Guys, I'm having an issue with my 11R and the sound quality. It seems like almost all of the patches that I like (heavy distortion, and even some clean) have an issue with hissing and noise. It almost sounds comparable to a ground loop problem. I know that this can't be the issue, because some patches are perfectly silent between notes.

I've replaced the firewire cable with a pro grade cable.
I have HumX's on my outlets.
I'm running direct to my MBox 3 Pro via S/PDIF.
I'm running the latest firmware, and Pro Tools 10.3.9.
I can run other amps direct without any issues.

However, I consistently have a high gain hiss or noise for most of the patches that suit my style and preference. I hear recordings from people using a fraction of the gear that I'm using, and they sound amazing. I just can't get the noise out, unless I turn the gate threshold up so high that it kills the sustain and sound altogether. Also, I can't seem to get the unbearable low end out of some patches. It makes palm muting next to impossible. The low end destroys the mix.

Any suggestions and / or advice would be greatly appreciated. I've Googled this subject for hours on end, but I can't seem to find answer.

Thanks in advance for your help.