It depends.
The pick up coils on an electric guitar don`t or are not pre amped.
The actual amp amplify s the pick up coils.
Now if you connected a source where it was pre amp.
And the volume was set high.
And the actual amp as well, the result would be a pop.
That is the sign of over extending the speaker cone damaging it. In other words it has oscillated the coil.
To far out of where it sit`s. And become stuck.
Attached to the cone of the speaker at the back is a paper tube wrapped with copper wire.
It sits between two magnets.
So if it becomes displaced or stuck it cannot oscillate properly. That results in a tinny sound or static scratching sound. Through overextending the cone, the tube pops right out of the two magnets.
and the tube can be bent or miss-formed causing sticking between the two magnets. as there should be a gap between them and the cone coil. It may just have to be re aligned as its not fully returned inside between the magnets and stuck on the face through over extending the cone.
http://www.djsociety.org/Speaker_1.htm
Or the amp circuit of the guitar amp since you sent a source that was pre amp to it via the keyboard.