Axo-Euro modular modular meanderings

#1

After perusing the various eurorack related threads it seems to me that the flexibility of what the Axoloti can do makes it hard to pin it down to a single ideal realisation as a Eurorack module. I quite liked the Euxoloti idea but as I read further into it felt it was a bit too complex.

I wonder if the expandable capability of the Music Thing Turing Machine, or the Expert Sleepers Disting might be a model for a good way to integrate the Axoloti into Eurorack.

Essentially the core module would be simply integrated in its power supply, the board would be split into two and the existing boards exposed to the world in a 'Core' Eurorack module that is not fully 'eurorack' integrated but just conveniently mounted and powered. It would however carry a header PCB that exposed its pinouts as expansion headers. The 'Core' could take on different personalities simply by booting up different patches from the SD card.

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Note that because Axoloti supports some of the Mutable Instruments algos, it could then effectively be sold as a way of getting a few of those into Eurorack which would in itself be a market.

Then a wider variety of DIY expansion modules could provide I/O and other UX. So suppose you could have two expansion headers one for UX and one for I/O. Each of those would only need a small PCB for the interfacing hardware eg: for voltage conversion. So they as whole would make very easy to build DIY kits. I've sketched these as AXO-IO and AXO-UI

For many musicians, even the UX needed to create patches on Axoloti could be a bit challenging, so for them, precreated patches on the SD card could make the Axoloti available as a meta module capable like the Disting of changing its nature depending on what patch is loaded from the SD card.

A small UI on the front of the Axoloti Core module could then be used along with a simple cursor button to loop through the list of patches on the SD card.

I think a big benefit of this concept could be of creating a module market for the board, and might then provide the economic impetus to expand and develop the concept further.

#2

This has been discussed quite a few times , in various forms....

I think only have a few have done it for a few reasons:

a) Axoloti is cheap , and Eurorack is expensive
so the markets don't overlap as much as we might think... there are a few of use with Eurorack, but are there enough to justify it?
Ive spoken to Johannes on this, and its didn't really seem to excite him, he designed Axoloti much more for the DIY/hacker market, as an affordable board - and eurorack is not that.
(of course, he'd be happy if someone worked in partnership with him to build a eurorack module)

b) complexity creep
so its easy to just create a module where Axoloti is powered from Eurorack,

but then complexities start creeping in....
audio out needs scaling up to modular levels
audio in needs scaling down from modular level

cv in -> analog in, needs scaling ... and you need to take care of connecting in - in
cv out... there are only 2 analog outs, and you'd probably want more, so this means not only scaling, but converting digital outs using an additional DAC, (or a simple PWM / RC combo( ?)) ... and then protection against someone connecting an output to your cv output.

c) protection
ok, I could do most of (b) with a few op-amps, but what would worry me most, is that if its not properly protected, I could easily damage the axoloti board (accidentally connecting an out to an out) , or even worst damaging an expensive eurorack module! is that really worth the risk?

( i.e. i have the confidence I could hack this to make it work, but I dont have the electrical engineering expertise to do it properly... and so might damage something)

I dunno, for me, its seems like theres not much of a commercial market - and its a bit too much for me to take on as a DIY project (though Ive considered it multiple times)

I even found this with Bela (which actually is easier to convert to Eurorack) , but I still ended up buying Salt (made by Rebel Tech/Bela built on Bela tech) because it felt 'safer'

also lets remember there are already 'flexible' eurorack modules out there e.g. ardcore, nebulae , o&c

for these reasons, Ive not really pursued eurorack connectivity, rather I have been exploring Axoloti with AE modular....

I like AE modular, because its cheaper, and this makes it much more 'DIY friendly' , and I think this fits really well with Axoloti.
The reason I haven't 'finished' it off... is that the axoloti board is a little big for AE modular - so I've been struggling to decide the best approach (external box? 5HP wide module?)

... I might give it another go soon though, as I recently did a arduino based module for AE, and that came out pretty well, and makes me encouraged to finish of the Axoloti project.

all that said, now Ive been exploring AE DIY modules more, and also building a few DIY eurorack kits,

I'd probably be more likely to try a Eurorack Axoloti project in the future - so never say never :slight_smile:

#3

That is very helpful. Your point about damaging gear is a very good one, I envisaged the expansion units having a board in there to provide circuit protection. Also I saw this as mainly a DIY thing, similar to the Music Thing Modular kits or board/panel partial kits.

For me Eurorack is too expensive, but there are so many modules available, and the DIY potential that it makes it interesting.

I may be happy to just physically host the Axoloti in the rack I have bought as its currently empty and if I end up with 2 or three, it would keep them organised, even if it doesn't directly interface with the eurorack bits I plan to get other than via midi.

Also I didn't know about the ardcore, nebulae etc.

#4

Seems to me... that there’s no real reason to convert an Axoloti to EuroRack. Designing a new STM32 F4 (or better) board with appropriate I/O and dimensions makes more sense.