AudioMixer. - Here is Circuit Schematic 6 Input Mixer using LM741. The mixer circuit above has 3 line inputs and 3 mic inputs. The mic inputs are suitable for low impedance 200-1000R dynamic microphones. An ECM or condenser mic can also be used, but must have bias applied via a series resistor. As with any mixer circuit, a slight loss is always introduced. The final summing amplifier has a gain of 2 or 6dB to overcome this. The Input line level should be around 200mV RMS. The Pinouts for LM741, LF351 ,TL071 and NE5534 are shown below. Pinouts for other IC's can be found on the pinout page.
|Figure 1. Schematic 6 Input Mixer using LM741|
The mic inputs are amplified about 100 times or 40dB, the total gain of the mixer including the summing amplifier is 46dB. The mic input is designed for microphones with outputs of about 2mV RMS at 1 meter. Most dynamic microphones meet this standard.