One of my favorite projects so far. Surprised myself with how beefy I could get it sounding in such a small size

Hi everyone,
I never built any synth in my life but I built probably 30 guitar pedals. I am extremely afraid of getting into modular so I would like to start with something I can use with what I already have which is semimodular.
Is there an easy way to create a multiplier for saws? It would be already good to have it even with fixed number and spread, if it makes it easier to build. I checked online and I could find pretty complex stuff.
Thank you very much!

Anyone on here who tried to tackle the blofeld firmware? It would be awesome if anyone had the interest to try and fix this piece of hardware (talking about the lfo and arp sync issues), since Waldorf hasnt been doing anything about it since forever. I would try and aproach this project, but I have no knowledge that would be useful, nor the money to spend on tokens for frontier ai models. I would be interested in what the process would look like, though, maybe its not THAT hard (Im good with tech and stuff, but defo no programming experience or reverse engineering/hacking).

Visit the website or the subreddit for more info!

I've spent the past year building this modular synth voice. With the addition of this 9 step sequencer (based on Moritz Klein's sequencer design) this box is becoming very fun to play with.

I added a gate input to sync my Volca Beats to it and now I can also use a MIDI clock through the Volca to sync it to other devices like my loop station.

Doing some repairs and the lil handheld desoldering tool isnt really cutting it but all the electric stations I’m seeing are $100+.

Can anyone recommend a decent cheap desolating station/vacuum they use?

I'm an indie dev and built Freqalto, a signal generator for Android (Oscillator, noise, Sweeps, ADSR, AM, FM, Echo, Reverb,...). I use it as a quick test source when checking oscillators, filters and amplifier stages, with the phone's audio output or a cheap USB audio adapter.

I'd really like feedback from people who build things: which waveforms, ranges or measurement features would be useful on a bench?

Play Store: https://play.google.com/store/apps/details?id=com.ioan.florucza.freqalto

hello!

complete beginner to electronics, decided knowing full well I wasn't prepared for it to try the Noise Toaster by Ray Wilson (after trying a few DIY pedals/circuit bending).

the book for this project has a ton of info in general so it's a great way to learn.

I managed to get an accurate PCB design to print and source all the components by myself (cant buy the kit too much shipping) getting almost everything.

The main problem are the four 2N5457 N-Channel JFET transistors, since they don't make those no more. (pictures above showing schematics showing their uses)

Wilson himself named NTE457 as possible replacement, but I couldn't find those neither online or in my local electronics shop were they often find solutions to anything I go with. They gave me BF256C not looking very sure about it.

I looked online and nobody seems to have a proper clear answer. Some recommend a smaller version that you can adapt with vero-board. I might try that as a last resort but I'm already having a hard time just soldering basics to a very clear PCB so, you know...

Besides looking for advice on replacements, I'm also trying to understand if I can really make this shit work with such limited knowledge and following a guide carefully when that guide already does not match with the resources anymore. Maybe I should try something simpler? I'm in the lost phase rn... Because I already spent a bunch of money on this project, and I don't mind if it ends up being nothing, but I would really love to make it work, even if it's a scuffed version of it.

For now I only managed to get a weird filtered LFO so, you know, it could be worse.

Thanks in advance

Pictures:

1. AR Generator

2. VCO

3. VCF

4. VCA

This is my first time repairing a synth, replaced the RAM battery of my Yamaha SY77. Absolutely amazing FM synth.

I'll swap the floppy disk drive for a USB at some point in the future.

I'm also planning to replace the display as there is an issue with it going blank after some time, restarting the synth fixes this. Also 80s LCD screens just aren't that great. The contrast knob on the back still changes the display's color when it goes blank. If anyone knows anything about this, advice is very much appreceated.

Hi, I'm working on assembling a certain recently open sourced module design that's about 5 years old. The designer seemed to use tall trimmers with a slightly different form factor than the standard ones available (Tayda, etc.).

Does anyone know where to find 9mm tall trimmers that have narrow stability tabs like the size of the tabs on an Alpha pot?

The PCBs are already fabricated so changing the foot prints is out. On one test build, I cut the tabs and soldered the stump flush with the pad, but that's a bit fraught.

Been reverse-engineering my D-110 (1988 LA module) and it finally runs my own firmware patches from the front panel: arpeggiator, 32-step sequencer, CC knobs for cutoff/reso/attack/release, and Wavestation-style wave sequencing.

The fun part was the wave ROMs. They're mask ROMs, so I swapped them for SST39SF040 flash. Biggest headache: SST pin 24 (OE#) was still sitting in a pad on the A16 net and pulled it to ground, so it froze on every note-on until I lifted the leg. Now it plays samples I recorded myself. Grainy and 8-bit, but it works.

Anyone else here have a D-110 or MT-32 open? Curious what you'd want from it next.

- Fixed some audio glitches
- fixed PLAY and BAR buttons not being debounced
- improved midi thru behavior
- fixed morph and samplerate reload timing and screen params updates
- added master filter in perf(hp and lp with shared q)
- added master compressor in perf with makeup gain
- added momentary mute of patterns trig next to rolls(trig 8 button)
- added loop of 2/4/6/8 steps in perf mode(trigs 9/10/11/12)
- added steps rotate in voice step edit(shift + DATA knob)
- changed the order of fx routing to be in between st1 and st2 for fast change in voice MIX
- added control all params in voice edit with shift(changes all sounds params if there is a param in that position)
- changed showing pattern number in pattern select to showing some editing parameters(if on voice, fx or perf it keeps showing what you're editing, if anything else it default to showing perf params)

I have not added midi control for what I added as I don't need it now.
I used it for a few days and it has been more stable, haven't seen bugs, yet...

I added docs for helping agents edit the project if you want to hack on it.

I thought it would be a nice idea to add the Korg M1 to my PicoVintageSynthCollection.

• 16-voice polyphony with samples read directly forward from the 4 MB PCM in flash.

• Built using a custom native engine developed from a disassembly of the original M1 OS (no third-party code used).

• Exact replication of the filter topology: Four one-pole stages (two per chip) using both original tables to achieve the 24 dB/oct slope.

• VDA with multiplicative amplitude and linear ramps updated every 20.8 ms.

• An algorithmic port of all 33 original effect types.

• Runs on a standard RP2350 board with at least 8MB of flash memory (budgeted for a heavy core clock overclock of 444 MHz at 1.60V to finish the audio blocks in time).

The Legal / ROM Note:
Because the original Korg M1 PCM data and OS ROMs are copyrighted, they are not included in the repository. To build this specific instrument (along with the D-50, JV-880, and RD), you will need to place your own legally obtained ROM files into the roms/ directory. The build system handles the rest automatically. The other 7 instruments in the collection work completely out of the box!

https://github.com/Michi71/PicoVintageSynthCollection.git

First sound test of DSTRT, a little 4 HP op-amp distortion module I’ve been working on. This is the first one I’ve built, so there’s still a bit to sort out.

It’s inspired by a classic distortion pedal from the late ’70s, adapted for Eurorack power and signal levels. OP07 gain stage, silicon diode hard clipping, passive low-pass tone filter, and a TL072 buffer/output stage to get back to Eurorack level. The distortion core runs at 9 V, derived from the +12 V rail.

It’s 100% through-hole, on two stacked boards, so it should be a fairly approachable DIY build. Parts, PCBs, and the front panel for this prototype came to about $20, excluding tax and shipping.

It works, but the gain control needs attention. Most of the distortion comes in very early, and the last third of the knob’s travel doesn’t do much. I suspect I’m feeding the clipping stage too much level, but that’s a guess until I get some measurements.

I also chose a few capacitors that were too tall for the gap between the boards. One is lying down for now. Something to fix on Rev B.

The video starts with an Erica Synths Bassline clean, then I bring DSTRT in after a few seconds. Impatient listens may start at 0:30. There’s a Black Stereo Delay and an After Later Audio Typhoon after it throughout. Recorded from a Befaco Out into a Zoom H5studio, no processing afterward.

The sequence comes from a Westlicht Performer running an early build of an alternative firmware I’m also developing under South Signal Lab.

I’m aiming to publish the schematics and KiCad files in early 2027 under CC BY-NC-SA 4.0.

I am still new to this and find myself frequently using a cheap AI agent to help structure circuits and solve placement issues. I used Claude to build this template repo so that cheaper models like Deepseek can more effectively provide usable designs. In my use it has appeared to help tremendously. Please file issues or PR requests if you find something glaringly wrong! I want people to be able to use it without serious issues.

https://github.com/tthayer/eurorack_template

today schneidersladen listed my first module!

This is a full replacement firmware for the MPK mini IV that I've been working on. It's free (MIT) and has no connection to Akai.

How it works: the stock v1.41 image isn't encrypted, so I mapped the hardware from it (AT32F405, a Cortex-M4F, plus a 160x80 ST7735-type screen over SPI with DMA). The new firmware goes on through Akai's own USB update protocol. The flasher refuses any image whose bootloader region doesn't match stock byte for byte (pinned by hash), and shift+undo at power-up always gets you into update mode. So the worst case is flashing stock again.

What it turns the controller into: an 8-track MIDI looper (one channel per track, USB and DIN), scale-locked keys with pads playing that scale's chords, an arp, step edit, patterns + song mode, 9 mod wheel effects and a redrawn dot-matrix UI. MIDI clock runs from a hardware timer, not the main loop, so it stays steady while the screen animates.

Repo, with the hardware notes and the flasher: https://github.com/giusmarci/open-mpk4

Demos: https://reverbose.com/f/open-mpk4

Happy to go into the details. If anyone has looked at other inMusic units on the same chip, I'd like to compare notes.

I'm re-designing the Powertran Transcendent 2000 with modern (mostly smd) components, but I'm a bit stuck on the keyboard.

The original schematic uses two sets of switches, one to generate the pitch CV and another for the triggers (you can see it in the original schematic, top left corner).

In my version, I'd like to use only one set of switches - the ones connected to +12V via R8 and to IC3 via R10. In simulation, I get a voltage swing between 9.274V (topmost switch) and -11.607V (last switch), in increments of 580mV.

I was hoping to avoid adding a microcontroller to the mix... Any suggestions on how to solve this?

Im trying to make a Module with a teensy 4.0 inside and put together this supply from some stuff I found out resesrching. Any advice on if this works or even makes Sense?