It is the effect used when "Mix down" to stereo track from multi track, or mastering the stereo track finally. Using multi-bank compressor/equalizer, the stereo track can be more powerful or comfortable for home use/portable audio equipment. You can make impressive sound quality as commercial CD.
Concerning the digital equipments, noise may be standing out to the ear when the input level is not suitable. Please make input level proper watching the blink of input level indicator. Proper level is that indicator becomes red, when the signal level is maximum.
Guitar cannot be connected directly, since input impedance does not match. Please connect guitar through any equipment witch has low output impedance, like guitar effects processor.
SEND/RETURN of guitar amplifier can be connected directly.