• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Quiz: which tube is this?

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So....Gurus and others.
1. Which tube do these curves belong to?
2. Do the curves indicate a linear tube?
3. Would you use it for a PP amp or a SE amp?
 

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Looks like you only have 20 Volts of grid change on that earlier plot. Here's the rest of the curves:

Plotting most any load line on them shows a 2 to 1 change in gain from one end to the other. Umm... 100 % distortion? Probably work OK in P-P though, where all that 2nd Harmonic would cancel.

edit: added curve trace of a low distortion triode for comparison (not a 300B, this only costs $3)
 

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OH, sorry. I think a 2 to 1 gain change is more like 20-25% distortion in class A.

That's at max amplitude of course. The dominant 2nd H distortion varies quadratically with amplitude below that. Would have to hit the books and a load line on the curves to calculate it the precise way from tangents/chords and all that.

2nd harmonic would cancel out in P-P anyway.
 
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