Simple mixer

Posted on Feb 6, 2014

I designed this circuit for one friend of mine to be used as a small portable DJ mixer. The circuit is an audio mixer circuit so simple as it can be. There are two dual logarithmic potentiometers in the circuit to adjust the input signal levels and some resistors to do the actual mixing. The circuit is totally passive, so no power supply is needed

Simple mixer
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. The circuit is suitable to be uses as a mixer between two line level sources and one HIFI amplifier input. This circuit have been successfully used for mixing signals form two CD players or computer soundcard and CD players. There are many situations where simple mixer would be useful and commercially available mixer desks are too expensive and big. This simple line mixer has two drawbacks: it attenuates the signal all the time (even sliders set to maximum) and the output impedance is quite high. The first problem can be solved by just turning a little more volume in the amplifier. High ouput impedance is no problem when connected to high impedance amplifier input with short wires (few meters). In the picture below you see the schematic of the whole mixer circuit. The potentiometer slides which are actually inside one dual potentiometers are connected together using one line. Every input and output pin has corresponding ground signal on the right side of the signal line. You can build this circuit easily to a small plastic box using two rotary dual logarithmic potentiometers, six RCA connectors and four resistors. You don`t need any special circuit board because there are so few components that you can just solder them going from place to place. If you want mixer which is easier to use, replace the rotary potentiometers with slider potentiometers. And if you want better shielding use metal enclosure. That line means that...

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