If you set it for Instrument & Mic - Instrument will be sends 1&2, mic will be sends 3&4.  Make sure that you've configured your recording software appropriately.

Not sure what your issues with the headphone output is.  Open up the POD Farm (or GearBox, or POD Farm 2) interface and make sure it isn't muted.

Hi,

I think the ux1 does allow 2 at once as BigChas has said. I have read another post that seems to suggest this.

Do you get any sound when you select mic and instrument?

You've probably tried this, but I just wondered if the following might be the solution. You may need to make a second tone line in pod farm. If you've got pod farm standalone, select a preset and then go into mixer view and then click on the button called 'Dual' and then click create empty tone. This will make pod farm allow two inputs. You can then change the first tone line to have the guitar effects and amp you want and add a mic preamp etc. (or whatever you wish for the mic), to the 2nd line. Select instrument in the first input box and mic1 in the second. (I am using a ux2 so I am not sure if these names are the same on the ux1). This should make guitar and mic work at the same time.

Its possible that the top line is the mic one and the bottom the guitar - I can't remember. IF you try both, you'll find out which it is.

God Bless,

David