Please don’t “blow everything up”!
Nothing will blow up if you are reasonable.

The A/D IN can be set to receive a Mono or Stereo Input.
When it comes to INPUT use you can select:
L Mono, R Mono, L+R Mono, Stereo

L Mono: Only the L channel is used.
R Mono: Only the R channel is used.
L+R Mono: The L and R channels are mixed and processed in mono.
Stereo: Both the L and R channels are used.

Translation: if you are using a Mono option… plugging a source into “L Mono”, or “R Mono” that Channel input jack is active.
When you select “L+R Mono” - realize that you must control the balance of output levels at the mono devices. You have only one Input gain control setting - the signal is merged before the Gain Control.

So if you’re thinking “L+R Mono” and your “R Mono” In is significantly hotter in level than the “L Mono” In, you cannot adjust for that in the MONTAGE… adjust the signal at the device.

So as long as you can account for the signals and their balance before they arrive in the MONTAGE you will not “blow everything up”…
The implications of this are: the gain requirements must be similar. For example, you cannot plug a notoriously weak signal (like a dynamic microphone) into “L Mono”, and a hot signal like a lead synth into the “R Mono” Channel… because you will not be able to resolve a difference in output levels that are that far apart; not at the devices, nor in the MONTAGE.

WHY? The dynamic mic connected to the left input might have an output as low as -50dBm while your synth in the right channel is pumping out signal at Line level +4dBm. That is typically what is being asked in questions like this (without saying the words) … I’m saying DO NOT DO THAT, don’t even bother trying it.

It is possible to damage your gear when you overload it severely enough. Think of the poor input port set to receive a weak microphone signal and you plug in a line level signal… picture this in your mind’s eye: you walk up to what looks like a water fountain, and you lean over to turn the handle and instead of the nice arching trickle you are expecting, the water comes out like it’s a fire hose.

If your lucky you only get extremely wet, if not, then your buying new gear or heading to the authorized repair shop. Seriously you cannot reconcile a Mic and a Line signal in the “L+R Mono” Input Mode. A refaceDX and a refaceCP - that might work… output levels are similar and the balance can be adjusted at the source’s front panels.

When ‘getting a mixer’ and ‘buying more cables’ is the best answer, don’t shy away from getting it right. It will sound better, and your gear will last longer. So like I said, you will not blow everything up, if you’re reasonable.

Will two microphones work? I don’t know, I’ve never tried it, but at least it passes the basic ‘smell test’… they are both likely to be weak (microphone) level outputs. It might work, you can try it because it’s “within reason”… where a Mic + Line would not be. Make sense?
I would probably do something else before I could convince myself that this is a good idea. But experiment, once you know where the danger lies (avoid the danger) and see what you get.

Thanks for the help on this. I dream of a day when there are no more cables. Everything is wireless and fast and has 1 million hour batteries in them 😀