questions on preamplifiers

[zeusandperseus]

can anyone tell me the principle and working of a preamplifier and its role in producing sound

 

[raghupb]

It amplifies a small signal voltage into a slightly larger signal voltage.
Chooses between inputs. Lends a bit of character to the overall sound.
Allows for connection to power amp of your choice.
Cheers,
Raghu