I just picked up one of these off eBay, and while it DOES affect my signal, there's a REALLY bad hum that it introduces. This isn't some small annoyance, but a HUGE flat out hum. Setup is a my '92 JP-90 going into the input on my Rocktron Gainiac (I've tried without this in the loop) going into the Dimension 3 going into my Hartke HA4000 head. The head going into a 4x10 and a 1x15. Regardless of the pickup choice, the hum doesn't change, and when I have tried going into either of the effects loops on the amp (against the direction of Hartke) the hum is still there. All 3 pieces of gear are mounted in a 4 space rack. My thought is that there's a grounding issue, so I tried the different grounds on the amp (no change). Obviously (or not) all 3 items are being plugged into the same circuit (either all on the same power strip or at least into the same duplex outlet). Any ideas what might be causing this? I don't believe the item to be defective because I actually read one review that mentioned a bad hum (I assumed that it was a setup problem). Any help would be GREATLY appreciated!