Normal Drive = Normal channel volume.
Bright Drive = Treble channel volume.
Master = master volume, which should be on 10 if you want it to behave like the real Plexi. It's a convenience if you want to make it a Plexi with a master volume.
Level = output volume.
When jumpered, you mix the two channels together using the normal and bright drive knobs. Functionally this is just like the gain knob on most amps, but without a master volume it controls volume and then the amount of distortion as the preamp starts overdriving the poweramp.
I don't mind the graphics or that they are simply a picture. I think they add a bit of flair. They are mostly there for the Focus function to have a background, and to be able to see what model you are using at a glance.
An issue that still exists on the Stadium is the lack of any grouping for controls. Here's a simple recolour to separate normal vs advanced controls. I think that would make it much easier to separate what is part of the amp and what's advanced, mostly unnecessary stuff.
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