Заполните форму ниже и мы свяжемся с вами
Ваши данные защищены политикой конфиденциальности
To order
Write the form below and we will contact you
Your data is protected by the privacy policy
AUDIOTECHNIQUE: Повышающий трансформатор SUT K25

NEW PUBLICATION / 28.04.2022
AUDIOTECHNIQUE: Step-up Transformer SUT K25


SALON AV: S.A.Lab White Knight Integrated Amplifier

April 09, 2022
Article on the reviewer's resource

Alexey Syomin's Sound Analysis Laboratory (S.A.Labs), the reputable designer of leading‑edge power amplifiers, has engineered a completely new amplifier on SIT-transistors, which we decided to put through a test. These are very unusual devices that combine the characteristics of silicon and electrovacuum devices. The model we tested is not spectacular in terms of power, but in designing this project, the main attention was paid not to quantitative indicators, but exclusively to the amp's ability to deliver wonderful music.

This unusual circuitry in a traditionally uncompromising implementation is a promising suspense debut!


Alexey's constant experiments with circuitry and dogged listening to numerous experimental options sometimes lead him to very unexpected projects. His arsenal includes not only tube amplifiers (most recently we listened to samples of the Thunderbird series), but also on various transistors — germanium and silicon, including bipolar, MOSFET, and so-called Static Induction Transistors (SITs). The reason for this diversity is his search for the sound Grail, the very sound that can convey music in such a way that the listener gets a tingling sensation. Each technology has its advantages, and I must say that Alexey leverages them to the maximum effect.

«2P926A are the first Soviet silicon devices, capable of operating in bipolar field mode.»

The same applies to SIT transistors, which are used as output in the White Knight. 2P926A are the first Soviet silicon devices capable of operating in a bipolar/field mode. They are made in a standard TO-3 package, capable of dissipating 50W of continuous power and up to 250W peak at a drain current of up to 16.5A. The supply voltage is up to 450V, and at the same time, the 926s have triode current-voltage characteristics. That, in fact, is like a tube triode in a transistor case. The output stages on SITs clip softer, with a shorter tail of hard HF harmonics. On such transistors, linear circuits are obtained without a common feedback, as, in fact, was done by the White Knight.
Generally speaking, it is possible to build both a 200 and a 300-watt amplifier on 2P926A, but the power source will be so huge that it will not be possible to fit into the dimensions acceptable to most users. Therefore, it was decided to limit the power to 2 x 30 watts, giving these watts the highest possible quality. And at the same time, the power here is mighty: a pair of 200-watt transformers (a real double mono!) And 10 capacitors of 22,000 mF for energy storage.

It is curious that the White Knight output stages, at the request of the customer, can be built not only on SITs, but also on germanium transistors or on metal–oxide–semiconductor field-effect transistors (MOSFETs). But, as it turned out during the auditions, 2P926A work better with acoustics that have complex crossover filters. There are a lot of these on the market, so the basic version of the amplifier is produced on the 926s.

«The power here is mighty: a pair of 200-watt transformers (a real double mono!) And 10 capacitors of 22,000 microfarads for energy storage.»

The K504UN2 chip is responsible for pre-amplification, in which there are several stages on field-effect transistors. It is used in many S.A.Lab products, including phonocorrectors, because it has a low noise level and a pleasant sound signature.

The White Knight model belongs to the Performance series, in the manufacturer's catalog it is a step above the budget Entry Level. And, as I have repeatedly noted, even in medium-level equipment (by the standards of S.A.Lab), most of the components are either of their own manufacture (mainly transformers), or custom-made at military enterprises.

Input switching is sufficient for a system with any architecture — three RCA line inputs and two XLR. There is a line-out recording output, as well as a 6.3 mm headphone jack. The 12V trigger input and output will enable the amplifier to be included in an automated home system.
The signal from balanced sources is fed to the own manufactured input transformer with silver wire windings. Volume control is implemented on a relay and a set of custom-made tantalum resistors with low tolerances.

The adjustment step is 2 dB, the set level (remote control is also possible) is highlighted by red 7-segment indicators. In addition, an overload indication is provided separately by the channels.

A potential buyer can choose not only the type of output transistors, but also the finish of the case, which can be painted in any of the 12 branded colors of Ferrari. The quality of the lacquer coating is impeccable. The front panel is made of polished artificial stone.

For our system testing, we used an Avid Acutus Classic vinyl player with an expensive MC head, the signal from which was fed first to a step-up transformer, and then to S.A.Lab Lilt Phono, a two-stage phono corrector. The [acoustic] load is the well-known Magico A3 acoustic systems connected by S.A.Lab cables with conductors consisting of 10,000 thinnest copper cores.

«In general, the sound impresses with its openness and clarity, it seems to have been cleaned off throughout the entire spectrum.»

To try it out, I put a couple of tracks from the Leftfield disc [1] — a mixture of progressive house, hip-hop and synthpop with a powerful bass component. With insufficient damping of the diffusers, the bass seems bloated and blurred, like a cloud, which is what I was afraid of. In our case, everything turned out to be much more interesting — the low synthesized notes acquired such a clear structure that the enveloping atmosphere that almost always occurs when playing this disc disappeared. Therefore, there is no heaviness in the sound, and the tonal balance does not seem too dark. Percussion sounds are transmitted sharply, in full, with "meat". And this is despite the fact that Magico A3 has fourth-order separation filters, i.e. the load for an amplifier without general feedback is not at all simple.
In general, the sound impresses with its openness and clarity, it seems to have been cleaned off throughout the entire spectrum. And, with a relatively low output power, it does not seem boxed in, i.e. limited in dynamics and space, solid floor-standing systems form an impressively large-scale picture with graceful transitions from quiet fragments to peak levels. This is especially noticeable in classical music [2] - the power of a symphony orchestra, in the sound of which the real range of instruments and the finest dynamic drops are conveyed.

«Our current test-object behaves selectively - it renders music carefully, accurately, and as if it were personally for each listener.»

If we compare the current impressions with the impressions gained from Thunderbird tube sets we recently listened to, then the White Knight sounds a little more transparent and contrasting in the upper band, and, if the tube-set literally covered the sound, then our current test-object behaves selectively - it renders the music carefully, accurately, and as if it were personally for each listener.

Moreover, the genre, as such, does not really matter - the ability to show all the nuances without mixing them into a mess favorably affects the perception of even the most brutal trends. The ease of perception is due not to the fact that the amplifier does not draw on the power component (it draws even more!), but to the presence in its sound of a light silvery touch in the upper middle and in the full tweeter band. What's more, the tonal balance does not lighten, and the emotional intensity does not weaken — heavy rock does not lose its gravity, and Bonham's drums pound on the "Heartbreaker" [3] until the ears are blocked up.

And at the same time, there is a lot of freedom in the sound, it is open, one can feel the desire of the system to show harmony, and the beauty of music with a powerful reliance on a low-frequency foundation is also felt. This makes the listening process look like watching a real event that was previously recorded on a media.

S.A.Lab (Russia)
Circuit design: push-pull, class AB
Analog inputs: 3 x RCA, 2 x XLR
Analog outputs: Record, acoustic screw x 8
Amplified frequency range: 20 Hz - 200 kHz (+/- 0 dB)
Output power: 30/50W (8/4 ohms
Harmonic distortion: <0.01% (50% power, 1 kHz, 6 ohms)
Signal-to-noise ratio: -105 dB
Nominal sensitivity: 1, 4 H
Finishing: artificial stone, car enamel 12 colors from the Ferrari catalog
Dimensions (W x H x D): 480 x 175 x 500 mm
Weight: 25 kg
Price: 480,000 rubles.

The editors would like to thank the Music House salon for their help in conducting the test

• Avid Acutus Classic Turntable
• Lyra Etna Lambda Head
• S.A.Lab STK-1 Step-up Transformer
• S.A.Lab Lilt Phonocorrector
• Magico A3 Speakers
• Cables: S.A.Lab

• Leftfield, «Leftism». 2 LP Columbia, 2005
• Peter Tschaikowski, «Der Nusknacker. Eterna», DMM, 1985
• Led Zeppelin II. Atlantic Records, 1969
• Van den Hul, «A Tribute to Analog». Carbon Recording, 2008
• Creedence Claerwater Revival, «Creedence Gold». Liberty, USA 1970