I love this thread/question.

Microphone splitting is a passionate conversation piece.

We must first discuss the type of program content involved. Why does that matter? Because we typically listen to approximately 10% distortion coming from PA systems. Nobody complains about that much. You probably won't hear it in your rock-and-roll recordings either. So for rock-and-roll, rock-and-roll gospel, contemporary jazz, etc., you might find the deleterious effects of splitting to be minimal, even for your recording. If you can hear it at all.

If you are recording operatic, orchestral, fine arts material, which also has to be amplified, a few more factors may determine your decision-making?

Most microphones want to see a 1500 ohm load or higher. Yes, I know the microphones are rated at 50/150/250/600 ohms. But 1500 ohms actually happens to be the typical load for most microphone preamps since there is a physical resistor placed across the microphone preamp input. If you use a "Y" cable, to plug into a second mixer, the microphone will see a 750 ohm load. Slap a third 1500 ohm load across that for the recording mixer and you're looking at about 500 ohms. What happens to the microphone? It won't hurt the nice microphone. Well that largely depends on the microphone technology utilized. Your typical SM57 PA microphone and equivalents, output along with frequency response will be somewhat diminished. But a condenser microphone is generally less affected since it has an active lower impedance output. Don't even think about it with a ribbon microphone. You'll have virtually no output level and a mangled frequency response, if not a destroyed microphone. So forget ribbons unless active splitters are employed.

When dealing with phantom powered microphones, there should only be a single preamp supplying that power. This also largely depends on whether a passive "Y" split is utilized in comparison to a ground lifted "Y" split, transformered or active splitter. Phantom power can actually be canceled out if 2 supplies are utilized simultaneously. Generally, phantom power cannot be provided through a splitter transformer or a ground lifted split as only the AC components are inductively coupled not the DC components. I.e., it doesn't pass DC phantom power at all. Active splitters have their own microphone preamps and with that, with phantom power supplies included within the splitter. So that's really not a splitter but a "multed" (many multiplied) output microphone preamp, whose output level has been knocked down so as to be able to plug into another microphone input. I've been plugged into those and really don't care for those. DON'T TRY THEM AT HOME KIDS.

The term "Transformer splitters" can be deceptive. How can they be deceptive? Because a transformer splitter generally includes a direct passthrough of the microphone while slinging a transformer across that microphone line. The output of the transformer is referred to as the secondary split. The direct passthrough of the microphone is called the first split. Generally, us recording guys love to have the direct "first split" since it really isn't a split at all. (but the primary first split must also provide phantom power, which has other ramifications) All other outputs come from the secondary output side of the transformer, with its inherent distortions & shortcomings. But on large venue jobs, this is rarely the case. You get the secondary side of the transformer or active split. I'd rather have a transformer it split than the output of an active splitter as I'll still get all of the benefits of my vintage Neve and/or API preamps (with an extra of free transformer thrown in) as opposed to some other so & so's crappy microphone preamp, with the gain improperly set.

So having recorded all three ways, four ways (forth as ground lifted as opposed to non ground lifted "Y" XLR cables). So basically, I'll take whatever I can get and still deliver a beautiful product regardless of method of splitting. I really don't care.

In fact, some folks are so anal about this, they'll only accept Jensen microphone transformer splitters and no others. I utilize Sescom 3-way line level splitters for my microphone splitters. This is against the recommendation from not only the company that made them but from all others. Why? Because distortion in the low frequency spectrum goes up at levels lower than line level blah blah, etc.. That would be applicable if my microphones were in fact outputting -50 DB levels. But they're not. At least not on rock-and-roll jobs. They're on screaming loud guitar amplifiers. Inside and on top of concussive drums. Not to be outdone by the lead singers trying to cough their vocal cords out. So certainly not -50 DB.

Now I wouldn't use this particular contraption while trying to amplify and record the Washington Opera Company or the National Symphony Orchestra because of the lower-level nature of that kind of acquisition. Yeah, right, where you need 80 DB of gain for that low output level ribbon microphone during the oboe solo. But generally you probably won't have to worry about that scenario much?

So it really all comes down to your mixing & engineering chops. Are you feeling lucky today, punk?

Dirty Ms. Remy Ann David not Hairy

RemyRAD wrote: ... Microphone splitting is a passionate conversation piece. ...

so true

almost impossible to add anything of value to Remy's excellent response

each situation needs to be seen in context
I use and love transformers

Where the budget allows, I use quality active gear
... perhaps even run all lines at line level ... preamps on stage

I have used Y cords many, many times
... for both live recordings
and for FOH and Foldback mixer splitting

I even done the bad thing
of a Y cord from two similar mics into one Mic channel
two hi toms into one fader

apply the technology with care and knowledge and almost anything is possible

Oh yeah Kev. It really seems to be rather popular to take a pair of tom microphones into a single input (when you are cheap)? I think we're all guilty of that at some point or another?

And for MS (middle side recording), I'll take a single microphones into 2 inputs on a console/my preamp, even loading down my ribbon microphones. Did I really say that?? WTF? What is with this broad? Only I know. It still works and nobody has complained. So don't tell anybody! I rarely follow my own advice. I'm only here to confuse everybody with lies and deception.

Deceptively good from the control room to the bedroom. (if you can believe that?)
Ms. Remy Ann David

Cool. I had to read it a few times, and i get most of it. (I Think) However, "a condenser microphone is generally less affected since it has an active lower impedance output...." Does this mean a "Y" cable is kosher with condesers or not"

err no
... again each situation in context
this can depend on the desks and the condenser mic

re-read Remy's parragraph the starts
" ... When dealing with phantom powered microphones, "

two phantoms can lead to issues
how you solve the issues can help the condenser work here
...
not all condensers are equal
SO
I would suggest that a low imp dynamic is more robust ... and NON active
therefore more likely to work
but
never kosher either

sorry to not give specific answers
I say again " apply the technology with care and knowledge and almost anything is possible "
if you need more detail
fire some specific facts at us and we will try to give sensible real life answers

know the rules before you break them