#1
Just picked up a 100w Orange Crush Bass amp and it's absolutely great. The direct out has already been great for recording, but I've been wondering what the two associated settings are for.

The 'GRN LIFT' I've figured out through trial and error cuts the excess buzz, and after reading the manual I didn't learn anything any more helpful. What does this actually do and what the hell is the point, why not just have it always engaged?

More importantly, the 'PRE POST' setting, all the manual says is it changed the direct out from pre to post mode, no idea what this means, and it doesn't seem to make any difference to the sound. Can anyone help me out?
#2
Here's a Wiki on Ground Lift (GRN LIFT). The "why not just have it always engaged" is covered in the SAFETY section of the Wiki.

https://en.wikipedia.org/wiki/Ground_lift

Pre-Gain and Post-Gain select the volume before or after the preamp. If you've got them set the same, you won't hear a difference.