Input transformers?

Unity gain input transformers can be used to isolate two grounded through the safety pin of the power cord devices, to eliminate ground loop hum. Band use "DI" units for this, which are op amp based, but input transformers are a more expensive solution. Put a 1/4 phone plug and in and jack out, and see how they sound between keyboard and PA amp in a band situation.

Keith Taylor

Paid Member
2007-11-04 2:06 pm
Audio transformers are quite a complex subject and really need more than a "suck it and see" approach to understanding how to best use them. If you are interested in doing some reading have a look here WELCOME TO JENSEN TRANSFORMERS, INC.
See applications/white papers/Audio Transformers 3MB PDF. The author, Bill Whitlock, has written several papers on transformers and interference/noise issues, a number of which have been published in the AES Journal.

Keith PS Don't know why the URL morphed into something different, but it gets you there.
Telephone transformers...

from old repeater modules are usually 600 to 600 ohms and make ideal ground loop isolation transformers. I swept one on a spectrum analyzer once and it was flat to 50K. So they're high quality. Its the capacitance in the telephone lines that makes telephone audio sound so bad.