I own a Marshall DSL 401 all-tube amp and I just can't figure out how the "Overdrive Volume" knob affects the sound, if at all. It just sounds louder when I crank it (obviously). I don't notice any change in the tone.
However, on the amp's manual, it says the following:
This control adjusts the level of sound coming out of the overdrive preamp channel and allows you to balance it against the Clean channel.
- To achieve the normal Marshall style heavy rock ‘punch & crunch’ especially at lower volume levels, this control should be used to keep the volume down and the output Master Volume should be kept higher. To achieve a squashier type tone, great for lead work, then use this control higher and bring the level down on the output Master Volume.
- When using the less gain/more level way of driving the power stage, keep the overdrive gain low and use this volume control to drive the power amp."
I think I understand the first part about using this knob to control the volume of the overdrive channel against the clean channel to balance them with each other when using both.
I think I also understand the part where it says that in order to achieve a heavy sound at lower volume levels, this knob should be kept at lower levels in order for one to be able to crank the Master Volume to achieve power-tube saturation, right?
What I don't understand is this "squashier type" tone, great for lead work. To achieve this tone, it says the Overdrive Volume knob should be kept high and the Master Volume should be kept low. (The opposite of achieving the "Punch and Crunch" sound, apparently.)
I also don't have a clue as to what the second user hint means.