Question:
So my new band has a decent PA system already and our next major purchase will be an in-ear monitor system. In that direction, we have a second mixer we'd like to use to mix monitors from the stage, just because it's easier for us to walk up and mix our own than to spend the countless soundchecks explaining and re-explaining what we need more and less of in our ears or, in the case of our current situation, in the floor monitors. However, the excessive cost of a split snake that will split the source signals to the house and monitor mixers is out of our reach now because one that's 16 to 24 channels is in the range of $600 and up. So in walks this adapter on Ebay:
I already use one of these to split the same signal into both sides of a stereo power amp so we're not daisy chaining 4 speakers together and creating dangerous impedance issues. My idea is to use 16 of these adapters to create a 'poor man's split snake' of sorts. I would plug the XLR coming from a source into the female end of this Y cable rather than going into the snake. Then one of the male ends goes into the FOH snake while another XLR cable goes from the other male end of the adapter to the monitor mixer.
My question is what kind of problems would this create, if any, for sources that require phantom power like overhead mics or certain DI boxes? Would phantom power from the FOH mixer work for this to both power the source item and not damage the monitor mixer by sending voltage to it? Hope that makes sense. If you're not sure of if this will work or not then I politely ask you to make that point clear. I'm not really looking for opinions as much as I want solid answers. I already have my opinion, and that's that it will work in theory, I just need to know for sure and that it will not have a negative effect on the mixer that isn't sending phantom power (and to an extent, that the non-phantom mixer won't suck any of that phantom power from the source item that needs it). Thanks for any help you can give.
Answer:
I was stumped on this one so I did a little research.

From the Whilrwind Website:

There are two types of passive splitters: parallel and transformer isolated .

PARALLEL SPLITS
The simplest form of splitter is the parallel type split. This involves taking a mic cable and simply "Y" connecting the plus, minus and ground wires to two other cables.

This method successfully connects the mic to multiple mixing consoles but connects the consoles directly to each other as well. Most modern consoles behave well when connected to each other but keep in mind that there is no DC isolation between them. Also, differences in the impedances of the legs in active balanced inputs of multiple consoles can make the system more susceptible to hums and buzzes caused by outside interference. However, if a system works well with a parallel split, this type is popular because they are simpler to construct and do not require the added expense of the transformers themselves. If a splitter is to be used in a noisy environment or is to be connected to many different systems (such as a mobile recording setup) the possibility of encountering problems can be lessened by using a microphone splitting transformer as described below.

TRANSFORMER ISOLATED SPLITS
In a transformer splitter, the microphone is wired straight through to a "Direct Out" and also to the input of a splitting transformer. (See figure below.) This transformer has a 1:1 turns ratio and its output side is connected to the second or "Isolated" split output. (Transformers with two or more secondaries are used for achieving more than one iso split.)

The transformer will pass the microphone's AC audio signal but will block DC voltage in either direction. Impedances are still reflected from the destination to the source across the transformer just as in a parallel split. Therefore, transformer isolation does NOT change the impedance loading of the circuit and does not allow for an increased number of splits over parallel splitting for impedance reasons alone.

One of the outputs is usually wired as a direct connection because the transformer will also block phantom power (DC). Remember to plan on connecting this direct leg of the split to the console that will be providing the phantom power.

A major benefit of using a transformer split is that it increases each leg's ability to reject interference by improving the "balanced" characteristic of the line (called "Common Mode Rejection" or CMR).

A disadvantage of this type of split is the added expense of the transformers. High quality transformers are essential for providing proper shielding and for preserving the frequency response of the mic signal - don't cut corners here!

Here's a link:
http://www.whirlwindusa.com/tech06split.html

I think the bottom line is that your idea will probably work, but may be more susceptible to noise and interferance due to the potential different loading of the two consoles. It makes sense to try it and if you have no problem you've saved some money. If you do have problems they may be restricted to certain channels only, and you can possibly look into isolating the problem channels with a transformer isolated box.


On another topic, I also split my signal to both sides of a stereo power amp like you mentioned, but I usually go into one of the XLR inputs, and then out the TRS input of the same channel into the TRS input of the other channel with a short balanced TRS to TRS male 1/4" cable. It's basically six of one half a dozen of the other, it's just a bit cleaner, and I don't have to monkey with undependable adapters.
Answer:
Wow, great find with that article. Pretty much exactly what I needed to know, aside from possible damage to the other console not providing phantom power. Even so, it sounds like the only real potential for problems is any phantom powered channel, of which we'll only be using 4 to 6 max, and probably less. That explains why the split snakes are so expensive. Most of them I've come across advertise ground lift isolation on each channel.
So that brings me to this... Seems like on any of the phantom powered channels I could let the FOH board supply power and put one of these in between the split and the monitor board. I can definitely see why phantom power on a non-lifted circuit going into another console would create a problem. It's all making more sense the more I think about it. Thanks a ton for the link.
Answer:
If the ground lift doesn't work (it should I think) you could try several of these instead.
Answer:
If the ground lifts didn't work I'd be selling the gear I bought to accomplish this and going the more expensive splitter snake route before buying mic splitters at $35 bucks a pop. We're getting into the "might as well do it the professional way" price range by then.
Answer:
You have some big bucks... here is the way to go: Aviom
everyone can control there own mixes
Answer:
If we can't afford a $600 split snake I'm real sure we'll go for a multi thousand dollar Aviom system... Not only that, but even if we had the money, an Aviom system is not a realistic solution for a portable sound system, even if portable takes up a whole trailer. Not one that is set up and torn down by the band anyway. Too much time to deal with an Aviom system. I've used them and wasn't that impressed anyway.