HT40 bias

[DreamTheater]

Does everyone bias their HT40 when changing power tubes? Or do you just plug and play. What results have you got going either way?

[thephantum]

It will need to be biased. Can you get away with not biasing it? Maybe. But you are playing Russian roulette with the new tubes as well as your tone.

Don't ask what bias should be set to because there is no such thing "standard setting". It is just like any other Class AB amp in a push-pull, fixed bias config: You need to measure plate, calculate bias, adjust it and repeat a few times until the amp is dialed in. You can use the cathode resistor or OT shunt method.

[8len8]

Yes, re-bias.

[Sonico]

I changed power and preamp tubes in my HT40 about a year ago and didn't rebiased because I don't know how.
My amp sounds beautiful since the change. Maybe Iam lucky!