 x 145 x 55mm for each unit and dress code is a black body with black or red fascia. Headphones used during R&D were Sennheiser HD600s, Audio-Technica ATH-AD700s, AKG 501s and Goldring DR150s. "Basically we tuned the sound with the HD600s as we think them very neutral and balanced. We tried many different impedance headphones to assure the amp performed well regardless of load."



The existing PSU upgrade for the T20 amplifier shown shares the resistor circuit with the Headquarters' power supply but the former's 13V/3A output spec has become 18V/1.25A for the HQ-1. "The biggest diffence is the transformer winding method but the PSU resistor circuit remains very silimar. We've had it in the field for a long time and with much excellent feedback and felt it was good and proven to be appropriate for the headphone amp so we retained that part of the design."

For review context, my AudioTechnica ATH-W1000 and BeyerDynamic DT880 headphones would slurp juice also from the outputs of my Peachtree Audio Nova and my two valve machines, Yamamoto's HA-02 and the mighty Woo Audio 5 with EAT 300Bs. Additionally, I had the Aura Note Premiere, Luxman SQ-38u and SQ-N100 on review. All of them are fitted with headphone sockets. It's been said often enough to grow moss but bears repeating: the most cost-effective way to arrive at bona fide high-end sound is to remove its greatest hurdle. That would be your room with all its acoustic signal interactions. Merely make accommodations for different soundstaging and body-slam vs. in-the-ear bass. Particularly with sealed headphones, you can listen when you want how loud you want without upsetting the neighborly or domestic peace. Dollar for dollar, it is impossible—impossible!—to replicate headphone fidelity with regular loudspeakers. If funds be tight but ambitions high, set yourself up with a superior headphone system. It will also seriously raise your standards to bypass certain speaker-buying mistakes when that time comes. More in due time.


KingRex website