Yeah, the biggest problem (as far as console gain) is that a lot of lower end consoles dont have a "Pad" you can engage on the channel.
Any sort of "line level signals" (most equipment that outputs XLR other than microphones) will need to be padded to keep from clipping the preamp.
If this is the case, even bringing the gain all the way down to the lowest setting MIGHT not be enough.
You will have to lower the output from the guitar, or put a pad inline.
One of the easiest ways I have come up with to do this (when using an acoustic) is to route the guitar into a direct box that includes a pad (or attenuator) to lower the output.

Personally, with my JTV I use a Pod X3L, and I just keep the master volume just a little lower than 1/2.

I have been wanting to get an inline pad, so I can turn on the fixed level output on the pod.

More details about your setup might help.

From the HD500, where does your signal go? Does it go to an amp, or direct to the Mixing console?

Are there any other effects or gear involved? (Before or after the POD, or in the effects loop?)
Do you still have the same problem if you monitor through headphones?

How is your acoustic patch setup on the HD500?

I can speak for others, but the setup on my JT59 is also less than ideal.  I've found that the nut was cut too deep, which also can add to buzzing issues.  Currently it's at my luthier for a complete setup, adjustment, and fret dress (Plek)  .  They caught the nut issue right away, and they're going to shim it.  I told them not to set the action too low, just because of the acoustic modeling.  I'm REALLY lookng forward to getting it back later in the week.