You can; it's easier to do it on the screen, but I will say that once you've spent a little with with it, it's pretty easy to do it on the unit itself, just not quite as graphical.
The only bummer about the unit at this point is that it's a MIDI interface to the computer, it really should be USB, and I'm sure it will be in the next hardware iteration. It's just one extra level of hassle to get your MIDI interface responding and interacting, and doing something like downloading new firmware to the unit takes way too long.
But once you've got the MIDI connection happening, it works fine.
I do like the way they have organized the various parameters, though; on the amp section, it's "basic," "advanced" and "amp geek" pages. That's where you can really get in and do the interesting stuff, like change the tone stack from blackface to brownface, or make the tone controls active instead of passive, adjust the bright cap or the presence frequency, how much sag is in the power amp, tube voltage, and so forth.
These are the three pages of settings for the Van Halen "brown" sound. No soldering required!
