There seems to be barely any noise after I unplug the guitar cable from the firebox. But when I plug in the 1/4 cable into the jack, that humming noise is there no matter what is connected to the cable (so it's not the guitar).
I have used a noise gate vst (cubase) and it does a good job but even after fiddling with the settings on it, it doesn't cooperate that well (cutting out high harmonics and sound).
I unplugged every thing plugged in, it's not a ground loop (though I could use a power conditioner... but I don't see that helping at all). Would a hardware noise gate function better than a vst?