What is a ground lift?

[Bassboy9764]

I recently played a show and the sound guy sent a line-out from my amp and asked if I had a ground lift. I said I didn't and he seem surprised for some reason and came over and confirmed that my amp (Ampeg SVT-4Pro) didn't have a ground lift.

Ever since I've been wondering what the heck a ground lift is.

[CapnSev]

Originally Posted by Bassboy9764

I recently played a show and the sound guy sent a line-out from my amp and asked if I had a ground lift. I said I didn't and he seem surprised for some reason and came over and confirmed that my amp (Ampeg SVT-4Pro) didn't have a ground lift.

Ever since I've been wondering what the heck a ground lift is.

Typically amps have a switch for the DI that when switched on, or "lifted", can eliminate ground loop hum from the wall socket that makes a lot of noise.

I'm surprised that your amp doesn't have one too.

[hall1k]

Does the ground lift actually mean that the connection is no longer grounded? Cause that could be dangerous (tho maybe it doesn't matter at such low power levels)

[billfitzmaurice]

Originally Posted by hall1k

Does the ground lift actually mean that the connection is no longer grounded? Cause that could be dangerous (tho maybe it doesn't matter at such low power levels)

The lift disconnects the ground of the XLR out, not the A/C supply. Explained here:
http://www.rane.com/note110.html

[jazzblade]

Yes Ground lift only has to do with the XLR out of your amp. In the case the recording console or PA mixer is on a different power circuit.

The two electrical circuits have a different electrical ground point which causes ground loops. By lifting the ground (wire) on the XLR connection between you and the sound guy, you remove that different ground potential,from each other removing the hum.