6MOONS: Integrated amplifier S.A.Lab Black Knight

Viacheslav Savvov
Artjom Avatinjan
September 03, 2018
Article on the author's resource

I have been following the progress of S.A.Lab, a Russian audio manufacturer, for a long time and with great interest. This reflect in numerous reviews I did for our national and these international media. Several S.A.Lab reviews published here at 6moons, most of them by me, some by Srajan. The first S.A.Lab component we reviewed was in December 2013. That was the Erato, ambitious on sound, weight and sight by being a massive 5-piece amplification combo. The majority of reviewed models had tubed schematic because those dominate the brand's portfolio. Exceptions are the 1st and 2nd generations of the White Knight, a pure transistor device. Today Alexey Syomin's Sound Laboratory offers the 3rd generation White Knight in hybrid tube/transistor circuitry and dual-mono architecture.
The object of today's review is the Black Knight integrated amp. In my opinion, it might be one of S.A.Lab's most significant achievements. That's because it remains virtually the only high-end hifi amplifier in formal production whose every stage uses Germanium transistors. Yet Alexey hasn't betrayed himself. We are familiar with his predilection for vintage parts whose advantages to him are indisputable. Until now this conviction and related engineering principle manifested mostly in his choice of rare tubes like the Ligeia's 14D13 or the Erato's ГУ-80. With his Black Knight, Alexey made the proverbial lateral knight's jumping move by implementing not another vacuum tube but rare transistors. In the past S.A.Lab produced amps of similar names but the White Knight's black brothers in arms then were more test projects which I never had a chance to see or listen to. Today's version is a formal production model.

Alexey tried to approach Germanium for a long time. His work on the current Black Knight—contemplating its circuitry, designing and prototyping its construction—took him about three years. Obviously his brain started working on it long before that.

What then is special about transistors based on the 32nd element of the periodic table? I'm writing these words whilst spotting among the neighboring hills out of my window the village of Boblovo where Mendeleev's estate is still intact. The legend says it was here where the famous chemist created the table introduced to him in a dream as a kind of solitaire. Alexey talks at length about the advantages of Germanium over silicon, about tube-like distortion and soft clipping. Comparing Germanium to silicon, chemistry experts would analyze sundry physical properties, the number of atoms across a cubic centimeter, the electrons' mobility, the carrier lifetime and more.

More significant to Alexey were the aforementioned 'tube' properties and associated musical advantages of Germanium. He explains the modern audio industry's lack of interest in these parts as being caused by the scarcity and high cost of Germanium transistors in the West whereas in Russia they are common and inexpensive; and by problems related to obtaining substantial output power. Germanium-based amps are inevitably rather expensive and manufactures are used to the fact that an expensive amp must be a high-power amp. Exceptions merely prove the rule. It's common knowledge that Germanium transistors' significant flaws compared to silicon equivalents are low current limits and approximately 50% lower operating temps. Alexey quipped that "the transistor is carried away to Germanium Valhalla as soon as its temperature reaches 80°C." Hence the difficulty to obtain what by high-end standards would be considered decent output power; and the high cost associated with each watt.
In hifi, Germanium gave way to more promising silicon parts about a half century ago. Production of Germanium parts closed down at that time and wasn't revived thereafter. Unlike vinyl, Germanium didn't experience its renaissance. Yet in the USSR, Germanium transistors continued to be manufactured until the beginning of the second Millennium. Hence their supply remains almost unlimited and cheap. To match pairs for the output stages of his amps, Alexey easily acquired 2'000 powerful 1T813 transistors. Four work per channel, two in each half of a push-pull class AB topology. The output cascodes with independent sub-cascode feeds, the phase inverter and driver stage all use Germanium parts. The 1T813 output stage in common collector mode and at 1A of current produces 50 watts into 4Ω. A twice as powerful version with a different circuit is already on the drawing board but considering the size and weight of the current unit, you already appreciate the price/power conundrum of the Germanium proposition.

The upper -3dB bandwidth is 200kHz, THD at half and full power is 0.03/0.1% respectively. Class A bias carries the first 18 watts and the schematic uses no global negative feedback. The circuit topology is true dual mono including the ground planes.
Each channel's power supply runs off its own 360VA toroidal transformer. A bank of 80'000µF smoothing capacitors sits in each branch of the push-pull circuit to add up to 320'000µF in total. That level of reserves precludes the need for voltage regulation.
Bearing in mind the current and temperature limits of his Germanium parts, Alexey paid utmost attention to circuit stability. For this purpose the Black Knight uses passive and active means. Current and temperature are controlled by an Arduino microprocessor. 5kg/ea. heat sinks flank each cheek. The chassis measures a bulky 48 х 310 х 50.5cm and a solid 29kg. Through the plumage-like slits made from thick steel plate, heat fins are visible. During our test with dynamic music at high levels, these hit about 40-45°C.

The inputs and volume control all switch by relays, the latter emit subdued clicks when prompted by the supplied remote wand. 4:1 RCA:XLR sources are supported and a separate direct input bypasses the attenuator. Large binding posts for spade terminals are designed and manufactured by S.A.Lab from silver-clad copper. The front panel features the traditional tri-function power/input/volume knob whose central eye confirms the volume level and input name whilst switching. Direct mode is activated with a touch-sensitive button. During power up, the display momentarily reads Pr-L and Pr-R to indicate that the circuit ramps up and DC protection is in place. An unusual feature carried over from previous S.A.Lab models is an hourly usage counter on the back panel.
The steel enclosure and Corian front panel are painted in one of twelve colors from Ferrari's automotive lacquer palette. Application happens in Moscow's Ferrari service center. The blue color of the test samples was Ferrari's Blue Tour De France. Its intensity greatly varied with lighting and viewing angle to change from light blue to indigo to almost completely black. Regardless, it's the Black not Blue Knight though actual black too is on offer. Being an experienced listener, I have the following personal rule. To estimate the sound of an audio system or single component, the first few minutes of the audition are the most important. Naturally some subtle nuances may reveal themselves hours or even days later but as I learnt long ago, the core qualities become clear immediately. Consciously or subconsciously, many experts follow this rule. For instance, while demonstrating a system at an audio show it's important to realize that one only has minutes to 'hook' a customer and therefore must use only the most effective tracks.
During my conversation with I.P. Veprintsev, chief sound engineer for the Melodya record company where he produced a lot of the most treasured works of classical music from the USSR and Russia, predominantly from the symphonic repertoire on LP, I received authoritative affirmation of this rule. Freely communicating with his wards in the studio at other times, Veprintsev demands absolute silence during the first minutes of sound balancing which he regards as crucial. He told me that our hearing is at its most acute and accurate immediately after a period of rest and just minutes later the probability of hearing errors multiply. Let me remind you that this came from someone whose hearing was regarded as golden by such musicians as Gennady Rozhdestvensky and Rodion Shchedrin.
The minute the audio system featuring S.A.Lab's Black Knight began playing, I heard sonic harmony of rare quality. I was instantly charmed by an uncommon level of neutrality yet my attention wasn't attracted by purely acoustical or hifi qualities. Few components are capable of creating such beautiful natural images. I immediately distinguished the exclusiveness of the audio signature which, given my familiarity with this catalogue's tube specimens, had to be the Germanium transistors. There was something absolutely special to this sound. Amongst sundry criteria used for sonic evaluations, I can use two to describe the Black Knight's style in the most precise way. The first one is accuracy or strict adherence which, unlike bench measurements, is a subjective response to music; and the second is the sonic aesthetic per se. The balance between these two is important in many ways including live concert practice.
Numerous performers are known to prefer musical instruments with specific sonic qualities. For instance, Richter loved the rather bland even slurry sound of Yamaha's grand pianos. In his opinion, the beauty of a piano's timbral palette was not to overwhelm his interpretation. Sofronitsky liked the rich sound of old Bechstein pianos manufactured before WWII. Violinist Vadim Repin once told that me he played Guarneri because its timbre was more neutral than that of a Stradivarius.
The mentioned features placed the Black Knight's sound in a personally ideal balance. Listening to piano, I experienced the depth and beauty of timbres, the spaciousness of images, the natural subtle detailing caused by the piano's mechanical parts whilst I was imbued by the essence of music and its interpretation. With comprehensive clarity, I understood the musical structure, timbre varieties and dynamic relief of complex orchestral scores like Stravinsky's Le sacre du printemps or Boulez' Pli selon pli. Whilst its modest power rating won't fire up one's imagination, the amp demonstrated absolute dynamic freedom in a 40sqm room on 96dB speakers. Here it never occurred to me that I might hit actual dynamic limits. Nabokov once wrote "does there not exist a high ridge where the mountain side of scientific knowledge joins the opposite slope of artistic imagination?" It's this slope of artistic imagination or reality that I used to glide along when enjoying music played back on the S.A.Lab Black Knight. Working with the spatial aspects of a particular track, the Black Knight adequately restored the size of a grand piano to more modestly occupy the center of the soundstage, a fiddle or sax never exceeded their sizes whilst a pipe organ seemed to take up all available space and still more just as it should be.
Control of the lower registers left nothing to criticize. This was proven by the bass section of a big symphonic orchestra, cannon shots of large drums and brass, the almost tectonic rumble of 32-metre organ pipes. However, I never perceived this bass as a separate quality. It was an organic part of a complex musical organism. After listening to many diverse tracks, I will summarize the most important feature of the Black Knight as being its ability to extract and sustain from any record its encoded artistic energy at a high level. This helps our natural concentration not on audiophile but musical qualities. Our emotions are excited, we can't help but think about the person who created the music we're listening to, its unique interpretation, its style and milieu. The sound convincingly combines premium features of tubes and transistors. It delivered the exquisite plasticity of music lines, shone a warm light from within and gave precedence to the horizontal dimension of melodious unfolding as a signature trait of S.A.Lab. But it also delivered speed, detail and substantial perfectly controlled bass impact.
I thus conclude that Alexey Syomin's three years in the virtual wood shed of his lab helped him master the unique potential of Germanium transistors. Here they are elevated to perform on an ultimate high-end plateau to seemingly exercise their voice to the fullest. One might call the Black Knight sensational but that would smack of hype. I prefer to say that I perceived it as less an electronic means of sound amplification and more like a musical instrument like those crafted in the Leipzig or Cremona workshops of yore.

Artjom Avatinjan

S.A.Lab (Russia)
S.A.Lab Black Knight