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

Until I started this test I was sure that any attempt to find a new way of designing a transistor amplifier was pointless. Reasonable specs were achieved long ago and it would be impractical to improve them for they are high enough to make further designers' efforts simply inaudible.

In my opinion here lies the deadlock of transistor schematic: designers change feedback depth, find faster semiconductors, increase energy input of power supply; they try out differential stages, current mirrors or 'broken' cascodes… Surely all these measures yield some result but for most listeners it's not perceptible. So is there a way out?

Alexey Syomin, founder of S.A.Lab, thinks the problem to be caused by the initially misguided approach to design. "Unlike tube, transistor amplifies current not voltage, — he said presenting a pre-market sample of White Knight integrated amplifier. — The main feature of this amp's schematic is the absence of amplifying stages in the ordinary sense of the word. Signal path consists of several emitter followers which amplify only the signal's power; its amplitude is 'accelerated' by several coupling step-up transformers with 5Hz–300kHz of bandwidth.

Output module is a one-piece casting radiator encasing a powerful follower based on 24 Sanken transistors. 18 of those create output signal and the rest regulate current, temperature and other operating parameters. Transistors are mounted on the radiator via beryllium oxide washers; the other elements are encapsulated in a heat-conducting compound and are heated while working (resistors are heated to 30o, electrolytic capacitors — to 50o, transistors — to 60o). Capacitors are heated to increase the speed of carriers (ions) flowing between plates. Amplifier with output of up to 20W works in Class A which provides the heating of circuit elements. All in all 6 kilos of expensive German compound are used for building a single amplifier.

«Signal path consists of several emitter followers which amplify only the signal's power; its amplitude is 'accelerated' by several coupling step-up transformers with 5Hz–300kHz of bandwidth»

Input module has similar architecture but on a smaller scale. The stages are coupled via step-up transformer with 1:4 coefficient. The input follower is terminated on 1:8 transformer. Thus total gain amounts to 32. In all fairness I must note that similar schematic was used by Bob Carver in his amps designed as early as 1970s.

Apart from coupling transformers the amp features four substantial toroidal transformers that provide separate feeding not only for each channel but also for each «+» and «-» bus. They are wound by precision machines to ensure the absolute equality of voltages in symmetrical shoulders. It's obviously a costly solution but it guarantees better elimination of power line interferences than the traditional ground-center tap design can ensure. Besides, double mono design with complete channel separation is noted for high level of crosstalk attenuation which enhances stereo imaging and clarity.

«Double mono design with complete channel separation is noted for high level of crosstalk attenuation which enhances stereo imaging and clarity»

Three line inputs are switched by hermetically sealed relays which have passed military formal acceptance. Ensured are speaker protection and Direct mode in which #1 input signal bypasses volume control unit. This mode provides for possible integration into home entertainment system with AV-processor or pre amp.

This device has standard size but its unique schematic stipulated for a record weight of 65 kilos.

While we were talking with Alexey and taking photos the amp was working in the background at several output Watts. Had I not been already acquainted with its architecture I would have definitely called it a tube single-ender comparable to Audio Note of the fifth level: the sound was neat, transparent, detailed and very musical. Undoubtedly White Knight doesn't exhibit a single trace of notorious 'first Watt' problem despite the fact that working with 4Ω ProAc Carbon Pro 8 speakers it can produce up to 360W. Intrigued, I changed volume level several times but it affected only dynamic range — the stage remained rock-solid retaining all timbres and nuances. Just for the sake of argument turn the volume handle on your amp and starting from some point you'll most likely note that aftersounds and small details tend to vanish making sound plain and bland. If this is not the case you've chosen a proper amp.

«Undoubtedly White Knight exhibits not a single trace of notorious 'first Watt' problem despite the fact that working with 4Ω ProAc Carbon Pro 8 speakers it can produce up to 360W»

Now we set the system volume to level optimal for the listening test — a bit short of creating discomfort caused by excessive sound pressure. And I must admit that there was almost no change to sound — with the exception of overall dynamics. Detail and musicality remained with no aggression in the upper region — despite the fact that ribbon tweeters tend to highlight even the tiniest of distortions.

The Knight's drive is truly gargantuan; electronic bass is conveyed in such a way that diffusors really start driving the room. Meanwhile the amp doesn't underline the lower register thereby widening soundstage and adding spaciousness to it.

«Transitions from piano to forte, from complete silence to peak sound amplitude were so natural that some chamber recordings closely resembled live sound»

Some audiophiles claim that transformer coupling circuit better translates energetics and drive, and I can readily agree with that. Transitions from piano to forte, from complete silence to peak sound amplitude were so natural that some chamber recordings closely resembled live sound. Yes, at high volume levels and while playing back complex tracks the upper midrange exhibited signs of slight intermodulation but it was probably the only flaw I've noticed. On the whole the specter of musical instruments — both acoustic and sampled — was conveyed with extreme neatness and credibility.

In our case the construction of audio stage depended exclusively upon speakers' dispersion and their interaction with the listening room acoustics. In this respect the amp, being intrinsically precise per se, gave its entourage a complete freedom for shaping and placing sound images.

Inputs: 3 х RCA || Input impedance: 10kΩ || Output (1kHz): 2 х 180W (4Ω), 2 х 90W (8Ω) || Input sensitivity: 0.707V || THD (50% output): 0.03 % || Signal/noise ratio (unweighted): –106dB|| Frequency range (±0,1dB): 20Hz– 34kHz || Consumption: 410VA|| Size: 190 х 460 х 460mm|| Weight: 65 kilos|| 2-year guarantee|| Price: 480 000 rubles.