Gramophone Dreams #74: Elekit TU-8900 kit amplifier

It was a cold March-in-Brooklyn morning. Clouds had been shedding wintery mix since daybreak. By 9am, birds were flash-mobbing my window, demanding suet. But I was frozen—unable to pull my mind loose from the grave flowings of American composer Ned Rorem’s Book of Hours, as performed by Les Connivences Sonores on the album Musikalische Perlen (24/48 FLAC, Ars Produktion/Qobuz). The sounds in my room were sensuous and mesmerizing, and I needed to float in their mysterious energy as long as I could.

I was listening through the most compelling sound system I had assembled since I started writing for Stereophile. The dCS Bartók DAC/streamer was funneling the harmonic purity and hypnomagik of Odile Renault on flute and Elodie Reibaud on harp into HoloAudio’s appropriately named Serene preamp, which was feeding Elekit’s TU-8900 300B/2A3 kit amplifier, which was sending a few of its triode-tube watts to the TAD’s $32,500/pair Compact Evolution One monitors, more compactly known as the TAD CE1TX. I reviewed these three-way standmount speakers last month, finding them to be the most exciting, accurate-sounding, well-engineered speakers I’ve encountered.

What was unique about this system was not how it sounded but how easily it enabled diverse forms of music to summon reverie and affect my state of mind—how it made rhythms linger in my head after the music stopped.

My review was finished, and I knew the TADs were leaving tomorrow, so I figured that day would be best spent bathing in the completely crazy fantasticness of an 8W, relatively inexpensive, made-in-Japan kit amp (!) driving a 4 ohm, 85dB-sensitive, also-made-in-Japan box speaker of the highest pedigree.

Well-recorded compositions for flute and harp leave no place for dry-sounding feedback amps or dull-sounding box speakers to hide. Both instruments’ harmonics must be fully exposed. For these high-energy instruments to have a touchable vibratory presence, a system’s upper octaves need to be information-rich, pure, extended, and harmonically complete. Somehow, on that day, that Elekit-TAD combo was doing what felt like a perfect job of being pure and harmonically complete.

The above-described pleasures were not, I believe, just a lucky consequence of a chance pairing of Elekit’s new (in 2022) TU-8900 300B/2A3 amplifier with an expensive three-way box speaker. There was more going on. What actually happened, I believe, was that the CE1TX’s easy-to-drive, highly descriptive nature responded very well to the flood of small data issued by an amplifier pumped up on three sources of information-preserving steroids: Lundahl’s made-in-Sweden LL2785C AM amorphous-core output transformers and Audio Note UK’s tantalum resistors and silver-foil coupling capacitors.

The North American version of the TU-8900 kit has been heavily parts-curated by the frugal, creative mind of Elekit’s Vancouver-based distributor, Victor Kung of VK Music (footnote 2). The result is a kit amp with the same quality of parts as many of the world’s finest and most expensive triode amplifiers. I have a globally respected Euro-friend who builds custom 300B amplifiers on commission, cost no object, deep into five figures, and he’s using the same level of Lundahl output transformers as the $1945 TU-8900 (below). The $15,000 Shindo Laboratories Cortese 300B amplifier uses them, too.

My TU-8900 kit came preassembled (a $375 option) with a clear acrylic top plate that allows me to admire the conspicuous legion of Kemet solid polymer aluminum capacitors (footnote 2) and the two large, symmetrically placed Audio Note 0.1µF silver-foil coupling capacitors. These are Audio Note UK’s highest-quality capacitors, a step up from the excellent copper-foil caps used in the $19,300 Audio Note Meishu reviewed by Ken Micallef in January’s Stereophile. VK Music sells Audio Note’s silver-foil coupling caps for $355 each. The Audio Note tantalum-resistor option replaces all 46 resistors in the signal path, two Amtrans AMRG resistors, and four Takman carbon resistors for $265. My TU-8900 came with the full Audio Note Silver upgrade, which costs $960 and includes all of that plus two acrylic brackets for securing the large silver capacitors.

The clear top plate, which is included in the cost of assembly (and a $35 option with the kit), turns an ordinary, classically styled tube amplifier into a dramatically visual, sci-fi–looking bit of audio architecture, one that manages to look futuristic and understated at the same time.

In addition to the Chernobyl-red LED light flooding out from the power supply modules stationed below the transformers and the orange glow of the Venus tubes protruding from the clear deck, bright twin LEDs flank and backlight the volume control at center front. These relatively large, symmetrically placed bulbs glow green on startup as sensors measure heater current to determine whether the power tubes installed are 2A3s, in which case the LEDs stay bright green, or 300Bs, in which case they turn blue.

With the abovementioned options, my TU-8900 costs $3280 without tubes. Choosing a start-up tube set is where many Elekit customers begin their tube-rolling journey.

The Elekit’s four tube-set options begin at $365, for two Cossor/LinLai Delux 2A3s and two Sylvania 12BH7As, and top out at $1525 with a matched pair of Western Electric WE300Bs (with a 5-year warranty) and two US-manufactured Sylvania 12BH7As. My review sample came with one of the middle options: two Cossor/LinLai WE300Bs and two made-in-England Brimar 6087/12BH7s for $625.

Altogether, this makes my TU-8900 a $3905 stereo integrated amplifier specified to output 8Wpc with 300Bs. With 2A3 tubes, it is specified to output 3.5Wpc. Both specs are at 10% THD.

Every single-ended tube amplifier, no matter how much it costs, starts with a simple one- or two-stage voltage-amplifier/driver circuit, which is usually one of several old warhorse circuits executed anew, with maybe a rectifying or tube-biasing twist and some fashionable upmarket parts. Or it can be an old warhorse with premium bits tweaked up to something even more lucid and authoritative by the addition of premium-quality transformers, like the TU-8900 I’m describing here.

The two-tube, three-stage circuit in the TU-8900, which was designed by Yoshitsugu Fujita, is a variation on a time-honored classic that every DIY tube person has encountered in schematic form. The TU-8900’s circuit differs from that of the TU-8600, which I reviewed in Gramophone Dreams #27, in that the ‘8900 eliminates the high-gain 12AX7 voltage-amplifier stage. In the TU-8600, one section of a 12AX7 dual-triode is capacitor-coupled to a paralleled 12AU7 twin triode, which in turn is capacitor-coupled to the grid of the 300B. Because the TU-8600 applies cathode feedback to the 300B circuit, it requires the additional drive of a paralleled 12AU7 and the additional gain of the 12AX7.

Because the TU-8900 does not use cathode feedback, it utilizes a different classic circuit, in which one section of a 12AU7 medium-mu triode is direct-coupled to the other section, which in turn is capacitor coupled to the grid of the 300B. That joining is where the expensive Audio Note silver-foil cap is used.

On the main circuit board, beside the left channel’s blue-green LED, is a jumper that allows users to add or remove the TU-8900’s 8dB of negative feedback in order to add or subtract gain and adjusting the sound character of the amplifier.

Also hidden behind the easily removeable front panel are two rectangular jumper-equipped bays that permit users to adjust the amplifier’s gain and output impedance of the ¼” headphone output to match a wide range of headphones.

Listening

For a while after the TADs left, I was disturbed by how compressed and clock-radio small my Falcon Gold Badges seemed in comparison. The Falcons put out an expansive soundspace but with no weighty presence or crisp details in the shadows as there was with the TADs. To their everlasting credit, the Falcons remained unsurpassed in tone truthfulness.

I’d been happily using the Elekit TU-8900 for at least five months and never once thought to disconnect that 8dB of feedback—until the TADs left. It’s probable that the CE1TXs worked as well as they did with this amplifier because the feedback slightly raised the damping factor. But after two days back with my LS3/5as, I got the discontented urge to change something, so I disabled the Elekit’s feedback.

I presumed that the effect of eliminating the Elekit’s global feedback would be subtle; instead it was obvious: A tense haze of grain and texture disappeared, replaced by a darker but more relaxed and vibrant presentation. I immediately got the sense that I was listening to a rawer, less filtered version of recordings.

Ever since I met Victor Kong and discovered the Elekit brand, at AXPONA 2018, I’ve been using a version of the TU-8600, first the TU-8600R, then the TU-8600S (with higher-nickel Lundahl outputs). Both of those amps delivered an appealing SET sound that emphasized what I considered the proper amount of 300B tube clarity and illumination. While I rarely paused to notice it, the TU-8600’s naturally bright demeanor was accompanied by a faint, misty grain I assumed was caused by the electromagnetic impact of its solid state rectifiers.

I noticed some of this grain in the TU-8900 with feedback, but it was overwhelmed by the dramatic 3D vibrancy generated by the ‘8900’s amorphous-core outputs. This enhanced vitality was so pronounced that I sometimes felt it was too much—that the amp was bamboozling me, making recordings sound better than they actually do, or should.

Then it hit me: What I was experiencing—the thing that was so dramatically different than the sound I had gotten used to with the TU-8600s—was probably the effect of the TU-8900’s new circuit with no cathode feedback. Well, partly that. More likely, it was that combined with those amorphous cores, the silver-foil capacitors, and the top-quality resistors.

It’s important to note that these amplifier-circuit ingredients, which are not free, do not enhance the TU-8900’s character. Best I can tell, what they do is eliminate material contaminants and time-domain disturbances that prevent the weaker parts of the raw signal from getting through.

After listening for months with Victor Kung’s parts-curated TU-8900, I can state with conviction that this kit delivered the nuance, intensity, and dramatic transparency of big-name 300B amplifiers costing many times its price. My long-serving, much-beloved TU-8600S does not reach these heights.

Footnote 1: EleKit, EK Japan Co., Ltd., Tofuro-minami 2-19-30, Dazaifu-city, Fukuoka, 818-0105, Japan. Tel: (81) 92-923-8235. Web: elekit.co.jp. North American importer: VK Music, Vancouver, British Columbia, Canada. Tel: (604) 931-8844. Web: vkmusic.ca.

Footnote 2: See content.kemet.com/datasheets/KEM_A4072_A759.pdf.

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