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Integrated amplifier

Audio Reveal

Manufacturer: ALTRONIK
Price (when reviewed): 37 700 PLN
(high gloss finish: +800 PLN)

Contact (European): MICHAŁ POSIEWKA
ul. Muszlowa 3 lok. 83
01-357 Warszawa | POLSKA


Provided for test by: NAUTILUS DYSTRYBUCJA


Images: Marek Dyba

No 203

April 1, 2021


AUDIO REVEAL AUDIO is a Polish brand specializing in the designing and production of Single-Ended tube amplifiers. We are testing a special, new version of the already well-known model, the SECOND, this time it’s a SIGNATURE version featuring a hot (literally and figuratively) novelty, the KT170 tube.

HE FIRST TUBE FROM THE TODAY FAMOUS BEAM TETRODE KT FAMILY, which became popular, was the KT66 introduced to the market by the British company Marconi-Osram Valve in 1937. At almost exactly the same time, across the pond, the RCA company presented another (albeit sharing quite similar parameters) beam tetrode, the 6L6 . These tubes were used in radio receivers and amplifiers, including ones for guitars.

As early as in 1956, GEC introduced a larger version of the KT66, called the KT88, probably the most famous of all KT tubes, designed from the scratch for audio applications. It offered features desired by the market, that is, above all, higher output capacity and lower distortion. In the 1990s, thanks to the Yugoslav company Ei, the KT90, considered a direct replacement for the KT88, hit the market, and in the even more recent years the Russian Sovtek introduced a "super-tube", the KT120. As always in the case of novelties related to our hobby, the latter two won some hearts among the music lovers, but the most popular choice was still KT88.

Finally, in 2013, the Tung Sol brand launched another model from the KT family, this time marked with the number 150. The new tube once again pushed the limits of the power limits that could be „squeezed” from a single (or multiple) tube(s), enabling the design of monstrous tube amplifiers outputting even hundreds of watts in class A, when using several of them per channel.

As many people, including yours truly, believe that the new tube outperformed all the older ones in terms of not only output by also, or most of all, sound quality, it quickly found its way into numerous tube amplifiers, also those offered by top brands. The generalized argument that high-efficiency loudspeakers are a must for use with tube amplifiers has ceased to be relevant due to, for example, Ayon Orthos II XS monoblocks (and other amplifiers), which offer up to 300 W per channel in pentode mode, and 180 W in triode mode.


IT SEEMS THOUGH, THAT THERE IS NEVER ENOUGH POWWER in the audio world. Or maybe Tung Sol was just looking for an additional income stream. Anyway, last year, I think in September, we saw a press release introducing yet another model of a beam tetrode, the KT170. For audio designers it meant a chance to develop even more powerful amplifiers. Due to the pandemic, lack of audio shows and generally speaking somewhat limited industry contacts (at least direct ones), some information about an introduction of new models of amplifiers using this novelty may have eluded me. For now, I know about two products that have been at least announced, or as is the case of the reviewed amplifier even already introduced.

I learned about the former a while ago directly from the designer. I mean the subject of this test, i.e. the Audio Reveal SECOND SIGNATURE. Literally a few days ago, I read that the French Jadis is going to introduce the I-70 integrated (as I’ve in the meantime learned from the Polish distributor, he expects first units to arrive in July) benefiting from the qualities of the newly introduced KT170 power tubes. Most likely in the next months we will witness more products using this tube coming to the market, but for now it seems that our Polish Audio Reveal is one of, or even the very first manufacturer, a pioneer one may say, of the application of the new Tung Sol tube.


AS OUR READERS SURELY REMEMBER, Michał Posiewka, the owner and designer of the Audio Reveal, based his debut product, called appropriately the FIRST, on the most popular tetrode, the KT88 (we tested this model in the 2019 January issue of HIGH FIDELITY and it was its PREMIERE; more HERE). I have always been open about the fact, that I am not a big fan of this particular tube, but the SE application proposed by Audio Reveal won my heart. For a reasonable (I mean considering today's reality) price, this model offers a quality and character of sound that it is very easy to fall in love with.

I was even more impressed by the excellent SECOND (also a SE design but this time featuring the KT150 in the output stage; yet another premiere in the HIGH FIDELITY, more HERE). It was capable of delivering twice the power of the FIRST which allowed a much wider range to be paired with it, plus it offered an even more resolving and refined sound which placed this model high on the list of my favorite tube amplifiers. That’s one of those not so many amplifiers I could spend the rest of my life with and be happy about it. Both models proved that their designer focuses on getting the best of a chosen tube/circuit in terms of sound quality, not on pushing it to the limits for the maximum output.

Mr. Posiewka has not changed his approach when designing the new product, which, despite featuring different output tubes, is obviously similar enough to the SECOND so that instead of calling it the THIRD, designer decided to use the SIGNATURE designation. By the way, he also shared another news with me - there is another, this time entry level model coming. It will be called JUNIOR. It will be bit smaller and simpler than the older brothers, it will feature the 6550 tubes also in the SE circuit. It should be available at some point in the second quarter this year.

As this is my first contact with the KT170, I asked the distributor, Nautilus, to deliver not only the SECOND SIGNATURE version, but also the "regular" SECOND version, to compare them as directly as possible (switches between tube amplifiers in one system take a few minutes). A brave crew of Nautilus Warsaw’s showroom delivered both quite heavy amps to my place overcoming several flies of stairs to get them here. However, due to the current pandemic situation, resulting in my whole family constantly staying in the apartment, I took the burden of unpacking and placing them on the rack myself, and my backbone hated me for it.

Simply, in both cases there is a lot to lift even if it is just less than a meter high from the floor level to the top shelf in my rack. So when I somehow got them both up there, to have a moment to catch my breath, I started to inspect them looking for differences. Earlier, during a telephone conversation, Michał Posiewka warned me that in response to customer suggestions, SIGNATURE had been finished with glossy black varnish. This is not my favorite finish - nothing catches dust and fingerprints as easily as black piano finish of audio components, but if the customers so wish, the manufacturer's task is to answer such (strange from my point of view - but who am I to judge?) desires.

As it sometimes happens with oral descriptions of the looks imagination kicks in. What I saw in my head was an amplifier shining like a... piono. Fortunately (at least from my point of view) it turned out that it was only the front panel that was painted this way. I should have had realized that, as with the predecessor, that featured this absolutely astounding wood finish, it was limited only to the front panel. Having only the front panel black and shiny limits my considerations significantly, as there is very low chance of dust gathering there (it’s a vertical surface after all - gravity should be an ally) or leaving fingerprint on the crime scene, I mean front panel, especially considering the fact, that the volume can be adjusted with a neat metal remote so there is not much need to even get close to the device (except for turning it on/off and selecting inputs).

The remote is also completely black in this finish version, which is a nice touch, as the units with wood finish are sold with a remote featuring wooden caps on both of the remote’s end matching the front panel’s finish. It’s a seemingly small, insignificant element, but it proves that the manufacturer takes care even about the smallest details, so that his products please not only the ears, but also the eyes.

Let me mention here, I asked the designer about it to make sure, that in the case of both models, SECOND and SECOND SIGNATURE, the customer can choose the preferred finish. The standard one features this beautiful wooden front panel, and for the extra glossy black one one has to pay PLN 800 more. Visually, both versions (SECOND and SIGNATURE) are very similar to each other. On their fronts there are three elegant metal knobs (on/off switch, potentiometer, input selector), and each of them is surrounded by a nice metal ring, and so is the „eye” of the remote control receiver. These are yet another „small, seemingly insignificant” elements, that make quite a different in the aesthetic perception of the Audio Reveal amplifiers.

The tubes sit in the top surface of the metal, black (regardless of the front finish) chassis, grouped separately on right and left side, respectively, for the right and left channels. Here, too, a clever and great-looking elements were used, which worked well for the SIGNATURE’s predecessor, i.e. horizontal metal plates mounted on top of the amp’s cover which (mostly) hide the tube sockets. In the front there are two signal tubes - and here is the first difference (compared to the standard SECOND) visible to the naked eye.the same type, the 12AX7, but this time sourced from Genalex.

Behind them one can find the main visual difference, i.e. the even bigger output tube - the KT170 (one per channel), the shape of which is ... quite exotic, so to speak. The set includes metal „cages” for tubes that one can slid onto the aforementioned metal plates. Each of these black, metal "baskets" covers the front, top and sides of all tubes for one channel.

In the center of the amplifier's top cover, there is a small knob that allows you to change the feedback’s depth (by about 3 dB). Behind it, there is a place for an elegant plaque with the name of the brand and model, but in the SIGNATURE version it looks like copper, not gold. The same applies to the small plaques on the upper surfaces of four transformer housings. These not only look great, but are also a reliable source of information. Firstly, they indicate that the power transformers are hidden under the two middle cans (additional info - there are two of them!). Secondly, they indicate another difference compared to the "ordinary" SECOND version, namely the use of even higher quality output transformers, ones with amorphous cores.

As the SECOND SIGNATURE is a variation of the model previously described in detail by Wojtek, let me direct our Readers interested in the technical description to his text. When asked about the differences, apart from those already mentioned, the designer also mentioned capacitors in the audio path, made of solid copper foil impregnated with oil, with a paper and polypropylene dielectric.

As we already know from the reviews of previous models and, as the designer himself admits, the output if all Audio Reveal amplifiers is rated highly conservative - for SECOND it is 20 W per channel, and for the SIGNATURE version it is ... 21 W. Firsthand experience with both previous models tells me that one should not worry much about the declared output values. Both FIRST and SECOND drove effortlessly loudspeakers that on paper seemed way too difficult for any of them.

It was no different in this case, as SIGNATURE was a great match not only for my GrandiNote MACH 4 speakers (which was not a surprise, as they are quite easy loading), but also the Ubiq Model One Duelund Edition. The latter already sounded good with the KT150 amplifier, but the new model drove them with more ease, truly effortlessly, in a way that is usually reserved for solid-state amplifiers. So in case you decide to own one of the Audio Reveals you won’t have to look for 95 or 100 dB loudspeakers for them. Although, as always in the case of tube amplifiers, relatively flat (without large drops) impedance curve will play a significant role - greater than the efficiency itself.


HOW WE LISTENED During the test, both SECOND SIGNATURE and SECOND drove the GrandiNote MACH4 loudspeakers, but at some point I also paired them with Ubiq Audio Model One Duelund Edition. Both amplifiers were placed on the top shelf of the BASE VI rack, and additionally on the Rogoz Audio SMO40 platform, which I placed on ceramic Franc Audio Accessories feet.

The source was my trusted J.Sikora Standard Max turntable with the KV12 tonearm and the Air Tight PC-3 cartridge, and the analog front end was completed with the ESE Labs Nibiru phono preamplifier. On the digital front, the main role was played by the reference LampizatOr Pacific DAC, fed with the signal from my custom audio server via LAN and USB cables (alternately), both by David Laboga.


Listening to this amplifier was quite a unique experience, as usually, especially (but not only) when it comes to tube amplifiers, I have certain expectations based on my previous experience with similar designs, and/or the same tubes. But the KT170 is a novelty, and the SECOND SIGNATURE is the first design featuring this tube that I had an opportunity to listen to. So I did not know what to expect, maybe apart from a good, classy sound that the previous designs by Michał Posiewka offered.

So I decided to give myself the first few days to casually listen to many different albums played both from files and vinyl records, and only then I started critical listening and ultimately a comparison against the KT150 version. Of course, this "casual" listening was quite so, I mean it was difficult for me not to try to recognize some sonic characteristics of the SIGNATURE.

In the notes from these first sessions, as often as in those from critical listening sessions, I found later comments regarding an extraordinarily clean, transparent, detailed and neutral sound. While the first features characterize the majority of (good) SET or SE tube amplifiers, the tonal neutrality or a detailed performance rarely belong to the prominent features of such designs. Listening to any tube device, one expects (among others) a warm, dense sound, but in this case, with both my quite neutral, and at the same time fantastically natural sounding sources, what I heard from my speakers, at least partially, differed from such expectations.

It is true that the SECOND with the KT150 tubes sounded, to some extent, similar, but as I thought and what was later confirmed by head-to-head comparison, it did sound a bit warmer, focusing a bit more on the presentation as a whole, rather than on details (than the SIGNATURE). The thing is not that SIGNATURE is somehow an extremely analytical device that performs vivisection of each played recordings, it absolutely doesn’t! I am rather talking about the fact that people who expect to hear the squeak of the chair when the violinist in the third row of the orchestra moves around will surely hear it with the Audio Reveal KT170 amplifier, and with the predecessor only if they try to hear it really hard. In my experience this feature is, probably partially, a result of usage (in the SIGNATURE) of the amorphous output transformers, not (or not only) the new KT170, as devices with these transformers seem to have a tendency to emphasize these tiny little details more, than other types.

Reading what I have written so far, someone might start to suspect that the SECOND SIGNATURE draws music paintings with sharp line down to the little details, while „forgetting” about a proper richness and weighting of the sound. To be honest, that’s what I thought for some time remembering the sound of the SECOND or my own GrandiNote Shinai.

All I had to do to realize how wrong I was, was to cue in an album that, for whatever reason, I had not listened to for a long, long time, La Stravaganza with the music of Vivaldi, with the amazing Rachel Podger on the violin and our wonderful ensemble Arte dei Suonatori playing period instruments. Just a few minutes with this music and not only a remarkable resolution and excellent differentiation in terms of timbre and dynamics became obvious, but also the absolute "fullness" or "completeness" of the sound. It's a relatively small ensemble, but its sound has quite a mass, slam, depth, because behind the strings there were clearly properly sized soundboxes amplifying and enlarging (in a natural way) the strings. The sound was tuneful (not colored!) and really dense, rich but at the same time extremely clean, open, full of air and while all these small details and subtleties were a bit more evident, so to speak, the the whole remained amazingly fluid, coherent and, as a result, beautifully natural . There was no harshness or aggressiveness in it, but there was that elusive element that excites, makes you listen to music while sitting on the edge of your sit, waiting for what will happen next.

I really love the way Matt Andersen’s live album sounded with this amp, confirming basically everything that I’ve written so far. In the foreground, there was the artist's dense, expressive vocal and the weighted, incredibly natural-sounding acoustic guitar and together they set the tone for almost all the tracks. In this particular production, neither the acoustics of the venue, nor the participation of the audience play such a big role as on some other concert recordings. Yet, SIGNATURE still had an opportunity to demonstrate its high precision of locating large, stable phantom images on large soundstage and ability to separate following layers/plane of the stage.

It achieved that while positioning the vocalist half a step behind the line connecting the speakers, building a large, deep, air-filled stage, and even the accompanying musicians playing behind the vocalist were placed with a truly Swiss precision. And although it was not a particularly complex performance with a limited number of instruments, it still contained a large portion of the energy characteristic for live events, but mostly lacking from recordings of those events. Some devices, including, as it turned out, the SECOND SIGNATURE, are able to extract enough of this live energy from high quality recordings to conjure up an electrifying spectacle that brings a smile on a face of a great fan of live performances (me!).

Equally perfect in terms of the presentation of tone and texture, with fantastic dynamics, but with even greater, more concert-like energy, the tested amplifier showed, for example, the three brilliant guitarists from the latest re-edition of Friday night in San Francisco, released by Impex on two 45 RPM albums. The quality of this release is simply insanely good, and thanks to the SIGNATURE I heard this material, known almost by heart, in a slightly different, more precise way, discovering even more smallest details and subtleties, an impressive energy and this overwhelming impression of witnessing a true lively contact between performers and the audience.

With the SECOND SIGNATURE the concert of Christian McBride's Trio from Village Vanguard, where both performances of the maestro himself on the double bass and Ulysses Owens Junior (I am not trying to take anything away from the brilliant pianist, Christian Sands), sounded breathtakingly at times. Precision and speed of each string pluck, followed by its equally rapid damping, the "depth" of the soundbox, the power of the sticks hitting drums, excellent differentiation of the brushes gently caressing the cymbals, plus the extremely realistic, present audience having as much fun as the musicians, all of these elements combined into a real spectacle, that did not allow me to sit still in my chair.

I mean a kind of a musical spectacle that encouraged me to turn up the volume, and then some more, and again a bit more... (damn, my neighbors are going to kill me!!, but hey, first me and them together are going to have some real fun listening to this fantastically played and reproduced music). Long story short - it got really loud really fast and still sounded absolutely fantastic! Importantly, increasing the volume even to a level that probably allowed most of the tenants in my building to join the party did not have the slightest impact on the purity, precision and coherence of the sound. So the question is - who really needs those solid-state beasts delivering hundreds of watts? :)

The Polish product did not make the mistakes of many competitors who, in pursuit of detail, super precision, and allowing the listener to see the deepest layers of recordings, lose sight of the music as a harmonious, inseparable, flowing whole. In such cases, the presentation becomes a set of elements that function side by side instead of co-creating a larger whole. That is why, although, as I wrote, it was a slightly different, deeper look at some well-known albums, the presentation was still not only an interesting, exciting new experience, but also a fully engaging one, offering great satisfaction from communing with Music. Yes, that’s not a mistake, that’s a capital "M". Also with a capital "M" when played from non-audiophile recordings.

Just as many emotions coming from the perfectly conveyed pace and rhythm, from the great drive of electric guitars, power and high-octane energy, came from, for example, AC/DC or Metallica albums, and even from Iron Maiden’s. Maybe a bit more than with the SECOND, or the Shinai solid-state amplifier, with SIGNATURE I felt a certain roughness in the treble, maybe I was more aware that the midrange was not as clear as it could be, but it didn't really matter. The so-called fun factor of this music and its presentation was so high that it was easy to ignore the minor technical flaws of the recording and to drwa a "pure" pleasure from powerful rock guitars and vocals, accompanied by bass guitars and drums.


A DAY BEFORE FINISHING THIS REVIEW THE DESIGNER CALLED ME, trying to find out, without asking me directly, whether I liked the SIGNATURE. The question itself could be interpreted in several ways. Did I like it? - The answer was a resounding yes! This is an excellent amplifier, one definitely belonging to the high-end class. Is it objectively better than the SECOND? Again, yes! In almost every aspect of the sound separately it outperforms its predecessor hands down. Almost in every one, because, for example, this slightly smaller prominent display of tiny details by the standard version creates an impression of a bit better "flow" of the music.

If I could choose one of these two amplifiers for myself, would it be the SIGNATURE? - This is the first question to which the answer is not so clear to me. This reminds me a similar (also, unfortunately, purely hypothetical) dilemma regarding Kondo amplifiers - the top model KAGURA is an objectively better amplifier than the SOUGA, and yet I would choose the latter, precisely because of the fabulous fluidity and smoothness of the sound.

In the case of the Audio Reveal amplifiers, the answer would depend on whether it would come from me, a music lover or me a reviewer. As the latter, I would definitely recommend the SIGNATURE. As the former ... to be honest ... I’m not sure. For a long time it seemed to me that the more "general" sound of the standard SECOND fits my preferences better. It’s just that when I actually finished the listening session I wasn't so sure about it any more, because the so-called fun factor of the SIGNATURE is higher, while the SECOND sounds a bit more relaxed.

Fortunately, I don't have to make a choice for our readers - listen for yourself and make your own choice. Each of them can be a good one for you and will give you many years of beautiful musical experiences. In appreciation of the remarkable performance of this device we would like to award it with out RED FINGERPINT.

Technical specification (according to the manufacturer):

Type: Single-Ended integrated amplifier, Class A, dual mono
Driver tubes: 2 x 12AX7 (ECC83) + 2 x 12BH7
Power tubes: 2 x KT170
Frequency range: 20Hz-20kHz (±0.5dB / 1W)
Output: 21W RMS (8 Ω, 4 Ω/1 kHz)
Inputs: 4 x RCA
Input impedance: 50kΩ Start-up time: 60s
Power consumption: 240W Dimension (W x D x H): 476 x 410 x 220 mm
Net weight: 30.2 kg

Reference system 2021

1) Loudspeakers: HARBETH M40.1 |REVIEW|
2) Line preamplifier: AYON AUDIO Spheris III Linestage |REVIEW|
3) Super Audio CD Player: AYON AUDIO CD-35 HF Edition No. 01/50 |REVIEW|
4) Stands (loudspeakers): ACOUSTIC REVIVE (custom) |ABOUT|
5) Power amplifier: SOULUTION 710
6) Loudspeaker filter: SPEC REAL-SOUND PROCESSOR RSP-AZ9EX (prototype) |REVIEW|
7) Hi-Fi rack: FINITE ELEMENTE Pagode Edition |ABOUT|


Analog interconnect SACD Player - Line preamplifier: SILTECH Triple Crown (1 m) |ABOUT|
Analog interconnect Line preamplifier - Power amplifier: ACOUSTIC REVIVE RCA-1.0 Absolute-FM (1 m) |REVIEW|
Speaker cable: SILTECH Triple Crown (2.5 m) |ABOUT|

AC Power

Power cable | Mains Power Distribution Block - SACD Player: SILTECH Triple Crown
Power (2 m) |ARTICLE|
Power cable | Mains Power Distribution Block - Line preamplifier - ACOUSTIC REVIVE
Power Reference Triple-C (2 m) |REVIEW|
Power cable | Mains Power Distribution Block - Power amplifier - ACROLINK Mexcel 7N-PC9500 |ARTICLE|
Power cable | Power Receptacle - Mains Power Distribution Block: ACROLINK Mexcel 7N-PC9500 (2 m) |ARTICLE|
Power Receptacle: Acoustic Revive RTP-4eu ULTIMATE |REVIEW|
Anti-vibration platform under Acoustic Revive RTP-4eu ULTIMATE: Asura QUALITY RECOVERY SYSTEM Level 1 |REVIEW|
Power Supply Conditioner: Acoustic Revive RPC-1 |REVIEW|
Power Supply Conditioner: Acoustic Revive RAS-14 Triple-C |REVIEW|
Passive filter EMI/RFI: VERICTUM Block |REVIEW|


Speaker stands: ACOUSTIC REVIVE (custom)
Hi-Fi rack: FINITE ELEMENTE Pagode Edition |ABOUT|
Anti-vibration platforms: ACOUSTIC REVIVE RAF-48H |ARTICLE|

  • HARMONIX TU-666M "BeauTone" MILLION MAESTRO 20th Anniversary Edition |REVIEW|


Phono preamplifier: Phono cartridges: Tonearm (12"): Reed 3P |REVIEW|

Clamp: PATHE WINGS Titanium PW-Ti 770 | Limited Edition

Record mats:


Headphone amplifier: AYON AUDIO HA-3 |REVIEW|

Headphones: Headphone Cables: Forza AudioWorks NOIR HYBRID HPC