Digitone/Digitakt breakout box [work in progress]

[eranrund]

Hi everyone!

Some time ago I wondered if I could build a device that lets you plug in a Digitone or Digitakt over USB and breaks out the individual channels, similarly to what can be done with Overbridge. I was curious because I had spare channels on my (analog) mixer and though it would be nice to be able to apply separate effects/sends and EQ to each of the four synthesizer channels on my Digitone. I wanted to do this without having a computer involved.

Fast forward a few months, and here we are:

As of tonight, this appears to be working well. I am able to output the 4 individual stereo channels, the master output and the external input!

Unfortunately, as you can see in the photos, the device is not very DIY friendly unless you enjoy SMT soldering. The software is still a huge mess, but my next goal is to clean that up over the next few weeks.

I’m curious to hear people’s thoughts - is that a thing that is of interest to anyone? Happy to share more details. I am still not sure what the end game is, but I thought it would be a fun side project!

Cheers.

[mokomo]

@eranrund

EQ to each of the four synthesizer channels on my Digitone.

Sounds very useful for EQ to digitakt
Other dreamy desirables:

• A midi thru mult: DIN and switchable TRS A/B
• Volume faders on top
• stereo fx loops per channel
• master mix out
• 3x 21700 rechargeable battery pack inside

Looks like an expert level of genius already though!

[rephazer]

Excellent and really interesting! What about latency? Always wondered why Elektron didn’t make some kind of standalone Overbridge mixer themselves already.

[macinski]

@eranrund

I’m curious to hear people’s thoughts - is that a thing that is of interest to anyone? Happy to share more details. I am still not sure what the end game is, but I thought it would be a fun side project

Are you kidding me That’s beyond cool!
Damn nice! I was thinking about fixing such box but you actually did it. Great work!

Please keep us updated.

It would be great if Elektron could chip in and resolve any doubts about future compatibility with custom devices like this one.

[rycolos]

This is awesome. Care to elaborate a bit on how you did it?

[tnussb]

@macinski

It would be great if Elektron could chip in and resolve any doubts about future compatibility with custom devices like this one.

IMHO they already made their (silent, but telling) statement by not releasing the protocol specifications. Why should they care to keep something compatible which is in no way official?

[macinski]

Maybe. It’s unclear to me since they could potentially bind this protocol to OB and hide behind some auth layer or smh. I guess it’s not about compatibility issues but more about accessibility.

IMO this has huge potential and it would suck to see Elektron blocking access when/if this gets some traction.

[Lauli]

This is the box I’ve been dreaming about since I first got the Digitakt, wonderful!

[Fin25]

If you build it, we will come.

[frosty_raver]

Very cool! I’d love to know more - are you planning on open sourcing the hw and fw? (I’d be very happy hand-soldering that for a personal box just for me if it was open source)
Is it straight usb from the DN or did you hack the hw?

[macinski]

Somebody already tried dumping audio in this gh repo:

droelfdroelf/dtdump

[vasidudu]

Very much interested, even in its DIY state.
Not a big fan at all of OB as it is unstable and a resource hog.

[tnussb]

@macinski

It’s unclear to me since they could potentially bind this protocol to OB and hide behind some auth layer or smh.

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:

OB for Linux (sorta ;)

I sniffed the USB communication between my Digitakt and the Audio Capture Tool in the standalone version of the OT software, and came up with a simple command line tool which captures all 12 audio streams to a 12 track .WAV file. It should compile on every OS where libusb and libsndfile is available for. Somebody could write a driver or JACK (linux sound server) adapter based on this, and you could have your magic single-outs adapter box (think raspberry pi plus USB sound interface with 8 to 12 …

[Ethosphere]

Incredible! Amazing work! Could you get 8 stereo channels out of the Digitakt? That would be awesome…

[slicetwo]

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.

[Adam9]

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…

[andreash]

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?

[eranrund]

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.

[clusk]

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.

[hausland]

Same here, I‘d buy one