DI boxes question

[samneal]

Okay, let's start this off with letting you guys know I'm new to the forum, and relatively new to sound engineering, although I do sound and lighting at my school, I wouldn't really call this proper "sound engineering"!

I've recently started doing sound for a local band, and have a few questions regarding DI boxes:

I generally don't worry too much about the settings on the DI box itself but am now curious as to what all the settings actually mean!

I'm using the DI boxes to run guitar/bass amps into the mixer to run through PA and I was hoping someone could explain the best settings for this out of the following:

1. INSTR/AMP - I think this one is self-explanatory.
2. FLAT/FILTER
3. GND/LIFT

Thanks.

[John Bell]

Hi Samneal,
The instrument input and the amp output, provide a method of tapping off a DI output and still enable a normal connection to the amp. The instrument will be DI'd and the amp will work as normal.
Some DI boxes allow a connection between the amp output and the speaker cab, to DI the amp output.
The flat/filter switch, could be a high pass filter to drop off the low end or a low pass filter to reduce any hiss.
The ground lift is very useful for eliminating earth loop hums safely.
Some DI boxes also have pads to reduce the input level, if the signal is too hot and sometimes a phase inverter to reverse the polarity, to prevent out of phase filtering effects, when mixed with other sources on the desk.
Some can be powered by an internal battery as well as from phantom power from the desk.
Just experiment to get the best sound.
John.