AES Convention Papers Forum

This is... a really really crazy idea.  It's not currently a practical one, but it's so off the wall that it has to be useful for something someday.

Let's say you wanted a 1:1 audio transformer, and you didn't need electrical isolation.  All you really needed was high CMRR.  In theory, you could replace that transformer just with a huge common-mode choke and get as good common mode rejection as you ever needed, down to whatever frequency the choke stopped working at.

Transmission-line transformers are a much more generalized notion of this same concept.  They are commonly used in the RF world where they are practical because the required inductances are fairly low.

The author discusses making moderate ratio transmission line transformers at audio frequencies for amplifier output stages, but a similar method might be effective for microphone input stages as well, if one could deal with the limited bandwidth and the severely reduced CMRR below the corner frequency of the inductances.

I don't expect anything will come of this work but it's so strange and ingenious that someone has to find some application for it somewhere.