This refers to input signal power (voltage) or / sensitivity of the signal. Line level is a very common input and most CD players iPods and other devices operate at line level.
Phono input refers to the signal that is encoded and decoded in order to correct the sound of vinyl. this was introduced as a standard and has an RIAA filter in order to replace some of the low and frequencies that I lost due to the physical boundaries faced when cutting vinyls. this was done to reduce the Skipping that takes place as a result of the Needle physically having to move to create sound and having more bass would mean deeper grooves causing more frequent skipping.
What this means is that if you have a turntable. You need to plug it into the right input at the back of the mixer and make sure you have the right input selected which is usually a switch on the top of the channel strip.
in order for the mixer to interpret the signal correctly, you must ensure that you plug your equipment in the right place as there a different physical inputs and these have different pre-amplifiers (before going into the channel path). you must make sure that you have the switch at the top of the channel strip on the right input ( becuase 1 channel can sometimes take multiple inputs, but it does not combine them and so you must select the right one).
This difference in Phono level signal level is due to the limitations of Vinyl Records themselves. The fact that The vinyl is a physical representation of music means that the almost microscopic bumps and grooves contain all the musical information. This means that the device that that picks up the sound, called the stylus, is physically moving up and down and side to side, and these vibrations are transduced into electrical impulses to emulate the music. One Of the issues with this principle is if there is too much low or high frequency content, the needle will start jumping out of place and this is when u ma incur skipping, when the needle actually jumps to a different place on the record and in turn causes some unwanted sounds and also messes with the timing of the song. Turntables also have a separate lead for ground, that is attached to the mixer to ensure that there is no ground noise or interference between the equipment.
Microphones Microphone and Microphone Inputs are very sensitive. They are more sensitive than turntables as they will usually be picking up very small Vibrations in order to capture, transduce and recreate sound accurately. As a general tip, dont ever plug anything else into a mic input that is not a microphone, such as a cd player or other device that could damage the very sensitive input. The most common microphone type is a Dynamic microphone and you can generally plug it straight into the DJ Mixer mic input. If your microphone requires Phantom Power (+48V on gain stage) you will need a phantom powered pre-amplifier before you can plug it in.