Here you can see a close-up of the first part of the power supply. I put some thought into building this part in such a way as to minimize switching noise from the rectifiers. As you can see, it is built close to the power transformer so as to keep the high-voltage secondary leads (the red ones) as short as possible. Huge current spikes flow out the secondary leads, through the rectifiers and the first filter capacitor, and back into the center-tap of the transformer. It is crucial to keep the area of this loop as small as possible, and to build it far away from the audio circuitry. Notice how the transformer leads are kept tight together right up to the terminal strip. This minimizes the electrical noise radiating from the transformer leads, because each current spike in a transformer lead is countered by an opposite spike in the center-tap lead.