I’m starting to expand my axo setup and entering the Eurorack world.
This might be a silly question, but can I connect the output of an eurorack VCO to the Axo linein?
I also have an Arturia keystep, and I would like to connect the keystep Gate to an Axo ADC.
I just want to be on the safe side, any advice on this will be much appreciated.
yes, both is possible. but.
depending on your VCO, eurorack audio levels are usually much higher than the consumer line level axoloti works on. so you will have to attenuate your eurorack signal until it sounds nice/doesn't clip your axoloti input.
worse for CV, because those are up to 3 times as high as the axolotis GPIO voltage range of 0-3.3v. So you need a level shifter/attenuation/protection circuit here as well or an external ADC that can take the higher voltages. alternatively just connect your keystep to axoloti via midi.
Hi, thanks for replying so fast and for the advice!
Thank god I asked this before entering in deep trouble!
As you said, I might go with MIDI for now, but will also work on the circuitry to shift levels from approx 12v to 3v3.
if you plan on expanding your eurorack use in the future it might be worth looking into either a standalone midi-to-cv thing, or implement another codec as a breakout shield from your axoloti, look at @paul's eurorack threadd or the max11300 thread.
I bought a Doepfer A-192 voltage-to-midi interface that turns 16 0-5V CV ins into MIDI CC commands. There are a few module makers who make them, It is not the cheapest way to do it but it is the safest and requires no DIY soldering or circuit building.
I also use the A-192 (as well as some other methods) to get eurorack CV signals to the axo. Some problems are triggers, the signals are often too short to be picked up by the doepfer...
For triggers I used https://sebiik.github.io/community.axoloti.com.backup/t/simple-cheap-cv-gate-input-on-axoloti-solved/5510 this solution and that works without a glitch. Also works for positive CV signals...
Kasper
I fit my Axoloti in a 5U module for my Modular Synth, I added some extra circuit to level/shift the voltages for audio and CV.
It s for 5U but you can use the same circuits with Eurorack as they will work with +-12V without problems.
for the audio side, ladik do some great modules e.g. a-525 - 2 ch line in, 2 ch line out - 40 gbp.
Yes, providing gates is another situation entirely. I have a Tesseract Nutella module that uses a Tsunami Wave player board (from SparkFun) as the main sound engine, and like the Axolotl, the Tsunami has low voltage input requirements for the gate ins. The Nutella uses a simple transistor circuit to switch the onboard regulated voltage and isolated the Eurorack voltages from the Tsunami. It is very simple, combining a input jack, a manual pushbutton and lights a lLED and looks like this:
