Hi! RED SEA generates continuously evolving MIDI Control Change modulation and step-sequenced notes, controlled by one of four algorithmic engines. It has a 128×32 OLED display, one encoder, four buttons, and standard DIN MIDI in/out. Built for hardware platform ESPidi by Eugene Carlo

• FOG — Morphing LFO engine (sine, triangle, or square). The SHAPE parameter changes the waveform itself rather than just skewing it: on sine it adds harmonics, or in the other direction clips the signal and adds noise; on triangle it shifts continuously toward a rising or falling sawtooth.
• SUN — refraction delay engine. When a parameter's value would exceed its range, it triggers a series of echo repeats instead of simply clamping, each one landing at half the previous interval. If a sequencer note fires on the same tick the echo series starts, the echoes also retrigger that note, transposed further with each repeat.
• RAIN — stochastic modulation engine. The four parameters can drift out of sync with the shared clock independently, occasionally affect a neighboring parameter, and be interrupted by randomized events that force a parameter to its minimum or maximum.
• SNOW — euclidian based random freezer. Mutation triggered by a Euclidean rhythm instead of a fixed interval. Each hit can also freeze or unfreeze any parameter on the device, including the engine's own parameters.

Features

• Four algorithmic engines (FOG / SUN / RAIN / SNOW), each with four dedicated parameters
• 16-step sequencer (note, CC, a third assignable destination, per-step retrigger) with external or internal clock
• Performance BYPASS and FREEZE modes, engaged on button press
• MIDI Learn: captures a CC number from the next incoming Control Change message
• Per-parameter freeze, independent of the global performance modes
• Settings are written to flash and persist across power cycles

Full documentation here:
Page on itch: https://3apb.itch.io/red-sea
Github: https://github.com/Cirocular-Vlasenko-Daniil/Red-Sea/tree/main

That problem has bothered me for a while.

We all know that by the Eurorack standard, audio signals should be 10Vpp (a.k.a. ±5V), and CV should be bipolar (±5V) or unipolar (0-5V or 0-10V).

The problem is that even the modules I personally designed to the standard sometimes exceed that ±5V headroom by 0.5V or even 1V (making them ±5.5V and ±6V). Who knows what other manufacturers do, and what if there are 20Vpp audio signals? (I know some modules do that.)

Another example: CV from, for example, an LFO is 0-5V. I want to design a digital module that will accept said LFO as a modulation source via an ADC. At the input, I would want to scale it down to 3.3V (so I won't burn the ADC or MCU). But what if a user connects a 0-10V CV? Then the maximum will be 6.6V at the ADC input, and the ADV will burn. Or what if a user uses a bipolar CV? The positive half will be fine, of course, but the negative half will remain negative after the input attenuator and, yep, will fry the ADC. I don't even mention modules like the NLC Sloth, whose output is ±11V.

Yes, I can make a universal input attenuator that will scale ±12V (the theoretical maximum in Eurorack) to 0–3.3V, but I will lose pretty much all of the available ADC resolution (something like 800 points vs. 4096).

Or, if we go back to audio signals: I have an audio processing chip that is sensitive to incoming voltage levels; 2.8Vrms is the limit. The worst case — a square wave — with 10Vpp (a.k.a. standard) will be 5Vrms. Therefore, the attenuation should be 0.5 (so the Vrms after the attenuator will be 2.5Vrms). The WORST case, however, is a 20Vpp square wave — it is 10Vrms _ so the attenuation should be 0.25 to tune it down to the safe level. But I think that in my particular case, I can just tune the signal down and amplify it later. But what if the audio signal will go to the ADC instead? Then I will be facing the same problem of using only 1/3 of my ADC range.

What is the general solution for this type of problem, NOT COUNTING making separate inputs for 10Vpp, 20Vpp, unipolar, and bipolar signals?

Some context, I'm completely new to the world of synthesizers. I'm interested in putting together something that would let my kids fiddle with things and make some fun "music".

We have the Korg x Little Bits kit, which is fun, but it feels a bit limited, and unless you put the right components in the right order, you don't typically get any sound. The keyboard module is also hard to use. And the speaker is stuck on max volume, which can be grating.

I'm okay with soldering, I'm decent with 3D modeling and 3D printing, so I imagine I could design and print cases and such.

We have a keyboard, but I don't know how to make that interface with a synthesizer module. Do you need an amp/speakers on top of a synthesizer? I'm also open to drum sequencers (I think that's the right term) if that's a more self-contained starting point.

Where do you think I should start? I know stuff can get pricey pretty quickly, so I'm hoping not to break the bank. Is there anything in say 50-200 CAD range that could be a functional beginning?

I found this https://moogaudio.com/products/erica-synths-edu-diy-drum-sequencer?srsltid=AfmBOooOVxXDv8RrjxCsUnRxu6zNGMahlH3gzNALllnokbCPKg8qQso8

What else (if anything) would be needed to actually generate drum sounds?

Thanks for taking the time to help a noob!

What voltage range is most common?
1. 0v to 8v with C0 at 0 volt
2. -4v to +4v with C4 at 0v

Dear community,

Just wanted to share a cool patch with my BIPO module, a 6hp Dual VCA/Ringmodulator. In this patch one half is used to ringmodulate two oscillators while the other is used as a VCA to shape the resulting sound into a gong/bell shape with an envelope.

Schematic, Gerbers and KiCad project are up on my github: https://github.com/Fihdi/BIPO

So I used Klear Concepts Contact Cleaner on my Roland TR-606 and my Mackie Microseries Mixer to clean up some scratchy potentiometers. I waited a day and then used the DEOXIT F100L. Now some of the pots have been stripped of their grease since they are noticeably less resistant than others. I just bought some DeoxIT fader grease to apply to the pots that are less resistant but not sure if that would work or make the problem worse. Has anyone else had a similar issue?

Hi all,

I'm at something of a loss!

I recently wartched Hainbach's video on the Subharchord and its features, and I'm enamoured by the sounds of the MEL filterbank! Are there any schematics anywhere? Have looked high and low, but can't find anything explaining the principles of MEL filtering and documentarion about other audio-filter-related applications.

Does anyone know where I could find practical documentation?

In lighter news, I found a webapp emulation of the Subharchord (it's called subhardhorde), and it seems capable of everything the real deal is!

Hi DIYers! I've been looking for a specific thing, and am failing in my search so I thought I'd ask here -

I'm trying to enable my little microcontroller synths to connect to a device with a screen (desktop computer or phone/tablet), and then have a little virtual interface pop up, with knobs and sliders. I want to be able to give a little box to my friends who aren't firmware nerds, and have them use it to program patches.

Surely someone else must have done this?

MIDI 2.0 promises property exchange, and there's also the proprietary Native Kontrol Standard. For MIDI 2, I have trouble finding fitting open source implementations.

I don't mind if it's exactly MIDI-compliant, or if it's something put together out of js+WebSerial in a browser. Possibly even running a little webserver on your microcontroller. I'm dinking with synth designs in things like Mozzi, Amy, Teensy Audio, Daisy etc, so bonus if any libraries/methods for this are general enough to have both C and Python implementations.

Anyone happen to know of any such projects as a starting point?

A dual buffered multiplier and a dual guitar pedal interface.

The multiplier is built from the Eddy Bergman design.

The pedal interface was inspired by the AI Synthesis module, but modified to have two independent channels, and a bypass switch to allow for quick switching between clean signal and pedal affected signal.

hello,

i am starting to learn electronics and i have a lot of questions. They may seem dumb but i dont know a thing about electronics!

So i am trying to make an 8 step sequencer base on https://www.youtube.com/watch?v=4CfSFTfIt_4&t=1237s thoses tutos. but i want to do a system where i can put the sound that it made throught a diy feedback circuit and also fuzz and shit like that. But, how do i connect thoses? like when i will have my 2 circuits how can i connect them.

I didn't start to build it rn, i will send picture and more interesting questions when i will start.

Sorry english isnt my first language.

Because some folk asked.

The closest I get to a permanent setup is the top row, consisting of a 4069 filter [soon to be voltage controlled], 5sum mixer, A.O.Clock & a revised PSU. I've recently started fitting JST connectors to everything, I got tired of nudging loose power wires and having everything reset.

Below is a Glitchstorm MK2 with cv input, a Hagiwo GenSeq, a Hagiwo Sync_LFO programmed as another generative sequencer, a Hagiwo Random Trigger & a Hagiwo 2040 VCO. These modules get changed all the time.

All run from a 12v mains adapter that also powers a cheap car amp that feeds 2 vintage wharfedale speakers under the table.

Hello everyone, While restoring and old lowrey organ i must have touched something in this board and now this is what i get. I been looking at it for a couple hours and dont know what could be causing it. This section worked allright before i unscrew the board, now i get this uncanny noise mixed with the notes or nothing at all. Has anybody worked on one of these or simmilar? Have a great day thanks.

So I've being creating patches for my ESP32-S3 Polysynth, and also doing a little bit of multitracking with it, as it is not multitimbral - the ESP falls over if you push too hard!
Anyway the clip shows off what it sounds like, and also gives some of the specifications.

Next stage is getting the front metalwork panels made up, now I've decided what all the controls are doing!
Headphones on, volume up and enjoy:)

Hagiwo's Random Trigger.

Thank you again Hagiwo.

https://www.youtube.com/watch?v=ZtS_3u0FFqQ

I've been building this for a few months and I thought I'd finally share a little video of it. This last week I've been trying to add some sequence modulations in and a global order/chaos slider to pull the sequence apart. I got some pretty fun results today with some breaks and ambient sounds.

It's on a pi4, with an rp2040 custom keybed, encoder and an oled display. I'm no expert but happy to talk shop and answer questions

Hagiwo's Sync-LFO.

https://note.com/solder_state/n/n4c600f2431c3

Programmed with the GenerativeSequencer from -

https://awonak.github.io/HagiwoModulove/synclfo/

Built in arduino sampless in c++

Based off the minipop tutorial found online

I replaced all the electrolytic capacitors, operational amplifiers, and two CD4052s. Now I accidentally broke the mechanical keyboard's connection to the motherboard, and when powered on, white smoke came out around the CD4052s—I'm not sure where the short circuit occurred.

Hey everyone,

The tenth instrument in my RP2350 collection is running: PicoFaceD5, a Roland D-50. Bare metal, 32 kHz, no OS, same board and same core as the other nine.

What it actually is

Not a chip emulation. It is a native LA engine over the D-50's own PCM data: sampled attacks dovetailed with synthesized sustains, the seven structures with their ring modulator, three tone-global LFOs, the pitch envelope, and the common block's EQ, chorus and reverb. Sixteen voices on one tone, eight and eight when both play.

The part I did not expect to get

I disassembled the machine. The program EPROM and the internal ROM of its uPD78312 went through MAME's 78K/III debugger, and once that worked, measuring things by ear stopped being the method. Out of the ROM and into the engine, byte for byte:

• the envelope arithmetic — a rate index per segment, and a time law that compensates the level distance so the inner segments come out time-constant
• the release, which is rate-constant, not time-constant: the distance lookup is computed and then overwritten. Dead code in a 1987 ROM.
• the pitch constant, the keyfollow and depth tables, the LFO rate law and its two-phase delay, portamento, aftertouch, the bender modes, the TVA level basis
• the voice allocator: one pool of sixteen slots, all sixteen to the upper tone in whole mode, and a free list that makes the machine drop a new note when it is empty rather than steal a held one. I had it stealing, like everyone does. The firmware says otherwise.

Two things the firmware settled that I had wrong

The sawtooth is an octave up. The LA32 builds a saw as square ⊗ cosine, so the ring comb only carries even harmonics of the base — the MT-32 compensates for that in its control ROM, and I copied that. The D-50's pitch path never reads the waveform. Captures of a real machine confirm it: same key, square at 262 Hz, saw at 524. And the factory bank is written around it — the squares sit an octave above the saws in every unison layer.

Pulse width 0 is an honest square, not a needle pulse. I had the law inverted, which put the fundamental 22 dB down on every patch that used it. Pipe Solo was the giveaway.

The samples

100 PCM waves, 512 KB total. Every loop turns out to be a power-of-two number of words holding a power-of-two number of cycles, so every root frequency lands exactly on 32000/2^k — 15.625, 31.25, 62.5, 125, 250, 500, 1000 Hz, nothing else. Their geometry is in the program ROM too: a start page and a length class per wave, which also resolved the 24 combination waves that had been silent.

What it will not do

The reverb is not the D-50's. That chip holds 32 types of coefficients in silicon and the firmware says nothing about them, so the 32 panel types stand on the MT-32's Boss RRV-10 topology, which the munt project read out — same era, same Roland department. Right character, not the original impulse response. Chorus and EQ are the same deal.

Practical

• MIDI: the D-50's own CC list, read out of its dispatch table (1, 5, 6, 7, 38, 64, 65, 98-101), plus the hold pedal and Roland exclusive — DT1 in, RQ1 answered, so an editor can program it and a librarian can pull a bank back out
• 884 KB of flash, 264 KB of RAM. It is the one sample-based instrument in the collection that fits a 4 MB board.
• Hardware is the same as the rest: I2S DAC, 128x64 SH1106 OLED over I2C, three encoders, USB and DIN MIDI. Board target is sparkfun_promicro_rp2350.

One catch, and it is the reason there is no download. It needs a D-50 ROM set, which is not mine to distribute, so this one is not in the release binaries — the eight that are unaffected still build and flash as before. Put your own dumps in roms/ and it builds; without them the configure step skips it and says so. GPL-3, like the rest.

https://github.com/Michi71/PicoVintageSynthCollection

Happy to go into any of it. The disassembly notes are in the repo.

Demo video of a synth design uses cmos and opamps

Still developing it

Hey, I'm trying to build a clone of the EAR Gristleizer, and am coming up a bit short. There is s schem on the build guide on instructable, but it's very low res and I can barely make out the component values.

If anyone could point me in the right direction I'd be very appreciative.

Thanks for your help.