Comment Re:looks like a hoax... (Score 1) 520
The little tubes are sometimes double valves - that is, there's actually two devices inside one glass envelope. At this scale, even 300V is too high. Typical small signal tubes will operate somewhere around 150V at low currents. As for an output transformer, they are typically used in the big power output stages. A small signal stage like this can be capacitor coupled or even DC-coupled (with some additional servo circuitry) without trouble.
It may not be a hoax, but it certainly looks like a cheap gimmick.
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