In general the hype around the Arcturus tubes does not seem to live up to the reality IMVLE. I have heard at least three NOS/NIB variants of the blue glass 27 (including the nippled globe version) and none of them could hold a candle to a good RCA sonically speaking. Heartbreaking really.
Just my ill-informed opinion and YMMV.
Just my ill-informed opinion and YMMV.
I saw an experiment in a textbook once where they colored the glass of a old (evacuated) lightbulb permanently blue. The bulb was immersed in molten salt (cobalt chloride maybe?) and the filament illuminated. A negative voltage was applied to the filament and a high positive voltage applied to the molten salt. The negative filament charged the inside surface of the glass with electrons. The positive cobalt ions diffused through the hot glass toward the electrons. The glass was slightly conductive at the elevated temperature. After some lengthy time the glass was stained blue. The salt gets cooled afterwards and washed off with water.
No guarantee that it wouldn't crack the glass on an expensive tube though.
Much easier to just put a blue LED under the tube.
No guarantee that it wouldn't crack the glass on an expensive tube though.
Much easier to just put a blue LED under the tube.
Don't know about the 56, but the 27 has definite issues with filament to cathode break down so it certainly would not be a good choice for use in a cathodyne phase inverter.
A design like this would seem to be the right place for transformer phase splitting, and a 27 could drive a splitter transformer.
A design like this would seem to be the right place for transformer phase splitting, and a 27 could drive a splitter transformer.
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