Other tubes favoured by Alexey are (in his own words) "the 6L6, EL84 and GU-80". About the latter he says that the "300B’s sound signature is very similar to the GU-80 but the 300B is easier to implement because the GU-80’s voltage is nearly 1kV whilst the 300B’s 450V are less than half." Various ley lines of fate, mind and heart drawn by me seemed to logically lead to the 2014 appearance of an amplifier with a 300B triode helming its tube set (it acted as output tube). This single-ended aggregation was coined simply 300B SE. By the way, a push-pull variant called 300BPP also arose. Alexey Syomin explained the main stimulus for designing a single-ended amp based on the 300B in several short phrases (short if we omit his words of love over this tube). He said: "Usually the 300B serves as the foundation for a small minimalist single-ended circuit with 5-7wpc aimed at sound connoisseurs with hyper-sensitive speakers. I decided to design a much more powerful device and run each channel with three output tubes connected in parallel but working in single-ended mode." The result was an amp with 25wpc into 8Ω but a switchable output-transformer mode by way of a rear-panel toggle which can increase this rating to 35wpc.


In his 300B SE, Syomin installed fresh 300Bs manufactured in the Russian city of Saratov. "I’ve compared 300Bs from Saratov with samples by Western Electric and found that the Russian tubes can on average generate 5 watts more power. It’s rather difficult to parallel Western Electric tubes in triplets and the cost difference between the vintage American and current-production Russian tubes is simply astronomical. Anyway, the quality of modern tubes from Saratov is very high both objectively and subjectively." In accordance with the designer’s ideology, the other tubes in the 300B SE amp are of the vintage NOS kind. In his 300B SE amp, Alexey realized the Lofting-White circuit named after engineers who published its description in the Radio News magazine at the end of the 1920s. This circuit stipulates three amplifying stages — an input, a driver and an output block. The most important feature of the S.A.Lab 300B SE is that all connections between tubes and stages are direct-coupled to eliminate signal-path capacitors. This decision required a large number of tube stabilizers, six per channel. The input stage is based on the 1967 Philips EL803 pentode in pentode mode. The driver’s heart is a 1959 Telefunken EL84 in triode mode whilst two trios of 300B connected in parallel work in the output stage.


As usual, our engineer paid great attention to his output transformers because he regards their influence on the sound as paramount. "In this respect we conducted unique research" was all he said without further elaboration. It must be pointed out that Alexey rarely uses the term 'unique' in connection with his own work though many things he does really are unique (i.e. thermo-stable transistor modules based on compounds with various heat conductivity in the White Knight; or a DAC based on a fully discrete circuit to be reviewed by Srajan later this year).


The output transformers use П-iron cores with metal imported from South Korea. Those are wound in a so-called ‘galette’ fashion with four galettes of nine sections. Each OPT exceeds 50kg which results in a prohibitively massive 150-170kg final weight. I frankly couldn’t move this amp across the floor by even a fraction. The 300B SE consists of two chassis: the amp itself and a power supply disguised as a quasi monoblock of the same size but considerably lighter. It only provides the supply voltages for the amp and serves no other purpose. One output stabilizer per channel is implemented with a 6C33C whose driver is an EC360. The input tube is stabilized with an SG4 stabilitron. The ground feeder supplies use 1967 French VR150 stabilitrons.


In his top class amps—and the 300B SE is undoubtedly one of them—Mr. Syomin always provides for separate anode/filaments circuits. Hence each channel of the 300B SE gets separate anode transformers. All stages are DC powered and stabilized with in-line chokes. In toto there are 10 chokes and 8 filament transformers. The anode voltage rectifiers are based on high-voltage Schottky diodes, each having two chokes in the power circuit. Therefore the 300B SE’s size and weight are caused by this approach to circuit realization and power supply schematics which should be quite close to no compromise. Alexey made it possible to switch off the tube heaters by means of the first of two switches on the rear panel (the remainder of the circuit remains in working mode). It’s also possible to turn the amp off whilst leaving the tube heaters on to keep the amp ready for immediate use. The second switch changes the transformer mode (25/35 watts). Outwardly the 300B SE has much in common with the other high-level SA Lab models of Ligeia, Erato and White Knight. They all use enclosures of the same shape. Only the size differs. Here the 300B SE slots between Erato/Ligeia and White Knight but closer to the former two. These cabinets stack horizontal Ply layers which lends itself to complex cross sections. Surfaces are subsequently polished and varnished in matte lacquer.