Input levels (mic/inst/line) and DI-Box

Question

Okay, I'm totally consused about the input levels. Let's say I have an audiointerface Presonus Studio 68. Inputs:

1. Mic/line/inst
2. Mic/line/inst
3. Mic/inst
4. Mic/inst

There is also a button "line" which converts inputs 1-2 to a line inputs, and also a phantom power button.

I have the following instruments to record:

1. Condenser mic (needs a 48v of course)
2. An electric guitar with active pickups through a passive DI-Box
3. A bass guitar with passive pickups through an active DI-Box
4. Some more guitars with active and passive pickups

So the questions I have:

1. To qhich input should I insert both an active di-box with a passive guitar and a passive dibox with an active guitar?
2. To which inputs should I insert all the rest of the guitars without di-box and different types of the pickups?
3. How can my 3-4 inputs be line and mic at the same time, when those are absolutely different input levels?
4. What happens to my inputs when I swich on a phantom power? Are they becoming a line inputs so they can handle amplified mic signal?

What confuses me most, is that 1-2 inputs are also instrument inputs, but they are not always line (because I have to switch "line" on). But at the same time inputs 3-4 are always line, are they?

This is driving me insane. Please, help me to understand al these stuff.

Answer 1

To which input should I insert both an active di-box with a passive guitar and a passive dibox with an active guitar?

MIC input without phantom power (unless the active DI box is powered by phantom power).

To which inputs should I insert all the rest of the guitars without di-box and different types of the pickups?

INST input.

How can my 3-4 inputs be line and mic at the same time, when those are absolutely different input levels?

These are combo connectors, the XLR connector is a mic level input, the TRS connector is a line level input.

What happens to my inputs when I swich on a phantom power? Are they becoming a line inputs so they can handle amplified mic signal?

When you switch on phantom power, the phantom power is activated on all mic inputs. A phantom powered mic does not deliver a line level signal.

As amazing as it may seem, the owner's manual provides useful information.

If I want to record vocals with a powered mic and a guitar through a passive DI Box at the same time, can I do this? Because I have to power the mic inputs, and passive DI is also connected to a mic input.

A decent passive DI Box shouldn't be harmed by the presence of unneeded phantom power on it's output, neither it's sound quality degraded. Nevertheless, I decline any liability about whatever might happen.