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Reviewer: David Kan
Digital Source: Philips DVP-9000S, Micromega Microdrive, Deltec PDM Two DAC
Speakers: Loth-X BS-1, Klipsch Synergy F2, Unity Audio Clearwater [on loan], Unity Audio Inner Spirit [on loan], Unity Audio Whitewater [on loan], Mark & Daniel Topaz [on loan]
Cables: Luscombe LBR-35 interconnect, Unity Audio Solid Link interconnect [on loan], OCOS speaker cables by Dynaudio, Unity Audio Solid Link speaker cables [on loan]
Power Cords: Unity Audio Link /Precision Link [on loan]
Power Line Conditioning: Monster Power HTS-3500 Mk II [modified by NuForce], Monster Power HTS-1000 Mk II
Room Size: 15' x 13.5' x 8' diagonal set up, 13' x 28.8' x 9' with openings on one side to hallway and staircase, short wall setup
Review Component Retail: $220 for T20, $190 for PSU
Eat your valve out
Ladies and gentlemen, please welcome another Blue Moon Award winner 2007, this one for heart-warming tube sound extruded from a cold-running Tripath-based amp: the KingRex T20. I didn't jump to this conclusion. The verdict is the result of many months of careful deliberation. I hope I'm not spoiling your fun by stating this upfront. The award-sighting logo above would have given it away anyway. I actually saved you from my drabbling and your middle finger -- from scrolling down to the last paragraph that is -- in case you hungered for the conclusion. To trace back what happened, a pair of KingRex T20 was delivered to me back in the first week of March - yes, a pair because I am a bi-amp freak. Since the KingRex amp was openly posted in my 'coming next' slot and I'm such a snail-pace worker, emails kept piling up in my mailbox. They all were concerned with just one question: "Which one is better, the Trends or the KingRex?" Truth be told, I couldn't say that question never crossed my mind. Curiosity is second nature. But the real question is, after the delightful big surprise of the Trends TA-10, would anything excite our senses like it once more?

Visually, definitely. The KingRex T20 is elegantly packed in a 180mm x 138mm x 45mm black box with 6mm thick aluminum face plate, prominently adorned by a matt polished silver chrome volume control knob in the middle, which is smooth to dial as well as to touch. The styling of the knob and contrasting black face plate resembles the Swedish Primare A10 integrated amplifier, albeit much smaller and without push buttons. I must admit it would have been even nicer if KingRex had made the four front-mounting hex screws disappear, or dimmed the blue power LED a little or made the indicator marking on the volume knob a little easier to see in low lighting... well, armchair designers all are so very creative, aren't we? The power on/off switch is located on the back panel, which also accommodates the basic connection amenities: one set of line input RCA gold-plated sockets,
two sets of banana/bayonet-only gold-plated speaker terminals and of course, the 12 volt DC power input. No 5-way binding posts? On such a slim back panel, the tight space already renders spades and thick naked wires defunct. I actually find these flush-mounted speaker sockets neat and tidy and befitting the compact design. The amp itself can operate on the factory-supplied AC/DC adapter, which is rated at DC 12 volt, 3A. The PSU, an optional power supply unit, takes up the same elegant chassis and also sports the same blue power LED. This power supply provides regulated DC at 13 volt/3A. Whether the amp is placed on top of or side by side with the PSU, together they make quite a high-end statement - on looks at least.

Now the inside story. Who is KingRex? Based in Taiwan and founded in 2000, KingRex Technology Co. Ltd. is currently going through a transformation phase of migrating from the manufacturing field of residential security systems, PDA batteries, memory modules for computers and RF modules for two-way radios to audio wonderland. The KingRex T20 integrated amp and PSU are their debut models. The lineup will soon be completed with the T20U (basically a T20 with built-in USB DAC) and the Pre-Amp, the latter of which will appear in Part 2 of this review. The heart of the T20 is the Tripath T2020-20 DPP (Digital Power Processing) chip also found in the DiyParadise Charlize and Autocostruire 2020-m units available in either kit or ready-to-assemble modules aimed at DIYers. Unlike some T-amps, the KingRex rejected surface-mount components and went through-hole all the way.

The printed circuit board is relatively spacious but all the components confine themselves to two-fifth of the total area. This is because Tripath specifies that critical components like power supply decoupling capacitors must be located closely to the power supply pins and grounding pins to effectively reject power supply noise and absorb voltage spikes. Similarly for the Schottky diodes' proximity to their respective output pins and VDD/GRND pins. Likewise for the output inductors to help reduce radiated emission. All this is for electrical stability and sonic purity. And KingRex not only follows the principle faithfully but also manages to mount a large heat sink onto the Tripath chip. The wastage of space, as I learned later, actually provides for the DAC in the sister model T20U.

While the Tripath 2020-20 chip is officially labeled as capable of 2 x 20 watts into 4 ohms, it should be noted that the performance of all Tripath DPP chips is governed by two factors: VDD and THD+N. The T2020-20 operates on a typical supply voltage or VDD, of 13.5 V whereas the tolerance ranges from 8.5 V minimum to 14.6 V maximum. When 14.6 V is fed to the chip, the output power actually increases to 2 x 24wpc. Don't get excited too soon. The Total Harmonic Distortion and Noise (THD+N) also rises to 10%. The optimized output at 0.1% THD+N, a prerequisite for audiophile sonic quality, is achieved at 12 watts into 4 ohm or 7 into 8. If you think the KingRex T20 is a powerful T-amp, think again. Statistically, it's negligibly more robust than the Trends TA-10, which utilizes the Tripath T2024 chip to deliver 11/6wpc into 4/8 ohm with a THD+N of 0.1%. However, I did try to drive the new Mark & Daniel 83.5dB low-efficient, current-gobbling, bi-wirable Sapphire with two KingRex T20s and two PSUs in bi-amp configuration. Truthfully, I dared not crank up the volume and only played soft music. It was strictly for fun and could hardly be recommended. In order to let the Tripath chip work below its 0.1% THD+N mark, the optimal being 0.03% at ten 4-ohm watts, loudspeakers with higher efficiency are definitely mandatory.

Curiosity-driven, I hooked up the KingRex in the same room that houses my four sets of Trends TA-10s permanently configured as a multi-channel system for SACD. Two Trends are used for front left and front right as stereo bi amps to drive stacked Loth-X BS-1 on each channel. That's precisely how I would put the challengers to the test when I requested KingRex to send me two sets of T20s (two amps and two PSUs). I used the PSUs right from the start so they could all break in at the same pace. During the first month, I was communicating with KingRex to express my concern over the AC/DC adapters. They were designed for 110V AC input/13V DC output but weren't of the regulated type. The power utility company in my neighborhood is constantly pumping 123V to 124V into the grid. So when those adapters were plugged in, they output no less than 15.8V DC as recorded on my multi meter. This far exceeds Tripath's 14.6V safety limit. KingRex then decided to change to auto-switching 100 - 240V AC/DC adapters for North America and had them shipped to me. The DC output is regulated at 12V, measuring +/-12.20V on my multi meter. That's safe enough. By that time, the amps were just about broken in. I replaced the PSUs with the new switching power adapters and began my inaugural audition. Redbook source was a Philips DVP-9000S, interconnects were Luscombe LBR-35 silvers and speaker cables were OCOS.

I had no intention to do a so-called shoot-out because the last man standing doesn't equate to audiophile supremacy. Stray bullets kill objectivity. Any sonic attributes of a piece of equipment are calibrated on an imaginary sliding scale. Designers determine gives and takes. Consumers decide on pros and cons. Subjectivity rules. Initially I didn't want to do an immediate A/B comparison due to what I call the pupil effect. Switching from A to B can be like walking from bright sunlight into darkness or vice versa. I don't have medical findings to support that notion but I do believe that the human auditionary reflex is far more stubborn and reluctant to change than our papillary reflex - there's audio psychology intervening. For weeks, I let myself relax and soak in the music oozing from the KingRexes. In my mind, the Trends TA-10 is like a miniature NuForce, with effortless layering, relaxed soundstage reproduction and a purity and transparency of sound that doesn't sacrifice musicality.

The KingRex T20 retains all of these attributes but adds a touch of mellifluous quality and warmth. No, the Trends is definitely not cold. It's just more neutral by comparison. Its higher definition somehow is more sparkly and bites more when it comes to flamboyant string playing like Sarasate's Zigeunerweisen as interpreted by Akiko Suwanai with Fischer conducting the Budapest Festival Orchestra [Philips 464 531-2]. The KingRex, while remaining faithful to the interpreter's intention, presents the piece with more lyrical finesse, adding more of a lingering richness to the harmonics. Obviously, I was still comparing from memory at this juncture. The only way to confirm my suspicions was the inevitable A/B comparison.

Since I have four pairs of Loth-X BS1, I could set up two independent bi-amp systems simultaneously. All connecting cables were identical, with the Philips DVP-9000S delivering the same source signals through its stereo outputs and front L/R outputs - the latter, believed to be of better sonic quality, were fed to the Trends system. Another discrepancy was that the two sets of speakers were not exactly at the same height and one was spaced farther apart. I had the inner set driven by the Trends. I opted to live with this minor injustice so that switching between A and B would simply be a matter of turning up the volume of one system and dialing down the other while keeping both systems fired up at all times. Since this exercise was not to decide which system was better but to expose differences if there were any, I couldn't think of a better side-by-side comparison, literally. To neutralize the pupil effect, I allowed for 20-minute intermissions and walked out of the room to flush out any aural aftertaste.

The Suwanai repertoire proved that my memory did serve me well. Three more SACDs set to 2-channel stereo confirmed it further. With the Trends TA-10, the brass and cymbals in Mahler's Symphony No.5 [DGG 4677 071-2] were brighter and the strings depicted more texture. The images of the violin and the piano in Richard Strauss' passionately youthful Sonata in E-flat major, Op. 18 [2L 34] were more chiseled and angular. The melodiously rich "Dies irae" and "Confutatis" from Sigurd Islandsmoen's Requiem [2L 36] were more forcefully extracted from the chorus. The pace of the KingRex T20 was more relaxed, stretching out more in an
expansive, more deeply set soundstage. The gloriously harmonized tone immediately made me think of the Dared VP-20 6L6 tube amp or the newer generation of 300B tube amps like Kallisto's Sinfonia 300. However, this valve bloom syndrome was not masking any instrumental definition or placement but rather, romancing them in a melopoeic way. The metallic sheen of the brass and cymbal in Mahler, for instance, was now seen through a polarizing filter.

When the PSUs were added to the pot, musicality thickened. There was more warm air filling up a more expansive soundstage. Bass got deeper, the midrange turned proportionally more pronounced to make the overall harmonics even richer. You can say that it also rounded off the bites and gnaws, somewhat at the expense of clarity and details. But it was a small sacrifice for big gain if your ears are tuned to vacuum tubes. In fact, this valve bloom was well controlled (again, similar to some of the latest tube designs) and didn't muddy up instrumental mapping even during thunderous orchestral climaxes. There were just thin layers of air cushions surrounding the instruments, making the fortissimos more polished and suave and the music more euphonious to the ears. The PSUs seem to filter out so-called digital garbage and turn the KingRex T20 into a quasi tube amp. If the Trends TA-10 is a miniature NuForce, the Kingrex T20 is a miniature Kallisto Sinfonia 300 without the glass. And the T20 remains stone cold after continuously running for over 12 hours. The PSU gets just mildly warm to the touch.

Is that added valve bloom from the PSU explainable? Let's try. Inside the compact chassis of the KingRex PSU sits a 45VA (since upgraded to 48VA) toroidal transformer coupled to a full-fledged regulatory circuit, which comprises, among other electronic components, eight high-quality Nippon Chemicon aluminum electrolytics, 5 x 2200uF at the AC input stage, 3 x 4700uF at the DC output stage. Low frequency transients draw on high-current voltage supplies continuously and the PSU provides more abundant reserves to meet that demand. It also irons out low ripple tension in the DC output so to speak. Imagine the AC/DC adapter as someone making money with the left hand while spending every dollar instantly with the right. The PSU is someone with a deep pocket, saving up all his money for the stormy days.

How about the Trends TA-10 running off the KingRex PSU? How about the KingRex getting off the grid, drawing power from a battery instead? The voltage requirements matched and my Xandrex batteries stood by so the answers were just a few cable swaps away. The effect was immediately noticeable in both instances. However, the TA-10 + PSU seemed to gain more than the T20 + battery. The lower octaves revived with more potency. Although the valve bloom didn't graft fully onto the TA-10, the clashing of cymbals and szforzando trumpet blasts definitely polished up. While layering was not compromised, it couldn't compete with battery operation. Naturally, in the case of the T20, battery operation further confirmed the key benefit of distilling resolution while bass and harmonic richness were somewhat sacrificed, especially when battery voltage dropped below 12.5 V. More reasonable performance can be expected when the battery is fully charged, its voltage hovering around 13.5 V. Still, you tend to lose some of the magic of the PSU.

So far, this review has been focusing on biamping two pairs of speakers in stacked D'Appolito arrays. Readers who intend to use a single amp to drive one pair of speakers shouldn't feel overlooked. I'll cover that in a minute. Before though, there are two points I'd like to cover. First, like Trends, the KingRex amp outputs inverted signal since all Tripath chips invert polarity. Although that doesn't bother a lot of people, my habit is to get everything right. In case you see some photos where speaker connections are reversed at either the speakers or amp, don't panic. Second, a question I've come across often since my Trends review: Can Tripath amps be bridged to increase output power? The answer is a definite nay since all Tripath chips are BTL or Bridged-Tied-Load as opposed to single-ended in operation, i.e already bridged. With low power Class-T amps, the sure-footed and effective way to double the output power is to double up the speakers and bi-amp them. More drivers move more air, not to mention the added bonus of better channel separation and left/right balance adjustments (useful for some recordings or certain room acoustics).

Having said that, just how adequate is a single KingRex T20 driving one pair of speakers? Should that be restricted to a small room or mid-to-high efficiency speakers other than my Loth-X BS-1 which obviously match? I put the little T-amp plus PSU to the test by going to a bigger room with smaller speakers. I had three Unity Audio review loaners. The black pair is the Clearwater model, the white pair the Inner Spirit and the Cherry laminate the Whitewater. I listened to each of them for two to three days without checking their specs
or pricing. The CD transport was a Micromega MicroDrive. The DAC was a Deltec Precision Audio PDM Two. Interconnects and speaker cables were both Unity Audio Solid Link. The 28" Mark & Daniel compound marble speaker stands originally designed for Maximus-Ruby suited all of these mini monitors perfectly.

The first pair I called upon to stand on trial was the Clearwater since they were similar to the Loth-X BS-1, with two drivers, front pot and a simple 1st-order/6dB crossover (one cap and one coil). I randomly played through a host of dance music and symphonic pop. The KingRex T20 + Unity Audio Clearwater combo passed this test even with demanding orchestral works like La Cumparsita and Pink Floyd's The Wall. I can confidently state that there was enough sound pressure to project to the back of the room 28 feet away. Bass in The Wall was quite reasonable for such a light-weight setup. Instrumental placement in chamber works like Rossini's Sonatas for Strings was spontaneously assigned. At this point, let me introduce my jury panel, four outstanding recordings that helped me pick my favorite partnering speaker for the KingRex.

Shostakovich: Piano Sonata No.2/Limpid Stream Suite played by the young Russian pianist Konstantin Scherbakov [Naxos 8.570092]. The most intelligently conceived chapter in Russian piano literature, Shostakovich's Sonata No.2 is interwoven with virtuoso marvels and poetic wisdom. The third movement in particular is a fugal improvisation with rhapsodic development. The first 31 bars, using solitudo yet inviting single notes, form a pulsating monologue that speaks to the heart. Listen to the harmonic resonance of these single notes and the complex polyphony that builds up progressively. The best loudspeaker should have the ability to unfold the changes in tonal shading and emotional transition. Limpid Stream, the third and last of Shostakovich's ballets output under the watchful ears of Stalin, is indeed indecently entertaining. The "Tango" from Act One is the ultimate test for dynamics and attacks. Scherbakov's miserly use of the sustain pedal makes it even more electrifying.

Glass: Heroes Symphony with Marin Alsop conducting the Bournemouth Symphony Orchestra [Naxos 8.559325], also the third and the last of Philip Glass' Berlin Trilogy based on the rock albums of David Bowie and Brian Eno. Two movements of particular interest are "Abdulmajid" and "Neuköln". The first, based on the original instrumental piece named after and dedicated to Bowie's wife-to-be, is charged with theatrical tension. The latter is somberly filled with tragic drama that strangely reminds me of the movie Gladiator. Compared to most modern works that try too hard to bombard listeners out of their indifference, the orchestration here is kept intricately minimal and has breadth more than weight. Use it to assess accuracy of tone, rendition of texture and conveyance of mood.

Stravinsky: The Soldier's Tale, the original full version for 3 actors and instrumental ensemble, Solisti New York conducted by Ransom Wilson [Chesky CD122], beautifully acted with female narrator Sally Goodman, soldier Ron Bohmer and devil Reed Armstrong. The suite version of this work has long been favored by audiophiles for its sonic opportunity propelled by minimalist instrumentation. Stravinsky casts magic spells with only six instrumentalists (violin, contrabass, clarinet, bassoon, trumpet, trombone) and one percussionist. Chesky's recording is holographic, period.

Orff: Catulli Carmina, with Eugene Jochum conducting the Choir of the German Opera, Berlin [DGG 427 878-2]. Part of a musical triptych but less popular than its predecessor Carmina Burana, Catulli Carmina is Orff's most daring and brilliant cantata set to text by the Roman poet Catullus who suffered from lovesickness due to his unfaithful Lesbia and was once in exile after openly insulted Caesar by parodying the ruler. Sung by tenor soprano (in this recording, the beautiful Arleen Auger), male and female choir, it is accompanied by four pianos and a huge battery of percussion. The lyrics are passionate as well as sexually explicit (at least in their original German). The rhythm is pulsating, even barbaric at times, and more shockingly creative than Carmina Burana. You haven't heard Orff at all if you haven't heard Catulli.

While the Clearwater speaker punched up the bass in The Wall, it somehow dried out in Shostakovich. The lowest octave was unconvincing. It hurt the most when I subconsciously compared this with the NuForce Ref 9 + Mark & Daniel Ruby combo. Soundstaging and layering in Heroes Symphony and The Soldier's Tale were satisfying, making up for the bass shyness. Here I came across an interesting question: Should the Clearwater be placed with its tweeters on the outside or the inside? My personal preference, contrary to popular belief, was to the outside for a more open soundstage and better detail - as in the chorus of Catulli Carmina and the subtle separation of harmonica and bandoneon in the symphonic "La Cumparsita". However, the upper octaves in the Catulli vocals did set off some high frequency ringing. One effective measure to salvage that was by adding the Enacom Speaker End Audio Stabilizer by Combak to the speaker binding posts.

Next to testify was the Inner Spirit. Though equipped with the smallest driver, this was the loudest loudspeaker of the three. With the Clearwater, the volume knob had to be set to 3 o'clock position most of the time. But with the Inner Spirit I could settle for 1 o'clock. While it clearly had sharper definition, it was even more bass shy. I felt less air around the instruments and the vocals, thinning the valve bloom magic conjured up by KingRex. I had a better time from this speaker with real tube amps like the Dared VP-20 and Kallisto Sinfonia 300. My summation would be that the Inner Spirit could bring out the best in tube amps and the worst in switch-mode amps, particularly with the high frequency distortion in the Catulli and Shostakovich. Unfortunately, the Enacom could only help that much.

The Whitewater was the last to stand on trial but soon proved to be the most capable. First of all, the ringing was under control, especially with the help of Enacom. Although one should not expect too much bass from this wideband driver-based mini bookshelf speaker, the lower midrange was rewarding enough to mask the insufficiency. The Shostakovich CD really exemplified superb balance of transient attacks and musical finesse. Both extremes were well maintained and truthful to their sonic characteristics. In "Sense of Doubt" from Heroes Symphony, the subtle piano contrasted with the lower strings and lower brass, depicting lots of inner detail. In Neuköln, the timbre of the dark strings, the haunting howls of tuba and trombone, the sonic fusion of the tubular bells and celesta, all came to life. The Stravinsky was as vivid as you should expect from this kind of audiophile recording. "The Pastoral" was peacefully
painted in three dimensions, the "Royal March" bubbled with gaiety," Ragtime" and "The Devil's Dance" sparkled with effortless virtuosity. The three actors/actresses stood right there among us without any trace of microphone presence. Yet the slightest sighs or giggles, smacking of lips, pecking of kisses, inhales, exhales, gurgled grudges, whispers - they were all spontaneously captured.

Only now did I allow myself to refer to the Unity specs and compare them with my findings to see if everything (primarily myself) made sense. The 2-way Clearwater boasts a 5" Silver Flute wool fiber woofer and a 1" HiVi soft dome tweeter (both Chinese drivers). Frequency response is 44Hz to 20kHz, sensitivity 89dB, impedance 4 ohms. The Inner Spirit incorporates a modified Fostex FE127E 4.5". Frequency response is 59Hz to 20kHz, sensitivity 93dB, impedance 8 ohms. The Whitewater utilizes a modified Fostex FE167E 6.5" widebander. Frequency response is 50Hz to 20kHz, sensitivity 94dB, impedance 8 ohms. My findings more or less coincided, except I still insisted that the 93dB Inner Spirit sounded noticeably louder than the 94dB Whitewater.

For those who prefer floorstanding loudspeakers, my all-time top recommendation to match the KingRex T20 would have to be nothing less than the Klipsch Synergy F2. As I wrote before, this is the affordable as well as space-saving version of the La Scala with a modern touch -- deeper bass and finer definition -- yet still retains that unmistakable Klipsch signature sound. Recently, I had the opportunity to compare it with the Klipsch RF-52, which is almost identical except for being rear-ported. The RF-52, though having finer drivers on the front baffle, better specs on paper and higher numbers on the price tag, turned out to be less Klipschy - very bright in the high frequencies and comparatively thinner in the low frequencies. (I felt so sorry for my friend who took the trouble of bringing them over. He kept muttering on his way out that he'd sell the RF-52.)

The F2 is more coherent throughout and happens to synergize with the KingRex T20 to perfection. The valve bloom is intoxicatingly augmented to be deceptive enough to make you believe that you're listening to a tube amp. The 95.5dB sensitivity of Klipsch makes the KingRex sound even more unrestrained. Even the barbaric Catulli Carmina becomes sugar- coated. Absolute ear candy. When I used two KingRex T20s to bi-amp the biwirable F2, the results put a lot tube monoblocks at 10 times the cost to shame. With optimum speaker placement secured (in my room they back off the wall by 8 feet and toe-in in 25 degrees), the soundstage was expanded to incredible width and set back to immense depth, although the piano sound was in no way comparable to the verisimilitude of the NuForce + Mark & Daniel combo.

It's a totally different world - a world in which only tube heads would find unalloyed happiness and swear unconditional loyalty. The sheer fact that this cold-running Tripath amp manages to exude such heart-warming musicality warrants my most deeply felt salutations. Tube amps, eat your valves out. Congratulations on a job well done, KingRex.

Quality of packing: Retail carton box, carton partition, content individually bubble-wrapped, enough protection for such compact, light-weight item. Additional outer carton box with bubble foam filling when shipped through DHL.
Reusability of packing: Can be reused multiple times
Ease of unpacking/repacking: Entirely unproblematic
Condition of component received: Flawless
Completeness of delivery: included generic power cord, AC/DC adapter, DC cord, warranty card - no owner's manual, one main spare fuse (1A), no on-board spare fuse (3A)
Quality of owner's manual: n/a
Website comments: Simple background information, basic performance specs
Warranty: 1 year
Global distribution: Taiwan, Canada, U.S.A., New Zealand, United Kingdom
Human interactions: Professional and courteous, timely responses to questions, adequate English skills despite being non-native English speakers, forthcoming about technical matters and everything was always accompanied with photos and captions.
Other: PSU reviewed has been upgraded since.
Pricing: Not the most affordable T-amp but arguably the most irresistible considering the total package of stylish design and PSU.
Application conditions: I've read about people partnering the amp with Mark & Daniel Maximus-Monitor. I'd caution such partnership. I blew the on-board 3A fuse inside the PSU when driving the M&D Topaz which is a lot more amp-friendly. Higher efficiency and higher impedance speakers are still my recommendation with this amp.
Final comments & suggestions: There might be still some old PSU stock in the market. Some people might prefer that and believe that the two-wire AC cord (no ground wire) helps to break the ground loop. The new PSU features three-wire IEC mains receptacle.
Manufacturer's website