The transformer
The transformer, fits the very low impedance of the ribbon, around 0.2 ohms, with the input of the preamplifier and increases the primary voltage to excite these better. In the first microphone transformers were made of sheet iron / silicon. Later improved with an alloy of iron / nickel, currently still used in many models, both well-known brands and all the LowCost microphones manufactured in China.
Some very famous brands have spent years riding transformers toroidal configuration, as they provide less loss, due to its better containment of the magnetic field, as well as lower electromagnetic noise. But their production is more expensive.
Currently have improved the materials. With the appearance of amorphous metal. Produced by the instantaneous cooling of the molten metal prior to crystallization was achieved a material that responds faithfully to sharp changes of magnetization, making it more efficient at high frequencies. With this material the most popular Swiss-made transformers are manufactured, but OrtizLuthiers have gone a step further. A new process has recently appeared amorphous metal cores and processed again to recrystallize but nanocrystals size. With this technique we get an initial magnetic permeability of the core 5 times higher than conventional amorphous. This results in increasing the inductance with far fewer turns therefore less and less parasitic resistance wire. In short, less noise and less losses. All our transformers are toroidal nano-crystallized amorphous metal.
We manufacture special transformers to avoid proximity effect, characteristic of the pressure gradient microphones, including ribbon. These transformers are tiny and are indicated in low signal instruments that require much closer source to the microphone. The grafic below shows the difference between a normal transformer and proximity effect correction. This is achieved by selecting a special inductances.
