atelier 13 audio

THÖRESS EHT Integrated MKII

"Reinhard Thöress set out to exalt the treasures contained in the Triode tube, through a classic approach that has proven itself and a deliciously Retro look, a sound result unlike any other in its density, its presence, its energy and its realistic spatial presentation, serving all the emotion contained in each recording. Those who are connoisseurs of Valve-halla will be delighted by the Thöress amplifiers and their rare musicality"

A Tribute to Professional Audio Components from the Golden Age of the Vacuum Tube!

EHT INTEGRATED MKII

"SYNTHESIS"

single-ended hybrid triode

THÖRESS EHT MKII

Single-ended Hybrid Triode Integrated Amplifier

Offers 2x20 watts of output power into a 6 ohm load combined with low output resistance (high damping
factor). Such providing excellent drive capability for loudspeakers with medium to low efficiency or critical
impedance behavior (which may present a challenge for our all-tube triode amplifiers) while offering an ultimate sonic presentation without involving exotic and costly power tubes.

The amplifier is based on a unique minimalist single-ended zero-feedback vacuum tube MOSFET hybrid topology which we call EHT Topology (E/intakt H/ybrid T/riode, single-ended hybrid triode).

Inputs : The amplifier comprises 4 inputs [ RCA jacks ] with equal gain status selectable via rotary dial.

Volume Control : Furthermore, the amplifier features a proprietary remote volume control based on high grade motor-driven dual-potentiometer presented with typical THÖRESS style and attention to detail. The potentiometers are made to our specifications for low angle sensitivity [ conveniently fine volume adjustment) by ALPS in Japan ]. Each individual part is selected from a large production batch for exceptionally good channel balance by careful measurement [ 0.3dB tolerance ].

Build : The amplifier is built with meticulous hand construction using our proven point-topoint wiring techniques, whereby much care has been taken in arranging each aspect of the internal construction to ensure low noise performance, ease of service and the highest reliability for many years to come.

The EHT Integrated is an ultimate component in every sense and, as such, a perfect complement to our Parametric Phono Equalizer [ The Phono Enhancer ]. When combined with reference quality high sensitivity loudspeakers, and particularly with our underhung voice-coil 1D66 or horn based 2CD12 loudspeaker, the sonic presentation of the amplifier is of the utmost refinement, and will certainly meet the expectations of even the most critical and experienced music lover.

EHT TOPOLOGY

The amplifier is based on a unique minimalist single-ended zero-feedback vacuum tube MOSFET hybrid topology which we call EHT Topology [ E.intakt-H.ybrid-T.riode, Single-Ended Hybrid Triode ].

We deliberately ignore the fact that many music lovers persistently believe in the myth that balanced technology ... and the associated XLR connectors and cable configuration ... is generally superior over single-ended concepts.

Readers who want to learn more about our view on balanced techniques and our general design approach are encouraged to read the "THÖRESS - Behind the Curtain" white paper, available on request.

The EHT topology consists of a single-ended triode gain stage (6J5GT,12J5GT or 7A4 vacuum tube) followed by a unity gain MOSFET output stage also operated in singleended (class-A) mode with high idle current. Basic analysis easily shows that ... The EHT principle represents the PUREST form of all possible single-ended triode power amplifier configurations!

Specifically, it can be shown that a higher output power can be more easily obtained with the EHT than with an all-tube amplification principle, without compromising sound quality. Simply, because in the former case the typical vacuum tube impedance matching output arrangement (power tube driven output transformer with high step-down ratio) can be fully omitted.

Therefore the driver voltage swing required for a specific power output is up to 10 times (!!!) lower for the EHT configuration compared to an all-tube topology, resulting in a proportional reduction of non-linear distortion. In fact this very crucial insight led us to the design of the EHT Integrated (and the EHT Mono Amplifier).

The EHT topology allows to fully exploit and mate the most desirable characteristics of both vacuum tube and solid state devices determined by their very nature.

STABILITY

The EHT Integrated Amplifier operates with impeccable thermal stability and is fully short-proof at the output without the aid of any kind of (sound degrading) protection circuitry. Moreover, a switch-on delay module (another protective feature often found in commonly constructed solid state or hybrid amplifiers) is also omitted because no disturbing noise or harmful signal is developed at the output when the amplifier is powered on or off.

BASS BOOST FUNCTIONS

The EHT Integrated Amplifier MKII [ launched in October 2022 ] includes two novel bass boost presets selectable via a 3-position toggle switch :

B1 boost style-1
B2 bass boost style-2.
When the switch rests in middle position, the tonality of the amplifier is neutral. i.e. flat frequency response.

The bass boost functions are useful for a variety of applications :

For equalizing loudspeaker components with slim bass response or limited bass extension.
For adjusting the bass response of the system to the acoustical conditions of the listening environment i.e. small loudspeakers in large rooms !.
For restoring tonal imperfections of the listening program, often caused by a lack of bass extension)
Or simply for switching to a more full-bodied presentation if one is in the mood for listening to music in an enriched and laid back way.
Notably : The two bass boost functions act in a much more subtle way than common bass boost facilities, and do not rely on clumsy and sound degrading conventional tone control circuitry. Both functions are realized by interposing solely one additional capacitor [ per channel ] to the neutral mode circuit !

MAINS TRANSFORMER

The EHT Integrated Amplifier is equipped with a proprietary mains transformer produced in-house to ensure the highest possible quality and reliability. This part features a highly elaborated dual-coil winding structure on a large tape wound cut core (C-core) and has been optimized for low body noise emission and low leakage.

Nevertheless, it is mounted to the amplifier chassis via isolation elements in order to eliminate even the slightest interference of residual transformer vibrations with the circuit. Since the mains transformer is produced in-house we can easily built transformers for all kinds of mains voltages on demand, for example 100Vac (Japan), 120Vac (USA, Canada), 220Vac (South Korea, China, Thailand, Indonesia), 240Vac (UK) or 245 Vac (Australia).

F E A T U R E O V E R V I E W

Vacuum Tube MOSFET Hybrid Integrated Amplifier with 20 watts of output power per channel into a 6 ohm load

Superior driving capability for critical loudspeaker loads due to very low output impedance (high damping factor)

Ultimate sonic excellence on par with no-compromise all-tube single-ended triode amplifiers, yet without involving exotic and costly power tubes

Unique minimalist zero-feedback EHT schematic: single-ended triode gain stage (6J5GT tube) driving a unity-gain MOSFET output buffer operated in single-ended (class-A) mode with high idle current

Total avoidance of protection circuitry

4 line level inputs (2x4 RCA jacks) with equal gain manually selectable via rotary dial

Remote volume control via high-grade motor driven dual potentiometer with excellent channel balance and low angle sensitivity for conveniently fine volume adjustment

High grade electrolytic capacitors made in Germany in the power supply

Low noise low leakage dual-coil C-Core mains transformer made in-house for 230Vac (115Vac via jumper setting), 100Vac (Japan), 220Vac (South-Korea, China, Thailand, Indonesia) or 245Vac (Australia)

Full hand construction, point-to-point wiring throughout

Non-magnetic aluminum casework, anodized printing on front and rear panel, powder-coated lids

Dimensions - mm :
- 434 W x 450 D x 184 H
- H / 184mm = 20mm (feet) +134mm + 30mm (tubes over case)
- D / 450mm = 434mm +16mm (speaker binding posts)
- Dimensions of the shipping crate - mm: 650 W x 650 D x 350 H
- Shipping weight : 18Kg.

Individually Made in Germany

MSRP $ 11,000

What the say ...

STEREOPHILE

Herb Reichert | Oct 4, 2023

With the EHT driving the Falcon LS3/5a's, at first all I noticed was smoothness, a deep spatial rendering, and a highly refined instrumental tone. That was before I played string quartets by my most beloved modern composer: György Ligeti (György Ligeti Edition, Vol.1, Arditti String Quartet 16/44.1 FLAC, Sony Classical/Tidal). I listened repeatedly to Ligeti's String Quartet No.1, Metamorphoses Nocturnes.

Sometime during my third listen, I realized how much recorded energy the Thöress amp was projecting during Quartet No.1's extended silences. This wasn't noise, or distortion (those things are static and inert); this was live, morphing, three-dimensional energy—energy that's on the recording—floating tangibly between, around, and above my Falcon Gold Badges. What made this noteworthy was that I couldn't remember experiencing energy like this before. I could hear and feel this near-silence energy coming through even during a hot day with my windows open and a fan turning at low speed.

I was not surprised by how nicely the Thöress danced with the 10" paper woofer cones in my DeVore Acoustics Orangutan O/93 loudspeakers. I guessed in advance that I'd get buttery-smooth, emotionally engaging vocals from Julie London, Frank Sinatra, and George Jones, and I did, but I never would have guessed that I'd prefer the EHT's brighter, more focused clarity to the First Watt SIT-3's lusher, deeper, but less-transparent presentation. Yet I did !

With the Thöress EHT powering the big-box Heretic AD614s, the presentation expanded and moved closer; more-distinct layers of low-level information were being rendered. I became engaged trying to follow what each musician was doing and admiring their individual talents, stopping only for a moment here and there to admire the electrostatic speed and flawless tone of the AD614s. Streaming Alfred Schnittke's Concerto Grosso No.2, performed by Gennady Rozhdestvensky and the Russian State Orchestra (16/44.1 FLAC CDK Music/Tidal), the EHT-Heretic combo made it sound much as it did when I owned Quad 57 electrostatics, but less compressed.

Most of all, this Heretic-EHT pairing reminded me how much I enjoy the feel of a sound system that pressurizes more air than the Falcons, which were designed to pressurize the back space in a little van. Like my friend's big RCA speakers in his church-size room, my room seems scaled perfectly for the Heretics: They play full and large but also squeaky clean and microtextured, no mud or blur. Plus! Their easy-to-drive series crossover permits me to examine amplifier flavors under unstressed driving conditions, a test the EHT passed with a perfect score. The fact of its transparency was obvious. What's more—the reason this was a superb pairing—the Thöress added some rosy cheek hormones to the Heretic's naturally dryish sound. The EHT's chorus of low-key intangibles made the Heretics sound more liquid and charming.

TWITTERING MACHINES

Michael Lavorgna | Feb 15, 2024

Some of the EHT’s standout qualities include a deftness that felt perfectly timed while offering a fitness and firmness that made music feel present, powerful, and graceful. This quality of lightness of touch, deftness, turned out to be addicting and never made music feel too fast or too slow, neither too thin nor too fat.

Coupled to this beat-perfect timing was a harmonic rightness, where the sounds of the things responsible for making music had full spectrum color, texture, and nuance. The sound image, regardless of the speaker in play, was laid out in real dimensional form while sounds appeared, receded, and/or went silent in accordance with what I’m used to hearing in real life from real sounds. All in all, the Thöress amp kept me on the edge of my respective couches, enrapt in whatever I chose to get lost within.

While I did call these standout qualities, the Thöress EHT is not a showy or flashy sounding integrated amp. There are no sonic traits in need of an aural plastic surgeon, nothing too big, too bold, or too flabby to be found here. Instead, music, all of the music I ran through it, felt just right with a lovely hint of sweetness that brought out the full flavors of the sounds that make up music. Lovely.

Sarah Beth Tomberlin or mononymously Tomberlin’s 2020 EP Projections, co-produced by Alex G and his bandmate Sam Acchione, is a lovely slice of folk-inspired intimate sadness. I’ve listened to Projections’ 18-minutes too many times to count but playing through the Mola Mola Tambaqui and into the Thöress EHT driving the DeVore O/96 on the Barn’s B-Side presented a special edition, a rich, right, ripe, and full sound that moved along as easily as Sarah Beth Tomberlin & Co.’s graceful movements on acoustic and electric guitars, violin, bass guitar, keys, and drums. This EP opens up in space like a time-lapse blossoming flower and this system reproduced that space and place in a physically and emotionally enveloping manner. A sit back and let it touch you kinda deal.

Sometimes I wonder if Kali Malone even needs to eat. All Life Long, her latest work of majesty and beauty, stretches out over an hour and 19 minutes comprised of Malone and Stephen O’Malley on church organs, choral music performed by the Macadam Ensemble, and the Anima Brass quintet. This otherworldly music moves along at a meditative pace, delighted in subtle movements stretched out over so the movement is, at times, barely perceptible shifting the listener’s focus to micro-events unfolding in space (and time). Malone and O’Malley, which sounds like an old time middleweight bout, perform their parts on the historical meantone tempered pipe organs at Église Saint-François in Lausanne, Orgelpark in Amsterdam, and Malmö Konstmuseum in Sweden so there’s that kind of cathedral vastness in play and the Thöress EHT projected this vastness into the space of the Barn with natural ease when driving the O/96 or the GoldenEar T66, with a brilliant sense of attack, tone, and decay—there’s that deftness again. This kind of music, which I’ll call minimal (but it’s actually maximal), needs proper replay in space to fully communicate and the more a system can recreate the full voice and touch and feel of each element, the more immersive the experience. To my way of hearing, the Thöress EHT is more than capable of delivering this full event.

Pick the one you like the looks of better. The Barn resident Leben CS600 integrated amplifier, that offers about 28 Watts per channel when equipped with a quad of EL34s in the output stage, currently costs $8995 compared to the Thöress EHT’s $10,995. The main differences between the sound of these two beauties, I like the way they both look equally, is the Leben sounds more heavyweight, a bit more forceful than the Thöress EHT, with the Leben also offering a richer more saturated sound. The fun thing about hifi is these differences are not good or bad, making one of these fine integrated amps better or worse than the other. They sound different and which you prefer is up to you. Let me say this another way: the Thöress EHT sounds more nimble than the Leben, more able to convey nuance and subtlety as compared to the Leben’s thicker, richer sound. See what I mean? Without the opportunity to hear both in the same system, ideally yours, you may as well pick the one you like the looks of better. There’s no losing choice here, only winners (if you want a wider choice, have a look at my Favorite Amplifiers made up of, you guessed it, all winners too).

Bar Italia’s 2023 release Tracey Denim, their third album and first on Matador, is a jangly-sounding post-something or other rocker. In no way a great sounding record, Tracey Denim is nonetheless a recent find that tickles a particular fancy. The trio is Jezmi Tarik Fehmi, Sam Fenton, and Nina Cristante who make skeletal sounding post-punk with gobs of drive and even more attitude that makes The Falls’ Mark E. Smith sound like Sinatra (comparatively speaking). The Thöress EHT/DeVore combo kicked this brashness into the Barn with delightful force and quickness with just enough tone, texture, and body to transcend their intentional lo-fi approach. The Thöress’ agility raised the in-Barn energy level to 11, sounding well poised to take on any genre and it certainly proved more than up to the task of making me fall back in love with days and weeks-worth of records, always wanting more.

The Thöress EHT MKII Integrated Amplifier won over my heart, mind, ears and eyes. Its performance, most notably when paired with the DeVore O/96, was exceptional in many ways but its greatest sonic strength was the ability to transform recorded sounds into pure musical magic !

Read full review here