2.3mH:2.3H has been nicely used to match 25Ω Grampian ribbon mic (and at the same time low cut adequately) to EF137 grid on Pleiades V6 mic booster amplifier

Inductance of primary, secondary winding (of audio transformer) gives more information than impedance ratio as one can calculate the low frequency response for particular microphone output impedance for example

http://www.technicalaudio.com/pdf/Arnold_Magnetics/Arnold_Magnetics_Materials_1956.pdf

Monopsony

An Adjustoroid in a Pleiades (R,L) adjustable slope and low cut frequency microphone filter

Hello to Canada and the United States

Variable inductance microphone input transformer

By using the following patents for example with 2 rotating magnets with respect to each other in the plane of the toroidal signal transformer core. Possible use variable low frequency cut for natural reproduction of recorded human voice or other musical instruments.


http://patentimages.storage.googleapis.com/pdfs/US2762020.pdf


https://patents.google.com/patent/US3100882