Auduino Dual Synthesizer Project

Dual Auduino Synth Project

For my next project that probably won’t get finished, I’ve decided on a synth, based on the Auduino source. I’m planning to use 2x Atmega168’s  – dual synth’s, for the left & right channels. Each Auduino will have it’s own set of controls, for Grain 1 & 2, Pitch & Decay. There will also be an Octave control for each Auduino, plus a Stereo Width control, and Master Volume.

I had some brushed aluminium sheet left over from another project that didn’t get finished.  I chopped this down to size using the scroll saw, with some WD40 sprayed on the blade to stop it clogging. I chose a size of 200mm x 120mm. These were arbitrary figures, with the only check done to ensure it was large enough for 12x knobs:

Brushed Aluminium Sheet

Aluminium front panel, before any work

 

I left the protective plastic on while I cut it out, and marked up the locations for each of the 12 controls:

Front panel, pre-drilling

Front panel, pre-drilling

 

I then carefully drilled & deburred each of the holes. And then, as I could bear it no longer, I removed the protective plastic! It’s starting to look a bit like a front panel now. As I was to later find out though, I would need to enlarge the holes for the rotary switches (octave control).

Front panel, post-drilling

Front panel, post-drilling

 

The knobs I chose for this project are the knobs used on some Ibanez guitars. They’re the right weight, they look great (in my opinion) and they’re readily available:

Ibanez control knob

Ibanez control knob

 

I really couldn’t be bothered with designing and etching a PCB for this, so I decided on stripboard. I started to solder up the circuit itself, following the instructions to run an Arduino standalone here. I’m using 2x Atmega168’s, with the Arduino bootloader, one for the left channel and one for the right. There’ll be the ability to adjust the stereo width, using one of the controls on the front panel.

Auduino Circuit, first stage

Auduino Circuit, first stage

 

To label up the front panel, I chose to reverse print onto transparency. That way, it should stop the printed text from rubbing off. I knocked up the graphic using GIMP, then reversed it and printed using the help of Irfanview (as nothing else would seem to print at actual size). Here are some images of the first experiment. I included the centre black dots to mark the positions for the pot mounts. These will stay in the final print, however the grey larger circles were only included to mark the circumference of the knobs.These did not need to be printed, and will be removed in the final print.

Printed transparency (1st attempt), overlaid on front panel

Printed transparency (1st attempt), overlaid on front panel

Printed transparency (1st attempt)

Printed transparency (1st attempt)

 

Here’s the second go at the front panel transparency. I’ve changed the font and added some more text. Also, the grey knob markers have been removed in this print.

Printed transparency (2nd attempt)

Printed transparency (2nd attempt)

A colleague with a much better toolshop than I made me a 8mm steel punch. I used this to easily remove the plastic where the pots will poke through. The knife work needed to tweak the 2 larger holes made it quite clear how handy that 8mm punch was (thanks Gary!). I knocked out the required plastic, mounted the 8x 4.7k linear pots and added some knobs so I could see how it was going to look. In the image below you can also see the key holes for the rotary switches (top 2 centre holes):

Front panel, partially populated

Front panel, partially populated

That’s all for now. Hopefully the next post with be with some sample audio!

Links:

The source code and Auduino home page: https://code.google.com/p/tinkerit/wiki/Auduino

Running an Arduino out of the dev board: http://arduino.cc/en/Main/Standalone