My-Dirty-Synth

Content:

• Main Arduino code of the synth : My-Dirty-Synth.ino
• Front panel PCB in kicad 6.0 : hardware - hardware - dirty synth folder

Infos

This git contains all the files to realize your own "My-Dirty-Synth" made with the Simple Synth kit made by synthux academy. The synth is based on a Daisy seed by electro-smith and uses their Arduino library DaisyDuino.

Each component of the synth (potentiometer, switch, jack) comes from the Simple Synth kit except what is linked to MIDI. For this, a custom PCB acting like a front panel has been made.

Daisyduino warning

I'm using the daisysp wavefolder, it is not yet in the daisyduino library (tested the 19.04.2024 with daisyduino 1.6.3).

You need to get them in the daisysp library:

• wavefolder.h
• wavefolder.cpp

You can put those two files in your daisyduino library path usually C:\Users\YourUserName\Documents\Arduino\libraries\DaisyDuino\src\utility\DaisySP\modules on Windows.

Then you'll need to do two modifications:

• on the wavefolder.h file, replace line 6 #include "Utility/dcblock.h" by #include "dcblock.h"
• on the daisysp.h usually located C:\Users\YourUserName\Documents\Arduino\libraries\DaisyDuino\src\utility\DaisySP\daisysp.h you need to add #include "modules/wavefolder.h" on line 18.

Architecture

Block diagram

Here is a block diagram of the synthesizer:

The design starts with an oscillator whose shape can be chosen between sinus, triangle, sawtooth, and square. In addition to the main frequency, it is possible to have the 1st and 2nd octaves mixed with the main oscillator.

The signal is then sent to the effects:

• a wavefolder
• a decimator

Both effects have a potentiometer to drive their strength.

A 3 positions switch helps to use those two effects combined:

• position 0: wavefolder only to maximum range
• position 1: wavefolder to maximum range and decimator reduced range
• position 2: wavefolder reduced range and decimator maximum range

When passing from one mode to the other, the range of value of the effect will slowly swipe to fit the selected range. This swipe last for ~2 secs.

The next module is the filter. You can change the filter resonance, cutoff frequency, and drive. With two switch you can change from

• no filter
• high pass filter
• low pass filter
• bandpass filter.

Finally, you can find the signal can pass through a VCA or lowpass gate with attack decay and release adjustable. You can either activate the VCA/LPG with the VCA Mode switch and then select what kind of system you want your signal to pass through:

• VCA
• LPG
• VCA+LPG

MIDI implementation

The MIDI listens by default to channel 1. It reacts to changes in note On, note Off, pitch bend, and control change. The control change affects the filter cutoff frequency.

• Note On/Off will change the pitch. Be sure to set the oscillator's main frequency potentiometer to its minimum to avoid interference with MIDI.
• Control changes will change the cutoff frequency of the filter. Be sure to set the cutoff frequency potentiometer to its minimum to avoid interference with MIDI.

A button hooked to D13 can be used to change the MIDI channel. When pressed, the new MIDI channel will be saved according to the oscillator type and filter type switches values in binary + 1.

For example, if you want to get MIDI channel 7, you will need to set the switch to 6 in binary 0b0110 which corresponds to Triangle oscillator and low pass filter, and then press the MIDI Channel selection button.

Gpios

Bloc	Description	Components	Gpios	Daisy pin	Simple Patch	Simple Pin	Notes
Oscillator	Main frequency	Pot	A11	35	6	43
Oscillator	Octave 1	Pot	A10	32	8	40
Oscillator	Octave 2	Pot	A9	31	13	39
Effects	Wavefolder factor	Pot	A8	30	22	38
Effects	Decimator factor	Pot	A7	29	33	37
Filter	Res frequency	Pot	A6	28	42	36
Filter	Filter drive	Pot	A5	27	44	35
Filter	Filter cutoff freq	Pot	A4	26	53	34
VCA/LPG	Attack	Pot	A3	25	67	33
VCA/LPG	Release	Pot	A2	24	69	32
VCA/LPG	Decay	Pot	A1	23	73	31
General	Main volume	Pot	A0	22	71	30
Oscillator	Oscillator type	Switch 2 pos	6	7	5	7
Oscillator	Oscillator type	Switch 2 pos	7	8	10	8
Effects	Effect mode selection	Switch 3 pos 1.1	8	9	28	9
Effects	Effect mode selection	Switch 3 pow 1.2	9	10	29	10
Filter	Filter type	Switch 2 pos	10	11	50	11
Filter	Filter type	Switch 2 pos	11	12	55	12
VCA/LPG	VCA Mode	Switch 2 pos	12	13	61	13
General	Gate out signal	Jack	5	6	66	6
VCA/LPG	VCA LPG selection	Switch 3 pos 2.1	4	5	78	5
VCA/LPG	VCA LPG selection	Switch 3 pos 2.2	3	4	79	4
MIDI	MIDI Channel selection button	Button	13	14	(16)*	14
MIDI	MIDI input	MIDI connector	1	2			UART
Output	AudioOut[0]	Mono Jack	AudioOut1	18	76	18
Output	AudioOut[1]	Mono Jack	AudioOut2	19			Not used

*The MIDI channel selection button can be put anywhere you want, accessible or not, depending on your usage. In my case, I put a discreet button on simple patch 16. I put it in this location, so it is not really visible and can be accessed through the front panel window, as shown in the following picture:

Pictures

Front panel design

Wiring

Contribution

Thanks the synthux academy community for their support and to lemkipper for contributing and putting the documentation to the test while building My-Dirty-Synth.