[quote name='27 frets' post='749263' date='Feb 18 2010, 09:10 AM']Ground lift separates the PA's earth/ground from that of the amp/head - this often a switchable feature on DI boxes, and sometimes on DI sends on amps. It removes the possbility of problems with earth loops, where amps and PAs are plugged into separate mains sources, which tend to give rise to hum rather than hiss.
It's worth swithing the earth lift in and out, to see if it brings an improvement in background noise levels.
One linked comment though is that if you're using a DI box and [b]no amp[/b] (e.g. for an electro-acoustic guitar/bass or keyboard), the instrument does need to be earthed/grounded to the PA for the output signal to work properly.[/quote]
I apologise if I sound a bit dumb, but what does earthing/grounding entail?
I'm wondering if it's possible for me to DI straight to the PA, without using an amp at all (I live on the top floor, without a lift, and have back problems!)