The four inputs are not just for mics: they are combo jacks that also accept a quarter-inch plug. Inputs 1-2 take line-level signals, such as the output from a synth or keyboard. Inputs 3-4 are "hi-Z" DI inputs with proper impedance for plugging in your electric guitar directly, without an amp or cabinet, to process your guitar sound through amp and cab simulation plug-ins in your host software.
The 4pre combo mic/guitar inputs are equipped with pristine, transparent preamps and offer individually adjustable 48V phantom power and -20 dB pad. All settings can be adjusted directly on the front panel, or from the 4pre's CueMix software running on your computer. Mic inputs can be operated individually or in stereo pairs, as needed.