Eurorack: ask questions here


Thank you very much! I’ll try this. But/and would this not then also work with an external LFO (or other modulation source) patched into channel 2, using that attenuverter to attenuate, and patching on to channel 3 using that to offset (as @edbkt is proposing if I got it right)? But if you say this wouldn’t work @alanza, how is then using channel 1 (and Maths own LFO) onto channel 2 (as @electret is proposing) different from what @edbkt is proposing?

Am away from system at the moment but will trial and error as soon as I can. Thank you all three!


My bad, forgot how to Maths for a minute.

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for an external source, you would keep channel 1 and 4 to neutral.
patch the external signal into channel 2, use channel 2 knob to attenuate.
use channel 3 to offset.
Sum output is result.

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Thanks a lot! (This is the same now as @edbkt is saying in their edited post, as far as I can see.)


Yes, sorry for being cryptically brief. in general with modular synthesis, you have to include some form of mixer whenever you could just include a “+” object in Max for Live.

Note that for a lot of modules there are typically two ways a knob responds when the corresponding CV input is patched: the most common is to act as an offset, but sometimes it will act as an attenuator or attenuverter instead


Not familiar w the Live device but essentially channel 2 of maths is providing attenuation (decreasing depth) then, when using the SUM output, the unpatched channel 3 amount (which is just a static dc voltage) is added or subtracted to/from the LFO providing your offset. Basically what this is is an attenuated lfo and a static dc voltage (say, 1 volt) both being added up in a DC coupled mixer with your final output being lfo with offset. Maths is great but can make simple things seem confusing at first :wink:


Thanks a lot @alanza and @addamm.

I still don’t completely understand how one channel of Maths knows to offset rather than attenuate. They’re both attenuverters, but one functions as an offset. How does that happen?

I really need to dive deeper into the depths of how CV modulation works. It’s confusing to me because oscillators and low frequency oscillators and how they work together with envelopes and VCAs and even sequencers seems to me fairly clear and straightforward (even though I might be deluding myself), but when it comes to fine nudging or sculpting of CV, my head becomes porous. I have a hard time really understanding what a module like Blinds does for example (I understand the words in the description, but I don’t understand what the result of using those functions are, in practice).

What you are helping me understand how to do with 2 channels of Maths here, do you have examples of how you would achieve the same result with other modules? Maybe this also helps to make it clearer.

And thanks so much again. Hopefully I am not the only one pondering these things!


the key is “normalling”: until you insert something into the inputs for channels 2 and 3, there will be a static DC offset present (+5V on one and +10V on the other as of the most recent Maths).

so the knob is dumb: it’s just attenuverting always, but the circuit designer was smart!

The Maths manual is actually a really great resource for your sorts of questions!


I found that having a visual representation for this kind of stuff is super helpful. This video has an oscilloscope throughout if you haven’t checked it out yet and is really thorough and straightforward.


This is true. I am reading it.

I understand most of it, but for the channels for instance, it says “Normalized to a +10V [for channel 2, +5V for channel 3, like you say] reference for generation of voltage offsets.” which I sooort of understand as well, although not completely maybe the word “reference” in this context. But perhaps this is moving beyond the scope of forum posts and I should just read on in the manual.


Thanks @merlatte! 20 chars

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I think “reference” is just electrical-engineering speak here and can be ignored


This is tricky to understand at first because it is a hardware thing. I’ll say what I believe is likely happening at channel 2 (for example) is that maths is generating a voltage at all times at the beginning of the chain in channel 2 which then goes to the attenuverting knob - so if the knob is fully CW it is just spitting out the full value at the output; knob turned to 12 o’clock should almost cancel this voltage (attenuated to close to 0v); knob full CCW is the inverse of that voltage (so, negative the original voltage created internally). Now what happens when you plug a cable into the input of channel 2 is that the connection between that original internal voltage source is physically broken/disconnected inside the input jack (look up like “guitar pedal jack normalizations” or something to see a picture) so that instead of that internal voltage being sent to the attenuverter knob whatever you plugged into the input is sent to it.

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Thanks for this. And I realized now that Intellijel Triatt and Quadratt functions the same way. It’s a thing. I just never got it before. Thank you for all the explanation. I still don’t understand precisely how this constant presence of either +5V or +10V normalization works, what it does to make the offsetting of the attenuates signal happen, but thanks to you grand folk I now know that I can use it!

Anyone know the history or origin of this function in modular synthesis? Or in synthesizers?

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offsetting? or normalization? Normalization is actually a common practice in electrical engineering, and most jacks, if you got one to look at, are built with it in mind: you’ll see that by default there’s a physical connection between where the signal would otherwise flow and an ancillary little pin. inserting the jack physically breaks this connection by moving the little pin out of the way. Electronically it’s why your phone knows to stop the music when you unplug your headphones: there’s a little circuit there that tells your phone “something is plugged in”

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I had to look up ancillary! First definition said: “connected with something, but less important than the main thing” (which sounds both very vague and very familiar).

I think I only thought normalization to mean that a signal is already routed under the hood to somewhere (the place it is normalled to), and that you can break this normalization by patching (if the thing is set up that way). I hadn’t heard it about the jacks like that, so that’s one more new thing learned today! Thanks @alanza.

But I was curious about the offset, and attenuation and offset modules as it’s own thing, in modular synths.

I see there’s also scaling. If you’ll all forgive me - what is meant by scaling?


I think they’re all related concepts: if you think of CV as being like automation in a DAW, as, like, having electricity turn knobs so you don’t have to, then all of these tools are attempting to solve the problem of “I have the right shape, but it’s too big / too small / in the wrong place”. Whereas in a DAW you could just move the automation around until it worked right, in hardware you have to work a little harder


@alanza with the brilliantly simple explanations yet again. :slight_smile:


But I have to work harder in my DAW to make the automation there feel alive. On my modular it’s like a having secret gang of friendly electric ghosts (some of them very musical, some of them more in it for sheer timbral adventure) turning the knobs, and often knobs I didn’t even know I had.


So here’s something I spent a good half hour trying to patch up today and I just couldn’t quite crack it.

Here’s a picture of my rack. I had a cool patch going where Rings was acting as a kick drum and I had Tides in the harmonic oscillator mode, with the sub signal going to to VCA, and the normal voice going through the Magneto and back to the VCA, and I tried to feed an envelope to the CV in to act as a sidechain on the effected signal, but I couldn’t get the timing right to suck on the beat and pulse between kicks. I know the sidechain is in there, I just need a little advice coaxing it out!

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