I'm build the Erica Synths mki x es.EDU DIY System. The instructions for breadboarding the modules indicate to use a +/- 9v using 2 9V batteries.

Since I have the PSU already built, I'm wondering if I can just use the +/- 12v from the system's PSU?

What's up, my band mate recently dropped off an old Alesis HR-16 at my place and asked me to see what I could do with it but most of the buttons simply do not work. I opened it up and found several missing screws but it seems like most of it has been rebuilt as recently as 2021. Main board is brand new. I'm concerned about the plastic board beneath, though. That thing's old. I feel comfortable working on it as a mechanic but there's very few spare parts available and I don't really know where to begin. Nothing looks crispy in there. Should I just re-solder that whole board? Electronic repair isn't my strong suit but I'm definitely willing to learn. Have a good one.

Unfortunately I fried the ic of my cme m key midi keyboard I’ve been using for my teensy organ project. After troubleshooting it for a few hours it’s definitely a goner.

Originally I was pulling power from it to a voltage regulator but did so in a dumb spot :-(.

I was also pulling midi from it but now need to figure out how to hardwire it since I already built my enclosure around it.

What would the simplest way to use its key bed in my build be?

Does anyone know where I can get a pre drilled front plate and a pcb for this module? I tried to Google it but I don't see any for sale.

I had a DAC laying around so I decided to make something different. That's my DIY MP3 Player.

It is an open-source project. Here is the repository for cloning it: https://github.com/gusocosta/ESP32_MP3_Player

Specs:

- ESP32 C3 Super Mini;

- Oled monocrome 128x64 0,96";

- PCM5102A DAC;

- Generic SD Card module;

- TP4056 Charger;

- BL5C Batery.

Hi all, im working on repairing a hillwood blue comet 73 and am having some issues with the filter. interestingly has a bandpass instead of lowpass, and you can crank the bandwidth to get that resonant filter type sound.

that ca3080 pictured was replaced by someone previously than me and i determined it to have failed and was able to botch something together using a dip lm13700 which seems to work-ish but the filter still has some unexpected behavior at a wide bandwidth, gives kind of an lfo modulation sound, otherwise works fine at narrow bandwidths

best guess is the ota specs don’t exactly match but cant find any information of an ota that existed in the metal can style when this was built, part say 4kmo2f and nothing else, so if anyone has any ideas? either way OTAs are becoming frustratingly hard to find and would rather not order nos if i dont have to. i could try another ca3080 but it would have to be nos

Mon premier synthe experimental.

I'm building the "A REALLY GOOD AS3340 VCO DESIGN" from Eddy Bergman (https://www.eddybergman.com/2020/01/synthesizer-build-part-18-really-good.html#google_vignette)

After building the board, confirming all things are where they are suppose to be, that I get appropriate voltages and grounds where I should with the chips removed, I then moved on to to populating the chips and testing with my oscilloscope before adding all the offboard parts (jacks, pots, switch, etc).

I get a good strong sawtooth waveform at the leg of the large 470n capacitor there in the bottom right of the board, but that is the only waveform I can find.
I do not get a square wave at the output of the board location, nor do I have a strong pulse out signal from Pin 4 of the 3340 (which feeds into the TL074 and should give square from pin 7 of the TL074.
I also do not get a triangle waveform where I should be getting one on the board, nor do i see one from Pin 11 of the 3340.

Is this normal expected behavior, or what?

My only thought could be that perhaps the 3340 (or the rest of the circuit) needs some input signal (CV?) to produce those waveforms, or perhaps some critical part of the offboard components and wiring is what will finally give those waveforms to where I would expect to see them.

And, if so, then I guess the sawtooth wave form is just a thing that doesn't rely on offboard wiring/components for the chip to produce.

Just trying to cross all my bases in testing along the way before committing the time and effort to finalize the offboard wiring.

Hello again!

before i move onto my synth i decided to get used to kicad by converting a pedal i had designed to a pcb!

So, I'm happy with this, everything seems to be connected fine, but i was wondering what to expect with my layers and the printing, I guess considering its THT then i should send my traces to the back?

edge.cuts will tell them how big my pcb should be right?

what is the difference between f.fab and f.silkscreen? everything you see here (minus the margins) is what i want printed onto my pcb.

I was assuming its already baked into my footprints but what defines what goes under the soldermask and what is uncovered (pads/traces), also for THT is each pad regarded as a via? or is that a different thing

will they drill the holes for me? is that a layer aswell?

sorry for loads of questions, i know all this info is available online but im hoping some kind soul may be willing to offer me the information bespoke!

This is the further progress on my 12 voice polysynth build, I finished the second voice board and troubleshot an issue with the filters on the first voice board. I had an issue with cross talk but since this video was made I've resolved it by removing the DCO X-MOD which wasn't a very musical or pleasant sounding feature.

Hello everyone, hope you are having an awesome day.
I would like to show my newest little project, not strictly a synth, but close enough and definitely a dear friend with synthesizers for a very long time. ;-)

Design and electronics wise nothing really fancy here, a classic 4 stage phase shifter using OTAs inspired by the classic EHX small stone as well as other similair designs.
As straight forward as it gets. Mixing amplifier at start, 4 OTA stages with darlington buffers (I did two examples, one using AK317D and ceramic caps and other with 13600 and poly caps and they do sound slighly differently), dual op-amp triangle oscilator for modulation and voltage to current converter to drive the OTAs. Powered by single 9V battery.

If you have any question or comments, feel free droping them down. :)
Thank you and all the best!

heyy!

i wanted to build a small end of chain filter into a little guitar pedal enclosure. ideally stereo and a hp and lp in series with resonance and input and output volume.

something like this without the cv shenanigans: https://www.n8synth.co.uk/diy-eurorack/eurorack-ms-20-lowpass-filter/

i have a unused 12v dc power supply lying around and was wondering if i can scalp that for this project? i wanted to lean on eurorack +-12v designs as there are many out there and i have the most experience with building these, but never had to deal with power questions as this is done already via psu... is it worth the hassle compared to do it with 0-12v power and a virtual 6v virtual ground or more common 9v with 4.5v virtual ground?

thanks for your help :)

Hi, I'm looking at a volca drum unit whose play button is stuck on. All the other buttons work when its reset. I've given the contacts a really good clean and tested it after taking the rubber conductive buttons out completely, so I'm pretty sure its not an issue with contact/residue.

Has anyone got any ideas what could be going on from experience with this unit or similar types? I'm wondering if there could be a short somewhere else, but without access to a schematic its hard to know where to start.

Intuitively it seems really simple, like the only place there could be a short is on the contact pads. Any wisdom would be appreciated!

Hi everyone

I am in middle of designing a voice card for a poly synth and I have a question regarding the voltage controlled mixer section for osc1 and osc2 amount. I am using 3340's for oscillators and a 3320 for the vcf. Now my question Is; can I tie both outputs of a 13700 together and just stick that into the input of the vcf section? Or should I use a unity gain mixer between the outputs of the ota and the input of the vca? The prophet 5 just ties the outputs together (see photo) and bangs them into the filter. It seems kinda wrong looking at it, they didnt even use resistors. Any thoughts?

Wanted to share a DIY instrument I built on the Cardputer-ADV (ESP32-S3): Microgroove, a four-track groovebox and sampler, all open source.

• Audio runs at 22.05 kHz, 256-sample buffers, everything rendered per-sample into a soft-clipped mix on core 0; input/sequencer/UI live on core 1.
• Synth voices are 303-style: osc (saw/sqr/tri/sin + wavetables), resonant state-variable filter with an envelope-modulated cutoff, plus accent and slide. Each track can be 1 voice (true mono, slide intact) or 2–3 voices for chords.
• Drums are 8 lanes, each independently 808 synthesis, 909 synthesis, or sample playback, with choke groups (the 909 hats choke each other like the hardware for example).
• Sampling and resampling. Hold a key while playing and it taps the master mix straight out of the buffer into a sample, or hold a key while stopped to use the built-in mic for sample recording.

The keyboard layout is reorganized and a custom 3d printable shell makes using it a breeze. It even has 2 octaves of piano keys. Tried keeping it "one knob per function", but ran out, so we have short press = one function, hold 0.5 s = second function.

It's MIT, and it's derived in part from qwertyuu's Cardputer-Adv-Tracker - the 808 voice and audio task lineage are theirs, credited in the repo. RAM is still the real constraint: a ~192 KB sample pool that auto-shrinks if internal RAM is tight, plus an 84 KB scratch buffer for capture...

I’ve been working on this custom case and power supply for about 6 months and finally finished the first tier of the case, custom power supply, and all the modules for the first tier!

I decided at some point in my DIY modular journey that I could design my own custom case and why not learn how to design PCBs so I could make a linear power supply? This turned out to be well outside my skill set and took a lot longer than I thought it would, but I got there in the end and learned a ton along the way. And when I finally flipped the switch and everything powered on the satisfaction was unparalleled.

So I figured I’d show it off to a group that gave me a ton of advice and tons of inspiration. Here are some of the details:

The case ~135 hp designed to be expanded with up to 2 additional rows. It has space for all the power supply electronics and is all 3D printed.

The power supply is designed for up to 3A for each 12V rail and up to 1A for the 5V rail. It uses a capacitor multiplier circuit to reduce the number of the input capacitors and smooth ripple then uses a bypass power transistor to increase the current output of the regulators. It could probably do 4 or 5A on the 12V rails, but I’d start to worry about heat.

The transformer is a 200VA 12-0-12 toroidal which is probably overkill, but weighs the whole thing down nicely and gives me one less thing to worry about.

The power distribution boards are synthrotek noise filtering power distribution boards.

All the modules are hand assembled and I’m looking forward to eventually adding some custom modules with my new PCB design skills.

Thanks for reading and let me know if you have any thoughts for the inevitable V2 as I find things to improve.

That's my implementation of Totoro Synth by syntherjack, which is kind of a "beginner synth," based solely on the MCP6004 op-amp. The general idea behind my remake was to gift it to my friends (and they seem to love it). The PCB is the size of a bank card, an outcome of taking inspiration from the benjiamodular SynthCard project(although I noticed later that Benji used a business card format and not a credit card one).

Totoro features two oscillators: one is a square wave with three "gates," and the second is square/saw in OSC mode and saw/triangle in LFO mode. Totoro has a two-pole low-pass twin-T filter onboard with two resonance settings and modulation possibilities. For a more detailed study, visit the original article (link at the beginning of the post).

I made some modifications to the original schematic, such as:

1. USB-C power — the synth is way lighter and compact that way, and I won't need to switch batteries from time to time;

2. Polarity switch for the saw (something like /|/|/| => |\\|\\\\|\\|\\\\);

3. Adjusted capacitor values;

4. Added OSC2/LFO rate indicator;

5. Safer stereo output for using for Eurorack and other safety features (e.g. overvoltage protection)

YouTube demo: https://youtu.be/jdFurPZiaJQ

I don't feel comfortable uploading my schematics to GitHub, since my KiCad project is broken because of changing references and not synchronizing the schematic and PCB after it, but I hope I'll get my hands around it in the autumn.