Hardware design


For those of you designing your own eurorack modules, I’d love to learn from you about tools you are using during the design process. Eagle seems to be the de facto standard for PCB layout? I’m curious to know if folks are using other tools to plan panel layout, or for the 3 dimensional considerations (eg: stacking multiple boards with an eye towards skiff-friendliness). Are there templates or pre-made design resources that make good starting points/guides?

I’m also curious about process. I’m attracted to the “panel first” design philosophy than Don Buchla says he tended to follow.

Thanks in advance for providing any shoulders I can stand on!

Electrical Engineering and Synthesizers

We use Eagle for our initial designs, mostly because that’s what people around here are familiar with. Personally I prefer KiCAD, but I don’t use it at Intellijel. Actually I don’t really do much on the schematics other than adjusting something once in a while, Danjel does most of it. We use a PCB layout expert to do the final layouts in Altium, which also provides the 3D view. For my personal stuff I do that in KiCAD as well.

Graphics, panels etc. are done using Adobe Illustrator with an image of the PCB on a layer to help with lining up all the components. We generally do everything panel-first, and print out the panels at full size and then put knobs on the paper to make sure it feels okay before we commit to make any protos.


@kisielk since you say “panel first”, but also mention using a PCB image as a guide, I’m guessing that means the process is somewhat cyclic?

  1. panel design
  2. pcb design
  3. panel revision
  4. repeat as necessary

Is that about right?


@infovore was kind enough to recommend in chat that I look for some libraries:

  • Eagle
  • Sparkfun
  • Tom Whitwell

Any others? Looking for common parts like jacks/pots/etc.


So: there are various alternatives to EAGLE - KiCAD, Diptrace - but it’s popular partly owing to its penetration and the volume of libraries available.

It’s worth noting that EAGLE is both a schematic tool and a PCB tool: you lay out parts in a schematic, and then, when all the ‘nets’ are correct on the schematic, it lets you make a board with those parts and nets. Some tools do one or the other (schematics and/or layouts).

Planning panel layout: I will sketch on pen and paper, maybe in graphics tools, but then I have to wrangle the parts into place and have to be constrained by how they’ll go together. Though I’m also more interested than some designers in ergonomics - I very much like Olivier Gillet’s attitude to “how big a finger is” rather than an obsession with fitting lots into 4HP.

So: sometimes parts don’t exist, and I have to make them - lots of staring at datasheets. But there are lots of good lbr files out there, in particular, I use the Sparkfun/Adafruit ones, and also a pile of the EAGLE defaults. But making your own is an important part of the process - even if the pins and pads are right, the silkscreen might need updating to personal preferences. (I have my own parts for things like Eurorack power connectors, particular silks for opamps and resistors, particular switches I couldn’t find existing parts for.

Stacking boards is a bit of a faff: some people like multiple EAGLE files, some people put them in the same file. The key is ensuring that, relatively, headers are in the same place; beyond that, there are good open-source examples to copy.

In terms of 3D: I’ve been known to make sketches in Fusion360 of 3D parts, to imagine how they’d fit together - even just as solid boxes - but most of my synthesizer stuff has been pretty easy to imagine flat.

I use OSHpark’s own CAM processor files for making Gerbers, and also for DRU - design rule checking. This will make more sense when you’ve started down that road.

The other thing is: EAGLE is really non-intuitive, and I learned all this slowly - and using a lot of the open-source files that are out there.


Any especially good ones you would recommend I look at?


All of the Mutable Instruments files. Tom Whitwell’s stuff like the Turing Machine mk2 or Radio Music. Alas, mine aren’t shared yet - I learned a lot from these, though. Not just about “drawing circuits” but also about electronics design and options for synthesizer layout.


Awesome. Thanks so much @infovore and @kisielk!


Yeah, you pretty much need to update the PCB any time you do changes to the panel… so it’s an iterative process.


Definitely worth noting: the PCB CAD market is one where you can spend a lot of money. Kicad/EAGLE/Diptrace are very much at the budget end of the spectrum. Altium; Orcad; oh good lord, these tools are expensive. Possibly with reason, but still. Blimey.


Illustrator first always. I often make designs and stare at them for 6 months before getting to a point where I’ll even consider how to physically create them.

Before I look at Eagle (planning to move to KiCAD after completing the next project), I spend time finding sources for the hardware components I want to use. Last thing you want is to prototype PCBs then find you don’t like the switch or pot you designed it around, or they’re not available in quantity etc.

Always PCB last, but granted there will be some push & pull between the two elements.

As an aside, I remember speaking with the QuBit guys a while back and they had added knob / jack panel mockup layers to their Eagle libs so they could do layouts at the same time as placing hardware. Personally I like the fully separated processes (with faux aluminum background included), but granted it is a pain copying the panel locations to the thousand of an inch everytime you move things.


I would definitely concur that CAD software is almost impossible to sketch in, which is where graphic design tools like Illustrator or a notebook are really handy. Eagle is very much interested in reality, and design often has to begin somewhere else.


Also: I feel somewhat idiotic talking about this around lovely, published/built designers like @Galapagoose and @kisielk and so forth.


@infovore no need to be shy. I am loving your 1U designs.

I have many years of Illustrator experience, but switched to Sketch a while back. I find it has a faster brain-to-results path.

A couple decades of software design has taught me well that you want to sneak up on reality slowly, if you have the luxury of time. :wink:


Honestly I don’t think our process is particularly sophisticated or novel. Everyone brings something to the table. I’ve been doing software for over 20 years now and still learn things each day.


EAGLE has improved considerably since Autodesk picked it up, nice!


I’m using Osmond (osx only) atm and it feels so much more fun than KiCAD or Eagle. It’s limited, but thats perfect for a beginner like me :slight_smile:


I use Eagle for AISynthesis, and then I pay Grayscale to design my panels, which he does in illustrator. I kind of use a panel first philosophy, in that I pre-spec the size I am looking for, and then rough the panel layout, and then pass it to grayscale who makes it better. I could probably do it myself and save money, but I love what he does and it gives my work a professional look and feel that I couldn’t do myself.


I use quite a chaotic process; sometimes I’ll start on breadboard (this was the Turing machine breadboard), to see if something sounds good. Sometimes I start in eagle, to note down the schematic and see how big the circuit might be. Sometimes it is a sketch of a panel. Sometimes it starts in code - a mockup in puredata or as a Radio Music firmware.
Further on, I usually have a real-looking panel layout in illustrator, and flip between the two - if I change the controls in illustrator I have to map them back into Eagle and vice versa. At the moment I have a nice, useful, compact module I’m working on but I just can’t get the panel to feel right.
The most interesting part of the process for me is deciding how much you can leave out; it’s easy to think ‘I could do x, and y, and z, and p, and q’, for me the hard bit is deciding that just q and y will make something useful and musical - that’s often the breakthrough.
The software/hardware thing adds a whole layer of extra complexity; do you complete the code before designing the panel, or make some decisions and stick to them?
The Mutable layouts are an incredible resource, and I still look back at Buchla circuits to learn.


This thread is an amazing resource…thanks to everyone who has contributed!

Does anyone have any experience with any of the Eagle to non-Eagle library conversion scripts? Or .brd/.sch conversions?

I’ve been learning Eagle slowly for the past couple weeks and I might stick with it, but I’m curious about trying KiCAD (or perhaps Fritzing or Osmand) and I’m curious if anyone has had good experiences with converting Eagle libraries (or design files) and then having everything work out with the end product in real life. Eagle is among the least intuitive programs I have ever used, so I’d be happy to switch to something else before committing to spending money on a license. At this point, I’m at least fortunate that I can go to the local makerspace to use a full Eagle license to work with larger PCB files, but that isn’t ideal.

Fortunately, half of a design degree (and the friends and software that came with it) help a ton in the aesthetic/ergonomic department :smiley: