The circuit diagram below shows how the +25V DC and -25V DC are obtained. In order to provide power supply for stereo amplifiers, a power transformer rating of 80VA with 240V/36V centre tapped secondary winding is used. The secondary output of the transformer is rectified by using four 1N5401 diodes together with 4 electrolytic capacitors to smoothen the ripple voltage. A fuse and a varistor are connected at the primary input to protect the circuit against power surge. Here you can see the circuit’sdiagram diagram
Although shown with 4,700uF filter capacitors, larger ones may be used. Anything beyond 10,000uF is too expensive, and will not improve performance to any worthwhile degree. Probably the best is to use two 4,700uF caps per side (four in all). This will actually work better than a single 10,000uF device, and will be cheaper as well.
It is essential that fuses are used for the power supply. While they will not stop the amp from failing (no fuse ever does), they will prevent catastrophic damage that would result from not protecting the circuit from over-current conditions.