Tuesday, October 10, 2023

Overcycler as a fully assembled SMT PCB


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!

Thursday, May 21, 2020

Sequential Circuits Multi-Trak firmware modifications release

Hello, I released version G.5 today with a fix for "Ext Clk" mode. After a few months of use, it seems it was the last bug left.

Here's the binary for 27C128 EPROM: mtrak.bin
And for 27C256 EPROM: mtrak32.bin (wider availability than 27C128 and compatible with this file)

Quick install how-to:
  • Dump patches and sequences thru MIDI. The upgrade procedure should not corrupt them but it's still safer to dump them before opening the synth.
  • Program the corresponding .BIN file to a regular erased 27C256 or 27C128 with an EPROM programmer. EPROM programmers (eg: TL866II) are not cheap but eg. there are services on the internet that do this.
  • Open the synth, remove the analog board.
  • Remove the old 28pin EPROM from the socket, keep it aside.
  • Fit the new EPROM, put the analog board and all back, and it should work fine!
  • To check the installed version number, press both "MIDI Channel" and "MIDI Mode" at the same time.

The project page: https://github.com/gligli/mtrakemu

I hope Multi-Trak owners will enjoy the added features of this firmware :) (by the way, I wonder how many of them there are in studios everywhere...).

Thursday, December 26, 2019

Sequential Circuits Multi-Trak firmware modifications

I started to work on a series of software modifications for the Sequential Circuits MultiTrak, mainly intended to improve usability in "live" or "jam" use.

As for the P600, I wrote an emulator of the digital part, which I used as a tool to code the modifications.

I had a setback: the MC68701 keyer from my Multi-Trak stopped working at some point, but I finally managed to read the contents of the chip and I was thus able to rescue it by reprogramming a new one :)
For those might have the same issue, here is the binary: mtrak_keyer_dump_MC68701S.bin
It can be programmed in an MC68701S or MC68701L but, beware, NOT in an MC68701U4L or an MC68701U4S.

Then, I finished the modifications of the main firmware, and managed to cram in the 3 that I wanted to do and everything seems to work well. I started from official version 2.2, which is the most recent and the most compatible. A version 3.0 exists but it is incompatible because the hardware is different, and therefore this modification will not work on it.
  • Synth voices can now be freely toggled ON/OFF, in sequencer mode (even when it is running, which brings a lot of options for "jam" use), in unison mode (to make 1-5 voices unisons instead of 6), or even in poly mode (alhough not very useful because the voices are still assigned).
    • "To Tape + track 1-6": Disable the corresponding voice, it really is a forced "note off" because the release stage is still played if the voice was sounding.
    • "From Tape + track 1-6": Re-enable the corresponding voice, the next assigned note can play again.
  • Pitch bender routing can now be changed from VCO to VCF:
    • "To Tape + Auto-Correct": Switch to Bender -> VCF.
    • "From Tape + Auto-Correct": Return to Bender -> VCO (boot default).
  • Disabled sending the sequencer notes to the MIDI output in "local off" mode ("MIDI channel + 9" to toggle it), allowing clean control of an external synth with the keyboard at the same time as the sequencer runs.
For technical reasons, these settings are not saved: there was about 50 bytes of free space in ROM, I already had to use many coder tricks to get everything in there!

I named the version "G.3", and it can be displayed as usual with: "MIDI Channel + MIDI Mode".

Here are the binaries:
And finally the project page on GitHub: https://github.com/gligli/mtrakemu

Version "G.4" up, fixing two bugs with "local off" feature, same links a before!
Version "G.5" up, fixing one bug with "Ext Clk" feature, same links a before!

Tuesday, January 22, 2019

Arturia BeatStep Pro to Yamaha CS-10 CV Trigger

A while ago, I made this cable to drive my Yamaha CS-10 CV Trigger using my Arturia BeatStep Pro.
It's a bit unusually made and takes advantage of the way the Yamaha CS line of synths do "Trigger out" but it's easy to make and works just fine!

PotatoCad schematics folllows :)


NB: I recently found something nice about this cable: it can also be used to loop the CS-10 audio out back into the filter. Just plug the blue 1/4 inch jack into "external input", the orange one into "output" and the BSP end into your mixer, set "Ext" mode and tweak the corresponding potentiometer to taste :)

Sunday, August 28, 2016

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:

Tuesday, October 13, 2015

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.

Thursday, October 1, 2015

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).