PSU Question

[serengetiplains]

Can someone explain to me what function a small capacitor, 1uF say, on the input of an otherwise choke-input performs? I understand the cap to reduce voltage gradients in the inductor? Where do those high voltages come from? Why is it desireable to reduce them? Appreciate any advice.

Cheers!

 

[SHiFTY]

Often it is to stop the choke physically buzzing, they dont like the ripply DC much.

Sometimes its also to lift the B+ a little.