Erica Synths EDU DIY Mixer Eurorack Module Kit - Manual (Page 13)

So we get an output voltage of -10 V. And again, ignoring the minus sign, the two input
voltages simply got added together – nice!
Conveniently, this idea works not just for 10
two channels – we can simply scale it up by adding in more jack sockets and 100k
resistors
. So let’s set this up as a three-channel version.
Once you’ve set this up, check if the circuit still properly mixes your input signals. If it
does, try simulating a silent input again and see if it a
ff ects the output volume of the other
signal(s). You should hear that the volume is not a ff ected at all. Great!
But now you might ask – why are we not running into any issues here if our mixer is
currently inverting the output signal? Simple: because with audio signals, this doesn’t
have much of an e
ff ect. They’re going to sound the same. To your ears, an upside-down
square wave is still the same old square wave .
But if you want to mix CV from an LFO or an envelope, for example, this inversion will
become painfully apparent. Simply because it means the di
ff erence between an open or a
closed filter, for example.
You can try this chapter’s circuit in a circuit simulator. I’ve already set it up for you right here: 10
https://tinyurl.com/2avnzll2 – you can change all values by double clicking on components.
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