IMHO there is simply no reason to hide it or add some auth layer above. They just don’t release documentations about it so they can change whatever they want at any time and don’t have to worry about 3rd parties (+ don’t have to put the extra work in to maintain the docs).
The protocol itself is quite simple and straight forward. It got re-engineered and open-sourced by @droelf (which AFAIK this box is also using).
The original thread is here:
Incredible! Amazing work! Could you get 8 stereo channels out of the Digitakt? That would be awesome…
Dude, I’d love this. It would make the Digitone even better than it already is. This would make my standalone setup so much more fun to use, too. So yeah, let’s make this happen.
Sold…i will take 2…add low cutt to each channel and this is brilliant…
One for DT
One for DN
Then i can finally turn my desktop computer into the perfect boat anchor…
Cool! Impressive work! 
But it’s a bit hard to clearly see all the interesting juicy parts on the pictures, are the two TSSOP28 the audio converters? Do you mind telling what converters you used? 
Hi! Glad to see excitement around this!!
I’ll try to address everyone’s replies - please excuse me if I forget anything.
The latency is very low but I have not measured it yet. The only test I’ve done is play the output from my thing mixed together with the Digitone output, and I can barely hear any difference when I add combine the two. I’m sure there’s some latency, but it appears to be very small based on this not very scientific method. I believe if the latency was higher I would hear some kind of flanger/phasing/delay effect.
I don’t expect any support from Elektron, so unfortunately future firmware upgrades could break this until adjustments to my code are made. I doubt that would actually happen, but you never know. My hope is that at least Elektron are okay with this kind of DIY work and that it is not a thing they would actively pursue to terminate.
In terms of how I did it: The first step was to look for other projects doing this, at which point I found OB for Linux (sorta ;) which was extremely useful. I have a good amount of experience with circuit board design and the microcontroller l used. Once I decided to move forward with this I ordered an evaluation kit, a USB analyzer (a device that lets you inspect USB traffic between a host and a device) and began writing the proof of concept software implementation. Once I got that working I moved into designing the circuit board, and sent that to fabrication and assembly.
I am planning on open-sourcing both software and hardware once I manage to find the time to clean and document everything.
With regards to getting audio out of a Digitakt - my understanding is that this would let you get 8 mono channels out of the Digitakt (one for each of the 8 parts), as well as 2 stereo channels - the master/fx and the external analog input. I don’t have a Digitakt so I am unable to test it.
The DACs that I used are PCM1681 8 channel DACs. I needed a total of 12 analog outputs (4 synthesizer stereo pairs + master/fx + external input). The microcontroller is an ST Cortex M7 (STM32F733)
I am contemplating selling a pre-assembled kit - either the circuit board as shown in the photo, or the circuit board and a matching enclosure. I would try and do that if there is enough demand since supporting users comes at a non-negligible cost, even though I do expect this to be mostly a plug-and-play experience since there’s no software to configure and the set of hardware it interfaces with is very limited (currently only Digitone and Digitakt once I get a Digitakt to play with). Since I won’t be benefitting from economy of scale manufacturing just a few units, I expect the price to be around $350 for a complete kit. How do you all feel about that? I wish I could get it done cheaper but for an initial batch I don’t think that would be possible.
One thing that I haven’t mentioned so far is that this is USB powered, which means you could easily power it with a portable USB battery pack. Unfortunately (but it makes sense that that’s the case) the Digitone/Digitakt do not output power over their USB port.
Thank you for your interest! Happy to answer any other questions, and if there is interest in a group purchase of this then I can look into how to get that done.
Well I’d definitely have one off you, I’ve always wanted to be able to break out the digitakt channels to play with other outboard stuff.
Same here, I‘d buy one 
Same ill buy two for DN+DT.
Best of luck with the project
Im on board as well.
Wow, amazing work!
Perfectly reasonable. If I have a stable income when they’re available (I don’t at the moment 
) I’ll buy one for sure.
This is really incredible, and something I have been thinking about for a long while. I had been thinking of a device that mounts to the bottom of the digitakt/digitone and gives individual outputs, as well as battery power for the DT/DN and perhaps a speaker. That is what I always dreamed of. Sort of like the game boy advance player that mounted to the bottom of the gamecube.
I have to be honest and say that I likely would not buy one for the forseeable future (year) as I am in a bit of a tough spot financially. If I had the money though I think It would resolve most of the things that I dislike about the devices.
The current design is small enough to fit under the DT/DN, but because the ports are on both sides (USB on one side and 1/4" PLs on the other) it will be suboptimal. I need to look more into enclosure solutions, and maybe I could find a way to put all connectors on one side in which case it would fit well under the DT/DN. I want to keep the price down so I won’t have a lot of wiggle room when it comes to figuring out the enclosure.
I’m very glad to see people are interested in this 
I’ll spend some time over the next few weeks cleaning up the code and making it updatable (so you could plug it into your laptop and download a new version, in case bugs are found or new device support is added for other Elektron gear). I will also spend time on figuring out what kind of enclosure I could put this in, and then hopefully try and set up a small group purchase for whoever wants to have one!
The first thing I thought about was a wedge shaped thing that sits under the unit and can act as a stand, with indentations on top so the feet can fit in and not slide
I think keeping it bare and letting people design their own enclosure would be a good economical option. I’d certainly try to design something for it. As you mentioned the outputs and usb plug are on opposite sides, it could be interesting to design something where the ports are hidden away and everything plugs in neatly underneath the unit… though that could require a bit more space.
This is so cool. Not something I have a need for myself but very impressive.
On a tangent, I wish that it was possible to write custom USB drivers on iOS, would be neat to be able to access the OB audio stream on a connected iPad but as far as I know this is not possible without a special licence from Apple.
That’s really nice!
Something I may be missing tho, there’s only one USB port, so you cannot use your device AND overbridge, right? What about a “USB thru”?
Type-b usb splitters are not that commons and it would be nice to be able to use both the external outs of your device and overbridge (you may want to send one channel to some pedals and bring it back to the DN via the external input and record it in overbridge, for example…).
I’m sure you’ll sell more of them if you don’t force people to choose between your device and overbridge.
But once again, I may be missing something there.
Cool very cool
I would buy two 1 for the DT and 1 for the DN
Very cool - I wonder if this could be adopted for other audio and midi over USB protocols such as Rolands aira link?
I’d love to see some kind of standard that would allow audio and midi over USB to be as universal as the midi protocol, it would benefit everyone I think, not sure how likely it would be though.
But great work @eranrund well done!
A splitter won’t work here — USB is an active, two-way digital channel, and two devices can’t have host status for the same device (unless it’s got two separate device ports, in which case it’s two different devices, as far as USB is concerned).