What the heck is bias anyway?

Bias is the power put into a tube to push the electrons across the vacuum in the tube.

I hate to keep picking on you; but once again a technical explanation that is just too wrong to ignore. It is sort of, kind of, talking about what is happening but it is in a nutshell... wrong. I don't understand why you continue to jump in offering technical explanations about things you obviously don't completely understand.

It doesn't require a 12 page essay but it does require something that is correct, The following one sentence explanation is correct.

Bias is simply a voltage applied to a tube to control how much current flows when it is idling.

To say "power put into a tube to push the electrons across the vacuum" is flat out wrong. First of all it is not power, it is a voltage; they are not the same thing; and it is the voltage from Plate to Cathode that pushes the electrons through the vacuum not bias; bias controls how much can get through.

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It wasn't "oversimplified." It was wrong. There is a difference. It is possible to put things in layman's terms without being wrong.

If I post something that is incorrect I hope someone jumps in and corrects it. People come her to share and learn. That is impossible if we allow errors to go unchallenged.

If Elizabeth enjoys posting misinformation as she says and that makes her feel smug then this forum is worse off for it.

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how the sound will be impacted? Will I get louder? Or does it allow to get louder? Will I get more bass? Does it related to the power rating in the specification?

The bias sets the point where the tube idles. When you apply a music signal the amount of current increases and decreases. Lets say for max power the current needs to swing plus and minus 40 mA from the bias point. If the bias current is set too low (say 30 mA) then it won't be able to make a full swing down since it wants to go down 40 but will hit zero and clip before it gets there. Even if you don't hit the zero point the tube operates in a non linear manner as it approaches zero so anytime you get near there distortion goes up.

If you set the bias current too high you might hit the limit on the plus 40 swing and clip, but even if you don't the tube will run hotter than it needs to at idle and shorten its life.

So you want to set it where it can make a full swing in both directions without running the tube too hard or swinging down into the nonlinear area near zero.

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