Using a CM Choke from EMI Filter as Transformer

[Frankentronics]

Greetings,

A friend of mind wants me to make him an interface to tap a phone line. The device is described here:

https://www.ranecommercial.com/legacy/note150.html

The schematic is here:



He is a musician and he wants to use the phone line to send and receive audio.

So, the device requires a 1:1 transformer and I like to use salvaged parts. Perhaps this is a crazy idea, but can I use a CM choke, salvaged from an EMI filter, to function as a transformer? Of course, it would have to be rotated 90 degrees, or wired "sideways", to be a transformer.

But basically, might that work for this particular application?

Thanks...

[srb1954]

It won't work very well at all. A common mode choke won't have nearly enough inductance to work at audio frequencies unless you are prepared to suffer enormous signal loss through the circuit.

A transformer designed for audio frequencies will have a winding inductance of at least several Henries whereas a common mode choke will typically be less than 1mH.

[james_s]

Small 600 ohm audio transformers are ridiculously cheap.

https://www.ebay.com/itm/10Pcs-Audio-Transformer-600-600-Ohm-Europe-1-1-EI14-Isolation-Transformer-DIY/173610350428

[Frankentronics]

Small 600 ohm audio transformers are ridiculously cheap.

https://www.ebay.com/itm/10Pcs-Audio-Transformer-600-600-Ohm-Europe-1-1-EI14-Isolation-Transformer-DIY/173610350428

Well, that's clearly the solution.

Thank you for taking the time to post the link.