HNMFXD
I had a HD500 for a while and dug it. You can basically create a global volume control by assigning the amp vol or adding a vol pedal in-line as exp 1 or 2, depending on what you have in the chain for the patch, in each of your patches.
That's not a very good workaround though, considering that when the Expression Pedal actually works, it's quite touchy. I used the EP as a Volume Pedal, mainly for lead boost, and usually assigned to the Amp Sim Master Volume. Your patches still need to be in very close output volume to one another, plus, you generally don't want the sweep range to go from 0-100% unless your only goal is to do swells. Still 100% of one patch might be half or twice as loud as the next one, so "Global" is not at all the case. When using it for a boost, I usually set the range from about 70-100%. Again, this only worked well IF the individual patches had the same overall output volume to begin with.
It didn't work at all once the notoriously flawed EP stopped working completely. In my reading today to satisfy my curiosity over the differences and upgrades between the 500 and the 500X, I find that the Expression Pedal is still just as big of a problem as before, as are the switches. Unfortunately, the pretty new switches are more expensive to replace than the old ones. In terms of sound, the increased power is a nice upgrade, but does nothing to solve the myriad volume issues.
I'm not "trying" to shit on the OP's new unit, I'm just relating my experiences with it's predecessor and what I know about the build Quality.
As a Studio tool, I think it offers insane bang for the buck. It can live a long, trouble free life in a studio where virtually all of the editing and controlling of the unit can be done without physically touching it. I have recorded some incredibly amazing stuff with my 500.
Gigging with it was a constant, very bad nightmare. Sure, it sounded great (when it wasn't either way too loud or way too quiet), but the volume struggles and the woefully poor reliability were just too much. I would never gig with one again unless I had an identical unit on stand-by as an emergency back up, and if/when the volume issues were solved. But, no fucking way I would buy two of them just to have to keep repairing one or the other.
Anyway, enjoy it. It really has amazing sounds.
Sent from Crab Nebulae via reverse engineered alien technology