DIY Arduino String Synth With Analogue Filter
I started by taking apart the MIDITECH and unplugging the ribbon cables;
Then using some ribbon cables I began to figure out how to connect the keyboards out’s with the Arduino’s In’s.
Feet…
With bottom panel size known, I sketched out the rest of the case…
The side panels;
All the parts have been cut here (the other bit of perspex with the dials on was temporary just to make sure it was still working);
Notice the pencil with my name written on it. That’s mine it is.
Then using my old friend Ponal Wood glue I started sticking everything together (including fingers, clothes and everything else);
Then it was time to design the front panel and the laser engrave it onto perspex. The smell was awful (and toxic)… I stayed in the room long enough to feel faint. I did sleep well that night though.
Running a test on card;
Burn!
After it was engraved I filled it in with white acrylic paint;
With the panels and case completed it was time to stain the wood. I used a mahogany brown stain, using two or three coats. The trick here is not to use to0 much and to keep it moving when it’s been applied, otherwise you’ll get an uneven finish.
Once this had dried it was time to add the varnish. Like with the stain, I find it’s best to use only a tiny amount and spread it out as much as possible to get the best finish (you can always add another layer later). With this synth I found one layer to be enough;
Once this has dried you can now put it all together. For extra security I also used some hot glue to do this (and it’s not fallen apart yet)
I added screws to secure the perspex panel but can’t find a picture of that. But I’m sure you can imagine what it looks like.
Conclusion
Overall I’m pretty happy with how it turned out, with only a few gaps in the wood caused by my rubbish cutting/maths skills. Should I make it again I’d move the output over to the far-right as I’ve noticed it’s possible to knock the cable when going mad on the filter (you should only touch a synthesisers knobs as if they are really hot, otherwise you’re not a real synthesist).
I’ve been learning C for a while, but it’s a massive mountain to climb. From here though I’ve bought the following book;
When I eventually get around to reading it, it should give me a better idea of what’s going on in the code, then I’d like to attempt a version 2 using maybe an Arduino Due and add some more controls.
Thanks!
****UPDATE****
SIMPLIFIED SCHEMATICS
Below is a simplified schematic for the string synth… Sorry it’s not the best quality I’ll try and take a better picture later, but hopefully this should be of help those of you new to schematics that want to try and build this synth.
The connections where it says ‘goes to keyboard’, you can see elsewhere in this blog for another detailed diagram of where and how these can be wired up to the keys. As for the potentiometers, I *think* I’ve drawn them the correct way (if you make this and the pots are working the opposite as you’d expect, swap around the ground and 5v connections on each pot). If the drawing is incorrect, let me know and I’ll re-do it. Even if this version is wrong, nothing will break & it’ll still work OK (just the pots will work in reverse).
You can see where the pots 5volt and ground connections need to go in the diagram, I didn’t join them in the picture because the wires would start overlapping and become confusing. It’s pretty obvious what to do though.
Also drawn is the audio out headphone socket, with the positive voltage/audio signal coming from the output D11, which then goes through the resister/capacitor (which acts as a filter to reduce some of the noise from the Arduino). The other side of the audio goes to the ground signal. If you don’t know how to wire up a audio jack, maybe google ‘audio jack pin-out’ or ‘audio socket wiring diagram’.
If you plan on adding the analogue filter, you’d leave off the audio jack and have the previously mention positive wire go into the input of the filter. You’ll have to learn to read the schematic for that I’m afraid, as I couldn’t really simplify it without it becoming more complicated than a normal schematic. Give me a shout if you get stuck though.
Good luck!
P.S
I’ll draw a simplified schematic for the Arduino drum machine soon.
****UPDATE PART 2******
Below is a wiring diagram to add a bypass switch to the filter;
…And if you were struggling to figure out how to wire up the Pots for the filter, I’ve drawn out a simple picture showing how (I’ve had to do this whilst away traveling, so it’s partly drawn from memory but I’m pretty certain it’s correct)…
Obviously the drawing only shows how the pots are wired and not the full schematic. Go look at the proper schematic for the rest of the plans, but this will give you a good idea of how to wire up the pots.
Powering the filter from a 9v Battery will give it it a bit more ‘oomph’, so if you’d like to do that, the below illustration will give you an idea. Further, should you want an LED indicator showing if the filter is switched on or not, see the chequered box;
Good luck!
***UPDATE Arduino Drum Machine****
Ok, so this ‘simplified’ schematic might not actually make things any simpler! But some people have asked for it, so maybe it’ll help clear somethings up a little bit – especially how to wire up the audio output and pots/switches. This was drawn from memory so I hope it’s correct – give me a shout if not and I’ll update (the pots might work in reverse, but they’ll still work). I’d also urge you to look at the schematic on Jan Ostman’s website for more help;
https://janostman.wordpress.com/the-o2-source-code/
Thanks!