Introduction: Quad Arduino Granular Drone Synth

About: 40something goofball who likes tinkering with electronics and other craft projects.

Here we are going to use 4 Arduino uno boards and a few other bits to create an analogue styled granular drone synth.

If you’ve ever seen single examples of these type of granular synthesizer projects in use, it soon becomes apparent that although they make some cool noises, they are a bit restricted when you try to use it to make actual we’re going to solve that by using 4, which will give you a drone that is much more ‘playable’ and can create a whole bunch of new merged sounds.... throw a few effects pedals in the mix and this becomes a truly awesome noise maker.

Here we go:-

Bill of parts-
4x Arduino Uno or uno clone
20x 10k potentiometers (other values will work).
Wire - various colours - 0.6 solid core is what I use.
8x 25mm stand off pins & screws

12v 2a DC power supply - this can happily power 4 Arduinos drawing 300-500ma.
Dc power socket kit (male and female).
Dc 4 in to 1 power cable (often used for CCTV kits).
2x aluminium sheets 300mm x 500mm.
Some wood to make a console - I used 25mm x 125mm for the front and rear, and some old scrap 12mm plywood for the cheeks.
A handful of screws to fix the timber.

For this instructable I will assume you know how to upload a sketch to the Arduino board via the Arduino IDE software. It's not difficult, and there are a bunch of tutorials that will show you better than I can explain it..

Step 1: Design Layout

Firstly, decide how you want your synth to look.
Make a few measurements of your components, and mark out your preferred design with a sharpie on the 1 of the aluminium sheets.
(if you are going to use potentiometer dials/gauges, you need to allow for those too)
I wanted an industrial kind of look and went for the setup in the pics.

Now, drill out the holes positions you have sharpied on the sheet.
There should be -
20 pot holes.
1 dc power socket.
4 audio out jacks.
1 led surround.

de-burr the alu sheet with some 180 grit sand paper or metal work files.
When you have removed all of the sharp bits, give the whole sheet a good sanding with the 180 to create a 'key' for the paint.

Get out your paint of choice, mine was a some cheap orange enamel. And give the front panel a good layer of paint and allow to dry.

Step 2: Build the Panel

Ok, so now you should have a front panel, drilled and painted.

Its time to start mounting the potentiometers, audio jacks, power socket and led surround.

Try to make sure your potentiometer terminals all point the same way, as it makes it a bit easier to daisy chain the wiring.

The order I do the panel build is
Pots first,
Then mount the stand off pins.
Audio jacks,
Power socket and led.

Step 3: Start the Wiring

Get your soldering equipment out and we'll start by soldering the potentiometer wires.
I tend to daisy chain one length of wire, from one potentiometer to the next. But you can use several short lengths of wire to connect them all if that's how you prefer to do it.

First we'll do the potentiometers 5v supply lead (red)

Step 4: Potentiometer Ground

Next solder the ground terminals on the potentiometers. (Grey wire)

Step 5: Signal Wires

Now solder individual signal wires to the centre pin of each pot.
(blue) approx 250mm long.

Step 6: Wire the Audio Jacks

Orange wire is ground.
Green is signal.

Cut 4 lengths of both colour wires, making sure they will stretch out to where your Arduinos will be sitting on the stand off pins.
Solder the grounds on each jack socket (orange)

and then solder the signal wires. (Green)

Step 7: Power

Solder two short wires to the dc power socket on the synth front panel.
(centre pin + vcc)
(outer shield - ground)
Then attach the MALE dc jack to those wires.

It’s a good idea to sheath this bit with some tape or heat shrink.......

Now plug that dc jack, in to the 4 in to 1 cable.
The insert each of the 4 jack plugs into the arduinos and fix them to the stand off pins using the supplied screws.

Step 8: Led Power Indication

Get two 300mm lengths of wire. I tend to keep to the red+and black colour scheme - so I don't mix up the polarity.
Solder a 1k resistor to the long leg of the LED, and attach the red wire. (sleeve with some heatshrink)
Solder the other wire to the short leg of the LED.

these wires will take a 3v+ feed and ground- off one of the arduinos to show that the unit is powered up.

Step 9: Header Pins, Connections and Uploading the Sketch

Now get the header pins that are supplied with your arduinos, and solder pins to the ends of each wire.

When you've finished that start inserting them into their respective boards..

Each arduino/potentiometer row should contain:-
1 red wire from potentiometers to 5v on the Arduino.
1 grey wire from potentiometers to GND on the Arduino.
5 blue wires from potentiometers to analogue ports A0,A1,A2,A3,A4
1 Orange wire from audio socket to GND on the Arduino.
1 green wire to port 9 on the Arduino.

Attach the usb cable to an Arduino board and plug it in to your pc.
Now we are going to install the synth sketch.

Open the Arduino IDE software, and check that you have the correct Arduino board type and port selected.

Open the sketch (see link below), and make any modifications you want to the code.
(there is plenty of scope to play around with the code and change the sounds produced)

There are lots of sketches for this project available online, and this one is a particularly good.

Synth sketch example

You can even add midi control, which is the next plan for this project...

Step 10: Build the Enclosure

Now you will build the enclosure.
I screwed two pieces of the 25mm x 125mm wood to the underside front and rear of the panel.
The cut some plywood pieces to make the the cheeks(side panels)
You can build this to look however you want, but I was aiming for an old modular analogue kinda look, so wanted it to be slightly tilted forward rather than laying flat.

So now we have the synth mounted on the timber frame and side panels fitted. Use the other piece of aluminium sheet to make a cover for the back of the synth to protect all of the circuitry.

Step 11: The Good Bit

So now we should have,
A painted panel with all components mounted, and wired to their respective ports on each Arduino.
Each Arduino connected to an audio output socket.
A working power supply, that feeds each arduino, with led indicator on the front panel.
Front, rear, sides and bottom of enclosure fitted.

Time to fire it up.

I use a very cheap 8 channel mixer ($18 off eBay)
It has 2 rows of 4 inputs and merges the signals, in to one of the 2 outputs.
So connect 4 audio leads to the mixer, and the mixer output to an amp or headphones.

Turn it all on.
And you should now be able to play each drone synth individually or merged through the mixer.

I will upload some short video clips later.

Step 12: Let’s Get This Thing Tested and Making Some Noise...

ok so we’re all assembled and ready to make some drone sounds..

Step 13: And Here’s the Quad Synth Being Used....

here we have the awesome, ROSEBUD, experimental noise-Meisters using the drone synth as part of their set..

Step 14: Wanna Know What the Synths Sound Like Individually?

Here is a short vid of a single drone i built, to show some of the sounds that are possible..

There’s also some footage of my light theremin/drone combo..

Audio Contest 2018

Participated in the
Audio Contest 2018