This camera is a JVC HD1. The external microphone is stereo. The HD1's external mic input is 3.5mm stereo. The microphone's connector is XLR. Using the XLR to mini plug adapter cable that came with the microphone to plug into the HD1's external mic connection I get a signal that is way too hot! I can actually hear my clothing rustle across my body as I breath. Using a Sign video mic adapter (similar to Beachtek) should allow me to get control over audio level, maintain stereo imaging, and keep the cable XLR from one end to the other, which is really the only option.

I have to make the XLR "Y" cable, but it is not working. This is where I need help:

The mic's wiring for the XLR cable is as follows:
Pin 1 - shared neutral.
Pin 2 - Left Channel
Pin 3 - Right Channel.

I need to "Y" that out to two XLR/M connectors.

My first plan was:
Mic - XLR/F Connector.
Two three conductor mic cable about 15" long.
Wire XLR/F connector as follows:
Pin 2 - Left channel cable red wire.
Pin 1 - Left channel shield wire (normal wire for pin 1)
Pin 3 - Right channel cable black wire.
Pin 1 - Right channel shield wire (normal wire for pin 1)
Note. Two cables have been soldered into one XLR/F connector, and one wire in each cable is not used.

OK, so far so good. Time to go to the other ends of the two cables.

Left channel XLR Connector:
Pin 2- Left channel cable red wire.
Pin 1 - Left channel cable shield wire.

Right channel XLR connector:
Pin 3 - Right channel cable black wire.
Pin 1 - Right channel cable shield wire.

This doesn't work, I think, because the neutral wire (pin 1 at the microphone) connects to chassis ground at the Signvideo/beachtek adapter, which is essentially a dead end in terms of wiring as no circuit is completed.

So, I re-solder the XLR/M connectors, moving the wires that were on pin 1 to the other, unused pin. Now, for both left and right channels, I have corrected mic positive/negatives where they should be in a typical unbalanced wiring diagram. Pin 1 is not used at this end.

Still doesn't work.

Using a single, properly wired XLR cable I get a clean and completely managable audio signal from the microphone through the Sign Video adapter, but it is no longer stereo.

What am I doing wrong?

Exactly what microphone make and model are you connecting? It is incredibly rare to see an XLR-3 connector used on a stereo microphone; stereo mics with XLR connectors usually use an XLR-5. A 3-pin XLR connector normally indicates you have a balanced MONO microphone where pin-2 is signal +, pin-3 is signal -, and pin-1 is shield. That is the wiring arrangment the Beachtek and Sign Video adapters expect for their mic inputs, signal + always on pin-2 on both the left and right channel inputs.

While you might be able to use a 'Y' to connect a single mono mic to two inputs, you run the risk it will degrade the quality of the signal. None the less. if you want to try it, pin-2 of the XLR-F should connect to pin-2 on EACH of the XLR-Ms, pin-3 to pin-3, and pin-1 to pin-1. In other words, signal hot from the mic goes to signal hot on both inputs, putting them in parallel with each other.

If your mic IS the one in a million that uses an XLR-3 for stereo (I've never heard of any that do but that doesn't mean they can't exist) your problem was in the right channel XLR-M. Pin-2 is always signal hot so your black wire should go to pin-2 instead of pin-3. But using that, with the left male pin-2 connecting to the female pin-2 and the right male pin-2 connecting to the female pin-3 will result in the left and right channels being phase inverted with respect to each other when used with a normal XLR microphone.

Hope this helps