Difference input gain on global settings

[derdoe]

I don’t know if there’s any official info on this, but the the (global) input gain in the I/O settings seems to have some scaling at certain points to optimize signal to noise ratio. So it has some influence on how the analog signal is processed. The input gain in the preset is just a digital gain.

If you want to go down that rabbit hole:
Basically at +9.3dB (and other points) the signal changes and reduces the noise floor.
So some people use this fact to set the global input gain to +9.3dB and the preset input gain to -9.3dB to effectively get a lower noise floor.

Thoroughly confused about gain staging and about to give up

This also improves the noise floor, because something happens/changes in the A/D conversion at +9,3db. You can clearly hear it when slowly turning the global input gain up step by step. Therefore I have my global input gain at +9,3db and the gain on my input blocks at -9,3db. But that doesn’t falsify the above argument of the blocks behaving the most realistic when they see a overall gain of ±0,0db - because that holds true here (+9,3-9,3=0)

Thoroughly confused about gain staging and about to give up

My guess is that it works a bit like the input trim you described, but it’s not continuous. If you just put some high gain amp and a cab on row 1, you can hear the noise floor even without a guitar. From 0 to 9.3dB you turn up the gain and you can hear the noise floor get louder. At 9.3dB, like DavidRSTV described, you can suddenly hear the noise drop. There are more breakpoints like this somewhere around 12+dB and after that. So I think the QC does only increase the gain on the digital side …