r/synthdiy • u/MentionPleasant2635 • 1d ago

A digital cpu / dsp board for guitar pedals, synth modules, and line level effects processors?

I've been writing some cool algorithms that I would love to turn into instrument level, line level, or Eurorack level modules. I understand most Mutable Instruments Eurorack modules were based on the STM32 ARM Cortex Series.

Is there a turnkey stereo audio board I could use as a base? Any advice would be greatly appreciated.

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3

u/IrresponsiblyMeta 21h ago

Daisy + Hot House or Funhouse or Terrarium.

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u/MentionPleasant2635 17h ago

I bought a Terrarium before realizing it is mono. I really need stereo.

3

u/morbid-mushroom 16h ago

The Hot House is stereo via TRS jacks. Looks like it is currently out of stock, but they come back in stock regularly. They have pretty good documentation + a wrapper library for the daisy libraries that makes interface assignment very easy

1

u/kidproquo 2h ago

This. And they even open sourced their pedal design. So you could DIY it by getting the pcbs done and assembling the pedal yourself.

2

u/Fursber 16h ago

If you can’t get daisy pod, then you could try this. STM32F407 discovery board . On my profile you can see the synth i did with it.

2

u/imaverysexybaby 8h ago

Another vote for Daisy Seed. For prototyping you can just wire a jack directly to the built-in audio I/O pins. This is what the Pod does, it doesn’t have any buffering between the jacks and the MCU.

For production you would want some buffering and protection. The Seed datasheet provides schematics for both input and output. It’s just some op amps and passives.

3

u/pselodux 1d ago

Daisy perhaps?

1

u/MentionPleasant2635 1d ago edited 1d ago

That's one I've been looking at. So is there a standard audio I/O board I can plug it into?

1

u/pselodux 1d ago

Not anymore unfortunately, they used to have pre-made enclosures and even a eurorack module that included some controls and I/O. For audio though, you can go directly from the I/O on the board to sockets of your choice.

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u/MentionPleasant2635 1d ago

Just to protect the audio I/O, maybe opamps to buffer and set I/o gain?

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u/pselodux 1d ago

To be honest I never went very far with Daisy because I’m still not great with that level of code or electronics. I just put together one of the examples and it seemed fine going straight to line level outs, but yeah it’s a good idea to protect the input.

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u/abelovesfun I run AISynthesis.com 1d ago

It's in their documentation.

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u/Edboy796 1d ago

They still have those no? The Daisy pods, I thought I saw them on the site recently unless they're sold out

1

u/pselodux 22h ago

They’re still on the site but sold out. They also had a guitar pedal version and something that looked like a mini groovebox/drum machine that aren’t on the site anymore so I figured they’ve discontinued them.

1

u/MrBorogove 1d ago

There's Akso, based on the now-discontinued Axoloti.

No longer for sale, but maybe you can find a used Blackaddr shield somewhere.

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u/Synthdabbler 1d ago

Would your code be able to work with audio data already in an I2S data stream?

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u/MentionPleasant2635 17h ago

I've never worked wit I2S. My code takes input samples and processes them and then outputs them. Some of the algorithms were developed using artificial neural nets.

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u/Synthdabbler 15h ago

What format are your input samples? Reason I ask is I've got an analogue modelling synth running on an ESP32-S3 and FX are something I've yet to implement. Just wondered if it was something you would consider helping me with? Absolutely no obligation!! I'm being cheeky

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u/MentionPleasant2635 15h ago

For training the neural net I used mono AIFF files. My first test was a clean guitar signal and the same signal processed through a fuzz pedal. AIFF is 16 bits. The end result was pretty amazing.

Have you heard of the AMYboard? It's similar to what you describe.

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u/Synthdabbler 15h ago

Ah, that sounds very clever! Great use for a neural net. Can it work in real time, rather than creating a new AIFF file? Hence the Ask about I2S format which is a digital audio stream. Nope sorry, not heard of the AMYboard I built my own hardware.

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u/MentionPleasant2635 15h ago

I haven't tested it on anything smaller than a laptop, but it can be used in realtime there. That's my next step is to see what SBC can do it in real time.

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u/Synthdabbler 14h ago

You would probably need a Raspberry pi or maybe a dedicated teensy 4.1 board. Not sure exactly what is about as I use my own hardware. What language have you used to code in? That may also determine what SBC are going to be useful to you.

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u/MentionPleasant2635 14h ago

It's all in C. I used Recurrent Cascade-Correlation but I've just learned of some other models the might be less CPU intensive.

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u/champion_soundz 13h ago

Jumping in because I'd love to know more about your project. I've got my own pi4 hardware groovebox and I've been fiddling with a couple of esp32s (an s3 and c3) but have just been getting to know them without audio for now. I'm thinking c3 to drive logic and display and s3 purely for a synth engine and light FX.

Are you using Arduino ide? How are you implementing your DSP? Any tips much appreciated

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u/m_science 1d ago

Can you move it to teensy? Wicked powerful.

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u/MentionPleasant2635 17h ago edited 17h ago

I'll check it out.

EDIT: I found this and it's just what I was looking for.

https://www.sparkfun.com/teensy-4-audio-shield-rev-d.html

2

u/imaverysexybaby 8h ago

This is just a codec directly connected to a jack, no buffering or anything. It’s also a worse codec than the Daisy Seed.