This is one of the best and only pictures that we have of any of Jonny’s AC30. This particular picture is of his standard 1998-ish Reissue Vox AC30 6TB, from the Le Reservoir performance. I believe that it’s in the high input.
I’m sure, though, that Jonny has used both the normal and the TB channels quite a lot, and with different settings depending on the recording or sound that he’s looking for.
Also note that the cut knob affects all channels.