Mikem is right but to amplify further line level refers to a certain voltage output range from a source device that a pre-amp boosts and then sends to the amplifier. A phono cartridge's output is much lower (millivolts I think) and needs to be boosted to line level. The tone characteristics of the output from a cartridge also has to be modified by passing it thru an equalization circuit defined by the RIAA (recording institute of america, I think). There was a much better explanation of this within the last year or so, if you search old threads. A preamp that only handles line level signals (from CD, tuner, tape) is called a line stage preamp.
