Вот выдержка из описалова по старой модели (топология не изменилась практически с тех пор)
The VK-50SE makes use of BAT's next-generation Unistage topology, said to improve power-supply management with higher-spec parts and better circuit layout. This reduces "phase shift, signal coloration, and distortions of multi-stage designs, while suffering none of the lackluster dynamics or component-matching problems common with passive designs."
Like BAT preamps of yore, the VK-50SE features a zero-feedback topology. Vishay bulk metal-foil resistors in the plate-loading circuit of the 6H30s improve resolution and lower the noise floor. The volume control uses an electronic shunt attenuator that "bleeds" some of the signal to ground. Only a single Vishay resistor per phase winds up in the signal path. With but a single component in series with the signal, the circuit is kept short.
The gain stage operates at a "truly spectacular" bias current of 150mA per channel. BAT points out that the output stages of many power amplifiers are run at far less. "Operating at this high current allows us to achieve a tremendous load drive without using cathode followers or buffers. The VK-50SE can source up to 40mA of signal current into a load—a feat normally reserved for power amplifiers and in sharp contrast to many preamplifiers capable of perhaps only 2mA or so."
Using the four sections of the eight 6H30s connected in parallel, one has, in effect, a tube topology yielding an amplification factor of 15, a combined plate resistance of 200 ohms, and a transconductance factor of 72mA. So the VK-50SE's differential plate-loaded gain stage delivers an output resistance of 200 ohms per signal phase and a load current delivery of 40mA. As usual at BAT, this is done without buffers and/or cathode followers.
Насколько примерно представляю, та же идеология по вдуванию тока в драйвере у Ламма ML3. А что, 6Н6П может столько же угля дать?