Hello... I'm admitting defeat and asking for help.
So, here is where I'm at... I just bought a new ART SLA-2 Power amp that I want to run my HD500x into. Problem is, I have to crank the ART and the HD just to get a volume loud enough to get over a drummer.
My set up is guitar > HD > ART Bridged mode (530 watts and 8 ohms) > 4x12 cab running mono 16 ohms.
Now, I know that running 8ohm head to 16 ohm cab will cut down the watts some, but It's crazy quiet.
If I set the HD to "Line" mode instead of amp, it's louder and and comes very close to getting loud enough in the mix, but it feeds back TERRIBLY and there is a constant unholy noise or robotic sounding hiss. (I have to max all volumes on the HD) I uploaded a video of the crazy noise that it emits... it's a cellphone video, but it gives you an idea.
I have tried all the various output settings and nothing seems to work. So, how can I set this up so that I don't have to crank all the volumes to get close to a useable live volume???