What does "G.N.D. Lift" mean on my 18" Powered Sub-woofer?

Terry_42, post: 43925, member: 1843 wrote: Basically what it tries to do:
If you have multiple things connected to one power outlet (for example by use of a 3 or 5 port electric extension cable) then the power adapter of all those things (amplifier, computer, …) might actually release some sort of “hum” back. This is especially bad for subwoofers as they would translate this directly to sound making a “hum” noise around 50-60Hz which can be heard if no music is played, but also make the subwoofer perform worse when music is played.
To eliminate this humming sound the ground lift button tries to separate exactly this frequency and not let it go to the speaker. However as this is mostly done by using special filters in the signal path it can influence sound a bit and hence it is made as a button that can be turned off.

So if you hear a humming sound when nothing is playing through your subwoofer and your head is close to it, then you can try to eliminate this sound by pushing this button.

The above description is not very scientific and eased down and I am aware that the actual physics work differently 😉

Chuck van Eekelen, post: 43957, member: 2756 wrote: Sorry to contradict my personal hero and example, Terry_42, but Ground Lift should not be a filter of any kind.

It is correct that ground lift is used to get rid of humm, specifically the 50 or 60Hz humm created by what is called a ground loop. This is indeed very audible in all equipment and extra so on subs.

Groundlift is normally found on equipment for balanced signal handling (there is a ground lift switch on every DI-box for example). What ground lift does in effect is “cut” the grounding circuit at some point, prohibiting ground loops.

As such, there can not be any sound quality deterioration (except you got rid of a nasty and loud 50/60Hz humm!) and it is safe to use. However, normally a ground link is available for a reason and if you are NOT experiencing humm, then leave the ground lift off (i.e. ground connected). If you have the humm, flip the switch and see if it cures your problem.

The funny thing is that ground loops occur more when you are not on the same power group (or same extension cord). Say you plug in your controller on one end of the room and your active speakers at the other end of the room. Both power outlets can be on two different groups, this is usually a recipe for some kind of ground loop problem.

Hope this helps.

Greetinx,
C.

Thank you guys for your help. So in other words, if I’m experiencing a “hum”, I should turn it on? If I’m not experiencing a “hum”, I should turn it off?

Chuck van Eekelen, post: 43985, member: 2756 wrote: No need to copy both our long replies in your reply LOL.

And I wish I could be so concise.

And, yes, you nailed the conclusion.

Greetinx,
C.

Sorry, still new to the forums (ducks head down in shame).

Thanks for your help!