Interesting tube - Type 49

[Mick Bailey]

Quite a few years back I built a really neat regent radio using the Type 49 tube as a detector/amplifier. I had a real interest in battery powered tubes, especially how they were exceptionally good for space-charge operation. I wondered why such tubes never got picked up much for low voltage guitar use - preamps, overdrive etc.

Anyhow, the Type 49 is interesting because it's a triode with two control grids. That's a contradiction, I suppose. So with four elements is it a tetrode? Maybe, in the Latin sense of the derivation. I don't think this arrangement of two spiral control grids survived as far as I can tell. With 9v operation it can drive medium impedance headphones directly, the gain control being by varying the heater voltage.

Maybe interesting things can be done with this tube - it's on my endless list of things to do.

[mozz]

No 49er's here but have some type 75 with sockets, which appears to be a single triode with a gain of 100. One day when i find the right chassis and power transformer, i'll string up 6 of them to simulate 3 12ax7's and find a suitable output pentode with a few watts.