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RE: Help identifying tubes

Hi Stian01 The 27 is an indirectly heated fairly low mu triode. It has a Unipotential Cathode which is the way tube development was going. For a single triode it pulls huge heater current. The tubes you show are both
ST glass - meaning not globular nor tubular. Earlier examples of the 27 and 45 would be made with globular glass envelopes in the same fashion as incandescent light bulbs of the time - late 20's. Try consulting the book Tube Lore by Ludwell Sibley. 45 Power Triodes were made in the millions for the exponentially growing home radio market. I would peg the year of manufacture circa 1933. The 27 follows the 26 in many many ways - another great voltage amp. The 56 is a close cousin too. Have fun and Happy Listening!


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