Simple sound processor with modulation options

Hi, I’m a system development student from Sweden. This is my first post here and I couldn’t find
any similar post in the forum, but correct me if I’m wrong!

As we will need to make a project in the last year of this program I was thinking about making some kind of audio processor that accepts control voltage for modulation. The hardest part for me now is that I really don’t know where to get started. I don’t know which micro-computer to use as I really am new to micro-computers.
I would assume that this would be easiest to achieve by coding in C, or would Arduino work?

Hopefully you people could give me a few tips on where to start and what hardware would be suitable for this? :slight_smile:

This pretty much describes the ER-301!

So not entirely sure what you are asking here… if you would like to play around with creating something along similar lines then yes, Arduino is a great choice as all the really hard work is done for you and you just have to write your application.

If you have any further explanation then perhaps we can help more.

I’m sorry if I were unclear. But think of it like a really downscaled version of a ER-301, maybe more towards a PICO DSP from EricaSynths with modulation…
I think something like ER-301 would be way to hard to make under the period of a year.

I’d like the finished product to be able to provide reverb, delay and maybe some kind of integrated modulation source like a sample and hold and on top of that accept CV to modulate delay times and feedback etc. Would this be do-able?
This is whole new ground for me and this may be way to complicated to achieve but please feel free to pull me down to earth again.

Hello Simeon and welcome to the forum.

You will need some kind DIY embedded computing platform with lots of community support which has DC-coupled ADC capability and an audio DAC or PWM output.

The Arduino UNO satisfies all of these requirements (6 ADC inputs for control and PWM output for audio) and is designed for beginners. For example, here is a page the gives step-by-step instructions for how to build a simple synth using the Arduino UNO:

With a little study, you can convert the knobs to CV inputs.

Ok I see, the best place to look is probably the OWL project:

If you study this (everything is open source), it will give you a great insight into what’s involved in building the kind of thing you proposing as it is essentially the same thing.

I can’t comment on how easy or hard this will be for you :wink:

edit: what @odevices said too!

Here is an interesting article over at CSOUND JOURNAL:

Building an FM oscillator in the Eurorack format using Csound, a Raspberry Pi, and an Arduino Uno

Wow, Great replies! Have been reading em trough really fast and it gives me hope. I think I’ll start out with the Arduino Uno because of the community and to get into the basics.
Just a thought, will an Arduino Uno provide enough processing power to handle the things I want it to? Was thinking that the 16Mhz looks a little wimpy when I see that the ER-301 is using a Cortex A8, but I guess it’s in a different league :wink:

Thanks to both of you!
@odevices @anon83620728

In the CSOUND JOURNAL paper, the audio engine is implemented on the Raspberry Pi platform and the Arduino UNO is used for CV-to-MIDI conversion. I would recommend getting started with the Arduino UNO only and then if you have time add the Raspberry Pi to the project for more advanced audio processing. Working with the Arduino UNO first will help you concentrate your learning on working with voltages as control signals.

Yes I think so too, it would be to much to take in if I were to work with a lot of hardware in the beginning. I have a little more then one and half year to accomplish this and I would love if it could become something useful, not just for me but for others.:slight_smile:

Will order a Arduino Uno right away. Is there anything else you think could help me out in this early stage? @odevices Or maybe it’s enough to just grind my teeth in the Arduino for a while maybe!

I would get the examples up and running and make little tweaks to the code so you can see the effects!

The Moog Werkstatt is an excellent learning tool too, the tutorials are very clear:

May I ask you to regularly report your progress here in this thread?

I’d love to follow along and see how it progresses, hear of any stumbling blocks you come across etc.

I will do that, just got to get familiar with the Arduino platform a little at first. Thanks for the Werkstatt tip, will check it out!
And of course I can keep this thread updated, no doubt I’ll also have a lot of question when I hit a wall or something. Great to have this as a little log then. @anon83620728


I’d be interested to hear about your progress too. I have a breadboard with an Arduino Uno set up on my dining room table and have declared that no one will eat dinner again until I have a working homemade Eurorack module.

Of course I’m kidding about depriving my household of dinner, but the rest is true. :slight_smile: Definitely interested in learning more about this subject.

1 Like

Sounds like we’re on the same level! you’re one step ahead of me since I just ordered mine :smirk:
I also really want to create some kind of module.
What do you want to make for kind of module, any ideas? @Joe

Also please share if you come up with anything cool!

I’m kinda in a similar position as @Joe too, done a bit, but hard to find the time so development keeps stagnating.

I just remembered that the Music Thing Modular Radio Music is Arduino based too, so nice options there if you want something quick and Arduino to get going with in modular.

Sounds awesome but what do you guys want to develop? @Joe @anon83620728
I’m really into making some kind of down scaled DSP as I mentioned. But the first thing I’ll create would be some sine LFOs that is out of phase, just to learn the basics of Arduino.
Actually I’m really excited about this!

I’m particularly interested in control surfaces as I think this is one area of Eurorack that is lacking, at least for me. These kinds of things should be fairly easy to build.

@Joe and myself have discussed various ideas surrounding a sequencer, but this is a much bigger undertaking than may first appear.

I have also been looking at analogue guitar pedal circuits and how those could be re-purposed for Eurorack.

I’m not especially interested in DSP, not not entirely disinterested either :slight_smile:

It’s all good, eventually I’d like to be able to have some capability in all areas, it’s a long journey!

1 Like

Here another diy project to look at that I’ve been playing with.

Essentially a pure data standalone patch player that you can map cv controls to. It piggybacks a raspberry pi. Pure data is fairly simple to navigate and has lots of free documentation around the net. Mxmxmx has done the hardware legwork for you too!


I’m not quite sure yet, @Simeon. So far I’m just exploring what’s possible and trying to get a gut level feel for how much time and effort might be involved for various designs. I probably have a million ideas but not sure how many would be realistically achievable given my time constraints.

I do have a background in electronics but my education in this field was 20 years ago, and I haven’t been actively using any of the hardware / low level programming skills so they’re pretty rusty. Technology in this space has probably advanced a bit since 1997 too. :slight_smile:

Here’s a little starter experiment I was working on. It’s not going to knock your socks off, but this is something that might be useful in my system that I don’t have. Buttons that can send high/low (0 or 5V) voltages but are configurable as to whether they send one gate/trigger per press, latch until pressed again, or are momentary (stay high while pressed).

1 Like

I’ve been looking a little on control surfaces too. Especially the Monome Grids, really cool! But I could tell it is way above my level at the moment. Guitar pedals sounds really fun to explore though!

Wow, interesting. Looks like you could make lots of interesting stuff with that. Is it from the creators of Ornament + Crime?

Sounds like me, I also need to dip my toes a little to find out what it really means to develop your own modules. Gates and triggers are always fun i think! I’ve a little experience in electronics too but it was soon 10 years ago since I worked with it so I’m like you, a little rusty :slight_smile:
Do you think I need an oscilloscope at the beginning?

Will be a little slow on getting started with trying to make the LFOs on my Arduino since we have two upcoming exams next week but after that I’ll begin my Journey.

Not to just get started, but if you have plans of working with AC waveforms, you’ll develop a need for one rather quickly. :wink: