Double Bass Piezo pickup hum and AC grounding

[littlebun]

I really appreciate when TBers share their knowledge. I was hearing a hum from my Full Circle pickup when plugging directly into an amp in another room, but no hum with the amp in my main room. After searching TB threads about it I gleaned that some AC outlets aren't actually grounded, in spite of the 3-prong outlet, and this can cause piezo hum. If I plug into a DC powered buffer first, it doesn't matter what's going on with the grounding of the amp and there's no hum. If I don't use a buffer first, an un-grounded outlet will create buzz in my system. Good to know.

 

[AGCurry]

I'm not sure you can say that a piezo element will hum, as it really doesn't need a ground. What might hum is the wiring, the connections, and/or the amplifier.

 

[Ric Vice]

The only pickup I’ve ever used that had a separate ground wire was the Fishman BP-100 which has a brass metal wire that you wrap around the ball ends of the strings. So just from my personal experience that hasn’t been much of an issue for me. Electric Basses and stage lights have been my big issue with grounding.

 

[Francois Blais]

Yes, as most BG pickups are magnetic.
Humbucker design is better than single-coil with hum issues, but doesn't sound the same either.