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The BMM Colour Palette, an Open Hardware Case Study


Welcome to the fourth and last episode in our series on open source modules. This time we’re taking a look at how an open source project can grow beyond what the original maker had envisioned, to the point of becoming something quite different. Let me introduce: the Colour Palette!

You’ve probably spotted it somewhere on the web in the last months. A black panel featuring a giant kraken emerging from the raging sea and three big coloured LEDs. The Black Market Colour Palette is a very peculiar Eurorack module: it’s basically a modular module, that lets you add small circuit boards, called colours, to a bigger host circuit called palette, so you can create your own, custom multi-effect processor (for lack of a better term). For example you could add WMD’s Wave Compiler (a wavefolder) colour, BMM’s own Woof lowpass VCF and a ZVEX Fuzzolo colour. Each of those has a VCA controlling the input level and 2 assignable CVs to control the parameters. The original idea for this device comes from a homonymous open source Series 500 module by a company called DIY Recording Equipment (DIYRE for short). For those not familiar with it, the Series 500 is a lunchbox system for studio outboard like EQs and compressors. DIYRE at one point had the idea to create a device that would let you add the “colour” of analogue circuits, without the need of putting the actual device in the effect chain. To add the flavour of a compressor, without compressing the signal so to say. This idea encountered the favour of many, among the DIY-inclined studio people, making the Colour Palette a pretty successful project.

I admit it, I have a special relationship with the Colour Palette, since at the very beginning, when BMM started to think about making the Eurorack module, I was called on board to take care of its interface and graphic design, and later even redesigned the Series 500 module’s front panel. Still this story was fitting very well into my open source series, so I decided to put all my positive biases aside (as much as humanly possible) and give it a go.

This said, let’s go back to the very dawn of the Colour Palette and read what DIYRE’s Peterson Goodwyn tells us about it.

Interview with Peterson Goodwyn from DIYRE


The DIYRE Colour Palette with 3 colours installed. Photo curtesy of DIYRE

Horizontalpitch: Where did the idea for the Colour Palette come from and what’s the story of its creation?

Peterson Goodwyn: When I was first getting into building my own gear, I was shocked to find out how simple (and cheap!) the audio circuitry of a lot of classic gear was. In most cases, what makes the gear big and expensive is the “housekeeping” stuff: chassis, power supply, jacks, knobs, etc. The Colour format attempts to remove all of that stuff, so that people can fill their studio with a bunch of analog colors for a fraction of the cost of buying a bunch of gear.

HP: The Colour Palette system was released under a TAPR license (as all of your designs, if I’m not mistaken), why did you choose to release it under an open source license?

PG: Nothing I’ve done with DIYRE over the last few years would have been possible without other people in the DIY community sharing their designs and knowledge for free. So it just feels right to give our designs back to the community. Going open source was also a way to make the Colour ecosystem friendlier to other designers. So that they can see exactly how the Palette works that their Colours will be going into, or so they can fork the format like Black Market did.

HP: How did the open source aspect of the Colour Palette (and DIYRE in general) work for you until now?

PG: It’s been completely positive. It’s primarily a way of communicating how we operate: no gimmicks, no “secret sauce” bs, etc. Most peoples’ fear is that someone will use our open schematics to “rip off” our designs and undercut us. This hasn’t happened so far, to my knowledge. But, to be honest, I think the point is moot. Anyone with the skills to clone our designs from a schematic would also be able to reverse-engineer them without a schematic.

HP: How did the collaboration with Black Market Modular happen?

PG: Eric of Black Market and I were both exhibitors at Potluck Con in 2015. At that point, I had already had a few customers suggest the idea of a Eurorack Palette. I mentioned this to Eric and I’m pretty sure we both knew right away he was the guy for the job.

HP: What do you think about the Eurorack Colour Palette system?

PG: It’s really gratifying to see Eric and William take Colour in a different direction. The addition of the CV pins was a brilliant stroke. Also, it’s not apparent to the user, but they went through some major design heroics to make the ColourCV completely compatible with the existing Colour modules. Well done!


The Black Market Colour Palette

Interview with Eric Fox from Black Market Modular

The original concept of the Colour Palette was then developed further by Black Market, adding very modular-specific features like VCAs and CV inputs, one to control the volume of the audio going into each colour, the other to control the parameters of the installed effects. The device really turned into something else, from a convenient way to add a certain colour to your mixes/masters, to a customisable, somehow minimalistic CV-controlled multi-effect processor. While BMM’s take shows many, sometimes radical changes, when compared to the original, DIYRE’s idea with the plug-in cards, and all related standards, have been kept intact.

We got in touch with Eric Fox from Black Market Modular to hear his part of the story.

HP: Where did the idea originate from and how was your collaboration with DIYRE on this project?

Eric Fox: I had met Peterson Goodwyn of DIYRE last year in 2014 at a pro-audio conference where our exhibitor booths were right next to each other. He was showing off his new Colour format in 500 series and my booth was showing off how to utilize a DAW like Ableton or ProTools to control modular synths. He was intrigued by my eurorack setup and I was fascinated by how clever his interchangeable sub-module system was. We started talking about how great it would be to do something using his open format, but with the ability for users to externally control parameters via cv. A month or so after our initial meeting and a few back-and-forth emails about how to bring such a device to the public, Peterson came to the conclusion that he didn’t have the time/resources and wasn’t really familiar with the modular synth world… yet he still loved the idea of this project happening.  That’s when he asked me if I wanted to take the reigns and run with it while he stayed on as a consultant.  Of course I jumped at the opportunity!  I immediately contacted my good friend William Mathewson (WMD) who loved the idea and came on as lead engineer. […]

* On a side note, Peterson Goodwyn has now hired Black Market to build and distribute his diy 500-Series Colour Palette and line of standard Colours. Until now, DIYRE Colour items were only sold in kit-form directly from his website.  Built versions soon will be able to be purchased at various dealers around the world.

HP: Is the BMM Colour Palette being made available with the same license as the DIYRE one?  

EF: The eurorack version of the Colour Palette itself isn’t as of right now… but all of the the Colours and 500-Series Palette are under the TAPR open hardware license.


An exploded-view illustration of the Colour Palette by Papernoise

HP: Would you say that the original Colour Palette having been released under an open hardware license, was an important factor in your choice to make the Eurorack version?

EF: Definitely!  Since I am involved in various behind-the-scenes areas of the modular world, I have been lucky enough to meet and become friends with some brilliant people over the past few years.  The idea that someone else would invest their time and talent to make a component that works in my module is really exciting and flattering.  I love the endless possibilities of what people could make from the awesome sounding ColourCV Wave Folder called VariFold [now renamed to Wave Compiler Ed.] being released by WMD to maybe someday a god-knows-what ColourCV that a designer like Olivier from Mutable Instruments could come up with (hint-hint).

The other important group I really wanted to appeal to was the DIY community. Since we offer a pre-made perforated prototyping board complete with grounding, stand-offs, and a header for under $5, the DIY crowd can get all of the designing specs on our website and easily create unique electronic masterpieces that they can then take to market and keep 100% of the profits or share with others freely.

I really am anxious to see what people do with this!  Everyone else’s ColourCV designs make this one of the most versatile modules ever made.  Without them I just have a really nice triple VCA.

HP: We could say that the CP is an open platform by design. Having a nice triple VCA is nice, but the real potential only comes when you have a bunch of colours installed.
How does that work from a licensing point of view? Do colour designers have to release their creations as open hardware?

EF: When it comes to the Colours people can to do whatever they want. By no means do I want to restrict them to only making it open hardware. Heck, my first two ColourCVs (WOOF and TWEET) both are not open. The important thing is that designers are free to create and control the fate of their own products.

HP: Do you plan on using open hardware/software licenses for other projects as well?

EF: For now I have my hands full with the Colour Palette and related products. There are some ideas to expand the line that would definitely be open hardware, but first I just want to sit back and be a fan while watching what other people create for this format. If I have inspired others to come up with new products, then maybe I will be inspired to come up with more of my own!

Despite the Colour Palette not being released as an open hardware project it still retains a certain degree of openness, freely offering all the specs and materials to make your own Colours. It can be used as a blank canvas to make your own module without having to mess with the power supply circuit or the interface and should be great for both circuit wizards and basement hobbyists alike.

The Colour Palette can be seen as a hardware counterpart to software-based modules like the OWL (or a more “permanent” version of the ADDAC Open Heart Surgery) and shows how an open source project can evolve and mutate in many ways, even to the point of not being completely open source anymore. While this is an aspect that might create some discussion, it shows that open source can be an enrichment in a world with mixed open/closed licensing approaches. It should also be emphasised that the the module basically consists of a triple VCA, the power supply and 3 slots for colours, the latter is the really relevant and innovative part and is also the one covered by the open hardware license. So while it is true that parts of the module are proprietary, the most important part isn’t.

We could still question BMM’s choice of not going fully open source with the Colour Palette, but then we would have to question many module makers who follow a proprietary licensing approach for their creations and often base their ideas on other people’s intellectual work, at least inspiration-wise. It’s certainly something worth discussing about, but also very difficult to judge, so for now, I’ll leave it at this.

This closes our series on open source. Thanks to all of you, who have been reading, commenting and sharing these articles!

Bonus interview

Let’s get a bit deeper into the BMM Colour Palette, its features and technical specs. These parts were removed from the main article, since they focus more on the module itself than on the open source aspect, but I thought some of you might be interested in reading them anyway.

HP: Let’s talk a little bit about the design of the Colour Palette and its features. For somebody who doesn’t know anything about the module, how does it work exactly?

EF: The Colour Palette is a “host” system for up to three tiny sub-modules called Colours.  There are two types of Colours.  The first are standard Colours designed initially for the 500-Series Palette that only gives you control over the level of an incoming audio signal.  The second is the ColourCV which does everything a standard Colour does but adds the ability for designers to add up to 4 extra CV controls over parameters of their choosing.  Both are “plug-n-play” with no adapter needed in the eurorack version, however to use a ColourCV in a 500-Series unit you would need to use our ColourADPTR that lets you hard-set the CV controls using tiny trim-pots.  The Colours simply “click” into place with no soldering or electrical knowledge involved.  It’s takes mere seconds to change out.
Without any Colours installed, the eurorack  Colour Palette has three built in VCAs and acts as a nice three channel voltage controlled mixer that can run in series or parallel along with a summed output that can be normalled or not to the individual channels’ outs.

[…] Peterson really pushed us hard to make sure everything was cross-compatible with the 500-series Palette.  I remember the biggest snag we hit was how to power “standard” Colours (used in the 500-series) that run at 16 volts in our eurorack version meant to use ColourCVs that run at only 12 volts.  Peterson was insistent that ANY Colour (standard or CV) run at the proper voltage and act the way the designers intended them to.  He was definitely right and I’m glad he pushed us.  I’m happy to report that the euroack Colour Palette ended up having two independent sets of power rails to accommodate either version running 16 or 12 volt exactly the way they were designed!

HP: Why did you choose to have only 4 CVs for 3 Colours? How does CV control on this module work?

EF: Technically I guess there are actually seven CVs.  1/ea for the already built-in VCA that is running in front of each Colour (often this acts as an input gain depending on the Colour), and then four shared CV controls for ColourCVs labeled CTRL A through D.  The reason for limiting it to four is that I wanted to keep it straightforward, yet powerful enough for designers and users to find useful.  Funny enough, the first few ColourCVs being released each only are utilizing up to two extra CV jacks for parameter control.
The CTRL A-D controls are shared across all three channels.  For example if you have two ColourCVs installed that both use CTRL C in some way, both would be affected simultaneously when adjusting that control.  If you had say the WMD WaveCompiler and Black Market TWEET! installed, then adjusting CTRL C would change the wave folder’s symmetry while changing the high-pass filter’s frequency.  Could make for some interesting sounds!
William Mathewson had the bright idea of installing on his ColourCV the ability to let the user choose an alternative CTRL for his parameter via a tiny switch.  So you can send “symmetry” to either CTRL A or C to help prevent unwanted overlap.  Of course I made sure we implemented that feature in my Black Market ColourCVs as well!  I hope a lot of designers use this idea.
A person could also use a ColourCV with the ColourADPTR and that would remove that specific ColourCV’s CTRL section from the Palette.  The only downfall would be that you just need to hard-set the parameters on the ColourADPTR and you wouldn’t have access to change them from the front panel when installed….but it would work in a set-it-and-forget-it situation.


Graphic designer, illustrator and soundmangler. He makes music as kurodama and as part of the electronic music duo kvsu. Together with his wife Elizabeth he runs Papernoise, a small design studio located in northern Italy, specialised in graphic design for the world of music.