the mixer circuit below has 3 line inputs 3 mic inputs. the mic inputs are suitable f low impedance 200-1000r dynamic microphones. an ecm condenser mic can also be used, but must have bias applied via a series resist. as with any mixer circuit, a slight loss is always introduced. the final summing amplifier has a gain of 2 6db to overcome this. the input line level should be around 200mv rms. the mic inputs are amplified about 100 times by 40db, the total gain with the mixer is 46db. the mic input is designed f microphones with outputs of about 2mv rms at 1 meter. most microphones meet this stard.
