The toroidal cow that is, toroidal transformer, in the amplifier as a power transformer, 220V AC mains through the transformer step-down rectifier, into a DC power supply for the amplifier to supply the power supply for the use of the machine.
The toroidal transformer is a type of electronic transformer due to the use of toroidal iron core and name. Because of its core without magnetic gap, magnetic resistance is small, minimal leakage, fewer turns per volt, small copper loss, high efficiency, etc., is widely used in medical equipment, telecommunications, instruments and lighting and other aspects.