The middle projection or tongue of the E is placed through the center of a coil of wire, and the I placed at the end like this' EI' so the iron forms a complete magnetic path through the center and around the outside of the coil.Now connect A to C and measure the voltage between B and D. In my example rated voltages might be 2 x 12V and 8V.E-I lamination: A flat transformer steel lamination composed of pairs of E-shaped and I shaped pieces. Those are unloaded voltages, and especially for toroidal transformers those may be much higher than the rated voltage. Let's say these are 19V, 19V and 12V.

Audio Transformers are transformers designed to be used in the amplifiers and high-frequency audio and voice circuits, for coupling ad impendence matching applications. This tells you that the turns ratio of that combination is 25:1.Audio Transformers. Then select the combination of two secondary lugs which measure about 1 volt. If the voltages are equal you can place them in parallel to double the current.Connect a variac to the primary side of the output transformer and set it to 25 volts.

Audio Output Transformer Wiring