Hey folks 👋

I broke ground on a new project: I want to make an Omnichord-style touch strip using a Teensy 4.1, 12 MPR121 capacitive touch sensors (144 touch pads), USB host, and TRS MIDI I/O.

Questions

1. I've seen mixed messages on designing the touch pads. Some people have said to expose copper with an ENIG finish. The MPR121 docs makes it seem like these pads don't have to be that exposed though - most of their examples are with a dielectric plate over them. Also Sparkfun had a product where the pads weren't exposed (link). Would there be a huge problem if I didn't expose the traces/ENIG and instead kept the pads under the solder mask to help prevent corrosion/wear?
2. Anyone here have calipers and an Omnichord? I'm curious about the dimensions of the pads: width, height, and distance between the pads. Anyone up for a quick measure?
3. I'm doubt anyone knows, but I was looking at a replacement plate and noticed the ribbon cable has 14 contacts for all >40 touch pads. Anyone know how this works? Are they just shuffling them and multiple touch pads trigger a single output?

Hi all,

I am looking to work out a cheap/easy/simple way to work out a sequencer.

I would like it to have:

• sequencer step buttons
• tempo and pitch adjustment
• volume adjustment
• keys
• maybe a sampler

I bought a breadboard and an ESP32 kit (https://a.co/d/5xxKGzd) and components but got stuck as I read somewhere that chip might not be powerful enough for my needs. I managed to get it to display hello on startup though.

Does anyone know if I am on the right track or I should try something else?

Thanks!

Hello, I'm building an instrument/playback device consisting of a couple of elements and I need some help with the soft and hardware. A couple days ago I posted a similar request but the project was described too vaguely.
I want to build a device that plays audiofiles and lets me influence them and use effects. I want to play the audio files with some buttons and a rotary encoder. The rotary is attached to a hand crank / wheel. I want the hand crank to influence the audiofiles like how vinyl works. Spinning shortly starts the music, another handeling pauses the music, spinning fasters speeds it up and spinning slower slows it down, reverse spinning reverses the music. Another rotary encoder or just a simple potmeter could be a volume knob. Then, for the effects I want to use a gyroscope (maybe mpu6050), xy could be cuttoff/filtering, yz could be delay and reverb. I dont want to use my laptop in the final product since it should all be as small as possible. some research leads me to using teensy 4.1 with audio shield. some say use mac mini with an audio interface. the sensors could be used with arduino. Max msp might work on the mac mini.
I hope someone understands, and can help me or give me tips for the hardware to buy, how to install, and the coding!

Hi guys,

I'm looking to get started in prototyping some eurorack modules, but (understandably) want to try and make sure I do this without damaging anything or frying myself...

Does anyone know of a prototyping-friendly power supply that I could build that offers protection against reverse current and short circuits?

I saw this: https://www.youtube.com/watch?v=eRB-JQNcmFM which looks great but doesn't offer any protection. Would adapting this PCB to include these features be very difficult?

I have also seen the Erica Synths Labor, but it looks like it might be a bit overkill for what I'm looking for in all honesty.

Edit: also come across this: https://pichenettes.github.io/mutable-instruments-diy-archive/module_tester/ which looks absolutely ideal! Anyone have any experience with building/using one of these?

Thanks in advance!

Hello! I'm relatively new to DIY electronics projects. I've built a few kits (for non-eurorack keyboards), and now I'm trying to build my first non-kit eurorack modules. I've ordered the PCB+Panel for a couple different modules from different brands, and now I'm trying to source the other components that I'll need to complete each build. Some module makers (like AI Synthesis [/u/abelovesfun], Free Modular, and Avalon Harmonics) publish very thorough BOMs, while other brands use a more sparse vocabulary in their BOMs.

One that I'm really struggling with is the BOM for the Dual OTA VCO by nonlinear circuits. (Despite the difficulty of understanding the BOM, apparently the actual build process is very easy for this module.) Here are some of the items it lists in the BOM:

• 100k trimpot (quantity: 2)
• 100k pots (quantity: 6)
• 1k tempco resistors (quantity: 2)

In the build guide, there are a few other notes about these components. It describes the 100k trim-pots as "blue" and "marked 104". It describes two of the pots as "threaded" and four of them as "unthreaded panel-pots".

When I went on Tayda, Mouser, DigiKey etc., I discovered that there are many different components, some of them even from the same manufacturer, with very different specifications yet still matching the description given in the BOM. How much voltage? How many watts? Physical size? All of these factors aren't listed in the BOM. And to make things more complicated, I discovered build notes from a few different people online (not affiliated with nonlinear circuits) who built these modules, and the exact tempco resistor that they use turns out to no longer be in production. So I don't know how to find a suitable replacement part.

Can somebody please help me understand how to filter the proverbial signal from the noise as I read BOMs? I feel like I'm either missing important context, or else maybe it literally doesn't matter which component I use in my build as long as everything the designer stated on the BOM is up to spec?

Good evening Reddit, currently working on a hybrid analog-digital synth for a capstone engineering project. We have an AS3310 that we are using for envelope generation, but I am still confused about how the envelope generator is used to affect the actual signal from the synth. We're using a Teensy 4.1 and two SPI DACs to generate the waveforms for context.

I do understand the purpose and mechanism behind the envelope itself, that much makes sense. How to harness the envelope signal is what's getting me.

Like the title says--I have a chip, but don't really need another oscillator. What else could I do with it? Make it an overpowered LFO? Maybe a clock? Something more clever than I can think of?

My power supply uses a 2.1mm 12VAC wall wart, but I can't find any 2.1mm panel mount jacks that will fit through a 3/4" thick wall. I prefer to bring the power into the side of the rack. Does anyone know of a deep panel mount jacks or have creative solutions?

Preliminary ideas are: route out a 3U slot on the side of the case and install a blank panel and mount to that, or find some sort of generic hole-filling blank that can fit 3/4" thickness and mount into that.

My Polivoks makes a sound when both oscillators are turned off. Does anybody know what this could be?

The adsr mode knob in the filter section is bent, I don't know if that could be it?

I'm a bit of a noob, hope somebody can help me!

This is a video where you can hear the problem. https://youtu.be/hN2hISe1KwM

Hi, Im building an instrument/speaker and i need some technical help! The device is a combination between a standalone dj controller and a barrel/street organ. So, I want to be able to play back audio files, pause, play, scroll through, etc. The knobs and deck wheels a common dj deck has will be replaced with barrel/street organ interactions and sensors. The most important is the winch/spinningwheel the organs have. I want that to make the music start playing, to slow it down and speed it up, and to pause and continue (really like vinyl). Then, I would have another winch for volume control, and some buttons to select tracks. I’m making another smaller device that you could see as fx control. so, with sensors (i think gyro would be perfect), I can control filter and delay/reverb for example.

The main question is what hard- and software i should use to be able to make this work. I dont want to have my laptop in the device because its too big, maybe a mac mini could work? I think I will have to use arduino to be able to make the sensors and buttons/knobs work. A rotary encoder for the main winch perhaps? I already know that arduino in combination with an mp3player is not capable of creating the vinyl playback effect I want.

Any tips and help are welcome! I’m quite new in this :)

Hi. I’ve got a project that has two discrete sections on two different arduinos. It’d be easier, and probably even cheaper (atmega328s are peanuts) to keep them separate and just pass information, as midi, between them.

Should I just wire them up with separate midi circuits (eg 2x optocpupler etc) for each arduino to send serial data.

For context it is a Casio SK1. One Ardunio circuit is managing midi in/out for the original components, the other is managing controlling new mods (RAM extension etc) and a display.

https://experimentalistsanonymous.com/diy/Schematics/

Hiya folks,

Does anyone have an example daisy seed project that uses the SPDIF interface available on D8/physical pin 9?

I'm working on a project and would like to make use of it but the documentation isn't clicking with me and I can't find any examples while searching.

Thanks

Hello all, every big trig/gate sequencer in eurorack frustrates me in some way or another, and all the ones that get closest to what I want aren't open source. I feel, perhaps naively, that I'm probably capable of pulling off making my own. So I don't reinvent the wheel, are there relevant C libraries available that sequencers tend to rely on? Timing stuff springs to mind. I'd be inclined to avoid C++ if I can but I'll use it if I have to. And any general advice is much appreciated - my chip programming is all PIC in C and Forth and most large sequencers seem to go for the arm platform, so I'm sure I'll be encountering new stuff.

It took me a while, but I eventually got a PD patch running bare metal on a RPI-Zero-1. I used Circle, which is the bare metal RPI kernel, and the Wasted Audio fork of hvcc, the Heavy Compiler.
Has anyone gone down this route before? I would love to hear about what you were able to make!

Hi!

Im looking for examples on MIDI USB send and receive with the tinyUSB library using the Earle Philhowers core.

Im some days peeking but I dont find examples. If anyone has some to share would be appreciated.

Thanks!

I need help finding a panel, standoff pins, IC sockets, and the power supply cable. (and all the other parts) for this diy filter. I also need to make a osc so any stripboard layouts for those would be great. where can I buy these parts for italy?

I live in Buffalo New York. I bought this keyboard used a few years ago. Had a local person work on it and it hasn't been right since. I was able to swap out the pitch bend potentiometer with one from Doepfer. But neither of them were giving the full range of 0 to 127. I ended up sanding off parts of both plastic Wheels so that I could get the full range. But it's not ideal. Anyone know where I can get replacements for these pots? Or do I have to create some sort of voltage divider with resistors? I believe the original says 10k 3608M PIHER. It's 10k linear with center tap 6mm plastic shaft with threads and 21mm body

Do you folks test new modules in your main case or do you have a separate case (or power supply) devoted to just testing? I'm in the process of building a bunch of modules for a new case, but as i'm completing them, I haven't tested anything since I don't have the new case yet and I'm a bit wary of powering them up in my main case. I've had the thought about building a small skiff just for testing so that my main case is protected in the event that something goes wrong with a new module. Is this unnecessary? I'd love to hear everyone's testing process when they complete a new build.

Has anyone found USB-C female panel mount connectors, like these:

JUZITAO 15PCS USB C Connector Type-C Female Charging Port Power Connector 30V 3A 24AWG Waterproof Female Socket Fast Charging Port Type-C Cable(Black) https://a.co/d/0l3da7m

But with resistors on their cc lines, so they work with USB-C to USB-C cables?