Well, I guess I'm a little late to the party, but in general, the way to go about these things is to eliminate one potential issue at a time. Most of the time, the best way to start de-humming a guitar rig is to try unplugging your pedals from their wall warts, and running them on batteries. It makes a huge difference. By giving each pedal it's own power source, there is no place for a ground loop to happen. If you don't want to do this all the time (those batteries get expensive!), you can get a transformer isolated power supply, such as the Voodoo Labs
Pedal Power 2 plus (that's the one I use). On the other hand, a lot of people think pedals sound better with batteries, because the power is cleaner (it is all but impossible, and rather expensive, to get all of the residual ripple out when you rectify AC to DC; batteries don't need to be rectified, as they start out as pure DC).
But that's probably not the issue on a two amp setup.
On most two amp setups, running everything off one power strip will help some of the time, but you will still run into venues where you have problems, because you still have two paths to ground that your signal can follow, which is what caused your problem in the first place. It will help if the destination is physically the same, but in some rooms the crap on the AC line will still be a problem.
Try a ground lift on one of the power cables to see if that is where your problem lies (on a two amp system that is clean when run on one amp, it usually will be), but under no circumstances should you EVER run it that way. It's not safe. Not all the time, but every now and then, YOU will be the shortest path to ground, which doesn't feel too good. If the splitter works, the way to fix it is simple - take one of the cables going from the splitter to the amp, open up one end, and cut the ground. Most of the time in a two amp setup, that will fix the problem, and it's a lot cheaper (and more transparent) than a transformer splitter box. You probably won't need or want this all the time (hell, some of the time this will make the problem worse - don't ask me, I don't get it, I just know that it is true). So, you carry one extra cable, and when you get to the gig, try them both.
A ground lift patch cable is perfectly safe, doesn't effect your sound (transformers probably will), and is also the cheapest way to deal with the problem - you just have to carry one extra cable with you.
Just make sure you mark that cable, or you will confuse the shit out of yourself when you try to use it from your guitar to your pedal board!
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M.K. Gandhi
