How does a Bassman work..........

[fingers23]

.................Well really the volume pot...........

Is the power tube always cooking at the same level and the volume controls the the input signal to the preamp tube (which of course changes the input to the power tube)?

Therefore.........Is turning the amp down & turning the level up on a boost pedal essentially the same as turning the amp up & turning down the level on the pedal?

OR

Does the volume control the level from the pre amp to the power stage and it is the tubes that are variable.......

.........In other words...is the volume control before the pre amp or between the pre amp and the power amp?

I think I know what I am trying to ask.....

[Chris Callahan]

I glanced at a 5F6A schematic and it looks like the volume is after the first tube stage and before the second. So I would say in the middle of the preamp.

[sjhusting]

A guitar signal is relatively weak, and you will almost always see at least two preamp (gain) stages in a guitar amp, and as many as perhaps 5 or so (gonzo high gain amps). The volume control is between the first and second preamp stages in a bassman. It attenuates the input into the second preamp stage. The power stage is essentially running full out all the time.

The second stage is followed by a cathode follower, which presents a low impedance to the tone stack. A cathode follower has at best unity gain, so it does not perform any amplification. Tone stacks are a major source of signal loss, and a low impedance output into a high impedance input minimizes voltage loss.

The tone stack is followed by a phase inverter (a "long tail" phase inverter) which feeds the signal to the power stage.

Hitting the first stage hard with a booster will sound different than hitting the second stage hard with the first stage. So is it the same? well, yes, sort of, on a conceptual level, I guess, but will sound different and imho the two are not the same at all.


steven