Eurorack Knob Idea | Hacker News Reader

Eurorack Knob Idea

mitxela.com

322 pointspo121 comments

>It's a nice dream, of a synthesizer where any knob can be pulled out and replaced with a patch cable, and any jack can have a knob plugged into it to set it to a fixed value.

What's even better, though, is a coupled knob + jack where the knob turns into an attenuator for the input when a cable is plugged in, and works as a standalone knob otherwise. I think this is quite a common design.

I believe I've also seen patch cables with built-in attenuators.

Another common pattern is jack + offset. The most useful is when you have jack + offset + attenuator… but most modules pick one or the other for space reasons.

Totally. Also, an attenuator is easier and cheaper to implement, because it just requires normalizing V+ into the jack plug. An offset requires an adder.

My preference is: attenuator < offset < attenuator + offset. I see no benefit of having to remove the knob to get to the jack as proposed in the article.

The benefit is saving space. Imagine a 10x10 grid of such jack / knob inputs.

The attenuator-inverter is super handy too. A gain knob that goes from -1 to +1 X.

That's a neat trick. Only way I can think of to do it involves two op amp buffers, one inverting one not and take the signal from the wiper.

There are dual-knob coaxial setups that are only slightly bigger than a single knob as well. I've seen them mainly used in a course and fine adjustment setup, but you could certainly use them as atten+offset.

the smartest pattern is used in mutable instruments beads, the "attenurandomizers"

it packs a ridiculous amount of functionality into a single plug & knob combo

This is why I really like Intellijel’s designs. They generally have attenuators on the inputs for which it makes sense, and those attenuators are the small stick knobs. While they use larger knobs for more central module functions.

Eg: https://intellijel.com/downloads/manuals/rubicon_manual.pdf

I like it, but the best modules already have knobs and jacks for everything. When you have CV going into the jack, the knob acts as an attenuator or attenuverter. This means that the modules are generally larger. Make Noise generally does this and their modules are consistently bigger than everyone else, and they're also some of the most popular. Look at Maths. It's a slope generator and a mixer. It's fucking huge. But everyone has it because it's patch programmable. The problem in Eurorack is instead of making things patch programmable, they try to fit in a ton of functionality into a small space, so you have a lot of modules that have multiple modes where buttons and knobs all have different meanings depending on what "page" you're on. Fuck that. Almost every time I try a module like that, I end up selling it.

He's right about the interface being the point of Eurorack. Plugging things into other things is the whole point. When I have a module that has hidden state, I forget what state it's in or what the knobs mean. I end up avoiding those modules. With cables and knobs, I can see the state of the whole system. I need good cable management to make sure it's not spaghetti, but I already do that in code already, and it's not that different.

Apologies if I'm missing something obvious, but why not just stick a potentiometer on the same axis behind the 3.5mm TS jack? Many 3.5mm jacks are open on the back, so you can give the knob a long shaft (longer than 3.5mm obviously), and that shaft can mate with the potentiometer.

Alternatively, Eurorack uses TS jacks as connectors for control voltage inputs, right? If you build a module with a TRS jack instead, you have an extra pin (R) that you can connect a removable potentiometer + knob to. And you can still plug in regular TS cables.

(Note: the article uses "TRS" loosely when it means "TS". I mean them literally.)

Yes, this sounds like a simpler solution - the major drawback/advantage would be that you'd need to insert the knob in just the right orientation so that the shaft end fits into the potentiometer's slot. Might be a bit fiddly. On the other hand, the poti would keep its state even when the knob is removed, and you wouldn't accidentally change the value when inserting the knob.

Just to nitpick the nitpicker: the knob's shaft needs to be longer than 15 mm, right? "3.5 mm" is the diameter, not the length of a small T(R)S jack.

Oops, yes, 3.5mm is the diameter. I was sleepy when I wrote that, and I knew it didn't seem right.

Good point about the orientation when inserting. I was thinking something like hex or torx or friction fit that would allow you to insert it without thinking about the orientation. But then that causes another problem: any visual markings on the knob aren't guaranteed to be in the right position. I'm not sure if there's a good way get the best of both worlds on that.

Something like this might work. When pushing the knob in, a spiral inside it rotates around the tongue that is attached to the potentiometer (or vice versa). Once it is fully pushed in, the groove in the spiral rests against the tongue, allowing the knob to turn the potentiometer. Would probably need a lot of fine-tuning to get all forces exactly right.

https://winterwind.org/_media/pasted/20250426-220417.png

It's an interesting idea (truly a clever way to accomplish this!), but I think it's addressing the symptom, not the problem. The symptom is that some jacks don't have associated knobs. The problem is that either the module designer or the module user is overly obsessed with miniaturization. The designer is at fault if it's a parameter that really should have had a knob with the jack and they avoided including one in order to keep things small. The user is at fault if they're trying to stay so space-constrained that they can't fit a module that outputs an DC voltage set by a knob into their case. There are numerous modules that do this (and often that attenuvert as well) and many of them are fairly small too.

The problem is that different people have genuinely different ideas on what kind of modulations are sensible. My go-to example on this is E-mu gear - a company that started out making big modulars in the 70s and went on to dominate the sampler/rompler space for about a decade before going bust during the dot com boom and being absorbed by Creative.

the nice thing about E-my synths was that they nearly all had big modulation matrices included, although users were often defeated by the 2-line LCD on their romplers. But one strange omission from the modulation destinations was filter resonance; all their later modules included a huge (arguably excessive) selection of filter types, but for reasons of computational efficiency you could not adjust the resonance while a note was playing. This wasn't too bad from the front panel because most people want to ride the cutoff rather than the Q, but the inability to modulate it inadvertently highlighted some limitations of the filter design.

I can see both sides, as I am a 'let me modulate everything' person when choosing gear but at the same time I quite admire 'opinionated' synth designs where flexibility is traded off against maximizing sweet spots. Sometimes it's better to have an instrument with limited sonic range but which responds very consistently within that, so 'you can't get a bad sound out of it'.

Interesting idea for sure, but how is the feel of actually turning the knob? Seems to offer short to no resistance, which would make fast but precise movements pretty hard, something that is important for things like performances.

What would be a huge bonus point (but maybe unrealistic? I don't quite understand how the current implementation actually works) would be software-configurable resistance (physical, not electrical). I've spent a lot of time for my DIY modules to find the right knobs, or the right process to adjust the resistance of my existing knobs, being able to control that digitally could introduce a whole new level of fun.

You might enjoy https://github.com/scottbez1/smartknob

The complexity of this approach (ignoring the display and flair) unfortunately means you won’t see this used too often due to cost.

That's so cool on so many levels, and I really enjoyed that indeed, now I have to fight the urge to try to build it myself, good thing it's weekend.

However, it does seem to miss the single most useful feature (for me) which is the resistance part. I understand there is a DC motor controlling the snap points and whatnot, but what I'd like is constant resistance I guess, to a configurable level, rather than snapping to specific points and such.

I don't think it would be possible to hack on top of the already made hardware, but didn't seem like it was already done in the software side of things, although I did skim through things so maybe I missed it.

Should be doable to add that. The BLDC needs to add a proportional (or any other function) force against the rotation direction until it reaches 0.

Sounds reasonable, wonder how that would actually feel in real life? As far as I understand, this would pass through digital parts, adding a little bit of (maybe noticeable) latency, but I wonder if the latency gets high enough for it to be a bit jarring that the resistance is dynamically changing as you apply torque.

This is all fairly normal in robotics, under a subset of (slightly overloaded naming sorry) “impedance control”

In practice, when latency is small enough (on the ~1ms level, which is trivial to achieve using even pretty cheap parts) it's imperceptible.

I sometimes develop control loops for prototype systems which use a motor to emulate a combination of spring + friction damper, and even though I know that my code only runs every 1ms, it's really remarkable how much it feels like a real continuous analogue system.

Another good example is power steering, which uses a motor to remove resistance instead of add it. If I understand it correctly, it senses you applying torque to the steering column and adds proportional amounts of boost - but because it happens so fast, it just feels like the steering is magically lighter.

A differently complex and smaller approach might be to combine the knob with with an axial flux PCB-BLDC, like what Carl Bugeja made [0, 1]. It might be suited to get haptics in something as small as the article's knob, although to get an in-built display you'd have to use one of those displays that fit in lego bricks [2, 3] with a slip-ring.

0. https://microbots.io/products/motorcell

1. https://www.youtube.com/watch?v=CVszJMlvZcA

2. https://github.com/AncientJames/uGrey

3. https://www.youtube.com/watch?v=0pUV_3qeHog

Many thanks for the links/references. I don't really care about the display itself (probably prefer without it actually), but never saw those other links before, interesting stuff.

My dream is a piano keyboard with entirely software controlled mechanical key response. Every key individually mounted on a servostepper. As a bonus it could be used as a fake player piano. Or for practice you could make the wrong keys hard to press. Endless possibilities.

Great idea and I’m shocked this doesn’t exist.

It would likely be very, very expensive.

A compromise that is affordable and does exist is programmable response curves to key velocity and aftertouch pressure. It can make sense to have different curves for eg. piano vs harpsichord even if you can’t change the mechanical key impedance.

I haven’t seen it in the wild, but using this you could make the wrong notes quieter/louder or even play a different sound. But I think we all know when we play a wrong note, so the utility might be small.

> key velocity and aftertouch pressure.

Just a tangential note to say whenever I see these terms in discussion of MIDI keyboards it reminds me how disappointed I am the vast majority of MIDI controller (and multi-thousand dollar flagship synth) keyboards still don't fully support per note velocity or polyphonic aftertouch. It's only been 40 years kids... (sigh).

Not really needed. A synthesizer is not a piano, it's essentially a wind instrument.

I personally disagree. That velocity and aftertouch is all fun modulation input to my eurorack synth. Sure, I have a limited number of polyphonic notes (4) I can support, but it's still more modulation possibilities.

> Or for practice you could make the wrong keys hard to press.

This seems like a pretty cool idea

I'm not convinced it would work very well on making you a better player but who knows. Either way, it sounds like a good way to injure yourself. Piano is a very percussive instrument and if you're hitting the keys with any force and they don't give the way you expect them to I imagine that won't be very great for your joints.

The Yamaha Disklavier has solenoids on every key, so you could disable every key but the one you want by moving them downwards.

It already has a similar feature called SmartKey: https://www.youtube.com/shorts/_Qj33POZCyA

This is what cars need. Only make the entire dial depressable instead of the embedded screen. Use different haptics for each setting so you can feel which setting you’re changing.

> the right process to adjust the resistance of my existing knobs

I too have "a thing" about the feel of tactile control elements ranging from the tensioning of knobs and joysticks to the dampening on sliders, the force on my emulation arcade cabinet buttons and, of course, the keyswitches, o-rings and lube on my computer mechanical keyboards.

However, I don't really feel a need for software control of the tensioning feel. For example, I have a few different high-end dual-joystick radio control transmitters for RC aircraft. These have fairly pricey hall effect joystick mechanisms and the good ones have a tensioning adjustment for each axis on the bottom. Whether on these RC transmitters, my arcade cabinet or high-end console game controllers I find it's sufficient to simply set the tensioning to my preferences once and I don't feel the need to change it again.

So for the EuroKnob, I agree having no tensioning would be pretty awful - as there's little worse than a floppily loose knob wiggling about - but for me a simple friction-based drag adjustment would be fine.

Ok, but why stop here? You've effectively created a rotary potentiometer in one dimension, you could add two more dimensions like an analog thumbstick on a game controller. Do any controllers have a twistable thumbstick?

Also, like other commentors have stated - this could be a jack too, so you could have a jack knob analog stick.

BUT WHY STOP THERE?

You could mount it on a linear pot/slider.

BUT WHY STOP THERE?! (help me)

You could daisy chain pluggable rotary analog stick jack stacks...

----

The madness has taken him

There are several 'joystick' controller modules (Doepfer a-174-4 or Intellijel Planar come to mind) and the Doepfer also produces 3rd signal by twisting the knob.

> Do any controllers have a twistable thumbstick?

Yes, several. For example, the main knob on the Komplete Kontrol S-series MIDI controllers (https://www.native-instruments.com/en/products/komplete/keyb...) combines a rotary encoder with four axis directional input, a push button and an LED indicator ring. I have an S61 and the implementation of the knob is delightfully intuitive, responsive and functional. To be clear, this implementation is not a joystick on a ball base with twistable knob, it's a flush-mounted knob that can be slightly nudged up, down, left or right with a single, satisfying click in each direction. I'd recommend trying it yourself, if only there were still any music stores that put a range of high-end midi controller keyboards out where customers could, you know, touch them.

I actually came here to suggest the same idea for the EuroKnob. The four axis directional input is basically a D-Pad module commonly used in game controllers. I find this kind of rotary knob + directional input control to be very effective. However, there's one critical caveat. It's apparently possible to implement this kind of control poorly because I've also seen a couple devices where the implementation is as bad as the S61's is great. It probably just requires a certain degree of engineering finesse to nail a good combination of responsiveness and tactile feedback.

> You could mount it on a linear pot/slider.

As much as I like and agree with your first thought, I've actually seen the idea of a rotary knob combined with a linear slider - although it's extremely rare. Having touched one myself I can confirm the reason it's rare is that it's not just bad - it's uniquely bad. By which I mean the combination of two controls which each work so well on their own into one combined control, is unexpectedly awful. I was unfortunate enough to try one first-hand (so to speak) at a tiny booth buried in the back of some long-forgotten NAMM show in the days when Cubase was still being demoed on an Atari ST. There was a bespoke mixer from a company I'd never heard of with rotary knobs on their mixer's sliders. I'm pretty sure when I tried to adjust the two parameters at the same time I may have reflexively pulled my hand back and uttered "Ugh!"

Usually I'm polite when trying out some novel interface idea but there must be something 'special' about trying to combine two very precise but divergent proportional motions on two different arm joins (wrist & elbow) at the same time that's deeply unnatural. It felt so weirdly wrong that I suspect some human factors kinesiologist has probably written an award-winning paper about how humans evolved to never, ever do this. But hey, one out of two ideas is still a great day! :-)

Thank you for taking my lunatic ravings semi-seriously!

I saw an encoder similar to the one you like in an ultrasound once. Here is another: https://www.ctscorp.com/Resources/Press-Releases/New-Three-i...

There is something satisfying in noticing the same solution applied to problems in different domains, like audio, medicine, and aviation.

Sanity wants you to stop? Just say no, sanity legally cannot stop you without your consent.

reminds me of The Parable of the King's Toaster...

it ends with:

The king wisely had the engineer beheaded, and they all lived happily ever.

IT consultant detected.

The king wisely had the computer scientist beheaded and they all lived happily ever after.

It's interesting. I haven't been sucked into the Eurorack thing though — do people want not just patch cables all over their mixing desk but knobs as well?

Eurorack (and modular synths in general) seem like funny things. Like guitar pedals, I sense there are a lot of enthusiasts that do a lot more tinkering than actually playing them. Watching Rick Beato and guests on YouTube ... seems like a lot of musicians are looking instead for simplicity. Like a few good sounding pedals that, ideally, each have just a knob or two.

Maybe the synth-heads are in a whole different headspace though.

It's somewhat similar to people enjoying developing their game engine more than their game in my experience. Provably why in attracted to it despite having little musical talent :)

> It's interesting. I haven't been sucked into the Eurorack thing though — do people want not just patch cables all over their mixing desk but knobs as well?

I don't personally feel the need of wanting more cables all over my current setup, but sometimes I have had the feeling of "Oh if I could just modulate the VCF Cutoff on my Zen Delay with a patch cable from my modular instead of doing it manually" for some of the desktop units I have next to the modular.

And on the other side, I've also felt the need of having some of the patch holes replaced by knobs, so I could just twist and turn it to evaluate if I want to modulate it, instead of having to actually setup the patch. I could see something like this knob-idea being very useful for that, basically prototyping patches.

> I sense there are a lot of enthusiasts that do a lot more tinkering

This is definitely true, large parts of the community is about tinkering more than making music. But the same is true for programming, large parts of the community is not about problem solving, but coding. That's fine, we all have different motivations :)

What I found really useful (for myself at least) is to try to connect with people who are artists first, who just happen to be using modular synths, rather than finding people tinkering with modular synths who don't actually produce/perform music.

> I haven't been sucked into the Eurorack thing though

Good for you :) A friend pulled me into this dark abyss a month ago. Lots of fun, so many distractions, but lots of fun. Helps that Barcelona (where I live) have a lively community around modular synths as well. It is expensive though, and VCVRack doesn't come close to providing the same experience.

> And on the other side, I've also felt the need of having some of the patch holes replaced by knobs, so I could just twist and turn it to evaluate if I want to modulate it, instead of having to actually setup the patch.

That could be an interesting spin on this idea. A freestanding PCB with a jack plug on the back and a knob on the front. Turn the knob, and the jack sends CV accordingly. Maybe with a velcro based system to have the PCB stay still while you twiddle the knob.

Maybe they are tinkering, but sounds still come out while they are tinkering. So maybe they're playing music after all? The idea that if you're not recording and releasing tracks you're doing it "wrong" is a bit silly IMO. Just strumming a guitar or playing some chords on a piano without recording any of it was always an "acceptable" hobby and not considered "unmusical", playing with synths and sequencers is no different IMO.

You're right. Someone's hobby could be "noodling" — with a guitar, synth, etc.

I've been asked for recordings from my system multiple times and I always tell people I just like to play it for me, in the moment. I have no desire to record it's output. I also go for more drone style output and tweak it constantly. But it makes me happy and that's all that matters in the end.

> Like a few good sounding pedals that, ideally, each have just a knob or two.

It makes for a nice narrative but I haven't found it holds much water; musicians are all over the place on this spectrum. You'll find both extremes very well represented, and a good chunk of people who compartmentalize their "dayjob" music and tinkering. I've found a lot of successful musicians love to tinker and are always on the search for new inspiration. Like any good craftsperson they take some amount of pride in their tools and I've been blown away by how technical many can get on the electronics side! It's always funny to see Reverb auctions go up for famous musicians and finding out a bassist in a pop punk band owns a bunch of weird synthesizers :)

Simple one to two knob pedals are a big deal but you'll see a very large number of pros touring with extremely complicated modeling setups and all sorts of gadgets. At a certain point you really know what you want, and having the ability to dial that in is important! I tend to gravitate towards simplicity in a band setting but I know a lot of people who want dirt pedals with 10 knobs so they can dial in the sounds they hear in their heads.

Your pedal board/modular synth is a reflection of your personality.

Just like real life I have a tidy put together functional board, then a disturbing spaghetti mess tucked away in a corner that few are allowed to see

Hahaha I feel that.

I swing bimodal on this. For a while I enjoy the most exotic modular patches and loaded pedalboard. Then for months I am all about piano and acoustic guitar, as vanilla as can be.

It’s all so deep I’m not going run out of fun in any mode.

100%, there's weeks I just plug straight into an amp because that feels right! At the end of the day it's great to have options.

I'm the same on the guitar side. I'll go weeks using a fractal fm9 straight into the PA. it's like playing through a computer which is awesome. however...

I'll get real sick of the complexity and go back to my cranked tube amp and one overdrive pedal.

If I had to choose one, I couldn't.

The knobs tend to be the "public API" and the patch cables the wiring up of the functionality to that public API. having a knob for each patch is akin to making every method 'public' instead of protected or private.

Watch some episodes of LOOK MUM NO COMPUTER for an example of the kind of tinkering/creativity some people at least love to have available in the physical realm: https://www.youtube.com/channel/UCafxR2HWJRmMfSdyZXvZMTw

A lot of the music is made just playing with different parts of the sound, and having all the controls exposed to be messed with can lead to more creativity.

IMO, kind of like how I enjoy Linux configuration files, in a way, more than I do a GUI that covers up 90% of the guts of an application or server software.

My favorite documentary I have not seen (yet), I Dream of Wires from 2013, about modular synthesizers. I know in some trailer there was a maker of modules saying something to the effect that if only people actually making music with their synths bought modules he would be out of business. Can't find that trailer now or I did not watch carefully enough now. There are a few different ones on youtube.

https://www.youtube.com/watch?v=rQSxqha62j0

I’m pretty sure the person who said that quote about non-professional musicians who purchase Eurorack modules was Paul Schreiber, who passed away about a month ago.

Gonna look it up, and I’ll edit this post when I find out.

Edit 1: Didn’t find the quote from the film yet, but did find [1]this video (unedited interview from I Dream of Wires) where Paul explains how he himself is not a musician, but rather an engineer.

[1] https://youtu.be/6ixv4F4XD4Y

Edit 2: Still haven’t found it.

I have the film at home, but I’m traveling in Europe at the moment, so it is out of reach for me currently.

Don't get sucked into modular hardware synths. They are TONS of fun, but it is a very expensive hobby. Monotrail Tech Talk has a few excellent videos on YouTube, but he must have spent a fortune on his gear.

I got sucked into it a little over a year ago, it's starting to wear a bit thin for me already though.

> I sense there are a lot of enthusiasts that do a lot more tinkering than actually playing them

It's called "sound design" :) Can't start on a song until the timbre of my never-quite-done-this-way-before saw tooth bass is juuuuuuust right.

i'm happy someone is considering new physical ideas/approaches at least as i find the trend in recent years of basically putting full "computers" into eurorack modules ridiculous. not just raspberry pi's behind a eurorack plate but with full configurability / user interfaces.

the release of the 4ms meta module was when i decided to be happy with what i have because it's becoming an unironic misguided circlejerk of sorts

For me I pretty quickly realized that I like synths to make sounds, or maybe a bit of programming (with wires!) to make an electronic music box.

But making songs? Just not for me... And that's a whole different thing.

> I haven't been sucked into the Eurorack thing though

I'm the same. I love playing around with making electronic music on a hobby level and I find the idea and look of modular synths appealing - and I'm also a pushover for most retro things, especially those with cool knobs and blinkenlights. However, if I'm honest, I don't really enjoy creating music with modular or vintage analog "knobby" synths. I haven't ever bought a modular rig and my vintage analog synths are lovingly packed away with my numerous retro Amiga, Atari and Commodore computers where they wait to be enjoyed in limited doses on special occasions.

So, to address your implied question, IMHO I don't think people like us are somehow "missing" something deep and great in modular synths. To me, the essence of the modular appeal is three things: 1) tactile feedback that's responsively immediate, 2) a set of compatible 'lego block' components which can be combined in creative ways, and 3) An element of randomness from the combined interactions on analog components.

While modular rigs offer all three of those things, having those three together doesn't require analog hardware or a dedicated modular rig. I think I can get a very similar creative feeling and joy of discovery (plus a smidge of randomness) from the right combination of high-quality MIDI control surfaces and a well-chosen set of synth plug-ins running on a computer. To be sure, some MIDI control surfaces are crap and not all synth plug-ins enable creative experimentation deep enough and easy enough to 'scratch that itch'. But, then again, it's possible to assemble an ill-conceived modular rig out of poor quality components that also fails to inspire creativity. While finding that unique balance of factors sufficient to trigger creative serendipity isn't trivial with either analog hardware or digital MIDI + plug-ins, to me the advantages of digital in cost, size, speed, repeatability and flexibility win out.

I guess it's possible there's some other essential element which analog modular rigs provide that I'm missing out on but if so, I haven't been able to discover what it is.

Some people want to try new ideas that you can't buy ready made in a commercial synth or effects pedal. For example, trying unusual modulations, feedback loops, and signal dependent effects depth/parameters. Without a Eurorack you have to build a custom circuit to try it. With a Eurorack you can plug in some patch cables and quickly try it out. Think of a Eurorack synth module like a math symbol, you can assemble them to create an equation that produces sound. It's actually very much like an analog computer, where you can write an equation and implement it in hardware. It is literally possible to write equations and see what they sound like. You can do the same thing with something like VCV Rack though it's somewhat more difficult since to get physical controls you have to map midi controllers and may need a lot of midi controllers, which probably means manually labeling all the controls so you can tell what they do. In a Eurorack module each control, input, and output is already somewhat usefully labeled and defined by the module it is part of. So for some sound designers Eurorack systems are sophisticated sound design tools. You might use one to design a new kind of guitar effects pedal or to create a custom tweak on a specific sound in a movie soundtrack. Not that you can't just play with them without a coherent design in mind also, just to see what turns up.

Thanks for explaining the unique value you find in analog modular hardware.

> With a Eurorack you can plug in some patch cables and quickly try it out.

I'm curious if it's possible to do the same kind of modular interconnection with virtual analog plug-ins like Kontakt or Cycling '74? I've played around with Kontakt and it seems enormously capable and able to hook up operators and simple circuits almost down to the level of math symbols. I haven't played with Cycling or similar DSP environments but my understanding is they're literally programmable down to that level.

To be clear, I'm asking because I really don't know. I have a vintage Prophet 5 and the best DSP emulations seem to emulate it perfectly but with even more flexibility, extensibility, repeatability and no need to avoid oscillator drift or clean dirty pots :-). But I'm also not a serious synthesist or sound designer and I don't pretend to have golden ears. I guess at a certain point it may be quicker and easier to just wire up modules rather than assemble code modules in Kontakt, Cycling or some other DSP environment (assuming you have the right hardware modules on hand). But once you have to order or solder up different modules, I assume the plus sign swings to the software side again? Once again, not questioning the value you get from what's clearly working for you. Just interested to understand. As I said, maybe I am missing something. It might be that it's just something I don't personally care too much about for my needs, so it's all good.

I'm a big fan of the Midi Fighter. I have the 16 knob version, but they make a 64 knob one as well.

https://store.djtechtools.com/products/midi-fighter-64

https://store.djtechtools.com/collections/midi-fighters-midi...

There’s definitely a thing in music, as in computing, or golfing, or whatever, where some people are more into the gear than the actual practice of doing the thing. Modular synths are a great outlet for those kinds of people.

I have a modest Eurorack setup and a few other synths and I find them a nice way to get into music making without looking at a computer. It’s nice to have a limited set of options, rather than a near infinite set of software plugins and presets. My gear can only make a certain number of sounds at once, and that’s it. The liberty of constraints.

When I get serious about a music project I inevitably end up working in a computer DAW but I often don’t find that an inspiring place to start.

> any jack can have a knob plugged into it to set it to a fixed value.

I'm kind of surprised he didn't start with a knob with a tiny accelerometer, mcu and battery in it to produce some sort of output signal into a stock plug depending on how the knob is oriented with respect to gravity.

Putting electronics inside the plug is nearly a mitxela trademark. https://mitxela.com/projects/flash_synth

I was wondering this - I'd buy this if I could just plug it into my existing sockets. I'm pretty sure you could get 50-100 hrs with a battery, but I wonder if you could have something that you wind-up like a mechanical watch.

Probably because pulling on cords can twist them. That’s what I thought when this occurred to me.

Profit margins on eurorack are pretty damn low. And you need a lot of knobs and jacks and plugs. Even a hall effect sensor may be out of the sweet spot for cost.

"It's a beautiful dream – a very expensive, but beautiful dream."

While that might be true, what is expensive for me is chump change for someone else. However, that is very difficult to grok as there was no prices mentioned anywhere that I could see. Sure, it'll be expensive to me because I have to ask. But I also know that I cannot afford a fully spec'd out MacPro, but at least I can see the numbers.

This looks super neat and probably a fun project to build.

> It's a nice dream, of a synthesizer where any knob can be pulled out and replaced with a patch cable, and any jack can have a knob plugged into it to set it to a fixed value. Whether it's actually practical to build a synth like this I'm unsure. It would probably only be worthwhile if you applied it to every single control on the modular, which rules out using other people's modules. You would have to invest heavily into the Eurorack Knob Idea. You couldn't even port other modules that easily, as many of them would expect a real potentiometer, whereas the encoder can only produce a voltage. Coupling it with a voltage-controlled potentiometer would work, but would be even more expensive.

Yeah, it's hard to imagine this fitting in nicely to everything since it's defintely more effort and work than just having a knob and a jack for the control of a particular thing. Esp. since most of the time, as a convention, you'll have a knob that controls the value, but when a jack is plugged in, this same knob acts as the attenuator for the signal.

I would have appreciated having an image or a pdf of the schematic for the design to understand it properly - i can get it from your github but I don't have kicad installed on this computer.

I'm esp. interested in the normalized behavior - ie. when you have a signal plugged in to the jack that is _not_ the potentiometer.. does it get passed through or does it have to go through this chip as well?

Having to supply a 3V to this to make it work as well is also an extra requirement of its usefulness in normal eurorack circuits - not a total dealbreaker but that does add extra requirements, and extra components to one's design.

Anyways... really cool idea :)

As a fellow Eurorack circuit designer and university teacher on thst issue one immidiate issue I can see is one of practicality. Decent potentiometers are maybe a Euro per piece if bought in bulk, they have a start and an end which is nice and for analog gear you have direct control over the parameter, with very clear feedback what is going on — that is the main reason people want physical gear. So add in a LED ring for visual feedback and endstops.. Might be nice for a digital module.

But even then I'd wonder if it worth it, because of the high pcb space usage. With potentiometers as attenuators or attenuverters you can fit two pots next to each other in a space of 20mm which neatly aligns with the standard panel widths. Theoretically you could certainly get smaller with thst solution, but the hall effect IC needs to be accounted for as well. With existing pots I can use the space underneath. If your module is just 10mm wide that space is pretty premium..

Very cool idea! It reminds me of how software works— you usually drag an LFO to the knob to modulate a parameter.

A few people have pointed out that the knob can act as an attenuator when it's being modulated via a jack, but sometimes the goal is space. I can also imagine a version of this that uses the same technique, but where the knob has an audio jack on it. You wouldn't need to unplug it to connect the incoming cable, and you could use the still-connected knob as an attenuator if you wanted to. This would get you the best of all worlds— maximum space, an intuitive interface, and attenuators if you so choose to have them.

I liked the video focused on his hands, where his gestures and expressing the rough size and orientation of things added to his verbal description. Not sure if this is a common technique, but works very well for this topic.

This Old Tony (a hobby machinist / welder on youtube) has made all of his videos in that format. It works very well!

https://www.youtube.com/c/thisoldtony/videos

1. I find Tim's work always so impressive and humbling. Compared to software, hardware projects seem infinitely more complex.

2. Speaking of knobs, I am writing a toy software synth for smartphones. Are there any design guidelines for mobile UI for audio? Knobs are hard to use and sliders take up a lot of space with only a little more precision. I experimented with curved sliders (inverted parabola or sine), but they are confusing since height doesn't really encode anything and the curvature is there only to make the slider longer. I didn't find any design systems focused on audio components.

Knobs shouldn't be hard to use - hold down the knob that needs the adjustment and then drag in either of two directions to set the value. Maybe have a pop-up over the knob that displays the value as it's in use.

Loopy Pro has a cool convention that I haven't seen elsewhere for this. Drag up or down to change the knob value. While doing that, drag left or right to zoom in. That makes the up/down movement more precise.

I will look into it! Is this for mobile or desktop? I would like to see how they introduce this interaction pattern and what feedback they provide as you interact with the knob.

It's an ios app. IMO it's really good. I own exactly one apple product, and it's an iPad that only runs Loopy Pro.

Here's a section from the manual that loosely explains the concept[1]:

> Adjust a slider or dial’s value by dragging up and down, or left and right for horizontal sliders. For finer control, move your finger away from the dial.

[1]: https://loopypro.com/manual/#sliders-and-dials

Thanks! This link is really great!

My only Apple product is also an iPad, and I mostly use it to make music with Auxy Studio:)

Do you use any fun apps on Android? Currently, my favorite apps are Digitron and Nanoloop. (No affiliation, but Digitron's upgrade was gifted to me.)

The only other music or audio app I use with any regularity is Reaper on Windows. I tend to do more performance-oriented stuff, and I try to keep everything outside the computer as much as practical. I don't use any software synths. I like the constraints and UX of dialing patches into my one keyboard/drum machine. I record some, but mainly I like to play in real time and not fiddle with VSTs and plugins.

Makes sense. Hardware is not something within my reach, currently, so I stick with software. I'm sure hardware can be a lot more fun.

Thanks! For me, this works well for knobs that don't require frequent adjustments. Currently, my knobs have little pills next to them that switch a knob to a "precision mode." It is a little quicker, but you may need to remember to disable this mode next time you use the knob.

I also played with the idea of letting users slide their finger off a knob (tap and slide away from the center). This allows for moving the finger over a longer circumference, hence enabling a great degree of precision. The problems with this approach are that it takes longer to operate such knobs, you need to communicate to the user what the max allowable distance from the knob is, it can interfere with scrolling, and it doesn't work for knobs close to the edge of the screen. (Your idea works well for knobs at the edges.)

And this is just knobs! There are many other components, interactions between them, as well as associated accessibility challenges, haptics, etc. Instead of reinventing the wheel, I was hoping that human factors people had developed relevant guidelines, but perhaps it simply is not a prevalent enough problem.

This is so cool and so clever I'm in awe, really. I'm grinning from ear to ear looking at this and jealous I didn't think of it. But the problem it solves is not quite one that anyone has. What does it offer over a built-in knob with a jack that overrides it beside compactness? A knob that's not designed for feel that you can misplace?

There's a miniature case study in thinking about innovation here. This is what the germ of a really neat idea looks like but you have to keep going and that's hard.

As he mentions in the video, the whole motivation is compactness. When your panel looks like https://learningmodular.com/the-eurorack-expansion-project/ , every mm^2 matters.

I'd be tempted to eliminate the patch cord altogether by using one of those pushbutton pots. Normally it would act like a traditional pot, but if you push it, it would go into a mode where you could choose from a variety of nearby inputs wirelessly.

The LEDs next to the pot would need to be an OLED display that indicates the selected input. Some form of extremely lightweight mesh network for control connections would need to exist, something with very low bandwidth and short range but also low latency. After 5 or 10 years' worth of tinkering, it might actually synthesize some sounds.

Right - it solves the compactness problem but introduces new ones. That said, from what I've seen of other people's modular setups, keeping them from growing without bound does not seem to be the highest priority in that world.

I'd also have to wonder how well a jack would hold up under regular use as a bushing. It's very common for engineers with little exposure to the connector industry (not my background either, but I read the data sheets and app notes) to underestimate how highly engineered and optimized for their use case even decades-old connector types are.

It would be nice to have something like the NKK display pushbuttons in the knob for a rotary encoder/pushbutton.

>After 5 or 10 years' worth of tinkering, it might actually synthesize some sounds.

Yeah.

Tangential idea, but I've wondered if it would be possible to make synthesizers a lot cheaper by only having a couple rotary encoders. You could have hundreds of parameters on the panel, but each parameter would just be a neopixel LED and button. You could link the rotary encoder with a parameter by pressing it and the parameters' button at the same time. Certainly not as nice as a dedicated knob for each, but you'd also get an interface that is ~$40 instead of ~$600...

There are loads of systems where every button and encoder has many functions, with modal or paged interfaces. But I'm trying to stick to a model of no hidden or ephemeral state with my modular, just for fun, I guess. Mostly analogue, so no non-volatile memory to store settings, the positions of the patches and knobs set everything, and the test is that if I power it down and back up it must come back doing what it was doing when the power went out (very long cycle lfos notwithstanding!)

When a laptop can simulate anything, the physicality of the interface is most of the attraction, so might as well go all the way...

For sure! The interface is the most important part these days when practically everything can be emulated.

In my design, I wouldn't say the state is hidden though—that's the point of having an indicator light with every parameter. The LED becomes the state visualization. So, write-wise, yes, it's overloaded, but read-wise it's not.

I'm just now realizing I didn't explain that well in the OP, lol. And really this is more of a budget-friendly approach, rather than a user-friendly approach. I'm trying to meet those half way...

The physical interface is an intrinsic part of the design of any eurorack module, including artistic elements. If you actually use these, then you quickly tire of menu diving for simple options, and only modules that do very particular things make it worth the bother. For everything else, the layout must be accessible, memorable, understandable, and not too crowded. And it helps if the visual of the thing conjures up memories of how it sounds or what it does.

There was a trend in 80s synthesizers along these lines: Yamaha DX7, Ensoniq Mirage, etc.

They were famously hard to program. The DX7 in particular is known for basically being a preset machine because almost no one could figure out how to build patches with it.

Muscle memory is really important and it's hard for users to build a mental model of the internal architecture if the external architecture doesn't reflect it at all.

If you had a little silkscreened circle around each parameter's LED, and a Hall effect sensor underneath, you could even make a passive magnetic knob that you could use to adjust parameters by simply placing it on top of them and twisting. It wouldn't feel great due to the complete lack of resistance but it's a fun idea :)

Ooh! Now that's an idea. Especially if you could 3D print a knob and hot glue a magnet in it.

It's not an obviously terrible idea assuming that your only goal in creating an instrument is cost minimization. (Consider that foreshadowing.)

Like all tools, it's rare for the cheapest possible option to be a good value. This is only a subtle difference to people who don't need to use the tool.

Eurorack is very cool and I totally understand the appeal of having physical devices to interact with but one thing I never understood is how you can recreate a specific configuration you liked later. Do you manually document every connection? Or just take pictures?

Neither, you just tell people about how great it was. Ideally, you don't record it either so that you can filter out the less imaginative people from your social circle. If challenged, you explain that you've moved on to a more abstract aesthetic, a musical plane which requires greater levels of commitment to attain.

Nailed it.

Once it's gone it's gone. That's part of what I like about analogue modular synthesizers. It's a liberating approach to doing music if you embrace it for what it is.

So it is more of a toy than an actual tool.

Wouldn't it be more universally compatible to have a powered knob that outputs a adjustable constant control voltage? You'd probably want trim adjustments on it too.

Yes, there'd be an extra wire to the power supply module, but that seems fine for a modular.

> Yes, there'd be an extra wire to the power supply module, but that seems fine for a modular.

Maybe other's modular synths look/work differently than mine, but when all the panels are installed, there is no way to pull a cable from underneath the panels/inside the case to the outside, without drilling new holes through some panel or the sides of the case. So not sure how you'd pull a cable from the power supply to the front side of a panel when it's closed like that. My case is a Intellijel Palette 104HP, maybe other cases expose the power supply to the outside?

Yes, but there are already many of these in modular form (usually attenuators normalled to +5V in the absence of input voltage or just fader modules without inputs). This is new :)

Be sure to check their other projects! Stylophone business card is one of my favs: https://mitxela.com/projects/stylocard

Anyone know what is being used to render the git repo for this? https://git.mitxela.com/euroknob

looks like it's this: https://git.mitxela.com/web-git-sum

I’m just waiting for the Eurorack Boombox revolution to hit.

Why not route out the FR4 under the TRS jack and sense the magnet from parts mounted on the other side on a single PCB?

been messing with gear for years and honestly the obsession with cramming everything into tiny boxes always cracks me up, but the idea of knobs you can move around is actually kinda sick. you ever feel like stuff gets too complicated and takes away from just having fun making sound?

It's like real life functional programming.

Can't wait for the y-combinator module.

I love the out-of-box thinking and clean execution by mitxela. But why not make it the other way round?

Downsides: you need enough magnetic knobs and store them when not in use. If this becomes popular, will all knobs be compatible? What if you loose some? If you buy a used module? This idea somehow creates a new set of problems.

Idea: Knob with a plug!

The outer dimension of a knob is limited by how easily you can grab it. Even if used as a socket, you need the sideways spacing anyway. But the knob face is not used. Why not have the socket in the center of the knob?

How to build this? You would need a hollow knob riding on a bearing surface around the socket. I vaguely remember magnetic position decoders that work off-axis? Or maybe have multiple magnets in the rim of the knob, in an orientation that creates a uniform magnetic field in the center? The current prototype would even be suitable for trying.

Benefits: no extra removable components. Knob and socket can be used at the same time. Can you still reach around a plugged-in cable? Is this even useful?

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Fantastic idea except for the proprietary 3.5" knob. From the video it appears the magnet is required to discern position.

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