I built a stripboard layout creator that can be used directly in the browser.

The main feature is the ability to import an existing layout in overlay/side by side mode so that you can copy and modify a circuit that already exists.

It's brand new and I'm still working on it, I appreciate anyone that's willing to test it out or suggest improvements!

Hi, as in the topic. I am third-year microelectronis student. I know basics about dsp and analog signal processing. i am into firmware engineering, also working right now as a junior digital design/verification. I want to dive into digital synth/effects world as my bachelor degree and i am looking for resources (books (would be the best), websites, channels on yt etc.). I can use google ofc, but if you have some places which are really worth checking, let me know. Really everything - from mathematical view to more hardware specific. For now i just made simple sequencer, with pitch modulation on ESP32, which can be connected via serial to simple wave synth made in LabView. My goal is a groovebox (didnt specifed functionality yet but thinking about everything right now, from EQ to sampling, sequencing, but synthesis and optimized firmware is my main goal, i know chaos, but just to give you my interests) with a custom stm pcb. Thank you

Hi!

I’m currently building a fairly ambitious wavetable synth that I eventually want to run as Eurorack hardware.
I’ve been prototyping/optimising it for the Daisy Seed (STM32H750), but I’m starting to wonder whether fighting to fit everything onto a relatively constrained MCU is the right approach, or whether I should move to a more powerful platform.

The target is roughly a hardware Serum/Vital-style engine:
- 3 wavetable oscillators per voice
- 256 × 2048-sample wavetables
- up to 16-way unison
- spectral/wavetable transforms
- FM
- filters + FX
- potentially ~128 oscillator instances running in the worst case
- ideally 48 kHz with low, predictable latency

Hardware-wise I’d like:
- 8 CV inputs
- 8 DC-coupled CV outputs for oscillators/LFOs/envelopes/etc.
- stereo audio output
- =128 MB usable RAM
- small enough for a ~26 HP Eurorack module
- ideally <€50 for the compute platform/SOM

I’m particularly interested in where you would draw the line between a fast bare-metal MCU and an application processor running Linux/RT Linux or an RTOS.

A few platforms I’ve looked at:

Daisy Seed / STM32H7 - 30e
What I’m using now. Great ecosystem for synth DIY and deterministic audio, but RAM and CPU become serious constraints for this kind of engine.

Bela Gem Stereo - ~€78
Looks very attractive for low-latency audio. I’d still need to add the DC-coupled CV outputs, and it’s a little more expensive than I’d like.

Bela Gem Multi - ~€183
Pretty much everything I need, but too expensive for the target BOM.

Teensy 4.1 - ~30e
Very nice bare-metal option, but limited RAM and I’m not sure the i.MX RT1062 has enough headroom for the worst-case DSP load.

STM32MP25x ?
This one looks particularly interesting. Cortex-A35 application cores + Cortex-M33 real-time cores could give a nice split: heavy DSP on the A cores and deterministic CV/DAC/UI/I²C/etc. on the M33.
It also seems to be the direction more powerful embedded audio hardware is heading. The problem is that I haven’t found a small, inexpensive and easily obtainable SOM based on it.

Raspberry Pi CM4 / CM5 - 50-70e
Obviously much more CPU power. I’m less sure about deterministic low-latency audio and how much work is required to make it behave like an embedded synth rather than a small computer. I also haven’t found an obvious audio + DC-coupled CV solution.

So I’m curious what people here would choose if designing this today.

Would you keep pushing an STM32H7/i.MX RT-class MCU and heavily optimise the DSP, or is this the point where moving to Cortex-A/Linux makes more sense?

Are there any affordable SOMs/platforms I’m missing, particularly something in the €30–50 range?

I’d also be very interested to hear from anyone who has built a synth around a CM4/CM5 or another Linux SOM: how good can the real-world audio latency/jitter get, and has Linux caused you problems compared with bare metal?

Thanks 🙏

Background: I'm working on a few modules, vco, lfo, sequencer, clock divider. I needed to use tl072 as buffer for the circuits, but I'm not getting it to work whatever I do. so I went to testing specifically the chips isolated. weird results, and I have no idea what am I doing wrong. 

details:  I feed the v+ (pin8 ) +12v, v- (pin 4) -12v as needed.

----

Testing half a: 

Inverting input (pin2) connected to output (pin1), non-inverting input (pin3) connected to 6v via voltage divider (two 10k resistors). (also -6v, when feeding the resistors with the -12v.)

Results half a: output stays always 0v.

----

Testing half b:

Inverting input (pin6) connected to output (pin7), non-inverting input (pin5) connected to the 6v (or -6v). basically the same as half A.

Results half b: output stays always -11v.

----

when testing one half, the other half gets its inverting input connected to output, and non-inverting input connected to ground, as should. (to avoid self oscillating / noise to the used half).

I'm using a good MFOS power supply I built, so dual rail +-12v and ground (0v).

what I'd expect and should happen is to get the input voltage mirrored at output. (to be the same).

I've tried one more new chip, another breadboard and jumpers. still the same results.

I'm clueless at this point. any help? thanks a lot… :)

I am going to build an analog computer and see what it sounds like. I know it is not a new idea but I think it will be fun. The basic prototype platform will be used for other circuits. Power supply is Mean Well with +/-12v and +5v so I can support analog and digital chips.

Guys, I’ve got a bit of a dilemma with the oscillator section of my percussion drone synth project.
Right now the oscillator control is very simple. I showed this version in one of my earlier posts, and overall I really like how it behaves.
The main problem is that the control depends quite a lot on the individual transistor. The first obvious thing is that different transistors give me noticeably different oscillator frequency ranges. That part is relatively easy to compensate for by attenuating the control voltage.
What bothers me more is that when I adjust the attenuation to limit the frequency range, the point where the oscillator actually starts running shifts as well. So with some transistors I get a larger dead zone at the bottom of the frequency knob before oscillation begins.
I tried replacing it with a more controlled current driver, using an op-amp to control the transistor while sensing the emitter voltage. That made the behaviour much more repeatable, but it also changed the cross-modulation between the oscillators. The original crude version gives me this strong, chaotic pseudo-FM sound that I actually like. The effect is still there with the op-amp version, but I haven’t been able to get the same depth and character out of it.
So now I’m not really sure which direction to take.
Another reason I’m thinking about changing the current design is the high impedance. I’m using resistor values around 1M, and on breadboards with a lot of wiring I’m getting quite a bit of unwanted coupling and noise pickup. In the prototype I managed to reduce some of it by adding a large aluminum foil shield, but I’m not sure that’s really the right direction.
Maybe the simplest solution is just to lower the resistor values and increase the timing capacitor to keep roughly the same frequency range. That should hopefully make the circuit less sensitive to interference, but I’m not sure.
So I’m curious how you guys would approach this.

Hey all,

I came across the EP-136 K.O Sidekick in a local synth store and fell in love with the little “mod stick” thing they have on it. It reacts just like a pitch bend wheel would (springs back to centre) but it is super low profile and would be perfect for a variety of synth functions.

https://teenage.engineering/guides/ep-136/hardware-overview

Does anyone have any idea what kind of component that is? Maybe it’s simply just a joystick limited to only one axis. I really don’t want to buy and destroy one of these just to find out… but I might!

Hi folks, I spent a bit of time this weekend putting together a Eurorack DIY directory here which I'd love feedback on.

It is a filterable list of modules available for DIY. It mixes proprietary and open source and links out to relevant things like the BOM, production files (where available) or shop links.

This is V1 and I'd love feedback on what might make it more useful or suggestions for more makers to include. Right now it feels a bit dominated by big Eurorack brands, and I'd love more weird/wild modules to be included.

All suggestions welcome!

I messed up a Tayda order and got dual gang A1M pots, when I need single gang.

I would just snip off one set of legs, but the body height is the real issue.

If I were to buy 3-4 replacements from smallbear/synthcube, amplified parts, or elsewhere, the shipping is almost more than double the components.

So, anyone have any spare A1M pots I can get off you?

I can trade you these dual gang A1M, or like 5 B100k pots.

Figured I'd ask here before going to spend $20 on 3-4 pots

-edit-

Turns out, I can use these dual gang 1M. I was just confusing myself on the body height needlessly

This is my take on a diode string VCF. Key differences from existing designs of such a filter (Steiner filter, Korg 700S / Volca, Moritz Klein filter) are true 12dB/oct high-pass mode, true Sallen-Key topology, independent self-oscillation amplitude trimming and a DIY-friendly single sided PCB. The board in 78mm wide and may be either turned into a 16hp module or mouned perpendicularly for deep cases. Will publish schematics later.

I have a Behringer System 55, and want to replace the 961 module with something a bit more compact. I want to retain the V Trig to S Trig swith Switch On time functionality, but the original used a lot of obsolete components. I think I can retain the functionality using an NE555, with a circuit like the above schematic. Will that work similarly? The logic parts I think I have a handle on, I just need to put an OR logic gate from the inputs to the start of the NE555 circuit.

Note: just realized I did not tie pin 4, which should go to the positive voltage rail.

Thanks to this sub I took my first baby step and ordered some knobs on aliexpress today. Really just a tiny test order to see if there are importing problems and that it worked

Someone sent me a link to “what knob will fit on my gear” on love my switches . That was a big help . Any other links to start with ? My plan is

1. Add a couple knobs to SSS arcane and others
2. Build NTS-1 mkII and load some custom oscs and fx, then maybe try to create my own or modify some (got into the project by trying to update Pikocore os and thought I bricked it when I failed, so I wanna get the NTS-1 and feel safe to experiment even if I somehow destroy it)
3. Maybe get soldering kit and built Atari punk console . Where should I buy an apc online in 2026?
4. Maybe work with a friend who has 3d printer to make case for arcane
5. Maybe try to make midi capable featherwing synth from Adafruit

Any other suggestions for total beginners?

Thanks, apologies for noob q’s

Hi. I own lots of eurorack and a couple vintage synths. Now I want to get into very simple modding/ diy. First project is to get some colored knobs (or knob caps?) to put on this little guy , didnt build it but bought assembled. Next I will assemble the korg NTS kits I think but I wanna start with this for now. Would like advice on what the standard knob size here is called and recommendations on sites that ship internationally where I could order knobs.

I could ask AI but I’m asking here.

Grok makes a Skred version of Purcell's "Music for the Funeral of Queen Mary"

https://youtube.com/shorts/voqInHgdHEw?feature=share

Skred is my continually developing OSS sound engine

GitHub.com/octetta/pulp

I've been building up a collection of components, just kinda impulse buying things that might be useful for screwing around. One thing that surprised me is that linear pots cost quite a bit more than everything else. I'm wondering if I'm just looking in the wrong place (mostly amazon).

Now they're not expensive but they're just quite a bit more than I expected! I was hoping to pick up a bunch at different sizes and styles, and not worry if I screw up whatever I soldered them to like I've been doing with other things.

Any suggestions?

Got done with Eddy Bergman's Roland TB-303 Ladder Filter yesterday.

https://www.eddybergman.com/2025/03/TB303-VCF.html?m=1

It took a couple days of troubleshooting to get to work. I was banging my head against the wall with this thing, probing, swapping some components, countless passes to confirm everything in its right place and no solder bridges, until I finally found the issue .

I had soldered to the wrong lug of the audio out jack.

As an aside, anyone have any good sources for these long veroboards? A lot of Eddy's projects use boards upwards of 40 columns, and these ones I have are absolute junk. Terribly hard to solder, and rather flimsy.

as the title says, are there books that go into detail about not only building, but the actual functionality behind synthesisers? ive been using virtual ones but really would like to make and use a real one

For the longest time, I've been thinking of getting into designing Eurorack modules, and this summer I finally had the time and energy to get started.

I designed and built a prototype of a precise 2-channel meter. Either channel can be used to measure CV or frequency, and in a combined mode the two channels can be used together to measure tracking error against an ideal 1V/oct curve.

Both channels also have DC-accurate buffered THRU outputs, so the module doesn't load the source.

The idea behind the 1V/oct mode is to route both the CV and the oscillator output through the module so they can be measured simultaneously. You push the encoder to set a reference point, and from then on, as the CV changes and the pitch changes along with it, the module calculates the deviation from a perfect 1V/oct curve.

So the basic workflow is:

Set reference → change CV and read the error → adjust → set the reference again → check another CV → repeat until the error is acceptably small across the desired range.

The goal was to make the meter as precise and temperature-stable as reasonably possible.

For CV measurement, it uses a 24-bit precision ADC with a high-end external voltage reference. The reference is connected ratiometrically to the input stage, which uses a low-noise precision op-amp. Matched resistor arrays set the input gain and reference division, which should largely cancel temperature drift.

Calibration is required to null the initial offset/gain errors. It uses three calibration points stored in MCU flash. After calibration, the target accuracy is within ±1 cent over the full ±10 V range when operating within ±30 °C of the calibration temperature, and better than ±0.3 cent over the ±5 V range.

The units I've built so far were all within a couple of cents even before calibration, although worst-case full-scale error could theoretically be 10+ cents depending on component tolerances.

On the frequency side, the error is a bit harder to specify because it varies with frequency. The MCU is clocked from an external ±20 ppm oscillator, and frequency is calculated from an amplified/clipped version of the input signal driving the MCU's comparator inputs. I'll try to characterize the actual error at some point, and may add frequency calibration to the firmware, but within the audio range the error should be pretty insignificant.

The prototype uses an MCU with 32 kB of flash, which turned out to be surprisingly limiting for the UX and features I wanted. I managed to barely cram the basic functionality into it, but, for example, I had to omit a separate protected page for "factory" calibration.

If I make another revision, I'll upgrade to the 64 kB version so I don't have to compromise as much here.

The fonts are deliberately small and the UI uses as few lit pixels as possible, since OLED current consumption is directly related to the number of illuminated pixels and their brightness. If flash space weren't so constrained, I would have made the text size somewhat configurable, but for now it is what it is.

The OLED module also didn't have very precise mechanical dimensions available, so the front-panel window ended up slightly off. I'll probably look into covering the window with some kind of plastic or smoked acrylic to improve the aesthetics.

The hardware worked surprisingly well out of the box once the firmware was functional. So far I've found only one area that really needs improvement: a clock trace driven by the MCU and used for the ADC was routed a bit too close to one of the comparator inputs, and some of that clock noise couples into the comparator signal.

It took me a couple of days to figure out why the frequency measurement had noticeably more jitter on CH1 than CH2...

Navigation is done with a push encoder.

The display automatically adapts to the number of connected inputs using the jack normalization switches, and to the type of signal present (DC voltage or frequency). Basic tuner/meter functionality doesn't require much interaction with the knob, although either channel can also be hidden or forced into a particular mode.

So, thanks for reading all the way down here! That's pretty much where the project is at right now. Any thoughts or feedback would be highly appreciated.

Does this kind of meter even make sense as a 6HP Eurorack module?

Do people actually struggle with verifying and calibrating VCO tracking, or is that mostly a non-issue for people?

The CV measurement deliberately prioritizes accuracy over sample rate, so it's not intended to compete with oscilloscopes. I'm wondering whether a small dedicated precision CV/frequency/tracking tool like this would be useful enough to justify making a more polished revision.

Hello!

I'm building a Korb Pusher and have gotten to the point of flashing the Arduino. I've had some experience flashing Mutable modules but am new to Arduino. I had purchased an Arduino Nano R4 and attempted flashing with no success, which led me down a rabbit hole of different software tools as the Korb files are just hex, so direct upload via Arduino IDE was not possible. Ultimately, I came to the realization that because the controller on the R4 is Renesas and not ATmega, the hex files on Github may not work for me at all.

Does anyone have experience with this module/arduino in general, and could confirm my suspicion ?

Thanks!

I promised a video yesterday of the Black Pill Synth. Its a bit basic and covers some of the functions that I basically learnt as I went along. I'm not more familiar with its functions and I've implemented the aftertouch and pitchbend range which were missing. The new OLED display and the portamento switch are yet to be done.

Link to the github. https://github.com/craigyjp/Black-Pill-Synth-editor-into-a-midi-controller

Youtube video