Get a decent splitter box with transformers and use the secondarys for the PA. Or when not recording swap to have phantom current from the PA desk.
Matti

If you just use a "Y" cable you will create an impedence mismatch. This is why you need the transformers in the splitter box.

I think you can

but before I make a fool of myself tell me exactly what mic-pres you have and the two desks you will interface with and which inputs you will use.

I'm guessing that the Mic-pres are 600 ohm outout ready
and
the cheap Alesis 12R mixer on line input is bridging (high imp)
and
the recording mixer ?? ... (hope it is high imp)

then it may work a treat ...

BUT
you need to be aware of ground loops and Phantom powers clashing.

you need to research and experiment carefully

Radial makes a microphone splitter. Here's a link.
Link removed
They make quality gear, and may be what you are looking for.

The mic pres are Seventh Circle A12 and N72, and an ART Digital MPA. The mixer is an Alesis 12R. The recording console is an 002.

So from what I have gathered so far, I should use a transformer isolated splitter box. I assume it is better to get a box that runs a direct signal through one output and the transformer isolated signal through the other output? Then I could hook up the "pure" signal to the recording board and the isolated signal to the mixer for rehearsal. Also, should I split the signal right from the mic or after the nicer mic pre?

I've just done a google on the Alesis 12R
it's a Mic mixer but it does have " 12 balanced TRS line inputs "
(and Phantom power switch - even though phantom is not on the line inputs)
I can't find the spec for input imp
but
First I'd be trying a direct wired y cord but with the addition of two earth lifts.
Both the 002 and the Alesis 12R are relatively high imp inputs
and
the Seventh Circle has grunt to drive 600 or less

I'll have to look up some specs on the ART Digital MPA.

there is a good chance the simple solution will be cool.
make sure phantom IS OFF and I don't see how any thing will get hurt
also the erth lifts will remove the ground return of any phantom.

What you describe is exactly what a mult does...easily set up with a patchbay...

Most pres these days (that I've run across anyway) can handle this with no problems...

Why not split the monitor outputs on the 002 back into the PA or use the individual outs to send back to the live room? No control over individual levels on your end but you once you're dialed in you should be good.

Well the main reason for not doing it that way is because we don't always want to record, so we don't always want to have to fire up the computer and pro-tools. We just want it to be easy when we are feeling "in the mood" to lay some tracks down. Otherwise a good idea though.