Wednesday, 19 June 2013

How to build MonotrOndes Part 2


Check out also the updated first part!

I'm using 3-pin DIN Connectors for connecting the Pitch Controller-module to Synth+expression-module of the MonotrOndes. I'm only using 2 pins and a ground point in this connector. You can choose a different type of connector. Or you can choose to make a non-modular version of MonotrOndes where everything is in fixed place without connectors and cables. But I have a point! The left-handed player can put the synth+expression-module on the right side of the pitch controller-module so he/she can play expression lever with his/her right hand. It's also nice to have a possibility to position the modules in a way that suits to your playing style.

 3-pin DIN Connector

 Here is an aluminum box that contains the multiturn pot. DIN connector at the top. 
Multiturn pot is connected to a pulley.

Here is the wiring inside the aluminum box. 

And here is the pitch control wiring inside the Synth+expression-module!

Stay tuned! :)

Thursday, 6 June 2013

How to build MonotrOndes part 1

This post is updated!  

At first I have to give credit to my twin brother Kalle. He came up with the name MonotrOndes.
My video has been very popular. I thank you all for your nice comments!
Someone even asked if I could build and sell these things. Maybe if there is enough people willing to buy them. I don't even know if it's legal to sell modified synthesizers without permission from manufacturer like Korg.

Pitch Control Electronics 


I assume you know a little bit about electronics and components. You should also understand that if you mod your Monotron, you loose all warranty! So please be careful and don't blame me if something goes wrong.

MonotrOndes is not using the original ribbon controller. There is a connector from the ribbon controller to Monotron board. You can disconnect the ribbon from there.

I removed one SMD resistor from Monotron's PCB. Instructions for removal and the location of that resistor are in this site:

Here is a new picture!

After removal of the ribbon and that SMD resistor I found out that monotron was playing continuously - exactly what I wanted. I don't know if it's necessary to remove that resistor. There might be an easier way to mod Monotron to play continuous sound.

For controlling pitch you will need two potentiometers - a trimmer (at least 47k) and a multiturn pot (100k). Of course you can use a normal potentiometer instead of a trimmer.
In the circuit the trimmer behaves as a variable resistor that sets the range of the pitch control. When you have found the right value for the pitch range you don't have to adjust it anymore. That's why we are using a trimmer type pot.

The multiturn pot's value changes when playing. Together the trimmer and the multiturn pot forms a voltage divider circuit. Monotron uses 3 volts to operate but there is internal circuit that magically (not really!) outputs 5 volts. The point in the Monotron PCB that outputs 5 volts is called VCC. That 5 volts is feeded to voltage divider that changes voltage value to smaller values. That divided voltage output is connected to pitch CV point in the Monotron PCB.

Now we have voltage controlled pitch!

I have to borrow unmodded Monotron for pictures. In the meantime check out this post from Din Sync blog.

There you can find picture of unmodded Monotron PCB. The important solder points are Pitch, VCC, Ground terminal and positive terminal.

You can see the important solder points in this new picture! Check out also a secret audio output point that bypasses Monotron's own volume pot. :)

Here is a schematic

Here is a picture of I/O connections

Saturday, 1 June 2013


  Welcome to Electronic Melodist!

This is a blog planned to be mostly about my DIY musical instrument projects and music production related things. I think the most enjoyable synth demo videos on Youtube are the ones where music sounds like proper musical piece. So I will not make videos that sounds like drone music or synth noise.

I'm from Finland. My English will not be perfect - sorry about grammar and spelling mistakes! :)

Above is the first picture of MonotrOndes - Korg Monotron that I hacked into
Ondes Martenot-style musical instrument. More pictures and info coming soon...

And here is a video that probably brought you here. :)

- Ville Aho -