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Integrated amplifier


Manufacturer: HAIKU-AUDIO
Price (in Poland): 21 900 PLN

Contact: Wiktor Krzak
ul. Ślusarska 9 (Zabłocie)
Kraków | POLSKA


Provided for test by: HAIKU-AUDIO


Text: Wojciech Pacuła
Images: Wojciech Pacuła
Translation: Marek Dyba

No 195

August 1, 2020

HAIKU-AUDIO is a Polish company with its headquarters in Krakow's Zabłocie - currently one of the most fashionable districts, specializing in the production of audio amplifiers. Established in 2012 by WIKTOR KRZAK, a musician and audio enthusiast, it took its name from the type of amplifier’s output circuit developed by the company named Talcomp. Almost exactly a year ago we tested the first-ever model with 300B tubes - now it's time for the 211 triodes.

perfectly remember the evening when we listened to the Kondo OnGaku amplifier with the band from CRACOW SONIC SOCIETY. Among us was also WIKTOR KRZAK, the owner of Haiku-Audio. Although the room was dimly lit, the attention was drawn to two glowing areas - the powerful 211 triodes in the amplifier and as shiny eyes of Wiktor, who then said:

For me this is a reference amplifier. Not technically, not in terms of parameters or specific system solutions, and not even in terms of specific acoustic properties, space, control or tonal balance, but in terms of conveying the emotions of the recording, the feeling of uniqueness of the spectacle in which we participate. I consider OnGaku to be more than just an amplifier, it is a complete work of art.

Krakow Sonic Society | meeting #108, more HERE

| SEnsei 211

One might have expected that the very same night the owner of Haiku-Audio would have run to his workshop, where his amplifiers were made, and he would instantly put together his own amplifier with the 211 triodes. And maybe he did. But it is also possibly that it all happened differently - maybe everything played out in his head, the way musicians "hear" music in their heads without any sound propagating through the air. I don't know how it happened, but there is a good chance that it was back then when the idea of the SEnsei 211 amplifier was born.

The evening I was talking about happened in February 2017. Yet, the amplifier I am writing about was created just a moment ago, so it took more than three years for this impulse to turn into a product ready for sale. During that time, Wiktor has developed many good amplifiers - both hybrid and tube ones, great devices from the Origami series, and above all the SEnsei 300B SE amplifier, which was - as I assume - a testing ground for the future project of 211 amp.

| A few simple words…

Owner, designer

Wiktor Krzak, with 211 triode

"Haiku is dynamic by its very nature," writes Toshihiko Izutsu in the essay Haiku as an Existential Event, which was included in the Anthology of Japanese Aesthetics edited by Krystyna Wilkoszewska.

The idea of the Haiku-Audio SEnsei amplifiers is placing the sound in the „hands” of a specific tube - placing the sound into the nature and essence of this tube (ed.). That's probably why I like this fragment so much: "dynamic by nature". There is nothing forceful about the SEnsei series amplifiers, everything is true to the nature of the elements and everything works within its optimal operating range.

The 300B tube is linear, but it tends towards delicacy, airy presentation, while the 211 is a transmitting tube that was expected to provide 100% fidelity, absolute truth, 1:1 transfer. This is something that captivated me in the OnGaku (Kondo). Haiku SEnsei 211's story is not about "how many watts it can deliver", nor about "what bandwidth it offers", nor about "what capacitors are in there". It is a spirit of ultra-true presentation. This is one of the reasons why all live recordings will offer a a new experience with it. All these wonderful chamber recordings: quintets, quartets, trios and soloists will suddenly appear in the recreated aura of the room, with the instrument's sound faithfully rendered. Sometimes we even say that the domain of 211 are live recordings.

The SEnsei series is also about the spirit of my masters Verdier and Kondo. I learned topology and assembly from Verdier, using the 211 as a power tube came from Kondo OnGaku, and the idea of a power supply featuring a large choke comes from the wonderful times of old tube technology. All these inspirations pushed me to prepare my own layout, with my art project and my haiku spirit, which, as is commonly known, in the theory of Japanese poetry, is called hai-i (I use the term after Toshihiko Izutsu).

Technically speaking, SEnsei 211 is a system combining two amplifiers, in which the first, three-stage one, based on ECC82, ECC81 and EL84 tubes controls the grid current of the power amplifier built on the basis of the transmitting tube, the 211. A very important component of the sound of this amplifier are transformers, built based on Haiku's design at Leszek Ogonowski's plant.

Often, if a powerful tube or a push-pull circuit is used, transformers are oversized, but this is not the way to go. Then there are parasitic inductances, problems with the frequency response and one has to calculate it really precisely. A good way is a different one. For the design of such a transformer one has to select materials of the highest quality, super-penetrating, thin sheets, and the windings must be calculated accordingly. Only then can one be sure of the result.

SEnsei 211 is also a visual concept that aims to present properly a transmitting tube in a contemporary room. Such a device placed in contemporary interior will create an accent similar to a radio transmitter, an engine room of the ship, perhaps an element of Captain Nemo's submarine. WK

The SEnsei 211 is an integrated amplifier with a nominal output of 33 W per channel (and therefore high). However, the manufacturer also gives the output measured for the tested unit - in the case of the one we received for the test, it is 39 W @ 8 Ω, 44 W @ 6 Ω and 36 W @ 4 Ω - the power is measured with a 2% THD so lower than it is assumed for tube amplifiers. The frequency response was determined at 14 Hz - 35 kHz (-1dB) and 8 Hz - 45 kHz (-3dB). There is also a version without a signal attenuator and input selector, i.e. a power amplifier.

From the outside, the tested amplifier is reminiscent of the 300B model, but with slight changes. The powerful 211 triodes instead of the 300B are especially eye-catching. They are controlled by the EL84 power pentodes, in this case by the Soviet 6П14П NOS tubes. There are two double triodes in the input stage - the ECC82 and ECC81, both from the current production of the Slovak company JJ Electronics. Unlike usually, it is not a circuit in which each channel features a separate tube, but one in which two channels use the same tube. This worsens the crosstalk but improves the thermal and physical fit of both channels.

| 211

The 211 is a powerful, four-pin tube with a bright color of light emitted by it. This is one of the most famous direct-heated triodes, and its most famous application is the Kondo OnGaku amplifier. It worked there in Class A in a single-ended mode, delivering 27 W per channel. It was developed in the 1920s in the USA as an emission tube for high-power AF and RF transmitters, as well as a tube for oscillators. It can work in Class A, AB or B. Its anode voltage is usually 1000 V, but even 1250 V can be used. Compared to the 2A3 and 300B tubes, its characteristics are much more linear. Currently, it is produced by several companies, mainly Chinese, and the Czech KR Audio also offers its version, but the highest prices are achieved by NOS tubes, costing from 3000 dollars and up.


The Haiku-Audio SEnsei 211 amplifier was placed on the Acoustic Revive RAF-48H anti-vibration platform, and the latter on the top shelf of the Finite Elemente Pagode Edition rack. It was powered by the Siltech Triple Crown cable, and the signal to the speakers was sent via a NOS - Western Electric WE274B cable with Eagle Cable plugs. I used two signal sources: the Mytek Brooklyn Bridge file player and the TechDAS AIR FORCE III turntable with the SAT LM-09 tonearm and the X-quisite ST cartridge.

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  • | SOUND

    Recordings used for the test (a selec- tion)

    • Billie Holiday, Body and Soul, Verve Records/Analogue Productions ‎CVRJ 8197 SA, DSD – rip z SACD (1957/2011)
    • Count Basie & Tony Bennett, Basie/Bennett, Roulette/Classic Records SR 25 072, “45 rpm series”, 4 x one side pressing, 200 g LP (1959/2006)
    • Dead Can Dance, Anastasis, [PIAS] Entertainment Group PIASR311CDX, „Special Edition Hardbound Box Set”, CD + USB drive, WAV 24/44,1 (2012);
    • Hania Rani, Home, Gondwana Records ‎GONDCD037, WAV 24/96 (2020);
    • Merl Saunders, Jerry Garcia, John Kahn, Bill Vitt, Live At Keystone, Fantasy ‎F-79002, 2 x LP (1973)
    • Modern Jazz Quartet, Reunion at Budokan 1981, Pablo Live D 2308-243, LP (1985)
    • Sonny Rollins, Tenor Madness (Rudy van Gelder Remasters), Prestige PRLP 7047, WAV 24/96 (1956)
    • Tony Allen & Hugh Masekela, Rejoice, World Circuit WCV094, 180 G lp (2020);
    • Tsuyoshi Yamamoto Trio, Misty, Three Blind Mice/Cisco Music TBM-30-45, „Twenty-Fifth Anniversary Limited Edition | No. 0080/1000”, 45 RPM, 2 x 180 g LP (1974/2004)
    • Vladimir Horowitz, Horowitz at the Met, RCA Red Seal ARC1-4585, LP (1982);

    In his text, Wiktor pointed out that the tested amplifier does better than well with the material recorded live. Following this clue, I prepared a few "live" CDs - and I'll get to them in a moment. First, however, I wanted to listen to some studio recordings, but recorded as if they were played live. And in the best possible way, too.

    The SEnsei 211 is an amplifier that emanates calmness. It is a device that does not force anything on us, nor does it force us to do anything. With it one listens to the music not as if one “had to do” something, but rather as one was „allowed” to experience something special. This is a completely different perspective, because it relieves us of stress and a kind of an "obligation". It is interesting that we usually associate this type of presentation with a soft and warm sound. The Wiktor's amplifier sounds a bit like that, but rather because everything is well-arranged and “harmonized” in it. But it isuswho interpret its sound as soft and warm, and it is not quite like that.

    The point is that when Tonny Benett sings, supported by the fantastic Count Basie, you can hear a slightly emphasized part of the upper midrange in his voice. We know that it has to do with the characteristics of the ribbon microphone that was used to record the material. But nothing bothers us about it, nothing annoys us. I will even say that it adds some "flavor" to the presentation, because it speaks of the "truth of the recording" and not its idealized version. Already in this short fragment you can hear the incredible ability to differentiate sounds, while maintaining a highly stylish presentation.

    The album with the Basie/Bennett duo was pressed by the Speakers Corner Records label on four 200g, one-sided discs. It is extremely dynamic. Same as an another special version, released by Cisco Music in 2004, the double-disc Misty by Tsuyoshi Yamamoto Trio. Both releases were recorded in analogue domain, mixed and cut in this way. With the SEnsei 211 they both sounded incredibly clear, on the one hand, and incredibly dense, on the other.

    Because it is an amplifier capable of effortless presentation of flavors and subtleties and large elements too. Its dynamics is very high, but we do not pay attention to it. It is like when everything is simply "right", everything is as we imagined. We just "are" and we don't have to look closer at anything, nothing demands our attention - everything has its place. It is similar with the tested amplifier. It has its "own character", there is no device that is completely "transparent", technology does not allow it. But if I were to point out designs that uniquely combine the objective "truth" with their own "truth", the SEnsei 211 would belong to this group.

    Its "own truth" is expressed, for example, in rounded bass. Almost the same day I received the amplifier, a package with a vinyl version of the Tony Allen & Hugh Masekela Rejoice arrived. It has a bigger bass than the digital file available on Tidal, but it is softer. The amplifier emphasized these two elements a bit and refined them. So the bass was rather caressing than attacking, it was large and full at the same time. It never lagged, though. It's an incredibly dynamic device, but its softness was very clear to me. Still, it was to be expected, each solution has its limitations - even in such version.

    Also the midrange seems smoother with the SEnsei 211. At least when I compare it to the Kondo OnGaku, or Air Tight ATM-3211 etc. The SEnsei 211 resembles in this respect what the Phasemation MA-1000. But also not entirely. You see, the amplifier prepared by Wiktor does not sound "soft", but it performs in such a way, that we think it does. It also does not emphasize midrange, but it presents this part of the range in such an engaging way and without any internal tension, that we perceive it that way. In a way, it is an amplifier that offers us what we expect from it, but under this layer there is something strong, well-thought-out, which does not allow for exaggeration.

    The treble is clear, strong with it, they have proper weight and vividness. Therefore, in this case we cannot speak of a stereotypical, "tube-like" sound. I heard it with the analog recordings I’d mentioned before, and with a fantastic concert by Saunders, Garcia, Kahn and Vitt entitled Live at Keyston. This is an analog recording from 1973, which sounded dense, warm, slightly soft, but also expressive, precise and dynamic. Usually these sonic features rule each other out, or at least neutralize each other, but in this case they were all presented nicely together. And they will be every time.

    Because the treble with this amplifier is sort of "forgiving" on the one hand and realistic on the other. So it was a pleasure to listen to each album, even those with such a clean and crisp treble as the Modern Jazz Quartet’s Reunion at Budokan 1981. This is a "live" recording from the Japanese Budokan, captured using the Mitsubishi X-800 multi-track digital tape recorder and mixed into the X-80 (more about Mitsubishi tape recorders HERE and HERE). SEnsei showed it precisely, but also with a feeling, swinging without distorting the treble.

    It seems to me that the amplifier owes it all to a large extent due to the fact that it is able to follow the signal peaks, delivering the right amount of current - even with very fast and large changes in the signal. It easily delivered the powerful bass from the Dead Can Dance’s Anabasis, and right after that to perfectly differentiate the recordings from the new Hania Rani album Home. Interestingly, this amplifier is so resolving that it was immediately clear that the 24/96 WAV file I listened this album from sounded better than the 24/96 FLAC, although both are identical. The only difference is that FLAC must be "unpacked" in the player, which results in a higher noise.

    It is also an amplifier that perfectly differentiates the volume of the sound - both at the level of individual objects as well as whole presentations. Because on the one hand, it presents large spaces beautifully - on the aforementioned Dead Can Dance and Hania Rani albums, for example, and on the other hand, Billie Holiday, played immediately afterwards, was presented in an intimate, close way. But it is not an amplifier that enlarges the foreground or brings it closer to the listener. If you expect such effect the SEnsei 300B will be a better choice. The 211 offers a more mature perspective, showing the air in front of and behind performers.


    The SEnsei 211 is simply a beautiful amplifier. It is resolving and coherent and smooth and precise and clear and sweet. It delivers powerful, big bass with momentum and no audible compression. It's not very selective, but that’s just such a device. It does not dazzle with details and subtleties, although there is abundance of both. It build a large soundstage in front of us, a vast sound panorama with very well marked layers.

    It is a well-thought-out, coherent concept with a big heart. So it’s audio at its best. The SEnsei 211 is the most expensive, but also the best amplifier from this Krakow-based company.

    | DESIGN

    The form of Haiku-Audio amplifiers is similar, regardless of whether it is a tube or hybrid amplifier. Their housing is made of thick, bent steel sheets with an aluminum front attached to them. Its stylized shape can be found in the company's logo; the exception is the Origami series, where the front is slightly different.

    On the outside, the SEnsei 211 is very similar to the SEnsei 300B, but it’s not the same. The large 211 tubes and the fact that the output transformers are now turned sideways towards them are noteworthy. It was probably done so because these triodes emit a lot of heat, or maybe simply the transformers in the previous setting did not fit. On the side you can see a very large transformer, and in front of it a choke - it is a design with a power supply based on chokes. Two more, but small ones, are hidden inside and are used to power small tubes.

    The large knobs on the front allow user to adjust volume and select input. The former is carmine red, indicating that it is a "special", limited project. On the back, there are single loudspeaker outputs, featuring high quality CMC components, and next to them there are five RCA line inputs. Wiktor uses green instead of white sockets for the left channel and places them below red ones - just like Mark Levinson used to do, and so does Ayon Audio.

    The audio circuit was spatially assembled with the use of auxiliary stands. One can easily spot polypropylene (MKP) capacitors by the Polish company Miflex, Ohmite resistors and speaker sockets. The power supply capacitors (BC) are mounted on one additional PCB. Volume control is operated by Alps rotary potentiometer; the amplifier has no remote control. There is a schematic of the amplifier on the bottom panel - just like in the good old engineering years.

    The SEnsei 211 is a very solid design, prepared with love and using great knowledge, with a nice external design and great performance.

    Technical specifications (according to the manufacturer):

    Tubes complement:
    211, EL84, ECC81, ECC82
    Class: A SE
    Nominal output: 33W
    Measured output:
    39W / 8Ω | 44W / 6Ω | 36W / 4Ω
    Frequency range:
    14 Hz - 35kHz / -1dB | 8Hz - 45kHz / -3dB
    THD (1 kHz, full power): 2%
    Power consumption: 250W
    Weight: 26kg


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