Geistnote's GN-C28: This transformer is a Chinese import of our own design.
On a budget? This is the transformer for you. You are getting a good transformer for a very low price.
Designing your own microphone? Make it sound great with this first. If you can do that, a high-end transformer will only make your microphone sound better. (Make sure the turns ratio is similar!)
Learning to Mod Ribbon Microphones? The GN-C28 is the Perfect transformer to practice with. If you hose the transformer, it won't be that big of a monetary loss.
The wiring diagram for the GN-C28 is the same as the GN-C36.