Please confirm that you are using the supplied power supply.
If so, make sure that none of the power supplies for other pedals are grounded. There must only be ONE ground connection in the whole system (usually the amp).
If this is the case, I'm out of ideas (hard to diagnose these things from a distance). The H9 could be faulty, but don't think so. You'll probably need to get someone to look at the system.
