Eurorack: discussion, advice, learning, questions

Both are nice VCA’s. I prefer the Intellijel because I like knobs more than sliders, plus it has a little more room to work with. I’ve got nothing against Veils at all (I use them both with some frequency), but between the two, I prefer the Intellijel. Hope that helps.


I can only speak to Veils but I really love the sound you get out of it when you overdrive it. It’s underrated as a saturator/distortion imo. (Maybe the Intellijel also has a nice overdrive too though?)

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When you find out, please DM me the details :wink:

The interface has nearly the same parameters as the R*S ResEq, minus one output and phase invert switch. Could it be a clone?

Random DIY question: if I were to make, say, a passive LPG, would it still need to be connected to the ground rail of the power supply? If so that answers my question (lol) but if not how are components connected to ground reliably?

I found the design of the Quad VCA confusing, as having the big knob be the offset doesn’t make sense to my brain. I have been much happier with Veils 2. It’s pretty perfect.


@kilchhofer’s release & thread might have some insights ! Kilchhofer Anklin - Moto Perpetuo


An LPG is a vactrol (a type of optocoupler); this means there is no electrical connection between the control side and the signal side. The signal side is effectively just an attenuator but with an LDR instead of a pot: The CV side connects the tip to ground (sleeve) via the LED in the vactrol (and a current limiting resistor); The input jack has the tip conneced to the tip of the output jack via the LDR (and a current limiting resistors); The input jack has the ground (sleeve) control to the ground of the output side. Finally there is a resistor connected between the signal and ground sides of that part of the circuit (completing the potential divider/attenuator). It’s a passive device that operates by virtue of the current provided to the CV input.

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Thanks for the detailed explanation! I’m new to electronics DIY coming from a software dev background and am 100% a “I need to know how it works before throwing together diagrams I found on the internet” person.

It’s really not very complicated for the most part but it’s critical you understand the basics of electronics well. The two most important things to remember are ohm’s law and that semi conductors (diodes, transistors etc) have a specific voltage drop across them; that plus kirchoff’s law and a circuit simulator (e.g falstad circuit simulator) is really enough to make anything. Your question suggests you have some basics missing from your understanding (e.g what purpose would the ground serve and to what would it be connected if it was provided on a power connector.

With a software background I went from “press a button and turn on an LED” to Google assistant controlled garage door opener; alarm when my washing machine finishes; euclidean rhythms generation eurorack module; a sequential switch based sequencer and many other things (custom schematics, and PCB and panel layouts) in about 3 months. A few hints for improving quickly:

  1. Analysing circuits, in particular looking at a basic circuit (like an attenuator) and describe why each element of the circuit looks like it does.
  2. Make sure you understand how transistors work and can build things like a “safe gate output” out of them.
  3. Read data sheets for ICs and search for multiple versions if they are common IC types: often then datasheet for one version is hugely helpful (example schematics for various use cases and useful practical descriptions) while some are very dry and technical and don’t offer any context about how you should use them (just what the pins do).
  4. Take the time to simulate your schematics and get quick at breadboarding designs.

All in all I was amazed how easy it was to go from basic theory to working designs that provide facilities that I actually needed (vs toys to experiment with): having an engineering mind already helps tremendously; as does having thoughts for things you’d like to make (preferably things that don’t already exist as doing “your version” of someone else’s circuit is far less instructive).


This is extraordinarily helpful. Are there any resources (YouTube, books, etc) you’d recommend to get up to speed on the basics of electronic theory?

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I was also struggling to make this choice, but the availability and cost of Quad VCA eventually made it for me. :grinning: I also thought the small knob/big knob priority was backwards at first, but I’ve found myself using the VCA as a mixer and O/A so often that I’ve actually come to appreciate it!

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Think this highlights how individual these decisions truly are. To me, quad vca’s “big knob is volume,” since offset here can be understood as initial volume, makes complete sense to me, whereas the veils approach was utterly baffling.

@eblomquist, it’s kinda hard to know what will make the most sense until you’ve tried both. That said, either way, you’ll end up with a capable workhorse VCA.


Haha, will do. It’s definitely a clone, but I want it for that tiny HP footprint. :paw_prints:


thank you Andrew! Working with contact mics sounds like a good starting point.

Thanks for the replies about the Quad VCA/Veils 2020 decision.

Lots to ponder!

I’m intrigued by the saturation gain on Veils, and am not sure how much I would use the cascading cv on the Quad VCA. Also I suppose that if I want to have the same cv into more than one channel on Veils I could always run it through a mult.

I’m thinking that the faders on Veils 2020 have two interesting benefits that knobs don’t, namely instant visual indication of all levels relative to each other and the ability to easily manipulate multiple volume faders simultaneously with one hand…

So I think I just talked myself into a Veils :sunglasses:


I agree the faders are a plus for those reasons. One additional thing I appreciate about Veils 2 that I don’t think has been mentioned is that there are LEDs to indicate both the incoming CV and the output per channel. For some reason many VCA modules only provide one or the other!


Your connectivity from space is pretty remarkable :joy:


Not a question I actually asked, but here’s the answer for future searchers: The ADDAC 601 (Fixed Filterbank) and ADDAC 802 (VCA Quintet Mixing Console) will fit inside a 4ms Pod 64x without any washers or standoffs. Just barely. I ordered them without looking at the depth and needlessly worried.


Firstly, thank you to all of you for your expert advice/tips/insights on this thread, it has proved very useful during the past couple of years for my dive into modular. I am having a brain freeze regarding a particular function within my modular system which I can’t think how to achieve. I am using Qu-bit bloom to sequence a “generative” system of sorts, it works great but occasionally it will spit out a high pitched random note within the scale but like an octave or two higher than is musical, so I just want some kind of voltage filter that only lets a voltage below a certain (user defined) threshold through but i want all other voltages to go through unchanged so the scale/spread on marbles and turing machine isn’t what I am looking for I don’t think, any pointers would be gratefully appreciated, probably something really obvious i have overlooked!

You can do this most simply with with an AND circuit, available on most logic modules. Two inputs: your maximum voltage, and your sometimes-too-high voltage. The output of the circuit will always be the lower of the two voltages, meaning it will never go above your max voltage

A more musical but more complicated approach would be a comparator controlling a precision adder. When the comparator detects the sometimes-too-high voltage is higher than your maximum voltage, it sends out a positive voltage. This could go to a voltage controlled switch which allows thru a e.g. -1V signal which you precision-add to your pitch CV to drop it an octave. (there are probably voltage-controlled precision adders so you don’t need the voltage controlled switch, but that’s the basics of the circuit you want)