You shouldnt plug it into strait into the mic port tho. It will work but it will burn out your cables alot faster because its a different impedance. its good to get a hiZ to LowZ converter. Or u can just buy alot of cheap cables

im kind of confused, whats the point of that mic input if you cant plug a guitar cord straight into it? would a direct box work to fix the impedence? what about if you ran a line out from your guitar head into the 404?

to plug in a microphone

why wouldnt it work? what you put into the 404 is what comes out. i make a lot of my stuff that way

It will work but, as an example, look at the 555. I think thats why they put the HiZ input switch on the mic line....to appease folks such as yourself and save some innocent cables.
Check into that HiZ/LoZ deal Frantic was talkin about.