I have a Crate GLX 212. When I turn it off, the clean channel light stays on for about 15-20 seconds, after its off, even if its unplugged. Its not a problem, im just curious.
There is a capacitor in the power supply circuit that is holding a charge for a while until the voltage bleeds off. That is what capacitors are supposed to do. (They hold a charge, *hence "capacity" measured in Farads is a unit of storage)
This the same principle that a stun gun or cattle prod uses, also a flash unit in a camera.