Originally Posted by FreshCream
and for building one the schematic would be simple, just two xlrs on one side of the xformer, one of the other? would anything be needed in that to block phantom power?
The transformer blocks the DC phantom power. No extra components are required.
There are two ways of making transformer-isolated mic spliters. One feeds the main path straight through, simply "tapping" the signal and isolating it through the transformer. This is the most reliable because it has nothing but wire between the input and output of the main path (to the venue system).
Another method was to use a separate transformer winding for each output. The mic winding is center-tapped and connected to a center tap of the main output winding. That feeds the phantom power through the transformer. But I don't think that method is in favor anymore. I had some transformers from Sescom (back when they still made OEM transformers) that used this method.
In any case, the circuit is trivial as the Jensen documents show.