B+ voltage effect on tone

[EtherealWidow]

Nothing happens in a vacuum

When you change one thing, you change other things, too. To hear the difference made solely by output tube B+, you have to hold everything else not constant absolutely, but constant relatively: the screens, the bias, the AF peak of the signal at g1. In theory, if you keep everything in the same relative place, a change in B+ should produce only a change in output power (provided you keep the tubes in the linear part of the curve).

Right. So if one only fiddles with the B+, ignoring the volume, would the change in tone come mainly from the extra current following through the tube with the higher B+?

[Firestorm]

With cathode bias, the resistor compensates (to a point). More current tries to flow, but because it passes through the resistor, the cathode voltage rises, rebiasing the tube. With fixed bias, the higher current biases the tube hotter, putting more of the output in Class A territory. All things being equal, you should get the same sonic effect just by reducing negative bias voltage.

[EtherealWidow]

Alright. That's kind of the idea that I was going for. Well, as usual, thank you all. This has been educational.