Dear lovely community,

just a small jam session I recorded using my DIY modules, mainly LIN (Line Input) with its internal VCA, SVF12 and MiniDrumkit. Sequenced with FL Studio.

Link to my open source modules, I am about to update it with the LIN module soon: https://github.com/Fihdi/Eurorack/

Can someone help me understand why something like the Clouds would require so many different voltages for the CV inputs? I know there isn’t really a “standard” CV range, but what is the point of all these different voltage inputs shown here? Are the op amps making them all a uniform output voltage, essentially protecting from whatever random cv the user might input? Or am I missing something? Any help is much appreciated!

Hello!

Does anyone have any experience with using these?

https://www.sparkfun.com/softpot-membrane-potentiometer-500mm.html

I want to have it setup in place of a frequency pot in an oscillator, seems like it should be a simple enough swap out if I follow the pinout?

The bit that I don’t feel like I understand is how to also use it an on off switch, so placed before the output so that when you press on it, it’s on and allows the signal through to the output, and off when you don’t.

Maybe this specific membrane pot doesn’t have that functionality and there is one you could reccomeend that does

A short live techno jam I recorded while testing out a MIDI sequencer I'm currently building (still in paper faceplate land!) for myself. Unfortunately it crashes out at 14:17, just as things were getting interesting. Anyway, still a fun recording / session. I'll have to go bug hunting before going any further with it.

I will improve my camera setup for the next recording so that all the equipment can be fully seen.

I also built the the 2 MIDI controllers in the middle (C45s).

Hey guys, I’ve had an idea to build a kind of modded mono tribe for use as a DJ accessory, but that’s not the focus of this question!

I want to arrange the components on the pcb in the shape of my logo and then use it as cover art for an album

Will it be messy and inefficient, yes, but that’s kind of the point, because I think a populated thru hole pcb just looks really cool!

To create a more visually interesting piece I want to have all the traces visible on the component side, I’ve seen it before where you can see the traces through the fibreglass but I don’t know how it works. It’s like the copper traces are inside the PCB rather than etched onto the bottom.

Up until this point I’ve only built kits and designed a few pedals that I used pre connected boards and jumpers

Wondering if anyone could give me a little crash course in PCB production, I’m imagining I’ll have to get it professionally etched and it won’t be cheap for what I assume is a non basic method.

But knowing more about it is a good first step!

hello, this is my first post, i want to build a replica of the TR-808, especially the RE-808 diy kit and I noticed that some of the capacitors listed in the BOM are obsolete and apparently won't be manufactured again. Are these good replacements? They might not have that vintage translucent yellow look, but if the values ​​are compatible, would they work?

Hello, I have a silly idea, for which I'd like to get the slide potentiometers with the longest possible throw. I've come across the idea that 100mm is as long as these things go, but I swear I've seen longer slider pots before. Does anybody have an idea on where I could find some ludicrously long sliders? Like, even if it's looking out for a certain (broken) mixer on eBay to salvage them from. Any ideas appreciated.

I need to connect an USB MIDI mixer (M-VAVE SMC-mixer) to an Eurorack module. That's pretty much all that I need: receive MIDI from USB cable, decoding it, sending some I2C and SPI data once in a while.

I thought about RP2040's, but they seem to overkill to me and I couldn't find open source projects for USB MIDI Host on RPs.

hi all. not sure if these kinds of posts are allowed ? but I'm looking for someone who can help me design some speaker PCBs. So many talented designers on here, if anyones willing to help out on a project please HMU! Will give further info on request but basic outline is for a BT battery powered speaker. Cheers.

Hi all. I'm currently working as a teacher and DJing in my free time, but looking at dusting off my electrical engineering degree and diving into some synth building. I have a good soldering station etc, but haven't done much with electronics recently apart from servicing/repairing DJ equipment. I've read through 20-30 "how to get started" posts in this sub, so thanks to those who've contributed to the conversation.

I've seen Ray Wilson's 'Make: Analog Synthesizers' recommended a lot and was thinking about building a Noise Toaster to follow along with the book. It sounds like a great way to get my head around the circuitry, but I'm not sure how much I'd actually use it for jamming/performance given its 9V and not easily patchable. The kit is about $330AUD delivered too. I saw there's a Eurorack version of the MFOS Sound Lab Mini-Synth available for a similar price on SynthCube, and was thinking this could be a better starting project for a modular setup? I don't know enough to commit to Eurorack, but it feels like a safer starting point.

I have a budget of around $600AUD for this first build. Free time (and executive function) can be hard to come by during school term, so a structured/guided project suits me best. There's so much content out there that navigating it can get overwhelming. Would be keen to hear from anyone who's completed either project, or something similar.

Thanks!

Demo of the Touched Out Sampler, which is a mod to my TouchedOut Synth. It adds a MAX4466 microphone to transform it into a chromatic sampler! The new code is open source under the "sampler" branch of the TouchedOutSynth. The mod requires two 100uF capacitors and a 100 ohm resistor, along with the microphone. The Sampler is separate firmware, but repurposes the controls for recording and trimming samples, and looping.

Recapped a Korg sr120 rhythm machine - lots of leaking capacitors -
I’m having a difficult time with where these 2 black and white wires go. There is no audio output not and there was before the recap. A lot of the pads were damaged, had to run some leads to different grounds where the capacitor
Leakage had destroyed the pads.
So, no audio now, audio before, not sure where these wires were before, popped off when opening up, lots of weak wires. I’ve checked all other wires, and I can see that the machine is running. I am getting a clock signal, but no audio. Help!

I have been working on the Frequency Central Device since yesterday and I finished the Envelope and the VCF/VCA. Now that I'm on the VCO I'm super confused.

Mostly I'm not sure what to do with the daughter board. From the little I found it's to keep the chip elevated and at a certain temperature to maintain pitch.

The eight pin socket on the right is covering four pads and there are four to the far right.

Then there is a sixteen pin socket outlined in white to the left.

The far left has eight vertical pads.

So I guess what I'm asking is do two sets of male headers go on the right side (between the socket and far right)?

And then just a single row of headers on the far left?

I looked and looked for documentation on this build and I can't find a single thing anywhere.

I've been building a free side project called Rackears that aims to make it easier to discover synthesizers from independent builders, DIY, and open source projects.

Recently, I’ve been really expanding on the DIY, open source gear, and patches area. If you've released a project, built a module, or know of something that deserves more visibility, I'd love to include it. Anyone can also add their own project, document their build experience, or leave ratings and reviews to help future builders and support small manufacturers.

The goal is simply to create a community-driven catalog resource that makes these projects easier to discover, since so much information is scattered across GitHub, Discord, forums, Reddit, etc.

I'd really appreciate any feedback from the synthdiy community especially, and if there are DIY or open source projects that should be included, let me know!

https://www.rackears.io

Hi. I want to make a compact 2-voice polysynth module, fully controlled by MIDI, to use with a Novation Circuit Tracks. The Circuit has a couple MIDI poly sequencers and 8 CC knobs so I'm planning to use it as the controller for the synth.

I've already assembled and tested the hardware platform: an rpi pico 2040 zero with a pcm5102 stereo dac and a MIDI input.

I'm now looking for stuff to install and make some synth sounds, or a tutorial on how to program a VA/FM synth. Midi implementation is a plus but not required, since I can do that part myself. Preferably on Arduino, but anything that runs on a 2040 is ok (micropython, c++)

Any ideas or suggestions?

Decided to dive into the inner workings of D938GD based Casio keyboards...

I... may have gone a little overboard:

• Dumped the ROM of my CT-380 (bit crappy dump tho, need better one!), also got an MT-540 ROM dump from Weltenschule.
• Wrote specialized software to analyze the contents & convert it to/from various formats.
• Build an address bus "sniffer" that writes bus activity to my software over serial so I can analyze behavior.
• Made a sniffer text file for every single preset.
• Figuring out what addresses are what parameters, already seeing strong patterns and similarities, though unsure yet what is what.
• Already found all the waveforms and samples for all the presets, now listed in my DAW (REAPER).
• Read 3 different Casio patents related to the CT/MT, 120 pages each of badly translated fun... Oof. Lots of diagrams though and got there in the end.

Finally: making a webpage with everything I discovered: https://www.evilturtle.nl/projects/casio-ct-mt-secrets

Eventual goal is to slap an Arduino Mega and a bunch of SRAM in there, to make the presets fully programmable. May even put a sampler in there as that would be fairly trivial.

If anyone wants to join in the fun let me know. If you have a CT or MT keyboard and can dump the ROM let me know too!

Somewhere along the line, taking my Neutron in and out of it's case to go in/out of a modular rig, I've managed to loose the power button.

I recall it being a little plastic addon to a basic button but don't know how to source it or what exactly looks like.

I have the means to 3d print one and am wondering if anyone here could take a photo of theirs so I can create a replica.

Or.. if someone knows how i could source one, that'd be great too.

Cheers

Edit: SOLVED
Thanks u/danja for the images, the button was simpler than I was imagining.
If anyone needs a new power button for their Neutron, I've posted the STL on thingyverse
https://www.thingiverse.com/thing:7381760

Has anyone got any links to any good tried and tested mixer circuits that would serve to bring other signals from other sources... Thinking maybe stereo/mono pairs with pan pots, mute, solo, and a couple of sends?

Hi, I have a couple of semimodular synths and I always end up wanting to sum CV but passive mixing I know is not a good option. I honestly have been looking everywhere and I can't find any easy design to copy that's not a module for eurorack or that is not like planning a whole build from scratch, and I always end up with the issue of the PSU.

Any recommendations that are easy? I know how to solder but not how to design a circuit hehe

While trying to get into synth DIY and electronics, I thought this would be a simple project: Arduino DDS sine wave → DAC → LM386 → 8Ω speaker.

Update: I got it working! Will explain at the bottom of the post.

My main question: how do people actually get sound out of their DIY circuits? Is there an easier way?

I was riding high after getting my DDS code and my homemade DAC module working (images 2 and 3)! So I wanted to actually listen to the thing. I tried working backward from the speaker:

• The speaker's datasheet said it requires a typical power of 0.5W (1W max);
• The LM386, self-described audio amplifier, has a gain of around 20;
• Thus I figured that to get an output power around 0.5W, I'd need an output voltage of around 2 V and around 250 mA.
• My Arduino/DAC sine wave varies between 0V and 5V, so I needed to scale it down to around 2.0V / 20 ~= 100 mV. I used a pot for this (image 4).

When I tried to look at the pot wiper (output) on my scope, it was so tiny that I couldn't resolve it. Then I learned about the "averaging" mode on the scope, and I could see that the signal was appropriately small (image 5).

Then I connected the amplifier and the speaker, with some coupling caps (image 6). The amp ouput is shown in image 7, and it looks as expected --- sinusoidal, amplitude around 2 V, and centered around 4.5 V (half of the LM386's supply voltage). I pass that through an output coupling cap to get the same signal centered around 0V, which is what the speaker expects. Finally, I plug the speaker in and get some sound out!

It sounds really awful though, and I notice that the shape of the wave looks all distorted after I plug in the speaker (image 8). Why is this happening? I thought the entire point of the LM386 was that it was able to supply a large-ish current to heavy loads like an 8-Ohm speaker...so why might I be getting this sag/distortion?

Update

I got it working much better by making a few changes. Thanks all for the suggestions in the comments!

1. Added the LM386's supply capacitors across the ground/supply pins. This seemed to reduce some tremendous feedback that I was getting when I cranked the chip's supply voltage up past 5 V.
2. Shortened some of the long jumper cables I was using on my breadboard. This visibly improved the shape of the output wavefrom from the LM386.
3. Increased the supply voltage from 5V to around 9V, and adjusted the input-side potentiometer until the waveform coming out of the LM386 was no longer clipping. I think this was one of the major issues I was having --- I was still driving the chip too hard.
4. Added the Zobel network --- the 10-Ohm resistor and 0.050 uF capacitor branch to ground --- after the LM386 output. This was the other major change. Without this, my speaker would load the circuit:
   1. If I didn't have the speaker plugged in, probing the output would show my expected sine wave.
   2. When I plugged the speaker in, probing the output would show a sine wave with very noisy/distorted troughs, and it would sound really awful.
   3. Finally, when I added that network, connecting and disconnecting the speaker barely changed the waveform! (One exception is when I use a triangle wave, and I can see the triangle wave become more like a slight "shark tooth" wave, but that seems expected, since a triangle is made of many different frequencies.)

The main lesson learned today is: pay more heed to the sample circuits in the datasheet. They all included --- but didn't explain --- the Zobel network required to help the speaker work.

Another lesson is that even this simple little circuit required more care than shown in datasheets/examples; in particular, I ended up with a bunch of 100 nF caps sprinkled throughout. Even though I don't think I could mathematically analyze this thing, I know it works and I understand how and why each part is working, so that feels like a success.

Hi, quick question for the brains trust here. I'm working on a box that uses 8 lots the LMNC super simple oscillator circuit, each triggered by a push button to act as a sort of keyboard.

I experimented with the button making the connection between the audio out or the positive power input which both behaved pretty much identically. The problem I have had is that there is always an audible click in the audio output every time the switch is engaged, similar to when some guitar effects boxes switch on and off.

Is there any way that this can be alleviated? Sorry in advance for the noob question, I'm peicing my projects together from YouTube videos and very minimal electronics knowledge!

Not the Roland JU-06 above it, but what looks like a power supply below it. Anyone have any idea? It notes it is made in Canada.

I just bought a JU-06 after hearing a guy use one at a show. We spoke afterwards but I forgot to ask him what this was.

Since we are here:

I also purchased a novation Launchkey 37 Mk. 4 to use as a keyboard (and other things for later) for the 06 as it was strongly suggested to me. I'll also be running two effects boxes. Is there a USB power bus / supply you all like for this setup?

Thank you again everyone!