Fjöl 4-Voice Midi synth

FIRMWARE AND HARDWARE STILL A WORK IN PROGRESS

Small demo video with non working LED's: https://www.youtube.com/watch?v=nTqA_WNiwQo

Current hardware uses the Daisy Seed platform from Electrosmith, which has 96kHz/24Bit stereo audio.

Fjöl is a 4 voice polyphonic Phase modulation synthesizer. Using only sine waves you can get the same sounds as an FM synthesizer.

• digital ladder LPF with resonance
• usb A on the back to update firmware
• 3 operator Phase modulation with 3 algorithms(so far)
• two endless encoders with CV input for adjusting 8 different parameters
• MIDI IN and MIDI THRU with type A midi minijacks as per MIDI standard.
• optional V/OCT and gate per voice expander also in the works

Encoder parameters are:

• stereo spread of voices(constant power)
• filter resonance
• filter envelope decay
• glide/portamento
• Operator 2 detune
• Operator 3 detune
• Operator 1 feedback (creates saw like wave)
• Operator 2 feedback

Potentiometers are:

• Operator 2 amplitude
• Operator 2 ratio
• Operator 3 amplitude
• Operator 3 ratio
• VCA Attack
• VCA Release
• LPF frequency
• Filter envelope amplitude

Algorithms so far:

Algo 1:

OP2 -> OP1

OP3 -> OP1

Algo 2:

OP3 -> OP2 -> OP1

Algo 3:

OP3 -> OP1

OP2 -> OUT

Where/how to order

It's all a work in progress.

Hopefully I'll have some beta testing units ready before summer 2023 :)

WELL that didn't work out. Putting this one on hiatus until I finalize the desktop version. It's a struggle to work a full time job and try and work on this regularily.

Designed With

• KiCAD
• Visual Studio Code(C++)
• Inkscape

Versioning

• 1.0 - [Hardware] Original PCB
• 1.0 - [Software] Original software

Authors

• Hallmar Gauti Halldórsson - Fjöl Hardware and Firmware
• Electrosmith - libDaisy and DaisySP libraries

License

Hardware: CC BY-SA 4.0

Software: CC BY-SA 4.0

But if you want to sell or do something with the software or hardware then it'd be nice to include my name and link to my Github somewhere :)

Acknowledgments

• All of Mutable Instruments designs have been an insparation and a solid reference for both analog and digital circuits. https://github.com/pichenettes/eurorack

• The whole idea of a 4 voice poly synth was planted in my head after trying MakeSynthsNotWar's String Theory module. https://makesynthsnotwar.com/modules/stringtheory/