It's over (cycler)

Hello,

After about a year and a half after the first Overcycler sold, I've chosen to stop manufacturing it...

Long story short, it is too burdensome to even produce one batch per month. I do love the fact that is sells well, being a labour of love, but for many reasons, it takes a bit of my health for each batch (stress, meeting deadlines, necessary attention to detail, ...).

I hope this project will end being manufactured again by some company in the synth business, I wouldn't ask for a lot of money on each sale to sell the rights even (and I do love Pi as a symbol of laicist love ;).

For now, the project stays open-source and free software and located at https://github.com/gligli/overcycler. Eg. it wouldn't require a huge effort to maintain the JLCPCB bill of materials, and besides PCBs, the rest is off the shelf form mouser, aliexpress, ...

As a side note, stopping production will also help me focus on my other projects and my music.

Of course I'll continue doing after-sales support but that's about it.

Fabrice GUILHAUME aka. GliGli.

Overcycler back in stock!

The new batch of Overcycler is now ready at https://gligli.store !

From now on, only the fully built version will be stocked.

 Edit: A new batch of 10 is available!

New Overcycler firmware release (build 2024-10-29)

What's new:

• New factory presets from Solidtrax.
• Firmware speed improvements, now the user interface won't slow down on modulation-heavy presets.
• New "Amplifier level" parameter, that can be used to level the volume of patches or to add even more overdrive at high levels.
• New "Wave Folder" WaveMod, that vertically (through amplitude) folds waveforms, ie. when they go past the maximum, they fold (or "bounce") back, and the WaveMod amount is the pre-amplification (from 1 to 16).
• New "Bit Crusher" WaveMod, that works by lowering the amplitude resolution of the single cycle (contrary to the "Grit" one, which lowers the frequency resolution).
• New "LFO Trigger" options, to reset the LFOs on each key press and to control how many periods they run.
• LFOs at speed 0 can now be used as a source of constant modulation.
• Patch names, that can be edited on a computer.
• Added "Perc" and "FX" as preset type.
• When the arpeggiator is in hold, new notes can be assigned regularly, allowing to play over an arpeggio pattern.
• Many user interface usability improvements.
• Bug fixes.

Download links:

https://github.com/gligli/overcycler/releases/tag/build_20241029

Edit: By the way, the synth will be back in stock next week! 

Overcycler demo by Solidtrax / next firmware release

Solidtrax ( https://solidtrax.nl/ ) posted a great demo of presets he made for the Overcycler :)(many of these presets plus some more he made will be factory presets for the next firmware release).

By the way, the next firmware is currently in beta stage and will be released soon!

Here will be the major changes:

• Firmware speed improvements, now the UI won't slow down on modulation-heavy presets.
• New "Amplifier level" parameter, that can be used to level the volume of patches or to add even more overdrive at high levels.
• New "Wave Folder" WaveMod, that vertically (through amplitude) folds waveforms, ie. when they go past the maximum, they fold (or "bounce") back, and the WaveMod amount is the pre-amplification (from 1 to 16).
• New "Bit Crusher" WaveMod, that works by lowering the amplitude resolution of the single cycle (contrary to the "Grit" one, which lowers the frequency resolution).
• New "LFO Trigger" options, to reset the LFOs on each key press and to control how many periods they run.
• Patch names, that can be edited on a computer.
  
• Many UI usability improvements.
  

Overcyler first batch ready

The first batch of Overcycler is now ready at https://gligli.store :)

For now, only the fully built version is stocked, DIY version will be available next batch!

GliGli's shop online!

I set up a shop to sell Overcycler, the link is: http://gligli.store (the first batch of 10 will soon be available there).

The final price for the fully assembled version is 314€ and the DIY will be 264€.

By the way, "Magical Synth Adventure" has posted a video showcasing Overcycler through sonicstate.com on Youtube :)

Edit: some photos of the synth:

Overcycler3 final prototype / factory patches demo

Due to issues with the first enclosure/PCB prototype, the project had a bit of delay, sorry for that!
The hardware is now based on a more "standard" PacTec PT-10 enclosure, and we had to redo the whole PCB so that it fits the form factor.

All in all, this made Overcycler way more ergonomic, with the panel now angled, and the 10 potentiometers and keypad below the screen.
This is also due to the reworked user interface, which uses digits to access 10 pages of controls, and A/B/C/D for options per page (* and # being global shortcuts).

I have made a video of the 15 (so far) factory patches. Finish will be slightly different in the final version (screws, ...) but this is very close to the final design.

Overcycler3 firmware done!

I have finished porting the firmware, and I am happy: I had no major modification to do on the prototype for everything to work :)

At a glance, what I added:
- Mono aftertouch (or "channel pressure").
- Automatic filter tuning.
- A bootloader, to allow easy and riskless firmware updates.
- A cleaner MIDI implementation with CC and NRPN.

By the way, I was able to implement the WaveMod called "crossover" in true polyphony, and even allow it on the 2 oscillators, a small demo:

This allows a 4 single cycle sound as "partials", here I modulate it with the oscillators envelope, we can also hear the aftertouch modulating the filter brightness.

Overcycler3 update

The PCB design is finished, and I received the (almost) entirely populated first prototypes from https://jlcpcb.com/ (they didn't have the SSI2144).

Here's a picture of the PCB:

I am now working on porting my firmware on this new version.

By the way, here's what has changed since my earlier post:
- One more envelope, dedicated to oscillators (the filter envelope was used beforehand, but it felt a bit cheap...).
- Instead of a SDCard slot, I now use a soldered flash chip, which will be accessable through USB.
- Shipped with a machined enclosure, the potentiometers, the display, the 16 keys keypad, the knobs, and probably a vinyl for the panel, assemble it yourself (about 250€), or entirely assembled (about 300€).

Overcycler as a fully assembled SMT PCB

Hello!

Now that there are cheap SMT clones of the SSM2044, I thought I could finally make this synth an affordable and easy to build DIY.

My idea is to offer this synth as a fully soldered (almost) entirely SMT PCB, and let the users wire the panel (10 potentiometers, a 40*4 character display and a 16 keys keyboard) and build the enclosure.

For now, it's hard to give a cost estimation, but let's say it would (probably) be around 200€ for a fully assembled board (add less than 100€ for the rest).

The firmware is now rather complete and well tested (by me :), here are the features:

• 6 voice polyphony using hybrid synthesis (Digital "single cycle" oscillators / analog VCF and VCA).
• 2 synchronizable oscillators per voice, duty cycle modulation on any waveform, 2 waveforms mix modulation (on oscillator 1), "grith" modulation (from a subtle veil to "ring modulation"-like sounds).
• 2 complete envelopes with lin/exp choice and looping.
• 2 complete LFOs with 6 modulation destinations.
• 1 noise generator.
• Voice panning on the stereo output.
• 400 patches stored on SDCard, Single cycles (AKWF, PRophetVS, ...) also stored on SDCard.
• Sequencer / Arpeggiator.
• USB Powered with USB MIDI and regular MIDI.

 If people show interest, I'll start designing the new PCB!

Overcycler2 updates

I made several improvements to Overcycler2 since my last posts:

• Added a new WaveMod for oscillator 1 that can dynamically blend 2 waveforms. The blending ratio can be set manually, with an LFO, or with the filter envelope. In that last case it's paraphonic (due to CPU limitations), that means the blending ratio always follows the last triggered filter envelope.

• Made the vibrato a fully featured second LFO.

• Added LFOs to filter resonance routings, this can create really interesting timbres due to the way resonance volume compensation drives the pre-filter mixer.

• Doubled the synth refresh rate (envelopes, LFOs, ....), now at 4Khz.

• Added basic support for lower sample count waveforms. That allowed me to use the cool ProphetVS waveforms.

• Various tweaks & usability improvements.

I also made a video demonstrating some of the user interface of Overcycler2 and then played some new patches:

Overcycler2 demo track

All sounds were made with Overcycler2, my DIY 6 voice hybrid analog synthesizer, drums included.
Effects: reverb, equalizer, limiter.

By the way, I made several changes since the patches demo:

• Oscillators sound improvements: 96KHz sampling, better interpolation (hermite) for improved treble response, major reduction of sound crackling (it can be heard in the last patch of previous demo).
• Added the polyphonic 2 track step sequencer from P600fw. 20*2 sequences can be stored for now.
• Added sequencer/arpeggiator and keyboard transpose.

Overcycler2 patches demo

Here's a demo of a few patches on Overcycler2, showing some of its sound palette.
They tend to have lots of overdrive to get an idea of the raw synth sound but by adjusting the pre-filter mixer levels, it's perfectly possible to get tamer sounds.


By the way, I recently started implementing oscillator sync, I didn't demo it yet because I think I can improve the way it sounds (there's a bit of aliasing on the upper range right now).

Overcycler 2 lives!

I finally received my PCB!

Unfortunately I found 2 bugs on the board revision I sent for production but it was too late, so there are a few small straps on it.

Anyway, I soldered all the components, did a bit of debugging and it finally worked, all 6 voices!
It works quite fine actually, better than on breadboard. Eg. the potentiometers ADC captured lots of noise while on breadboard which made adjusting values hard. Here the noise usually doesn't exceed 1 bit.
Overall much less noise on the PCB, which make the VCAs really quiet when closed.


Pic of the board (sorry, cellphone quality):

(The heatsink is temporary, I will use the case itself as a heatsink.)

Now I just need mount the board inside the case, solder the connectors (I have yet to receive them) and the synth will be done :)

Overcycler 2, the return

Overcycler, my homemade polyphonic hybrid synthesizer, while being a working synth that I made music with, had quite a few caveats in its design, here are a few of them:

• Being a 5 PCB design, I tought it was a good idea to have voice cards but it just complicated the design and made the enclosure a lot harder to build.
• The enclosure was too small, not very practical, and overall badly built. The fact that it was too small also forced me to make a lot of hacks to fit everything inside.
• The display was too small, which made parameters hard to read fast.
• VCAs were noisy, bleeding audio even when fully closed and gain staging was wrong, which made the sound too tiny past the filter.
• Using the VCA to compensate for resonance volume loss, it seemed like a good idea, saving the cost of one more VCA per voice but it made the synth sound small with resonance, as the SSM2044 lose its overdrive the more you added resonance.
• DAC / sample & hold mechanism for CV control. Not a bad thing in itself but very sensitive to noise.
• Link capacitors in some parts of the voice design had too small values, leading to poor bass response.
• Overall just a prototype that was left unfinished.

So, as the title says, I'm making Overcycler 2, a full rebuild / redesign of Overcycler. Besides having a more enjoyable synth to make music with, I hope this will make it a properer DIY project that others can build. As you can guess all the previous issues were addressed:

• Single PCB design, roughly A5 size (153mm x 209mm).
• Bigger, better built, nicer enclosure, with wooden sides for that vintage vibe :)
• Bigger display, 40x4 characters instead of 20x4.
• Lots of work on gain staging, to try to make the synth always sound good.
• Using the pre-filter mixer to compensate for resonance volume loss, requiring no additional parts and nicely doing the job. That was kind of an eureka moment when I thought about it :)
• 8 channel DAC chip to handle the CVs. They are quite expensive so I chose to ditch multitimbrality (which never worked on overcycler) to keep the costs low.
• Bigger and better quality link capacitors.
• This time I really want to make it proper. 

By the way, I added a voltage controlled noise generator of my design and also removed the VC master volume to replace it by a dedicated potentiometer.

Right now I have a fully working voice on breadboard, a prototype PCB that is sent for production and I just finished drilling / preparing the enclosure, here are a few pics of it:
 

Now compare it to this and you will see what I mean by better built :)

To be continued when my PCB arrives!

Project page: https://github.com/gligli/overcycler

Overcycler patches demo

I recently added a lot of what was missing to make it usable, I still need to handle multitimbrality and write a sequencer, but it's already a fully working polysynth ! :)

As you can hear in this demo, it's very versatile, from huge analog pads to gritty digital sounds, going through all the inbetween possibilities. A great addition to my other analog synths !

Overcycler, the software

I worked on the software these last days, it's of course based on a good chunk of P600fw (envelopes, lfo, assigner, midi, storage, ...)

Besides a few PCB bugs I worked around in software, or using the soldering iron, the hardware works great :D

The microcontroller is really powerful, which allowed me to use very high sample rates (90Khz wih 2x oversampling, so effectively 45Khz), there is very little aliasing up to the highest MIDI notes.

Something I wasn't sure about was CV sample and hold performance (basically, it's a modern simplified version of the Prophet 600 design).
I was happy to see that it's very stable, and slew rate is great :)
 Here's a VCA envelope example:

 We can see that the fastest attack speed is below 100 microseconds (most analog synthesizers are 10 times slower !).

Noise was a problem at first, but  using various tweaks, it got much better (signal to noise ratio goes from 50db for oscillators to 100db for the master mixer now).

--

Here's a little demo I made recently: http://sfx.gligli.free.fr/zik/overcycler/overcycler3.mp3
(Simple saw patches, I can't use the potentiometers to tweak the sound for now)

And an older one: http://sfx.gligli.free.fr/zik/overcycler/overcycler2.flac
(I had noise problems at that time, but it' a better raw sound demo)

I also set up a github repository for code and schematics: https://github.com/gligli/overcycler
(PCBs are still buggy tho)

PS: That's all for now, have a nice read :)

Overcycler, the hardware

I have now finished designing and building the hardware:

I have some more pictures there: http://sfx.gligli.free.fr/zik/overcycler/hw_done/
 
It's made of 5 PCBs:

- 3x Voice Card, each one having 2 voices.

ICs (per card): 2x SSM2044 VCFs; 2x MCP4922 dual 12bit DACs; 1x 74HCT4051 multiplexer; 1x TL074 op-amp.

- The VCA Board, implementing the 6 voices VCAs, and 2 more for the master mixer.

ICs: 2x SSM2164 quad VCA; 4x TL082 / 1x NE5532 / 2x TL074 op-amps; 1x 74HCT4051 multiplexer

- The Main Board, hosting the power supply, the microcontroller, the potentiometer multiplexer, the master CV DAC, and various digital I/O (MIDI, screen, footswitch, ...).

ICs: 1x mX-LPC1768-S; 1x MPC4921 single 12bit DAC; 2x 74HCT4053 multiplexers; 1x 6N138 optocoupler

--

I used this microcontroller kit: NGX mX-LPC1768-S It's based on the ARM Cortex M3, has plenty of peripherals, and is ultra fast.

The 12 ocillator DACs are driven by the µC through a fast SPI bus.

The analog chips are driven by control voltages generated by the master CV DAC, through sample and hold mechanisms (1 to 32 demultiplexer into reservoir capacitors into high impedance voltage followers, basically).

The master mixer has an hardwired left to right voice panning, to allow for some spatialization (inspired by the Oberheims).

Screen and keypad communicate with the µC through a standard serial connection.

I use a MicroSD card for storage, I use a MicroSD to SD adapter I soldered on the main board.

I plan to add USB-Host, to be able to plug an USB-MIDI keyboard directly, and maybe USB-Device to allow for mass storage access to the MicroSD.

My prototype PCBs had some bugs, which I hack-fixed for now, otherwise everything works nicely :)

Overcycler, a DIY 6 voice hybrid synthesizer

I'm now working on a fully DIY synthesizer project, I started it about 3 months ago.

It will be:
- An expander, in a slanted box ( http://www.hammondmfg.com/1595eBI.jpg ).
- 6 voice polyphonic with separate outs, 4 part multitimbral.
- Hybrid , two 12bit DACs per voice (wavetable oscillators for now), one SSM2044 filter, and 1/4 of SSM2164 VCA.
- Using a 20x4 characters LCD / 16 keys keypad / 10 potentiometers user interface.
- Using relatively simple hardware, strongly based on the KISS principle :)
- Having a strong character, each stage will allow some overdrive (filter, VCAs, ...)

I learned a lot while working on the Prophet 600, and I thought it could help me design a slightly different synth from the usual analog ones, more or less inspired  by the PPG Wave.

Nothing groundbreaking, Mutable Instruments have done this for a while, but I had an unused set of SSM2044/SSM2164, and I wanted to see how far I could go in simplifying a polyphonic hybrid synthesizer.