AUDIOMAGAZINE: S.A.Lab White Knight Integrated Amplifier

THE KNIGHT'S MOVE

Audio Magazine repeatedly investigated what from both an engineering and a musical point of view were very interesting S.A.Lab amplifiers designed by a Russian engineer Alexey Syomin. Grandiose three- and five-chassis amplifying edifices called Ligeia and Erato described in issues 105,107 and 108 (Erato was described twice) should be called masterpieces like we would for pieces of art or music. Those interested in the workings of Syomin regard him as a tube addict, especially vintage tubes plus their corresponding schematics and sound. So finally now as they'd say in a novel there's a twist in his fate. But is it relevant? We are about to find out.

Alexey Syomin's commitment to vintage tubes is known not only to Russian audiophiles. In 2010 several major internet resources published an article focused on this designer's specificity. Alexey told me that in his search for the desirable sound he fine-tunes his circuits carefully selecting components in accordance with their technical specs and musical signature, by paying special attention not only to the output tube but to the entire circuit down to the last tiny detail. It often seemed that when he talked tubes e.g. output triodes like 14D13 (Ligeia)? ГУ-80 (Erato) or his favorite 300B Alexey virtually anthropomorphizes them and keeps the entire tubes' harmony balanced the way a choirmaster or a conductor polishes the musicianship of his charges.

This time Audio Magazine presents his integrated transistor amplifier S.A.Lab White Knight. Our readers probably remember that the article on Erato (issue 107) mentioned the Knight's subsequent launch. As usual the very name creates a string of associations — with the polar nights in Saint-Petersburg (a pun of 'knight' and 'night'), with chess figurines, with Medieval History (White Knight of the Temple). But enough fantasies — Knights of the Temple came to a tragic end, didn't they? Besides for Alexey these connotations weren't intentional. Why White Knight? Because there was a Black Knight first. It's logical? Like one of the sequels to popular Twilight novels being called Breaking Dawn.

Late last year at one of Moscow's hifi shows Syomin demonstrated his transistor amp Black Knight. I didn't have the chance to get acquainted with it properly, so swiftly did it find a new owner. According to Alexey all Knights are identical from the schematic point of view. The differences are minimal and about the output transistors and other small things. And surely the armor is different. One is black, the other is white. They definitely don't look alike. At the S.A.Lab White Knight launch on February 7th 2014 there prevailed a club atmosphere unusual thing for such event). The amplifier showed with TAD CR1 loudspeakers (an exceptionally revealing combination!), Thorens TD-550 turntable, flagship TAD D600 CD-player and Studer A810 open-reel tape recorder. And we didn't notice people hurrying home to watch the opening of Sochy-2014 Olympics! Several days before this presentation I got acquainted with the amplifier tete a tete and talked to its designer. So, "who are these people clad in white robes and where do they come from?" (Revelation, 7:13).

Naturally I first of all asked Alexey why he decided to make a white knight's move away from tubesSurely that was just a temporary move. Unlike a transistor a tube presents him with wider creative opportunities. Let's be mindful that real engineers regard their activities essentially as a creative process. Almost any tube has some unique features and an interesting character unlike the pigmy transistor, a plain lump of silicon with one unquestionable advantage— a decent technical spec. In short, the opposition between tubes and transistors is linked to a fundamental hifi problem: has playback gear the right to express individuality or is it a prerogative only of music itself (what is permitted Jupiter…, or 'quad licet Jovi'?) Everywhere we notice the more or less audible echoes of this polemic, a sort of ideological tug of war on what is permitted or not and to what extent. As a result we get some 'not very tube-like' tube amplifiers, 'not quite transistor' transistor amps, not 'quite analogue' analogue components and digital machines that are not 'quite digital'. One of these 'not quite transistor' amps ('not quite' if you judge by its sound) is S.A.Lab White Knight.

At the dawn of his career as an audio engineer about 30 years ago, Alexey Syomin worked only with transistors. In his own words: "I remember that after testing a tube I realized that I'd found something with a really good sound. That's why for the last 15 years I simply didn't touch any transistors. Meanwhile I couldn't get rid of the notion that I'd left something undone, unfinished. 15-20 years ago Russian engineers were very limited in their choice of components. It was nearly impossible to create anything truly worthwhile. There were three or four kinds of transistors and that was that. Practically any tube sounded better and more musical. Now the situation is different. Semiconductors have made great progress. Their diversity is enormous and their quality very high. When transistors appeared by the end of 1950s and at the onset of the 1960s, the transistor schematics were similar to tubes. A transistor worked as a transformer for coordinating impedances between amplification stages. I'm well acquainted with the best amps created then. All of them were shit although there were some amps with interesting sound". Syomin concluded that each element in the circuit has to do only what it's capable of. The tube by its structural essence is best suited for voltage gain. It's not really capable of amplifying current properly. It amplifies voltage in a linear way and coupling transformers turn low input current into a high load current. "You have to agree that OTL amps never sound right. A tube can't get by without a transformer. Transistors work differently. When amplifying voltage they are crooked like a corkscrew because they've been created for current amplification". In Alexey's words this is the road to harmony, both technical and (what's crucial) musical. While designing White Knight it wasn't easy to design coupling transformers compatible with solid-state parameters. The key to solving this problem happened to be core iron from Japan. "At first it seemed to me that lower resistivity was the easy way to build a transformer. A totally erroneous conception! There are many issues but the proper opportunity arose with the arrival of suitable iron". And we must never forget about the quality of the parts. In the White Knight Alexey used compounds with various thermal conductivity. He compared the current modules of this amp with a generator in an atomic clock (long ago he created something of the kind for the government). "Exceptionally important was to sustain optimal temperature for a crystal or a component with the exact temperature you've calculated. I did it by using compounds with various thermal conductivity".

FROM OUTPUT TO INPUT

White Knight works in class А up to 40 W whilst its max power is 180 W and nominal power is 100 W. "It's commonly known that transistors clip rigidly once the signal exceeds a certain level. Why am I talking about 100 W of nominal power? Working with sinusoidal signal the amplifier produces undistorted 180 W (THD is less than 0,001%). But add 2-3 W and it starts clipping. These figures are for a 4-ohm of load. For 8 Ohm they are half".

The input cascade of the amp is class A emitter repeater driving a transformer. Then there is a more powerful intermediate stage driving a transformer and finally the output stage is another emitter repeater. Output transistors are Motorola MJ15025, two per channel. Stabilized power supply unit with a specially designed thermostable module also features Motorola components. There is no global feedback.

Knight's weigh is more than 60 kilos mainly because of numerous transformers. Eachchannel has interstage transformers of less than 400 W each. A kilowatt transformer works in the output stage. A 300 W transformer is in the input stage plus there isa transformer for servicing electronics and a mains transformer in the power supply. Each channel has capacitors of a total capacitance of 1 F. As a result the amplifier is very well armed with energy.

The schematic solutions are more or less clear, but how did Syomin developed the voice of the amplifier? Where did he start? "I began with the output stage. I've tuned it the way I wanted, then moved backwards watching for alterations to not change its character. In other words I was moving from output to input. The fine tuning included among other things the careful selection of components. For instance I first installed certain capacitors, but the amp didn't sound right. I put in other capacitors and the sound improved radically. I wound all transformers myself with Japanese iron cores. The transistors in every stage are of just one type. Resistors in the output stage are Riken Ohm; in the output stage they are Kiwame. The operational mode is established by AudioCore transistors of 100 W total power.

There are no printed circuits. Syomin preferred point-to-point wiring. He tried printed circuit board but didn't like the sound. Point-to-point wiring greatly complicated assembly to quarantee optimal temperature conditions for various parts.

ARMOR AND ARMS

The only control of White Knight combines three functions: volume (based on an array of resistors), input selection (push and rotate) and on/off (push and hold for 2-3 sec). There are two displays: the lower one (on the base) indicates actual main voltage (most of S.A.Lab amps tested by us have such a display) and the upper one displaying the level of actual amplification. Two dancing poles of plasma indicators above the tri-mode knob reflect the momentary level changes.

The main wooden carcass is manufactured by a profile treatment of super-thick stacked Plywood layers. On a larger scale we've already seen the same shape in Ligeia and Erato models. All surfaces and curves are faultlessly polished and decorated with transparent matte lacquer. The narrow front, rear and perforated upper panel are thick plates of stainless steel and polished. The frontal metal part is covered with a 10-mm thick glass rectangle. The monumental shape of White Knight is softened by a cheerful club-like glow of two displays and indicators, and light tones of wood are balanced by the coolness of glass and metal.

Beside 4 RCA inputs the engineer provided a line output, which by addition of another Knight helps organize bi-amp connection (control of two amplifiers by means of one amp).

FAITHFUL TO STYLE

I have to admit I began the listening test with a great degree of apprehension. I'm very keen on the S.A.Lab tube gear, but what to expect of an amp built on entirely new ideology? Nobody likes to be disappointed, and in creative work success is as common as failure. Moreover I'm well aware of the fact that my tastes in music are quite different from Alexey's. But it turned out that our hearing was similar.

At the beginning the amplifier drove Wilson Audio Sophia Series 3 speakers, then TAD CR1. The first combination was not entirely satisfactory so the latter one became the default because of its unquestionable advantages.

I'm perfectly well acquainted with the outstanding sound of TAD CR1 monitors especially with TAD electronics. So I was able to determine precisely the contribution of S.A.Lab White Knight. Fortunately my apprehension was groundless. This contribution turned out to be very substantial and positive. It was obvious that the desirable partner for this amp is exactly this type of extremely honest speakers.

As soon as I started listening, I got a feeling that the amp was very quiet i.e. noiseless. I immediately recalled the claimed 104dB S/N ratio. It was meaningful then that the buzz of a fluorescent lamp and some low frequency street noises quite unnoticed earlier started to annoy me. It was that very sound the English-speaking reviewers refer to as a completely black background. Usually our hearing doesn't identify the noise as such although our electronics almost invariably serve musical dishes with a touch of a subdued but discernible noise garnish. In this very rare case there was nothing of the sort. It was during the White Knight test that it occurred to me how greatly we tend to underestimate the audio system's ability to manipulate silence when operate on the verge of sound and silence.

Very few amps are capable of controlling the low register as successfully as S.A.Lab White Knight does in any dynamic mode (its damping factor is close to 1000!). I came to this conclusion listening to grandiose organ recordings saturated with complex bass notes and dynamic extremities. These recordings were Midnight at Notre-Dame and Requem by John Rutter (Reference Recordings, one of Robert Harly's favorites).

The amp has enough of 'smart energy' to reflect the macro dynamic relief of everu complexity level and frequency range. It also has plenty of delicate subtlety for ultra-detailed description of exquisite gracefulness of the musical filigree. The proof of it all was in the playback of the abovementioned 'Requem' and Dynaudio's CD Accentuations. Guitar Impressions.

I was pleasantly surprised that an amp that not built according to the company's primary tube ideology nevertheless had the unique Alexey Syomin sound which I've noticed before and described in my other articles. Its main unique features include the exceptionally expressive delivery and even the accent of melodic horizontals (the amp's singing is incredibly beautiful on the same level with the best tube amps and equally enchanting is the representation of vocal music. This never rigid but polished transparent sound has expressive and flexible colors and 3D signature with impeccably worked-out sharply graphic attention to details. It's a pity that the Audio Magazine test format doesn't give me an opportunity to tell about S.A.Lab White Knight twice or thrice as much…

SPECIFICATIONS [AS PUBLISHED BY MANUFACTURER]

No global negative feedback
Output power (max) 4/8Ω 180/90W x 2
Frequency response (±0.3dB) 10Hz—250kHz
THD (1kHz, 1W) < 0.001%
Signal/noise ratio (unweighted) 140dB
Dumping factor 950
Inputs analogue (RCA х 4)
Line output RCA
Power consumption (while signal is absent) 150W
Size 580 x 440 x 500mm
Weight 64kg

PRICE

600 000 rubles

TEST TRACT

Thorens TD-550 turntable
Studer A810 tape recorder
TAD D600, dCS Puccini CD Players
S.A.Lab step-up transformer
Audio Valve Sunilda Phono amp
TAD CR1, Wilson Audio Sophia Series 3 Speakers
S.A.Lab interconnects and acoustic cables

THE MUSIC

DISC 1 John Rutter. «Requiem. Five Anthems» (Reference Recordings RR57-CD)
DISC 2 «Midnight at Notre-Dame». Oliver Latri (Deutsche Grammophon, 4748162)
DISC 3 «Accentuations. Guitar Impressions» (Dynaudio)
DISC 4 Tüür. Symphony № 4, «Magma» (Virgin, 385785-2)
DISC 5 Debussy. Kate Royal (EMI, 394419-2)
DISC 6 Stravinsky. «Rite of Spring». Ivan Fischer (Channel Classics CCS SA 32112)
DISC 7 «Pletnev plays Schumann» (Deutsche Grammophon, 474 813-2)