


This is indeed one function, but more sophisticated ones do level control
and ground-lift (separating the keyboard and mixer earths) aswell.


Simple ones are just that - a transformer. A decent quality audio trans-
former will cost most of that $50. They are wired thus...


       HOT   --------------|  |----------------- HOT
                           )||(
     Input from            )||(                Balanced out to mixer
     Keyboard              )||(
                           |  |----------------- COLD
                           |
       GND   --------------|-------------------- GND

The ground-lift switch disconnects the GND line from the mixer. The
transformer ratio depends on the precise application, but around 10:1
turns ratio may be a good place to start.

Christopher