Toroidal transformer interference

I have no choice as to where to locate a toroidal transformer for a power supply I built for my bass amp, except on top of a cover for the amps tube output section power supply capacitors. I understand the flux from the hole is huge and concentrated. This cover plate is sheet steel and I wonder if the flux from the toroid is going to effect the capacitors underneth. Hey, will I create a flux capacitor and send my amp back to the future or will I just create interference? Any physics majors out there. KMcC:confused: