My wah hums when I put it on the floor :?

[Chris Goodson]

My wah pedal is really messing with my head.  On the floor it hums but when I put it up on the table it's quiet as can be.  This is hard to understand considering it's totally shielded.  I've even tried different patch cables with no avail. :?
The circuit is one I found on the internet a few years ago that has two inductors that can be added together in series with a switch.  I'm not sure if it's around anymore though, I can't even remember where it came from.

[Mike Burgundy]

shielded or not, inductors are brilliant antennas. There might be a slight imperfection in the shielding letting nasties in. Does the hum go away when you alter the wah's position/angle on the floor? I live above a router/serverroom and the interference is horrible. We're so used to problems coming from above (fluorescent lighting, etc), that leads in or below the floor often get overlooked.

[Chris Goodson]

I tried moving it around and it never seemed to make any difference.  But, if I move it off the floor or flip it over there's no hum.

[Mike Burgundy]

sounds ,like some kind of lead in the floor - make *very* sure the shielding of the case is ok and properly grounded, without groundloops.
I assume putting the wah on the floor in another room/building doesn't cause trouble? If it DOES, there's something weird and probably machanical going on. My guess is it won't hum everywhere, so it's a combination of some slight grounding/shielding problem (measure for conductivity and once again check for lops) and local conditions.