(please note, this version of mac salad is officially deprecated. no additional updates will ever be made, no additional documents will ever be posted. this material is posted here purely for reference.)
A utilities module for eurorack
Inputs have a white line and are grouped to the left. If there is a signal normalized to the input, it is listed next to the jack with a dotted line.
Outputs have a silver line and a silver arrow and are grouped to the right
Seven jacks have a little flower growing on them. The six inputs with the flower, in addition to their regular function, form a mixer routed to the output jack with a flower, “Da Kine” (more on this later).
There is a big knob and an input jack labeled “Scoop”. The signal at the jack (bipolar signals are fine) is summed with the knob’s offset (+/-5V). The result (I’ll just call it Scoop from here on out) is used internally in several locations, either as a normalled connection or a control signal.
This section has four inputs: right, left, fade, and offset. Right and left are normalled to +5V and -5V respectively. Fade is normalled to Scoop. There is also a knob for attenuating the signal at Fade.
It’s got two outputs: right and left.
Essentially, it’s two crossfaders that work in opposition to one another.
So with Fade at -5V, you get 100% of the left input and 0% right at the left output, and 100% right, 0% left at the right output.
As you increase the voltage into Fade, each output fades from one input to the other. So at 0V, you should get equal parts left and right inputs at both the left and right outputs. And at +5V, you get 100% of right in the left output, and vice versa.
So using 2 inputs and 1 output is a crossfader; 1 input and 2 outputs is a panner; or 1 input and 1 output is a VCA!
The fourth input is Offset, it simply sends signal to both inputs.
There is also a trimmer around back for adding offset to the Fade control. This is usually gonna be at or near zero, but it’s an adjust-to-taste situation.
One last note on the fader section… It’s made of four vactrol-based VCAs. So the response is a little weird and nonlinear, and they don’t turn off as fast as they turn on.
It’s not a bug, it’s a feature!
They definitely aren’t mathematically ideal VCAs. But they have some character! They work mostly like how you expect them to, but when they don’t, they usually do it in a musically interesting way.
There are a bunch of trimmers to help match all the VCA levels.
We have an OR circuit and an AND circuit, both w/ two inputs, one output.
Analog logic can be weird if you’re used to digital logic, but it’s exactly the same. For OR, if either one input or the other is high, the output is high. The only difference here is that you can use analog input to get analog output. Whichever OR input has higher voltage at any given moment is the signal you’ll see at the output.
AND works similarly, except that it always outputs whichever signal has lower voltage at any given moment.
You can maybe see how the two outputs here would be complementary. As such, the first AND input is normalled to the first OR input, and both second inputs are normalled to Scoop. With a signal going into OR(1), OR out will always show any part of the signal above Scoop, and AND out will show whatever portion of the signal falls below Scoop.
Rectify is a simple one. One input, one output. It’s a full wave rectifier!
Basically, whatever goes in, you get the absolute value out. Any part of the signal that falls below 0V gets flipped positive.
Something fun: if you put in a saw wave, you get a glitchy triangle wave out. If you put in a triangle wave, you get another triangle wave at double the frequency out.
Follow is an envelope follower based on the one in the ARP2600. It has no input of its own—it takes its input from the Rectify input jack.
Basically if you feed it audio, it generates an envelope/control voltage according to the volume of the input.
So feed it, for instance, a kick drum. Every hit of the drum would generate a little envelope at the Follow jack, which could open a filter. Or you could invert the output and send it to a VCA and you have a basic sidechain compressor effect!
Puka is a weird one. It’s a sort-of wavefolder…
Basically, anytime the input is positive, Puka adds a -5V offset to the output; and when the input is negative, a +5V offset is added. The result is a 10V discontinuity at every zero-crossing.
It’s kinda hard to grok without looking at the result. But if you send a sweep from -5V to +5V, the output starts at 0V, will climb to +5V until the input hits 0V…at which point the output swings instantaneously from +5 to -5V, then climbs again till 0V.
...(which means “wander aimlessly”).
This is the most idiosyncratic circuit in the module—I’m not aware of any other eurorack module besides Cold Mac that includes anything similar. (I think there’s some Buchla or maybe Serge modules that have something similar?)
One output, takes input at the Puka jack.
This is actually an analog computing circuit. The output is the integral of the input…if calculus is your thing.
If calc isn’t your thing…
Basically anytime the input is positive, the output will climb; and when the input is negative, the output will fall. The amplitude of the input, either positive or negative, determines the rate at which the output moves.
So if the input is 1V, the out will sloooowly drift up, no matter its current value. If the input goes to 5V, the out will drift up much faster. And if the input goes to 0V, the out remains at its current level.
Everything else in Mac Salad can technically be replicated with other modules. Even Puka can be put together with a comparator, an inverter, and a mixer. It’s more about how it’s all pre-connected that makes it so useful.
But Holoholo… you can’t really build it from other blocks! As a function, it can’t really be broken down into simpler bits. It’s, uh, not super useful, but it is really neat.
One cool function for it though: I realized you could combine two of these with a joystick controller to control the X and Y coordinates of a point. The further you push the joystick in a direction, the faster the point will move in that direction. If you let the joystick snap back to center (0V), the point will stop where it is. Neat! Analog video games on your modular synth!
Ok so I mentioned the jacks with the little flowers before—the Da Kine circuit—now a little more detail.
There are six inputs with flowers. Besides the regular functions they go to, they’re also sent to Da Kine. First they’re AC-coupled (removes any DC offsets, which makes this circuit audio-only, no CV), then sent to a unity mixer, and then finally sent to a VCA. Scoop controls the VCA.
Simple, and gives you a handy way to use inputs that would otherwise be left unused in a patch!
As I worked up the schematic, I ended up with an extra VCA. Very simple, one in, one out, controlled by Scoop.
It is normalled to Right…for no real reason 😅 I thought maybe there could be creative ways to use it alongside the crossfader/panner, but I haven’t come up with any specific applications beyond “hey, free VCA.”
That said, Right is itself normaled to +5V, the effect of which is that a bipolar signal going into Scoop and out Mauna will be scaled to fit between 0-5V
There are a lot of interesting ways to use this module. Some are more apparent than others.
You put one CV signal into Scoop and right off the bat you get nine different variations on it. And the big ol knob can add even more flavor by messing with the offset.
Or you can use it like six or seven totally separate utility modules!
Combine multiples for wildly complex patching.
Fun stuff :) I’m excited. 😁
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