4 Channel Mixer Project

Todays project is a very, very simple 4 channel mixer. For an active mixer, I don’t think it could be any simpler. And for a simple mixer, it’s got quite a few nice features. These extra features of it are: individual gain adjustment, master gain adjustment, mute switches for individual channels, and LEDs for signal indication… Very helpful for when there’s an annoying buzz coming somewhere from your synth but you just can’t find it!

In this stripboard layout, there are a couple of mods you can do to improve its performance. The first is to add 2 x 100nF capacitors on the power supply. One for +12v to ground, and the other from -12v to ground. Make sure these are not polarized! Fitting these will significantly improve the noise emitted by the power supply and ICs. You’ll see them in pretty much all eurorack synthesizer designs, and as they don’t cost much, it’s worth fitting them anyway! I haven’t included them in the stripboard layout, purely for simplicity for beginner synth DIY builders.

Another mod that you could do for this circuit is to add as more inputs. You can add as many channels as you’d like! All you need to do, is copy the input section from what is already there, and just add it again to pin 2 of IC1. So you’ll just need a pot, switch and 100k resistor in parallel with pin 2 on IC1… Can’t really get much simpler than that. Look at the schematics at the bottom of the page to make more sense of what I mean.

For now, here is the tried & tested stripboard layout for the circuit:​

Stripboard Layout for the 4 channel mixer by duskwork.net

It looks more difficult than it actually is, just make sure you read the notes for it and it should be easy enough to follow.

If you’re interested in adding more inputs to the mixer, or you’re interested in how it works, here are the schematics…

4 channel mixer schematics

This is also the first ever project that I had PCBs made for to try to give a little more professional look to my synth.

Main PCB for the 4 channel mixer
Input/Output sub-board
Front panel for the 4 channel mixer

6 thoughts on “4 Channel Mixer Project

  1. I really like the design for this mixer. I never cared about led level indicating per each channel let alone for mixer output but the simplicity of the design for an led at each channel had inspired me to build another mixer and I’ll include that part for sure. I wonder why ac coupling isn’t present at each channel input but I have another concern that is more important for me and it has to do with the power supply filtering which is so important; such a smart idea. What I’ve been trying to learn about is ferrite inductors( are they inductors?). Ferrite components seem to me to be so ambiguous because of the rating and how they are categorized, like how do you tell what is what for ferrite component value and aside from that for the task of power supply filtering, or specifically your design would any ferrite component work? And now looking at the picture of the module it looks like you just used jumpers.
    Thanks and keep up the good work!

  2. Love how much youve provided here, as someone who is thinking about trying my hand at designing a few modules.
    One area that I’m always curious about – how do you go about handling the panels? Did you have to provide some schematics to a professional which cut them for you? do you make them yourself?

    1. Thanks for the kind words!

      The front panel for this was designed by me using Easy EDA schematic & PCB editor, and then produced by JLC PCB in a standard matte black PCB material. Very easy to do once the basics are nailed.

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