About
Arithmetics is an utility module, mainly focused on different add/subtract operation combinations. It consists of 2 coefficient setters (read: one attenuator and one attenuverter, but with +12v normalized into the input so you could use it as an offset voltage generator) and 4 independent operations - that take some input and process them somehow. First 3 ones are summators of one sort of another, the last one is a comparator at its core, but if one treats it as a literally broken-out op amp, they can build interesting feedback patches with it.
You can see a fifth operation on my build down below - it was supposed to be a 4-quadrant multiplier, but both AD633s (one-chip 4-quadrant multipliers) that came in some days ago were damaged/faulty, so it has a very strange transistor circuit behind it instead. It kind of multiplies, too, but one day i will make an actual preciese four quadrant multuplier module... as a RETALIATION move for this one!
Anyhoo, the top operation is the inverse sum of two signals. It adds them togethers and inverts the sum, as simple as that. If only one signal is patched in - it's just an inverter.
Below is the second operation, which is a sum of normal first input and inverted second input. Patch the first coefficient out in the first input of this operation as an offset, some CV into the inverted in, and you get an offseted inverter! Or use it for harmonic subtraction of filtered sound from clean sound, for example.
Next is the third operation. This one is mainly meant to be used as a mini audio mixer, since it (virtually) divides all incoming signals by 3 before summing, so even at top voltages at the same time, the mix will never clip against power supply rails. So you can just throw your sounds together into it and get a clean equal-power mixdown. But it, of course, is DC-coupled, and you can use it whichever other way with CV and audio.
Finally, the fourth operation with the infinity sign! It's basically an op amp that is kind of.. free to use? In its raw form, it will act as a comparator. Of course we can't get infinite voltage here, it will clip against the power supply voltages, but if the difference of the two inputs is just a bit positive - the output will skyrocket to +12v. Likewise, if the difference is a bit negative, so - the second (B) input voltage is a tad bit more than the first (A), it will instantly drop to -12v. This one is also a crazy feedback experiment gem.
Generally, Arithmetics is a nice multifunctional utility that's easy to build for a beginner. As a bonus, you get one excess op amp and can show some creativity and think of your own fifth operation around it, instead of my failed multiplier attempt! Another comparator? Three-channel inverting mixer? Or maybe a half-wave rectifier? Up to you!
