Separating signals in conduit/cabling

[mn1247]

After reading a number of the threads here, I am re-thinking my plan for wiring my humble studio. But, there are a couple of things that I'm still confused about.

Briefly, I plan to run flexible-metal conduit between by control room and sound booth - about 25 feet. I will need to run microphone, guitar, and line signals, as well as headphone signals. Avoiding all power lines is not possible in my situation, but I'll try to maximize the distances. This is a small home studio, for personal use... I don't have the luxury of totally re-wiring the existing (finished) space.

Here are my questions...

1) I've heard conflicting reports as to whether mic/guitar and line signals can be in the same multicore or conduit. Could someone clarify? How important is it to separate these? If they must be separated, can I just run two cables in a single conduit, or do they need separate conduits?

2) My understanding is that the headphones MUST have their own conduit. True? Or, can I just run a separate cable inside a single (common) conduit instead?

3) What gauges of wire are needed? Is 26 AWG okay for mic/guitar (I have some Motagi 8-core)? Do the line signals need 22 AWG, or will 26 AWG work? And the headphones? What do they need?

Thanks in advance for any assistance. You guys/gals are great.

Eric