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

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.

>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.

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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 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 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.

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.

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 :)

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.

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.

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

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.

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..

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...

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The madness has taken him

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.

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...

It's like real life functional programming.

Can't wait for the y-combinator module.

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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?

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.

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.)