Here is a very simple way to build a 1:1 ratio balun. This one it’s being used on a “cat moustache” dipole and it’s working really fine. I used a toroid type T106-2 which is very easy to find on the old desktop PC power supplies.

To do it, you can use the same enameled copper wire that came with the toroid removed from the old power supply. You’ll have to build 3 coils with 16 turns each. The connections between coils are shown below:

Here is a table with some more information about toroids. It’s in .pdf format

This is the electronic schematics of a microphone pre-amplifier. You can try the assembly in a bread-board, but be careful with ground and shield, because it can arise some unwanted noise.