DIY IR+mic pedal: Axoloti

[Cuki79]

Thank you very much!

I have updated the workflow.

1) Now the select pot browse all the parameters (up and down) and pushing the select pot let you choose to adjust. It is WAY more convenient than before.

2) I also added a load/save option that enables you to save all the parameter on the SD card. However... there is a flaw, it saves the setting but not the pot "actual" position.

So let's say
1) I save the Highpass filter frequency to 100 Hz
2) Then I tweak again the pot to 245 Hz and want to come back
3) I load the preset and get back to 100 Hz
4) however whenever I touch the pot again, it will jumb back to 245Hz...

Annoying. It looks like nothing but I have to reprogram half of the whole thing to solve that.

I am very happy, it does sound great, and address most of the problems.

The only thing I miss is the room in the plain middle for a footswitch. I initially planned a "mute" footswitch but have also prepared the program for a "single footswitch" looper with the TC electronic Ditto workflow... I will have to give up on that.

Of course I could save space by making a proper PCB instead of the veroboard... But I don't see the benefit since I am not sure to produce more units. I probably will jump into the PCB rabbit hole if I buy another guitar with K&K just to include the high-Z buffer. The current pedal does not need 1Mohm input impedance since it is made for the my Trance Audio Amulet equipped HD-28.

When it is finished, I will make a proper demo. I need a friend to help me do that because someone has to tweak the pots when the others is playing and singing
I will also post all the schematics and programs on the axoloti forum when this unit is finished.

Cuki

[Cuki79]

I finally got it right.

The Menu interface program looks like this:



The square pattern in the middle with all the wires are the 16 virtual pots that are ruled by the select pot + switch.
On the left of the square pattern, the big box with all the blue dots lined vertically is the "load parameter function". It will feed the 16 virtual pots with presets values from the SD card.
On the right there are two boxes with blues dots lines vertically. One captures all the virtual pots positions to save them as a preset on the SD card. The other just send the values to the OLED screen.

It's funny to think that the user interface with 5 pots and an OLED screen is way more complex tp buid that the actual signal processing.

I don't know how stable it is going to be but it seems to work.

Next post should be a demo...

PS: I also need to make some measurements inside the box. The battery and mic preamp are not safely fixed in the box. I need to 3-D print some plastic pieces to hold everything tight.

Cuki

[Cuki79]

Here is a little demo of the axoloti pedal. It took me a some time because I added a synced sample player.

The output is recorded straightaway by a focusrite 2i2


Overall:
Rechargeable Li-ion Battery operated
Compact size
Mute footswitch
Samples/song stored on micro-SD card

Guitar:
1) High pass filter on IR path (Frequency tunable in the menu)
2) Full PEQ on IR path (Frequency, Gain, Q-factor tunable in the menu)
3) Semi PEQ on IR path (Frequency, Gain tunable in the menu)
4) Blend (analog pot always at hand)
5) Volume (analog pot always at hand)

Microphone:
1) 12V Phantom power
2) Quality analog gain circuit with +/-12v voltage rails
3) Gain pot (always at hand)
4) High pass filter (Frequency tunable in the menu)
5) Volume (tunable in the menu)

Rythm/Sample track (Dozen song on SD card right now)
1) External digitech FS3X controlable
2) Track A: looping a cajon beat with shakers and percussion
3) Track B: looping a Drum beat with congas
4) Track C: looping a twice long sample. Can be trigged before or after the beat, it will start sync'd.
5) Count in (setup in menu).
6) Volume (tunable in menu)

The workflow is the following
You have 4 footswitches
* Axoloti main: (n°1)
* FS3X called: Mode/Down/Up

When n°1 is in play
> Mode: Play/Stop tracks A+B (B is usually muted)
NB: only first press on Play includes a "count in", so you can use Play/Stop to make breaks
> Down: Unmutes Track B to add a drum beat
> Up: Launches the sample.
NB: if the footswitch is pressed before the beat. Axoloti wait for the beat to play the sample in sync then loop it until another footswitch press.
If the footswitch is pressed slightly after the beat, the sample is not played from the beginning. It calculate how late you are and play the sample as if you pressed "on-time".

When n°1 is in mute
> Mode: Trig the "count in", so the next "Play press" includes a count in.
> Down: Browses the song list down
> Up: Browses the song list up


The packaging is the same with an input for the external footswitch.

PS: Sorry in French rhythm has only one "h".

The patch can be downloaded here:
link for download

All you need is a €65 axoloti core, one rotary encoder, few pots, some jacks, an OLED screen, a mic preamp board (mine is home made, but it can be found anywhere) and a lithium battery.

Nota Bene: The pedal does not make IRs like Tonedexter... You still have to figure that by yourself.

[martingitdave]

Well done! Knowing how much effort you put into building a DIY sequencer, drum machine, IR loader, and Mic effects, I am amazed at how good the finished product is. Great job!